US20140013786A1

US20140013786A1 - Steam generation system

Info

Publication number: US20140013786A1
Application number: US14/007,517
Authority: US
Inventors: Masayoshi Kanamaru; Akinori Kawakami; Mika Tasaka; Akio Morita
Original assignee: Individual
Current assignee: Miura Co Ltd
Priority date: 2011-03-31
Filing date: 2011-10-26
Publication date: 2014-01-16
Also published as: JP2012215320A; WO2012132082A1; JP5136968B2; CN103459925B; KR20140023273A; CN103459925A

Abstract

There is provided an efficient steam generation system capable of reducing a temperature difference in heat to be drawn by a heat pump. A first heat pump (2) includes a first evaporator (7) and a second evaporator (8). A second heat pump (3) is connected to the first heat pump (2) via an uppermost condenser (10) serving as the first evaporator (7). A heat source fluid is passed through a second evaporator (8) of the first heat pump (2) and an evaporator (12) of the second heat pump (3) in sequence. Then, steam is generated by application of heat to water in a condenser (5) of the first heat pump (2).

Description

TECHNICAL FIELD

The present invention relates to a steam generation system for generating steam by means of a heat pump. This application claims priority on Patent Application No. 2011-079370 filed in Japan on Mar. 31, 2011, the contents of which are hereby incorporated by reference.

BACKGROUND ART

As disclosed in Patent Literature 1, heretofore, there has been known a heat pump in which an evaporator draws heat from a hot drain or the like and a condenser generates steam by application of the heat to water.
As disclosed in Patent Literature 2, moreover, there has been proposed a system including a multiple-stage heat pump in which heat pumps are vertically disposed. Herein, feed water is passed through a heat exchanger (serving as a condenser of the lower heat pump and an evaporator of the upper heat pump) that connects between the upper and lower heat pumps, so that heat is applied to the feed water. Then, steam is taken out from a condenser of the uppermost heat pump.
As disclosed in Patent Literature 3, further, there has also been proposed an apparatus including heat pumps disposed from side to side in parallel. Herein, water is passed through condensers of the respective heat pumps in sequence, thereby obtaining hot water.

Patent Literature 1: JP 58-40451 A (FIG. 2)
Patent Literature 2: JP 2006-348876 A (FIGS. 1, 2)
Patent Literature 3: JP 60-23669 U (FIG. 2)

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

According to the invention disclosed in Patent Literature 1, the heat pump is a single-stage heat pump. However, the efficiency of the heat pump is poor because there is a large temperature difference in heat to be drawn, i.e., a large temperature difference between the evaporator side and the condenser side.
According to the invention disclosed in Patent Literature 2, the heat pump is a multiple-stage heat pump in which heat pumps are vertically disposed. However, in the case where heat is drawn from only the evaporator of the lowermost heat pump, there is a large temperature difference in heat to be drawn as a whole of the heat pumps, as in the invention disclosed in Patent Literature 1. Therefore, the improvement in efficiency of the heat pump is restricted.
According to the invention disclosed in Patent Literature 3, the heat pumps are disposed from side to side in parallel. However, in the case where the right and left heat pumps have an identical configuration and heat is drawn from only the evaporator of the lowermost heat pump, there is a large temperature difference in heat to be drawn, as in the invention disclosed in Patent Literature 2. Therefore, the improvement in efficiency of the heat pump is restricted.
Further, in a case where a heat source fluid is hot water, exhaust gas or the like and undergoes a decrease in temperature while applying heat (sensible heat) to the heat pump, when the heat source fluid is merely passed through the heat pumps which are the same in configuration as each other and are disposed in parallel, the temperature of the heat source fluid is decreased in the downstream heat pump. Therefore, there is a necessity to take the decrease in temperature into consideration.
It is one object of the present invention to reduce a temperature difference in heat to be drawn as a whole of a system, thereby improving the efficiency of the system. It is another object of the present invention to provide a steam generation system capable of dealing with a decrease in temperature caused in a case where a heat source fluid applies sensible heat to a heat pump.

Means for Solving the Problems

The present invention has been devised to solve the problems described above. An invention of claim 1 is a steam generation system including: a single-stage or multiple-stage first heat pump in which at least the lowermost heat pump includes a first evaporator and a second evaporator; and a single-stage or multiple-stage second heat pump connected to the first heat pump via a condenser of the uppermost heat pump, the condenser serving as the first evaporator of the lowermost heat pump, wherein a heat source fluid is passed through the second evaporator of the first heat pump and an evaporator of the lowermost heat pump in the second heat pump in sequence, and steam is generated by application of heat to water in a condenser of the uppermost heat pump in the first heat pump.
According to the invention of claim 1, heat is drawn from the second evaporator of the first heat pump and the evaporator of the lowermost heat pump in the second heat pump, so that steam can be generated in the condenser of the uppermost heat pump in the first heat pump. Herein, the heat source fluid is passed through the second evaporator of the first heat pump, and then is passed through the evaporator of the lowermost heat pump in the second heat pump. Thus, the second heat pump is capable of making up the heat drawn from the heat source fluid in the second evaporator of the first heat pump, thereby drawing heat again from the heat source fluid passed through the second evaporator. Moreover, the first heat pump is capable of reducing a temperature difference in heat to be drawn, restraining power consumption in the compressor in accordance with the reduction, and improving the efficiency of the steam generation system.
An invention of claim 2 is the steam generation system of claim 1, wherein the second heat pump is a single-stage heat pump, heat is drawn from the heat source fluid passed through the second evaporator of the first heat pump and the evaporator of the lowermost heat pump in the second heat pump in sequence, and steam is generated by application of the heat to water in the condenser of the uppermost heat pump in the first heat pump.
According to the invention of claim 2, the steam generation system includes the single-stage or multiple-stage first heat pump and the single-stage second heat pump. Herein, the heat source fluid is passed through the second evaporator of the first heat pump, and the evaporator of the lowermost heat pump in the second heat pump in sequence. Thus, steam can be generated in the condenser of the uppermost heat pump in the first heat pump.
An invention of claim 3 is the steam generation system of claim 1 or 2, wherein the first heat pump is a multiple-stage heat pump in which some of or all of the heat pumps each include the first evaporator and the second evaporator as an evaporator, each of the first evaporators connects between the vertically adjoining heat pumps, and the heat source fluid is passed through the respective second evaporators in sequence from the upper heat pump toward the lower heat pump.
According to the invention of claim 3, the steam generation system includes three or more heat pumps as a whole. Herein, the heat source fluid is passed through the respective second evaporators of the first heat pump in sequence from the upper heat pump toward the lower heat pump, and then is passed through the evaporator of the lowermost heat pump in the second heat pump. Thus, steam can be generated by application of heat to water in the condenser of the uppermost heat pump in the first heat pump.
An invention of claim 4 is the steam generation system of claim 3, wherein the heat pumps in the multiple-stage first heat pump each include the first evaporator and the second evaporator as an evaporator.
According to the invention of claim 4, the heat source fluid is passed through the second evaporator of each heat pump in the first heat pump, and then is passed through the evaporator of the lowermost heat pump in the second heat pump. Thus, steam can be generated in such a manner that heat is drawn with good efficiency with a simple configuration.
An invention of claim 5 is the steam generation system of any one of claims 1 to 4, wherein in the heat pump including the first and second evaporators in the single-stage or multiple-stage first heat pump, the first evaporator and the second evaporator are provided in series or in parallel on a refrigerant channel from an expansion valve to a compressor, or a first expansion valve and the first evaporator are provided in parallel with a second expansion valve and the second evaporator on a refrigerant channel from a condenser to a compressor.
According to the invention of claim 5, the first evaporator and the second evaporator are provided in series or in parallel. Alternatively, the first expansion valve and the first evaporator are provided in parallel with the second expansion valve and the second evaporator. Then, heat is drawn in the second evaporator of the first heat pump and the evaporator of the lowermost heat pump in the second heat pump. Thus, steam can be generated in the condenser of the uppermost heat pump in the first heat pump.
An invention of claim 6 is the steam generation system of any one of claims 1 to 5, wherein the first heat pump and the second heat pump are connected in accordance with one of the following relations (a) to (c): (a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange without mixing both the refrigerants, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump; (b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump; and (c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the first heat pump to the expansion valve of the second heat pump without being passed through the expansion valve, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump.
According to the invention of claim 6, the steam generation system can be configured in such a manner that the first heat pump and the second heat pump are connected to each other via the indirect heat exchanger or the intermediate cooler.
An invention of claim 7 is the steam generation system of any one of claims 1 to 6, wherein when the first heat pump and/or the second heat pump are/is a multiple-stage heat pump, the adjoining heat pumps are connected in accordance with one of the following relations (a) to (c): (a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange without mixing both the refrigerants, and serves as a condenser of the lower heat pump and an evaporator of the upper heat pump; (b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump; and (c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the upper heat pump to the expansion valve of the lower heat pump without being passed through the expansion valve, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump.
According to the invention of claim 7, the first heat pump and/or the second heat pump can be configured with a multiple-stage heat pump. Moreover, the steam generation system can be configured in such a manner that the adjoining heat pumps are connected to each other via the indirect heat exchanger or the intermediate cooler.
An invention of claim 8 is the steam generation system of claim 6, wherein when the first heat pump and the second heat pump are connected in accordance with the relation (b) in claim 6, the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor, in place of or in addition to the supply to the intermediate cooler.
According to the invention of claim 8, the refrigerant from the compressor of the second heat pump is prevented from being supplied to the intermediate cooler. Thus, the heat exchanger that constitutes the intermediate cooler can be made small. Moreover, the invention of claim 8 is capable of preventing lubricant for the compressor of the second heat pump from retaining in the intermediate cooler and is also capable of preventing the compressor of the first heat pump from being out of oil.
An invention of claim 9 is the steam generation system of claim 6, wherein when the first heat pump and the second heat pump are connected in accordance with the relation (c) in claim 6, the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor in the first heat pump, or a refrigerant channel from the expansion valve to the intermediate cooler or compressor, in place of or in addition to the supply to the intermediate cooler.
According to the invention of claim 9, the refrigerant from the compressor of the second heat pump is prevented from being supplied to the intermediate cooler. Thus, the heat exchanger that constitutes the intermediate cooler can be made small.
An invention of claim 10 is the steam generation system of claim 6, further including: a separator for separating the refrigerant from the expansion valve of the first heat pump into a vapor phase and a liquid phase when the first heat pump and the second heat pump are connected in accordance with the relation (c) in claim 6, wherein the vapor-phase refrigerant separated by the separator is supplied to a refrigerant channel from the second evaporator to the compressor.
According to the invention of claim 10, the separator is provided for preventing the vapor-phase refrigerant from being supplied to the intermediate cooler and/or the second evaporator. Therefore, the heat exchanger that constitutes these components can be made small.
An invention of claim 11 is the steam generation system of any one of claims 1 to 10, further including at least one of: (a) a first sub-heat exchanger for performing heat exchange between the water and the refrigerant from the condenser to the expansion valve in the uppermost heat pump of the first heat pump; (b) a second sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the evaporator to the compressor in the lowermost heat pump of the second heat pump; (c) a third sub-heat exchanger for performing heat exchange between the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump and the refrigerant from the compressor to the first evaporator in the second heat pump, in a case where the first evaporator is an indirect heat exchanger; and (d) a fourth sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump, wherein with regard to order of distribution of the water and steam to the condenser of the uppermost heat pump in the first heat pump, and the first sub-heat exchanger in the case where the first sub-heat exchanger is provided, the first sub-heat exchanger is provided on the upstream side in the case where the first sub-heat exchanger is provided, with regard to order of distribution of the heat source fluid to the second evaporator of the first heat pump, the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump, and the second sub-heat exchanger in the case where the second sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump is provided on the downstream side, and with regard to order of distribution of the refrigerant to the first evaporator of the first heat pump, the third sub-heat exchanger in the case where the third sub-heat exchanger is provided, the second evaporator of the first heat pump, and the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the first evaporator and the second evaporator are provided on the upstream side of the third sub-heat exchanger and the fourth sub-heat exchanger.
According to the invention of claim 11, the first sub-heat exchanger is used as a refrigerant supercooler, the second sub-heat exchanger is used as a refrigerant superheater, the fourth sub-heat exchanger is used as a refrigerant superheater, and the third sub-heat exchanger is provided as appropriate. Thus, the efficiency of the steam generation system can be improved.
An invention of claim 12 is the steam generation system of any one of claims 1 to 11, wherein the heat source fluid is a drain from a steam-utilizing facility.
According to the invention of claim 12, steam can be generated by recovering heat from the drain discharged from the steam-utilizing facility.

Effects of the Invention

According to the present invention, it is possible to reduce a temperature difference in heat to be drawn as a whole of a system, thereby improving the efficiency of the system. It is also possible to deal with a decrease in temperature caused in a case where a heat source fluid applies sensible heat to a heat pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a steam generation system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating order of distribution of a heat source fluid to a fourth sub-heat exchanger, a second evaporator of a first heat pump, a second sub-heat exchanger, and an evaporator of a second heat pump.

FIG. 3 is a diagram illustrating order of distribution of a refrigerant in the first heat pump to a first evaporator of the first heat pump, a third sub-heat exchanger, the second evaporator of the first heat pump, and the fourth sub-heat exchanger.

FIG. 4 is a graph illustrating a comparison between the steam generation system of the present invention and a conventionally well-known two-stage heat pump in terms of a coefficient of performance.

FIG. 5 is a graph illustrating a comparison between the steam generation system of the present invention and the conventionally well-known two-stage heat pump in terms of a compressor intake volume flow rate in each of upper and lower heat pumps.

FIG. 6A is a T-S diagram illustrating an ideal cycle.

FIG. 6B is a T-S diagram of a conventionally well-known single-stage heat pump (inverse Carnot cycle).

FIG. 7 is a T-S diagram of the steam generation system according to this embodiment.

FIG. 8 illustrates a case where the number of the heat pumps is increased in FIG. 7.

FIG. 9 is a schematic diagram illustrating a steam generation system according to a second embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a modification example of the steam generation system according to the second embodiment.

FIG. 11 is a schematic diagram illustrating a steam generation system according to a third embodiment of the present invention.

FIG. 12 is a schematic diagram illustrating a modification example of the steam generation system according to the third embodiment.

FIG. 13 is a schematic diagram illustrating a steam generation system according to a fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating order of distribution of a refrigerant in a first heat pump to a first evaporator of the first heat pump, and a third sub-heat exchanger, and order of distribution of the refrigerant in the first heat pump to a second evaporator of the first heat pump, and a fourth sub-heat exchanger, in the fourth embodiment.

FIG. 15 is a schematic diagram illustrating a steam generation system according to a fifth embodiment of the present invention.

FIG. 16 is a schematic diagram illustrating a modification example of the steam generation system according to the fifth embodiment.

FIG. 17 is a schematic diagram illustrating a steam generation system according to a sixth embodiment of the present invention.

FIG. 18 is a schematic diagram illustrating a first modification example of the steam generation system according to the sixth embodiment.

FIG. 19 is a schematic diagram illustrating a second modification example of the steam generation system according to the sixth embodiment.

FIG. 20 is a diagram illustrating a combination of layout of a first separator, a second separator and a third separator.

FIG. 21 is a schematic diagram illustrating a steam generation system according to a seventh embodiment of the present invention.

FIG. 22 is a schematic diagram illustrating a steam generation system according to an eighth embodiment of the present invention.

FIG. 23 is a schematic diagram illustrating a first modification example of the steam generation system according to the eighth embodiment.

FIG. 24 is a schematic diagram illustrating a second modification example of the steam generation system according to the eighth embodiment.

FIG. 25 is a schematic diagram illustrating a steam generation system according to a ninth embodiment of the present invention.

FIG. 26 is a schematic diagram illustrating a first modification example of the steam generation system according to the ninth embodiment.

FIG. 27 is a schematic diagram illustrating a second modification example of the steam generation system according to the ninth embodiment.

FIG. 28 is a diagram illustrating a combination of layout of a first separator and a second separator.

FIG. 29A is a schematic diagram illustrating one example of a steam generation system according to the present invention, the steam generation system including three or more heat pumps.

FIG. 29B is a T-S diagram in a case where a first heat pump is a single-stage heat pump and a second heat pump is a two-stage heat pump.

FIG. 29C is a T-S diagram in a case where a first heat pump is a multiple-stage heat pump in which each heat pump includes a first evaporator and a second evaporator and a second heat pump is a single-stage heat pump.

FIG. 30 is a schematic diagram illustrating one example of a steam system using the steam generation system according to the first embodiment.

FIG. 31 is a schematic diagram illustrating a modification example of the steam system illustrated in FIG. 30.

EXPLANATION OF REFERENCE NUMERALS

- 1 Steam generation system
- 2 First heat pump
- 3 Second heat pump
- 4 Compressor (of first heat pump)
- 5 Condenser (of first heat pump)
- 6 Expansion valve (of first heat pump)
- 7 First evaporator (of first heat pump)
- 8 Second evaporator (of first heat pump)
- 9 Compressor (of second heat pump)
- 10 Condenser (of second heat pump)
- 11 Expansion valve (of second heat pump)
- 12 Evaporator (of second heat pump)
- 13 Indirect heat exchanger
- 14 First sub-heat exchanger
- 15 Second sub-heat exchanger
- 16 Third sub-heat exchanger
- 17 Fourth sub-heat exchanger
- 18 Intermediate cooler
- 19 Intermediate cooler
- 22 Separator
- 27 Steam system
- 29 Steam-utilizing facility

PREFERRED MODE FOR CARRYING OUT THE INVENTION

A steam generation system of the present invention includes a multiple-stage heat pump. In the multiple-stage heat pump, some or all of the heat pumps excluding the lowermost heat pump each include a first evaporator and a second evaporator. Each of the first evaporators connects between the adjoining upper and lower heat pumps. A heat source fluid is passed through the respective second evaporators in sequence from the upper heat pump toward the lower heat pump. Steam is generated by application of heat to water in a condenser of the uppermost heat pump.
Hereinafter, detailed description will be given of specific embodiments of the present invention with reference to the drawings.

EMBODIMENTS

First Embodiment

FIG. 1 is a schematic diagram illustrating a steam generation system 1 according to a first embodiment of the present invention. The steam generation system 1 according to this embodiment includes a first heat pump 2 and a second heat pump 3.
The first heat pump 2 is of a steam compression type and is a single-stage heat pump in this embodiment. Specifically, the first heat pump 2 includes a compressor 4, a condenser 5, an expansion valve 6, an evaporator 7 and an evaporator 8 which are sequentially and cyclically connected to one another. Herein, the first heat pump 2 includes the two evaporators, i.e., the first evaporator 7 and the second evaporator 8 which are connected in series in this embodiment. That is, a refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7 and the second evaporator 8 in sequence (or in the reverse order as will be described later), and then is fed to the compressor 4.
The compressor 4 compresses the gaseous refrigerant to make the temperature and pressure thereof high. The condenser 5 condenses and liquidizes the gaseous refrigerant from the compressor 4. The expansion valve 6 allows the liquid refrigerant from the condenser 5 to pass therethrough, thereby decreasing the pressure and temperature of the refrigerant. The evaporators 7 and 8 evaporate the refrigerant from the expansion valve 6.
Accordingly, the first heat pump 2 has the configuration that the refrigerant is vaporized by absorbing heat from the outside in the evaporators 7 and 8 and is condensed by dissipating heat into the outside in the condenser 5. With this configuration, the first heat pump 2 draws heat from the heat source fluid or the like in the evaporators 7 and 8, and applies heat to water, thereby generating steam in the condenser 5.
The heat source fluid (the heat source for each of the heat pumps 2 and 3) is not particularly limited. The heat source fluid to be suitably used herein is a fluid applying sensible heat to each of the heat pumps 2 and 3, i.e., a fluid undergoing a decrease in temperature while applying heat to each of the heat pumps 2 and 3. Examples of the heat source fluid may include a drain from a steam-utilizing facility, exhaust gas from a boiler, and the like.
Desirably, a circuit of the heat pump 2 may be provided with an oil separator on the outlet side of the compressor 4, a liquid receiver on the outlet side of the condenser 5, an accumulator on the inlet side of the compressor 4, or a liquid-gas heat exchanger performing heat exchange without mixing the refrigerant from the condenser 5 to the expansion valve 6 with the refrigerant from the evaporators 7 and 8 to the compressor 4. The similar things may hold true for the second heat pump 3 in addition to the first heat pump 2. In a case where each of the first heat pump 2 and the second heat pump 3 is configured with a multiple-stage heat pump, the similar things may hold true for each heat pump in the multiple-stage heat pump.
The second heat pump 3 is of a steam compression type and is a single-stage heat pump in this embodiment. The second heat pump 3 is basically similar in configuration to the first heat pump 2. That is, the second heat pump 3 includes a compressor 9, a condenser 10, an expansion valve 11 and an evaporator 12 which are sequentially and cyclically connected to one another. Unlike the first heat pump 2, however, the second heat pump 3 does not necessarily include two evaporators. The heat pump 3 draws heat from a heat source fluid in the evaporator 12, and applies heat to the refrigerant in the first heat pump 2 to condense the refrigerant in the condenser 10.
The first heat pump 2 and the second heat pump 3 are connected as follows. That is, an indirect heat exchanger 13 is provided for receiving the refrigerant from the compressor 9 of the second heat pump 3 and the refrigerant from the expansion valve 6 of the first heat pump 2 and performing heat exchange without mixing both the refrigerants. The indirect heat exchanger 13 serves as the condenser 10 of the second heat pump 3 and the first evaporator 7 of the first heat pump 2. The refrigerants in the respective heat pumps 2 and 3 may be the same as or different from each other. The refrigerant to be used herein is not particularly limited, and a suitable example thereof may include: hydrofluorocarbon (HFC) having four or more carbon atoms (e.g., R-365mfc) or a mixture thereof with water and/or a fire extinguishing agent; alcohol (e.g., ethyl alcohol, methyl alcohol or trifluoroethanol (TFE)) or a mixture thereof with water and/or a fire extinguishing agent; or water (e.g., pure water or soft water).
The heat source fluid is passed through the second evaporator 8 of the first heat pump 2 and the evaporator 12 of the second heat pump 3; however, the detailed description thereof will be given later. Accordingly, the steam generation system 1 draws heat from the heat source fluid in the evaporators 8 and 12, and applies the heat to water, thereby generating steam in the condenser 5 of the first heat pump 2.
The steam generation system 1 may include at least one of the following various sub-heat exchangers 14 to 17 to be described below.
(a) The first sub-heat exchanger 14 is an indirect heat exchanger for performing heat exchange between water and the refrigerant from the condenser 5 to the expansion valve 6 in the first heat pump 2, and functions as a refrigerant supercooler of the heat pump 2.
(b) The second sub-heat exchanger 15 is an indirect heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the evaporator 12 to the compressor 9 in the second heat pump 3, and functions as a refrigerant superheater of the second heat pump 3.
(c) The third sub-heat exchanger 16 is an indirect heat exchanger for performing heat exchange between the refrigerant from the expansion valve 6 to the compressor 4 in the first heat pump 2 and the refrigerant from the compressor 9 to the first evaporator 7 in the second heat pump 3, in a case where the first evaporator 7 is the indirect heat exchanger 13, and functions as a refrigerant superheater of the first heat pump 2.
(d) The fourth sub-heat exchanger 17 is an indirect heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the expansion valve 6 to the compressor 4 in the first heat pump 2, and functions as a refrigerant superheater of the first heat pump 2.
Next, description will be given of a route of distribution of water and steam.
Water is supplied to and then steam is derived from the condenser 5 of the first heat pump 2 and the first sub-heat exchanger 14 to be provided as desired. With regard to the order of distribution of the water and steam, in the case where the first sub-heat exchanger 14 is provided, the first sub-heat exchanger 14 is provided on the upstream side of the condenser 5 of the first heat pump 2. Typically, saturated steam is derived from the condenser 5 of the first heat pump 2. As illustrated in FIG. 1, the condensers 5 and 10 of the respective heat pumps 2 and 3 are provided one by one. However, a plurality of heat exchangers may be provided in series or in parallel.
Next, description will be given of a route of distribution of a heat source fluid.
The second evaporator 8 of the first heat pump 2, the fourth sub-heat exchanger 17 to be provided as desired, the evaporator 12 of the second heat pump 3 and the second sub-heat exchanger 15 to be provided as desired are provided in appropriate order, and the heat source fluid is passed therethrough. As the route of distribution of the heat source fluid, one of routes of distribution illustrated in FIG. 2 is employed.
FIG. 2 is a diagram illustrating the order of distribution of the heat source fluid to the fourth sub-heat exchanger 17 to be provided as desired, the second evaporator 8 of the first heat pump 2, the second sub-heat exchanger 15 to be provided as desired, and the evaporator 12 of the second heat pump 3. Numerals in FIG. 2 indicate the order of distribution to the respective heat exchangers 17, 8, 15 and 12, and “0” indicates that the relevant heat exchanger is not provided. The heat exchangers indicated by the same numeral are provided in parallel and can be interchanged with each other. As illustrated in FIG. 2, the evaporators 8 and 12 of the respective heat pumps 2 and 3 are provided one by one. However, a plurality of heat exchangers may be provided in series or in parallel.
Some specific examples will be described below. For example, “1”, “2”, “3” and “4” are shown in the first row. Herein, the fourth sub-heat exchanger 17 corresponds to “1”, the second evaporator 8 of the first heat pump 2 corresponds to “2”, the second sub-heat exchanger 15 corresponds to “3”, and the evaporator 12 of the second heat pump 3 corresponds to “4”. In this case, the heat source fluid is passed through the fourth sub-heat exchanger 17, the second evaporator 8 of the first heat pump 2, the second sub-heat exchanger 15, and the evaporator 12 of the second heat pump 3 in sequence.
Moreover, “1”, “2”, “1” and “3” are shown in the second row. Herein, the fourth sub-heat exchanger 17 corresponds to “1”, the second evaporator 8 of the first heat pump 2 corresponds to “2”, the second sub-heat exchanger 15 corresponds to “1”, and the evaporator 12 of the second heat pump 3 corresponds to “3”. In this case, the heat source fluid is passed through the fourth sub-heat exchanger 17 and the second sub-heat exchanger 15 in parallel, and then is passed through the second evaporator 8 of the first heat pump 2, and the evaporator 12 of the second heat pump 3 in sequence.
Further, “1”, “2”, “0” and “3” are shown in the fourth row. Herein, the fourth sub-heat exchanger 17 corresponds to “1”, the second evaporator 8 of the first heat pump 2 corresponds to “2”, the second sub-heat exchanger 15 corresponds to “0”, and the evaporator 12 of the second heat pump 3 corresponds to “3”. In this case, the second sub-heat exchanger 15 is not provided, and the heat source fluid is passed through the fourth sub-heat exchanger 17, and then is passed through the second evaporator 8 of the first heat pump 2, and the evaporator 12 of the second heat pump 3 in sequence.
In any order of distribution of the heat source fluid, basically, it is preferred that the evaporator 12 of the second heat pump 3 is provided on the downstream side. In other words, the heat source fluid is passed through the second evaporator 8 of the first heat pump 2, and then is passed through the evaporator 12 of the second heat pump 3.
FIG. 3 is a diagram illustrating the order of distribution of the refrigerant in the first heat pump 2 to the first evaporator 7 of the first heat pump 2, the third sub-heat exchanger 16 to be provided as desired, the second evaporator 8 of the first heat pump 2, and the fourth sub-heat exchanger 17 to be provided as desired. Numerals in FIG. 3 each indicate the order of distribution to the respective heat exchangers 7, 16, 8 and 17, and “0” indicates that the relevant heat exchanger is not provided. Moreover, the heat exchangers indicated by the same numeral are provided in parallel.
Some specific examples will be described below. For example, “1”, “3”, “2” and “3” are shown in the first row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “3”, the second evaporator 8 corresponds to “2”, and the fourth sub-heat exchanger 17 corresponds to “3”. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7 and the second evaporator 8 in sequence, then is passed through the third sub-heat exchanger 16 and the fourth sub-heat exchanger 17 in parallel, and is fed to the compressor 4.
Moreover, “1”, “3”, “2” and “4” are shown in the second row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “3”, the second evaporator 8 corresponds to “2”, and the fourth sub-heat exchanger 17 corresponds to “4”. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7, the second evaporator 8, the third sub-heat exchanger 16 and the fourth sub-heat exchanger 17 in sequence, and is fed to the compressor 4.
Further, “1”, “3”, “2” and “0” are shown in the fourth row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “3”, the second evaporator 8 corresponds to “2”, and the fourth sub-heat exchanger 17 corresponds to “0”. In this case, the fourth sub-heat exchanger 17 is not provided, and the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7, the second evaporator 8 and the third sub-heat exchanger 16 in sequence, and is fed to the compressor 4.
In any order of distribution of the refrigerant in the first heat pump 2, basically, it is preferred that the first evaporator 7 and the second evaporator 8 are provided on the upstream side of the third sub-heat exchanger 16 and the fourth sub-heat exchanger 17.
As described above, the steam generation system 1 according to this embodiment employs, for example, a drain as the heat source fluid. In one example, a drain at 158° C. is supplied to the second evaporator 8 of the first heat pump 2, and is discharged at 125° C. Thereafter, the drain is supplied to the evaporator 12 of the second heat pump 3, and is discharged at 80° C. In the second heat pump 3, the temperature of the refrigerant is changed to 75° C. on the low-temperature side (the inlet side of the compressor 9). In the first heat pump 2, the temperature of the refrigerant is changed to 120° C. on the low-temperature side (the inlet side of the compressor 4), and is changed to 163° C. on the high-temperature side (the outlet side of the compressor 4). In the condenser 5, steam at 158° C. is generated.
In the steam generation system 1 according to this embodiment, the heat source fluid is passed through the second evaporator 8 of the first heat pump 2, and then is passed through the evaporator 12 of the second heat pump 3. Thus, even when the drain is cooled in the second evaporator 8 of the first heat pump 2, the second heat pump 3 makes up for the drawn heat, thereby drawing heat again from the drain passed through the second evaporator 8. Moreover, the first heat pump 2 is capable of reducing the temperature difference in heat to be drawn, reducing electric power for the compressor 4 in accordance with the reduced difference, and improving the efficiency of the steam generation system 1.
In other words, the steam generation system 1 seems to include the plurality of heat pumps 2 and 3 (two heat pumps in this embodiment) as a whole, and draws a part (typically, half) of energy from the middle heat pump, thereby increasing a coefficient of performance. Moreover, the steam generation system 1 is capable of reducing energy to be drawn from the lowermost heat pump (typically, into halves), and therefore is capable of reducing the capacity of the compressor 9 in the lower heat pump (i.e., of the second heat pump 3).
FIG. 4 is a graph illustrating a comparison between the steam generation system 1 according to this embodiment and a conventionally well-known two-stage heat pump in terms of a coefficient of performance. In FIG. 4, a solid line indicates the steam generation system 1 according to this embodiment, and a broken line indicates the conventionally well-known two-stage heat pump. FIG. 4 illustrates a case where a drain is used as the heat source fluid, the horizontal axis indicates a final drain temperature after the drain is passed through the evaporator 12 of the second heat pump 3, and the vertical axis indicates a theoretical coefficient of performance. A refrigerant used herein is R-365mfc, and consideration is given to the conditions described above, i.e., the case where the drain having the initial temperature of 158° C. is used for generating steam at 158° C. (5 kgf/cm²(G)).
As illustrated in FIG. 4, the steam generation system 1 according to this embodiment operates with higher efficiency as compared with the conventionally well-known two-stage heat pump, irrespective of the temperature of the heat source fluid (drain). Herein, the conventionally well-known two-stage heat pump has a configuration equal to the configuration that the second evaporator 8 is not provided and heat is drawn from only the evaporator 12 of the lowermost second heat pump 3 in FIG. 1.
FIG. 5 is a graph illustrating a comparison between the steam generation system 1 according to this embodiment and the conventionally well-known two-stage heat pump in terms of a compressor intake volume flow rate in each of the upper and lower heat pumps. In FIG. 5, a solid line indicates the steam generation system 1 according to this embodiment, and a broken line indicates the conventionally well-known two-stage heat pump. FIG. 5 illustrates a case where a drain is used as the heat source fluid, the horizontal axis indicates a final drain temperature after the drain is passed through the evaporator 12 of the second heat pump 3, and the vertical axis indicates a compressor intake volume flow rate.
As illustrated in FIG. 5, the steam generation system 1 according to this embodiment is capable of reducing the compressor intake volume flow rate, irrespective of the temperature of the heat source fluid (drain). Accordingly, the steam generation system 1 according to this embodiment operates with higher coefficient as compared with the conventionally well-known two-stage heat pump.
FIG. 6A is a T-S diagram in a case of ideally drawing heat (hereinafter, referred to as an ideal cycle) under conditions of saturated water in which a state of the fluid receiving heat at the inlet is T_h, saturated steam in which a state of the fluid receiving heat at the outlet is T_h(i.e., sensible heat is given to the fluid receiving heat), saturated water in which a state of the fluid giving heat at the inlet is T_h, and supercooled water in which a state of the fluid giving heat at the outlet is T₁(i.e., sensible heat is drawn from the fluid giving heat). Herein, the vertical axis indicates a temperature, and the horizontal axis indicates entropy.
The area of a triangle enclosed with this ideal cycle, i.e., a solid line corresponds to a minimum power (ideal power) for realizing the conditions described above. A coefficient of performance COP at this time is obtained as follows:
COP=2×(T _h/(T _h −T ₁)).
On the other hand, FIG. 6B is a T-S diagram of a conventionally well-known single-stage heat pump (inverse Carnot cycle). However, FIG. 6B illustrates a case where losses at the outlet of the expansion valve and losses by overheat of the compressor are ignored so that heat exchange performance becomes infinite. In this case, the coefficient of performance COP is obtained as follows: COP=T_h/(T_h−T₁). The similar things may hold true for the case where the heat pump is configured with a two-stage heat pump in which two heat pumps are vertically disposed, as shown with a chain double-dashed line A.
It is apparent from a comparison between FIG. 6A and FIG. 6B that a power derived by subtracting the area of a triangle in FIG. 6A from the area of a square in FIG. 6B corresponds to an extra power relative to the ideal cycle, and the coefficient of performance decreases in accordance with this extra power.
On the other hand, FIG. 7 is a T-S diagram of the steam generation system according to this embodiment. In this case, the coefficient of performance COP is obtained as follows: COP=(4/3)×(T_h/(T_h−T₁)). That is, the efficiency of the steam generation system 1 is 4/3 times as large as that of the conventionally well-known single-stage heat pump. Herein, the following relations are established: t_m=(t_h+t₁)/2 and S_m=(S₁+S₂)/2. As compared with FIG. 6B, the right bottom portion can be eliminated, so that the efficiency can be improved since the power corresponding to this eliminated portion is reduced.
In the example illustrated in FIG. 7, the number of heat pumps is two. When the number of heat pumps is increased, an area to be enclosed with a cycle can be further reduced as illustrated in FIG. 8, so that the efficiency of the steam generation system 1 can be further improved. When the number of heat pumps is set infinite, the following relation is theoretically established: COP=2×(T_h/(T_h−T₁)). That is, the efficiency of the steam generation system 1 can be made twice as large as that of the conventionally well-known single-stage heat pump. A specific configuration of the steam generation system 1 in which the number of heat pumps is increased will be described later.

Second Embodiment

FIG. 9 is a schematic diagram illustrating a steam generation system 1 according to a second embodiment of the present invention. The steam generation system 1 according to the second embodiment is basically similar to that according to the first embodiment. In the following, therefore, differences between the first and second embodiments will be mainly described with the corresponding components denoted with the same reference sign.
The second embodiment is different from the first embodiment in a configuration of connection between a first heat pump 2 and a second heat pump 3. In the first embodiment, the first heat pump 2 and the second heat pump 3 are connected via the indirect heat exchanger 13. In the second embodiment, on the other hand, the first heat pump 2 and the second heat pump 3 are connected via an intermediate cooler 18.
Specifically, the intermediate cooler 18 receives a refrigerant from a compressor 9 of the second heat pump 3 and a refrigerant from an expansion valve 6 of the first heat pump 2, and brings both the refrigerants into direct contact with each other to perform heat exchange. The intermediate cooler 18 serves as a condenser 10 of the second heat pump 3 and an evaporator 7 of the first heat pump 2. More specifically, the intermediate cooler 18 is a hollow tank (direct heat exchanger) that receives the refrigerant from the compressor 9 of the second heat pump 3 and the refrigerant from the expansion valve 6 of the first heat pump 2 and brings both the refrigerants into direct contact with each other in the tank, thereby condensing the refrigerant from the compressor 9 of the second heat pump 3 and evaporating the refrigerant from the expansion valve 6 of the first heat pump 2. Then, the intermediate cooler 18 feeds a liquid refrigerant obtained as described above to an expansion valve 11 of the second heat pump 3, and feeds a gas-liquid mixed refrigerant to the compressor 4 via a second evaporator 8 of the first heat pump 2.
In the second embodiment, the refrigerant from the expansion valve 6 of the first heat pump 2 is basically fed to the compressor 4 via the intermediate cooler 18 and the second evaporator 8 in sequence. Since the refrigerant is boiled also in the second evaporator 8, the refrigerant to be fed from the intermediate cooler 18 to the second evaporator 8 contains a vapor phase and a liquid phase in a predetermined mixing ratio. The mixing ratio is adjusted by, for example, adjusting the apertures of valves (not illustrated) provided on a refrigerant channel for the vapor phase and a refrigerant channel for the liquid phase from the intermediate cooler 18, respectively.
In the second embodiment, a third sub-heat exchanger 16 is not provided. The other configurations are similar to those in the first embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the second embodiment. In the modification example, differences from FIG. 9 will be mainly described, and the similar configurations will not be described here. In the following description, moreover, corresponding components are denoted with the same reference sign.
FIG. 10 is a schematic diagram illustrating the modification example of the steam generation system 1 according to the second embodiment. In the steam generation system 1 illustrated in FIG. 9, the refrigerant from the compressor 9 of the second heat pump 3 is supplied to the intermediate cooler 18. In this modification example, on the other hand, as shown with a chain double-dashed line A, the refrigerant is supplied to a refrigerant channel from the intermediate cooler 18 to the compressor 4 in the first heat pump 2, in place of or in addition to the supply to the intermediate cooler 18. Herein, the channel shown with the chain double-dashed line A may be connected to either an inlet side or an outlet side of the second evaporator 8. Alternatively, in a case where a fourth sub-heat exchanger 17 is provided, the channel may be connected to either an inlet side or an outlet side of the fourth sub-heat exchanger 17. Further, as shown with a chain double-dashed line B, the refrigerant from the compressor 9 of the second heat pump 3 may be flown into a refrigerant channel from the expansion valve 6 to the intermediate cooler 18 in the first heat pump 2.

Third Embodiment

FIG. 11 is a schematic diagram illustrating a steam generation system 1 according to a third embodiment of the present invention. The steam generation system 1 according to the third embodiment is basically similar to that according to the first embodiment. In the following, therefore, differences between the first and third embodiments will be mainly described with the corresponding components denoted with the same reference sign.
The third embodiment is different from the first embodiment in a configuration of connection between a first heat pump 2 and a second heat pump 3. In the first embodiment, the first heat pump 2 and the second heat pump 3 are connected via the indirect heat exchanger 13. In the third embodiment, on the other hand, the first heat pump 2 and the second heat pump 3 are connected via an intermediate cooler 19.
Specifically, the intermediate cooler 19 receives a refrigerant from a compressor 9 of the second heat pump 3 and a refrigerant from an expansion valve 6 of the first heat pump 2 to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from a condenser 5 of the first heat pump 2 to an expansion valve 11 of the second heat pump 3 without being passed through expansion valve 6. The intermediate cooler 19 serves as a condenser 10 of the second heat pump 3 and an evaporator 7 of the first heat pump 2. More specifically, the intermediate cooler 19 is an indirect heat exchanger that performs heat exchange without mixing a fluid in a first region 20 with a fluid in a second region 21. The refrigerant from the compressor 9 of the second heat pump 3 and the refrigerant from the expansion valve 6 of the first heat pump 2 are directly subjected to heat exchange in the first region 20. On the other hand, the refrigerant is passed from the condenser 5 of the first heat pump 2 to the second region 21 without being passed through the expansion valve 6, and then is supplied to the expansion valve 11 of the second heat pump 3. In this case, the refrigerant from the compressor 9 of the second heat pump 3 is subjected to intermediate cooling using the refrigerant from the expansion valve 6 of the first heat pump 2, in the intermediate cooler 19. Then, the refrigerant is changed to a high-pressure, high-temperature gaseous refrigerant in the compressor 4 of the first heat pump 2, and is condensed in the condenser 5 of the first heat pump 2. A part of the liquid refrigerant is fed to the first region 20 of the intermediate cooler 19 via the expansion valve 6 of the first heat pump 2. On the other hand, the remaining liquid refrigerant is decompressed in the expansion valve 11 of the second heat pump 2 via the second region 21 of the intermediate cooler 19, and is evaporated in the evaporator 12 of the second heat pump 3. Thereafter, the gaseous refrigerant is returned to the compressor 9 of the second heat pump 3 again.
With this configuration, the third sub-heat exchanger 16 is not provided in the third embodiment. The other configurations are similar to those in the first embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the third embodiment. In the modification example, differences from FIG. 11 will be mainly described, and the similar configurations will not be described. In the following description, moreover, corresponding components are denoted with the same reference sign.
FIG. 12 is a schematic diagram illustrating the modification example of the steam generation system 1 according to the third embodiment. In the steam generation system 1 illustrated in FIG. 11, the refrigerant from the compressor 9 of the second heat pump 3 is supplied to the intermediate cooler 19. In this modification example, on the other hand, as shown with a chain double-dashed line A, the refrigerant is supplied to a refrigerant channel from the intermediate cooler 19 to the compressor 4 in the first heat pump 2, in place of or in addition to the supply to the intermediate cooler 19. Herein, the channel shown with the chain double-dashed line A may be connected to either an inlet side or an outlet side of the second evaporator 8. Alternatively, in a case where a fourth sub-heat exchanger 17 is provided, the channel may be connected to either an inlet side or an outlet side of the fourth sub-heat exchanger 17. Further, as shown with a chain double-dashed line B, the refrigerant from the compressor 9 of the second heat pump 3 may be supplied to a refrigerant channel from the expansion valve 6 to the intermediate cooler 19 in the first heat pump 2. Herein, in a case where a separator 22 to be described later is provided on the refrigerant channel from the expansion valve 6 to the intermediate cooler 19 in the first heat pump 2, the refrigerant may be supplied to a refrigerant channel from the expansion valve 6 to the separator 22. Alternatively, a vapor-phase refrigerant from the separator 22 may be supplied to a refrigerant channel 23.
In this modification example, further, the separator 22 is provided on the outlet side of the expansion valve 6 of the first heat pump 2. In this case, a liquid-phase refrigerant separated by the separator 22 is supplied to the intermediate cooler 19, and the vapor-phase refrigerant is supplied to the channel 23, i.e., the refrigerant channel from the intermediate cooler 19 to the compressor 4 in the first heat pump 2. Herein, the channel 23 may be connected to either the inlet side or the outlet side of the second evaporator 8. Alternatively, in the case where the fourth sub-heat exchanger 17 is provided, the channel 23 may be connected to either the inlet side or the outlet side of the fourth sub-heat exchanger 17.
In place of or in addition to the provision on the refrigerant channel from the expansion valve 6 to the intermediate cooler 19 in the first heat pump 2, the separator 22 may be provided on the refrigerant channel from the intermediate cooler 19 to the second evaporator 8. In this case, the liquid-phase refrigerant may be supplied to the second evaporator 8, and the vapor-phase refrigerant may be supplied to any position on the refrigerant channel from the second evaporator 8 to the compressor 4.

Fourth Embodiment

FIG. 13 is a schematic diagram illustrating a steam generation system 1 according to a fourth embodiment of the present invention. The steam generation system 1 according to the fourth embodiment is basically similar to that according to the first embodiment. In the following, therefore, differences between the first and fourth embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the first embodiment, the first evaporator 7 and the second evaporator 8 are provided in series. In the fourth embodiment, on the other hand, a first evaporator 7 and a second evaporator 8 are provided in parallel. That is, in this embodiment, a refrigerant from an expansion valve 6 of a first heat pump 2 is supplied to a compressor 4 via the first evaporator 7 and a third sub-heat exchanger 16 to be provided as desired, and is also supplied to the compressor 4 via the second evaporator 8 and a fourth sub-heat exchanger 17 to be provided as desired.
FIG. 14 is a diagram illustrating order of distribution of the refrigerant in the first heat pump 2 to the first evaporator 7 of the first heat pump 2, and the third sub-heat exchanger 16 to be provided as desired, and also illustrating order of distribution of the refrigerant in the first heat pump 2 to the second evaporator 8 of the first heat pump 2, and the fourth sub-heat exchanger 17 to be provided as desired, in the fourth embodiment. Numerals in FIG. 14 each indicate the order of distribution to the respective heat exchangers 7, 16, 8 and 17, and “0” indicates that the relevant heat exchanger is not provided. The heat exchangers indicated by the same numeral are provided in parallel.
Some specific examples will be described below. For example, “1”, “2”, “1” and “2” are shown in the first row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “2”, the second evaporator 8 corresponds to “1”, and the fourth sub-heat exchanger 17 corresponds to “2”. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through a refrigerant channel from the first evaporator 7 to the third sub-heat exchanger 16 and a refrigerant channel from the second evaporator 8 to the fourth sub-heat exchanger 17 in parallel, and then is fed to the compressor 4.
Moreover, “1”, “2”, “1” and “3” are shown in the second row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “2”, the second evaporator 8 corresponds to “1”, and the fourth sub-heat exchanger 17 corresponds to “3”. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7 and the second evaporator 8 in parallel, is passed through the third sub-heat exchanger 16 and the fourth sub-heat exchanger 17 in sequence, and then is fed to the compressor 4. Alternatively, the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7 and the third sub-heat exchanger 16 in sequence, and is passed through the second evaporator 8 in parallel therewith. Thereafter, the two refrigerators are merged, and the merged refrigerant is fed to the compressor 4 via the fourth sub-heat exchanger 17.
Moreover, “1”, “0”, “1” and “1” are shown in the fourth row. Herein, the first evaporator 7 corresponds to “1”, the third sub-heat exchanger 16 corresponds to “0”, the second evaporator 8 corresponds to “1”, and the fourth sub-heat exchanger 17 corresponds to “1”. In this case, the third sub-heat exchanger 16 is not provided, and the refrigerant from the expansion valve 6 of the first heat pump 2 is passed through the first evaporator 7, the second evaporator 8 and the fourth sub-heat exchanger 17 in parallel, and then is fed to the compressor 4.
In any order of distribution of the refrigerant in the first heat pump 2, basically, it is preferred that the first evaporator 7 and the second evaporator 8 are provided on the upstream side of the third sub-heat exchanger 16 and the fourth sub-heat exchanger 17. The other configurations are similar to those in the first embodiment; therefore, the description thereof will not be given here.

Fifth Embodiment

FIG. 15 is a schematic diagram illustrating a steam generation system 1 according to a fifth embodiment of the present invention. The steam generation system 1 according to the fifth embodiment is basically similar to that according to the second embodiment. In the following, therefore, differences between the fifth and second embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the second embodiment, the vapor-phase refrigerant and the liquid-phase refrigerant are supplied in the predetermined mixing ratio from the intermediate cooler 18 to the compressor 4 via the second evaporator 8 and the fourth sub-heat exchanger 17 to be provided as desired. In the fifth embodiment, on the other hand, a refrigerant channel connecting between a vapor-phase part of an intermediate cooler 18 and a compressor 4 and a refrigerant channel connecting between a liquid phase part of the intermediate cooler 18 and the compressor 4 are provided in parallel. Moreover, a second evaporator 8 and a fourth sub-heat exchanger 17 to be provided as desired are provided on the latter refrigerant channel. Herein, the vapor-phase refrigerant from the intermediate cooler 18 is directly supplied to the inlet side of the compressor 4. Additionally, in the case where the fourth sub-heat exchanger 17 is provided, the vapor-phase refrigerant from the intermediate cooler 18 may be supplied to the upstream side of the compressor 4 as shown with a chain double-dashed line A.
The relation between the fourth and fifth embodiments corresponds to the relation between the first and second embodiments. The other configurations are similar to those in the second embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the fifth embodiment. In the modification example, differences from FIG. 15 will be mainly described, and the similar configurations will not be described. In the following description, moreover, corresponding components are denoted with the same reference sign.
FIG. 16 is a schematic diagram illustrating the modification example of the steam generation system 1 according to the fifth embodiment. In the steam generation system 1 illustrated in FIG. 15, the refrigerant from the compressor 9 of the second heat pump 3 is supplied to the intermediate cooler 18. In this modification example, on the other hand, the refrigerant is supplied to a vapor-phase refrigerant channel from the intermediate cooler 18 to the compressor 4 as shown with a chain double-dashed line A, or supplied to a liquid-phase refrigerant channel from the intermediate cooler 18 to the compressor 4 as shown with a chain double-dashed line B, in place of or in addition to the supply to the intermediate cooler 18. In the latter case, the channel shown with the chain double-dashed line may be connected to either the inlet side or the outlet side of the second evaporator 8. Alternatively, in the case where the fourth sub-heat exchanger 17 is provided, the channel may be connected to either the inlet side or the outlet side of the fourth sub-heat exchanger 17. Further, as shown with a chain double-dashed line C, the refrigerant from the compressor 9 of the second heat pump 3 may be flown into the refrigerant channel from the expansion valve 6 to the intermediate cooler 18 in the first heat pump 2.

Sixth Embodiment

FIG. 17 is a schematic diagram illustrating a steam generation system 1 according to a sixth embodiment of the present invention. The steam generation system 1 according to the sixth embodiment is basically similar to that according to the third embodiment. In the following, therefore, differences between the sixth and third embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the third embodiment, the refrigerant from the expansion valve 6 of the first heat pump 2 is supplied to the compressor 4 via the intermediate cooler 19 and the second evaporator 8. In the sixth embodiment, on the other hand, a refrigerant from an expansion valve 6 of a first heat pump 2 is supplied to a compressor 4 via an intermediate cooler 19, but is not passed through a second evaporator 8. In parallel therewith, the refrigerant is supplied to the compressor 4 via the second evaporator 8, but is not passed through the intermediate cooler 19.
As shown with a chain double-dashed line A, the refrigerant supplied from the expansion valve 6 of the first heat pump to the intermediate cooler 19 may be merged with a refrigerant supplied from a compressor 9 of a second heat pump 3 to the intermediate cooler 19. As shown with a chain double-dashed line X, moreover, the refrigerant from the intermediate cooler 19 to the compressor 4 may be supplied forward of a fourth sub-heat exchanger 17 in some cases.
The relation between the fourth and sixth embodiments corresponds to the relation between the first and third embodiments. The other configurations are similar to those in the third embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the sixth embodiment. In the modification example, differences from FIG. 17 will be mainly described, and the similar configurations will not be described. In the following description, moreover, the corresponding components are denoted with the same reference sign.
FIG. 18 is a schematic diagram illustrating a first modification example of the steam generation system 1 according to the sixth embodiment. In the steam generation system 1 illustrated in FIG. 17, the refrigerant from the compressor 9 of the second heat pump 3 is supplied to the intermediate cooler 19. In this modification example, on the other hand, the refrigerant may be flown into the refrigerant channel from the expansion valve 6 to the intermediate cooler 19 in the first heat pump 2 as shown with a chain double-dashed line A, may be supplied to the refrigerant channel from the expansion valve 6 to the compressor 4 via the second evaporator 8 as shown with a chain double-dashed line B, or may be supplied to the refrigerant channel from the intermediate cooler 19 to the compressor 4 as shown with a chain double-dashed line C, in place of or in addition to the supply to the intermediate cooler 19.
FIG. 19 is a schematic diagram illustrating a second modification example of the steam generation system 1 according to the sixth embodiment. In this embodiment, a separator 22 (22A to 22C) is provided on the outlet side of the expansion valve 6 of the first heat pump 2. The refrigerant from the expansion valve 6 of the first heat pump 2 is branched to a channel 25 to the second evaporator 8 and a channel 26 to the intermediate cooler 19 via a common channel 24. The separator 22 may be provided at any position on the channels. The separator to be provided on the common channel 24 corresponds to the first separator 22A, the separator to be provided on the channel 25 to the second evaporator 8 corresponds to the second separator 22B, and the separator to be provided on the channel 26 to the intermediate cooler 19 corresponds to the third separator 22C. These separators can be provided by a combination illustrated in FIG. 20. In FIG. 20, “1” indicates that the separator is provided, and “0” indicates that the separator is not provided.
In FIG. 20, the pattern in the first row indicates that no separators are provided. The pattern in the second row indicates that only the first separator 22A is provided. In this case, the liquid-phase refrigerant separated by the separator 22A is supplied to the intermediate cooler 19 and the second evaporator 8, and the vapor-phase refrigerant is supplied to any position from the second evaporator 8 to the compressor 4 as shown with the chain double-dashed line A.
Moreover, the pattern in the third row indicates that only the second separator 22B is provided. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is supplied to the intermediate cooler 19 and the separator 22B. The liquid-phase refrigerant separated by the separator 22B is supplied to the second evaporator 8, and the vapor-phase refrigerant is supplied to any position from the second evaporator 8 to the compressor 4 as shown with the chain double-dashed line A.
Moreover, the pattern in the fourth row indicates that only the third separator 22C is provided. In this case, the refrigerant from the expansion valve 6 of the first heat pump 2 is supplied to the second evaporator 8 and the separator 22C. The liquid-phase refrigerant separated by the separator 220 is supplied to the intermediate cooler 19, and the vapor-phase refrigerant is supplied to any position from the second evaporator 8 to the compressor 4 as shown with the chain double-dashed line A.
Further, both the second separator 22B and the third separator 22C may be provided as shown in the pattern in the fifth row. In any cases, the separator 22 is provided for preventing the vapor-phase refrigerant from being supplied to the intermediate cooler 19 and the second evaporator 8, so that the heat exchanger that constitutes these components can be made small.

Seventh Embodiment

FIG. 21 is a schematic diagram illustrating a steam generation system 1 according to a seventh embodiment of the present invention. The steam generation system 1 according to the seventh embodiment is basically similar to that according to the fourth embodiment. In the following, therefore, differences between the seventh and fourth embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the fourth embodiment, the first evaporator 7 and the second evaporator 8 are provided in parallel, and the refrigerant passed through the common expansion valve 6 is passed through the first evaporator 7 and the second evaporator 8. In the seventh embodiment, on the other hand, a refrigerant from a condenser 5 of a first heat pump 2 is passed through a refrigerant channel including a first expansion valve 6A and a first evaporator 7 and a refrigerant channel including a second expansion valve 6B and a second evaporator 8 in parallel, and then is supplied to a compressor 4. The other configurations are similar to those in the fourth embodiment; therefore, the description thereof will not be given here.

Eighth Embodiment

FIG. 22 is a schematic diagram illustrating a steam generation system 1 according to an eighth embodiment of the present invention. The steam generation system 1 according to the eighth embodiment is basically similar to that according to the fifth embodiment. In the following, therefore, differences between the eighth and fifth embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the fifth embodiment, the vapor-phase refrigerant channel and liquid-phase refrigerant channel from the intermediate cooler 18 are provided in parallel, and the refrigerant passed through the common expansion valve 6 is passed through the vapor-phase refrigerant channel and the liquid-phase refrigerant channel. In the eighth embodiment, on the other hand, a refrigerant from a condenser 5 of a first heat pump 2 is supplied to an intermediate cooler 18 via a first expansion valve 6A and, in parallel therewith, is also supplied to a second evaporator 8 via a second expansion valve 6B. A vapor-phase part of the intermediate cooler 18 and a compressor 4 are connected to each other via a refrigerant channel. The refrigerant from the second expansion valve 6B is supplied to the compressor 4 via the second evaporator 8 or a fourth sub-heat exchanger 17 to be provided as desired. The other configurations are similar to those in the fifth embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the eighth embodiment. In the modification example, differences from FIG. 22 will be mainly described, and the similar configurations will not be described here. In the following description, moreover, corresponding components are denoted with the same reference sign.
FIG. 23 is a schematic diagram illustrating a first modification example of the steam generation system 1 according to the eighth embodiment. In the steam generation system 1 illustrated in FIG. 22, a refrigerant from a compressor 9 of a second heat pump 3 is supplied to the intermediate cooler 18. In this modification example, on the other hand, the refrigerant may be supplied to the refrigerant channel from the intermediate cooler 18 to the compressor 4 as shown with a chain double-dashed line A, or may be supplied to any position on the refrigerant channel from the second expansion valve 6B to the compressor 4 via the second evaporator 8 as shown with a chain double-dashed line B, in place of or in addition to the supply to the intermediate cooler 18. Alternatively, the refrigerant from the compressor 9 of the second heat pump 3 may be merged with the refrigerant from the first expansion valve 6A of the first heat pump 2, and then may be supplied to the intermediate cooler 18, as shown with a chain double-dashed line C.
FIG. 24 is a schematic diagram illustrating a second modification example of the steam generation system 1 according to the eighth embodiment. In this modification example, a separator 22 is provided on the refrigerant channel from the second expansion valve 6B to the second evaporator 8. Thus, the refrigerant from the second expansion valve 6B is separated by the separator 22 into a vapor phase and a liquid phase. Then, the liquid-phase refrigerant is supplied to the second evaporator 8, and the vapor-phase refrigerant is supplied to any position on the refrigerant channel from the second evaporator 8 to the compressor 4 as shown with a chain double-dashed line A.

Ninth Embodiment

FIG. 25 is a schematic diagram illustrating a steam generation system 1 according to a ninth embodiment of the present invention. The steam generation system 1 according to the ninth embodiment is basically similar to that according to the sixth embodiment. In the following, therefore, differences between the ninth and sixth embodiments will be mainly described with the corresponding components denoted with the same reference sign.
In the sixth embodiment, in the first heat pump 2, the refrigerant from the common expansion valve 6 is passed through the intermediate cooler 19 and second evaporator 8 in parallel, and then is supplied to the compressor 4. In the ninth embodiment, on the other hand, a refrigerant from a condenser 5 of a first heat pump 2 is supplied to an intermediate cooler 19 via a first expansion valve 6A and, in parallel therewith, is also supplied to a second evaporator 8 via a second expansion valve 6B. The refrigerant from the second expansion valve 6B may be merged with a refrigerant from a compressor 9 of a second heat pump 3 and may be supplied to the intermediate cooler 19 as shown with a chain double-dashed line A. The other configurations are similar to those in the sixth embodiment; therefore, the description thereof will not be given here.
Next, description will be given of a modification example of the steam generation system 1 according to the ninth embodiment. In the modification example, differences from FIG. 25 will be mainly described, and the similar configurations will not be described here. In the following description, moreover, corresponding components are denoted with the same reference sign.
FIG. 26 is a schematic diagram illustrating a first modification example of the steam generation system 1 according to the ninth embodiment. In the steam generation system 1 illustrated in FIG. 25, the refrigerant from the compressor 9 of the second heat pump 3 is supplied to the intermediate cooler 19. In this modification example, on the other hand, the refrigerant may be flown into a refrigerant channel from the first expansion valve 6A to the intermediate cooler 19 as shown with a chain double-dashed line A, may be supplied to a refrigerant channel from the intermediate cooler 19 to the compressor 4 as shown with a chain double-dashed line B, or may be supplied to any position on a refrigerant channel from the second expansion valve 6B to the compressor 4 via the second evaporator 8 as shown with a chain double-dashed line C, in place of or in addition to the supply to the intermediate cooler 19.
FIG. 27 is a schematic diagram illustrating a second modification example of the steam generation system 1 according to the ninth embodiment. In this modification example, a first separator 22A is provided on the refrigerant channel from the second expansion valve 6B to the second evaporator 8. Accordingly, the refrigerant from the second expansion valve 6B is separated by the first separator 22A into a vapor phase and a liquid phase. Then, the liquid-phase refrigerant is supplied to the second evaporator 8, and the vapor-phase refrigerant is supplied to any position on the refrigerant channel from the second evaporator 8 to the compressor 4 as shown with a chain double-dashed line A. Further, a second separator 22B may be provided on the refrigerant channel from the first expansion valve 6A to the intermediate cooler 19. Thus, the refrigerant from the first expansion valve 6A is separated by the second separator 22B into a vapor phase and a liquid phase. Then, the liquid-phase refrigerant is supplied to the intermediate cooler 19, and the vapor-phase refrigerant is supplied to any position on the refrigerant channel from the second evaporator 8 to the compressor 4 as shown with a chain double-dashed line B.
FIG. 28 is a diagram illustrating a combination of layout of the first separator 22A and the second separator 22B. In FIG. 28, “1” indicates that the separator is provided and “0” indicates that the separator is not provided. As illustrated in FIG. 28, both the separators 22A and 22B may be provided, only one of the separators 22A and 22B may be provided, or none of the separators 22A and 22B may be provided.

Tenth Embodiment

In each of the foregoing embodiments, the first heat pump 2 is a single-stage heat pump, and the second heat pump 3 is also a single-stage heat pump. In the respective heat pumps 2 and 3, however, the number of stages can be changed as appropriate. In other words, each of the foregoing embodiments describes the steam generation system 1 that includes two heat pumps as a whole by the combination of the single-stage first heat pump 2 and the single-stage second heat pump 3. In the heat pump that constitutes the steam generation system 1, however, the number of stages can be changed as appropriate. Examples of a multiple-stage heat pump may include a one-way, multiple-stage heat pump as illustrated in FIG. 9, a multiple-way heat pump as illustrated in FIG. 1, and a heat pump obtained by a combination of the two heat pumps.
For example, FIG. 29A illustrates an example that a first heat pump 2 is a two-stage heat pump in which heat pumps are vertically disposed and a second heat pump 3 is a single-stage heat pump. In other words, a steam generation system 1 includes three heat pumps. Herein, the second heat pump 3 may also be a multiple-stage heat pump in which two or more heat pumps are disposed, as in the conventionally well-known two-stage heat pump.
In the steam generation system illustrated in FIG. 29A, except the lowermost heat pump (the second heat pump 3), the respective heat pumps (the heat pumps 2A and 2B in the first heat pump) include first evaporators 7A and 7B and second evaporators 8A and 8B, respectively, as an evaporator. Each of the first evaporators 7A and 7B connects between the vertically adjoining heat pumps, and a heat source fluid is passed through the second evaporators 8A and 8B. Herein, the vertically adjoining heat pumps may be connected in accordance with any relation described in the foregoing embodiments. More specifically, the vertically adjoining heat pumps are connected via an indirect heat exchanger 13 (13A, 13B) as illustrated in FIG. 29A, but may be connected via an intermediate cooler 18, 19 as described above. In the first heat pump 2, the configuration of each heat pump is not limited to that described in the first embodiment, and each heat pump may be configured as described in the other embodiments. Typically, the heat source fluid is passed through the respective second evaporators 8 (8A, 8B) in sequence from the uppermost heat pump toward the lowermost heat pump.
Preferably, in the case where the steam generation system 1 includes three or more heat pumps (in other words, in the case where the first heat pump 2 is a multiple-stage heat pump), except the lowermost heat pump (the second heat pump 3), all the heat pumps 2A and 2B in the first heat pump 2 include the first evaporators 7A and 7B and the second evaporators 8A and 8B, respectively, each of the first evaporators 7A and 7B connects between the vertically adjoining heat pumps, and the heat source fluid is passed through the respective second evaporators 8A and 8B in sequence from the uppermost heat pump toward the lowermost heat pump.
The reasons why the foregoing configuration is preferable are described as follows. FIG. 29B is a T-S diagram in a case where the first heat pump 2 is a single-stage heat pump and the second heat pump 3 is a two-stage heat pump. FIG. 29C is a T-S diagram in a case where the first heat pump 2 is a two-stage heat pump in which heat pumps include the first evaporators 7A and 7B and the second evaporators 8A and 8B, respectively, and the second heat pump 3 is a single-stage heat pump. A comparison between FIGS. 29B and 29C shows that a hatched area corresponding to a loss in FIG. 29C can be made smaller than that in FIG. 29B. Therefore, it is preferable that in the steam generation system 1, except the lowermost heat pump 3, the first heat pumps 2A and 2B include the second evaporators 8A and 8B through which the heat source fluid is passed.
In the case where the steam generation system 1 includes three or more heat pumps (in other words, in the case where the first heat pump 2 is a multiple-stage heat pump), if a first sub-heat exchanger 14 is desired to be provided, the first sub-heat exchanger 14 may be provided on the uppermost heat pump (the uppermost heat pump 2A in the first heat pump 2).
Moreover, in the case where the steam generation system 1 includes three or more heat pumps, if a second sub-heat exchanger 15 is desired to be provided, the second sub-heat exchanger 15 may be provided on the lowermost heat pump (the lowermost heat pump in the second heat pump 3).
Further, in the case where the steam generation system 1 includes three or more heat pumps, if a third sub-heat exchanger 16 and/or a fourth sub-heat exchanger 17 are/is desired to be provided, the third sub-heat exchanger 16 and/or the fourth sub-heat exchanger 17 may be provided on the heat pumps 2A and 2B in the first heat pump 2, respectively. In this case, in the lowermost heat pump 2B in the first heat pump 2, the third sub-heat exchanger 16 serves as an indirect heat exchanger for performing heat exchange between a refrigerant from an expansion valve 6B of the lowermost heat pump in the first heat pump 2 to a compressor 4B and a refrigerant from a compressor 9 of the second heat pump 3 to the first evaporator 7B. In the upper heat pump 2A in the first heat pump 2, however, the third sub-heat exchanger 16 serves as an indirect heat exchanger for performing heat exchange between a refrigerant from an expansion valve 6A of the upper heat pump 2A to a compressor 4A and a refrigerant from the compressor 4B of the lower first heat pump 2B to the first evaporator 7A.
FIG. 30 is a schematic diagram illustrating one example of a steam system 27 using the steam generation system 1 according to the first embodiment. For convenience of the description, it is assumed that the second evaporator 8 of the first heat pump 2, the fourth sub-heat exchanger 17 to be provided as desired, the evaporator 12 of the second heat pump 3, and the second sub-heat exchanger 15 to be provided as desired are each a heat-drawing heat exchanger (8, 17, 12, 15). It is also assumed that the condenser 5 of the first heat pump 2, and the first sub-heat exchanger 14 to be provided as desired are each a steam-generating heat exchanger (5, 14).
The steam system 27 includes the steam generation system 1 and a boiler 28. Herein, the steam generation system 1 has the configuration described in the first embodiment, but may be configured as described in the other embodiments. In any case, the steam generation system 1 draws heat from a drain in the heat-drawing heat exchanger (8, 17, 12, 15), and generates steam by application of the heat to water in the steam-generating heat exchanger (5, 14). Thus, a drain from a steam-utilizing facility 29 is passed through the heat-drawing heat exchanger (8, 17, 12, 15). The method of causing the drain pass through the respective evaporators 8 and 12 as well as the respective sub-heat exchangers 17 and 15 each serving as the heat-drawing heat exchanger (8, 17, 12, 15) is described on the basis of FIG. 2.
On the other hand, a feed pump 30 is operable to supply water to the steam-generating heat exchanger (5, 14), and the steam-generating heat exchanger (5, 14) is capable of storing a desired amount of water. Specifically, pure water or soft water, or the drain from the steam-utilizing facility 29 in place thereof or as mixed therewith is supplied to the steam-generating heat exchanger (5, 14) via the feed pump 30, a feed valve 31 and a check valve 32. The method of causing water or steam pass through the condenser 5 and the first sub-heat exchanger 14 each serving as the steam-generating heat exchanger (5, 14) is also described in the foregoing embodiments.
The boiler 28 is typically a fuel-burning boiler or an electric boiler. The fuel-burning boiler evaporates water by burning fuel. Herein, the existence/nonexistence and amount of fuel are adjusted such that the steam pressure is kept at a desired level. The electric boiler evaporates water by means of an electric heater. Herein, the supply/non-supply and quantity of power to the electric heater are adjusted such that the steam pressure is kept at a desired level. The boiler 28 can be supplied with water via the feed pump 33 and the check valve 34, to keep the water level in the can body of the boiler 28 at a desired level.
A steam path 35 from the steam-generating heat exchanger (5, 14) and a steam path 36 from the boiler 28 are merged with each other. This merge can be achieved using a steam header. Further, on the steam path 35 from the steam-generating heat exchanger (5, 14), a check valve 37 is provided on the upstream side of the merged portion. Accordingly, steam from the boiler 28 is prevented from flowing reverse to the steam-generating heat exchanger (5, 14) during a halt of the steam generation system 1.
Furthermore, on the steam path 36 from the boiler 28, a boiler steam feed valve 38 is provided on the upstream side of the merged portion. The boiler steam feed valve 38 is assumed to be a self-operated decompression valve (secondary pressure-regulating valve) in the illustrated example. The upstream side of the boiler steam feed valve 38 is kept at a higher pressure than the downstream side by the boiler 28.
Steam from the steam generation system (5, 14) or the boiler 28 is fed to one or more steam-utilizing facilities 29. A drain from the steam-utilizing facility 29 is discharged into a hollow vessel-shaped separator tank 40 via a first steam trap 39. The separator tank 40 has an upper part connected to a first channel 41 and a lower part connected to a second channel 42.
On the first channel 41, the heat-drawing heat exchangers (8, 17, 12, 15) and a second steam trap 43 are provided in sequence from the side of the separator tank 40. Because of the configuration described above, the drain from the steam-utilizing facility 29 is discharged under a low pressure by the first steam trap 39. Thereafter, the drain is passed through the heat-drawing heat exchangers (8, 17, 12, 15), and then is discharged under a lower pressure (typically, under the atmospheric pressure) by the second steam trap 43. That is, the drain from the steam-utilizing facility 29 is discharged via the first steam trap 39, so that flash steam and condensed water thereof are obtained. The steam and the condensed water are passed trough the heat-drawing heat exchanger (8, 17, 12, 15) to be cooled (or supercooled), and then are discharged from the second steam trap 43. In such a configuration, a fluid giving heat to a refrigerant in the heat-drawing heat exchanger (8, 17, 12, 15) can be kept at a temperature exceeding 100° C. at a pressure exceeding the atmospheric pressure. A drain from the second steam trap 43 may be disposed as it is, may be supplied to a feed tank 44 for the boiler 28 and/or the steam-generating heat exchanger (5, 14), or may be used as feed water to the steam-generating heat exchanger (5, 14) without being passed through the feed tank 44.
On the other hand, a discharge valve 45 is provided on the second channel 42. The discharge valve 45 is a self-operated decompression valve (primary pressure-regulating valve) in FIG. 30. Because of the configuration described above, the drain from the steam-utilizing facility 29 can be discharged under a low pressure by the first steam trap 39, and then can be discharged under a lower pressure (typically, under the atmospheric pressure) by the discharge valve 45. The fluid from the discharge valve 45 may be disposed as it is, may be supplied to the feed tank 44 for the boiler 28 and/or the steam-generating heat exchanger (5, 14), or may be used as feed water to the steam-generating heat exchanger (5, 14) without being passed through the feed tank 44.
For the use in emergency and power failure, preferably, a normally-closed type electromagnetic valve 46 is provided between the separator tank 40 and the heat-drawing heat exchanger (8, 17, 12, 15) on the first channel 41, and a normally-open type electromagnetic valve 47 is provided in parallel with the discharge valve 45 on the second channel 42. In this case, normally, the electromagnetic valve 46 on the first channel 41 is kept open and the electromagnetic valve 47 on the second channel 42 is kept closed. At the time of emergency or power failure, the electromagnetic valve 46 on the first channel 41 is closed and the electromagnetic valve 47 on the second channel 42 is opened. Therefore, the drain from the steam-utilizing facility 29 is discharged without being passed through the heat-drawing heat exchanger (8, 17, 12, 15).
The steam-generating heat exchanger (5, 14) is supplied with pure water or soft water, the drain from the steam-utilizing facility 29, or mixed water of the drain with the pure water or soft water. A water feed system therefor is not particularly limited, but may configured as follows. The drain from the steam-utilizing facility 29 may be in a liquid phase alone and in a gas-liquid two phase (flash steam and condensed water thereof generated when the drain at a pressure exceeding the atmospheric pressure is released under a lower pressure).
(A) As shown with a chain double-dashed line A, a drain comprised of a liquid separated by the separator tank 40 is supplied from the upstream side of the discharge valve 45 to the inlet side of the feed pump 30.
(B) As shown with a chain double-dashed line B, a drain passed through the heat-drawing heat exchanger (8, 17, 12, 15) is supplied from the upstream side of the second steam trap 43 to the inlet side of the feed pump 30. The heat-drawing heat exchanger (8, 17, 12, 15) includes a plurality of heat exchangers. As shown with a chain double-dashed line B′, however, the drain passed through some of the heat exchangers may be branched off, and then may be supplied to the inlet side of the feed pump 30.
(C) As shown with a chain double-dashed line C, a drain passed through the heat-drawing heat exchanger (8, 17, 12, 15) is supplied from the downstream side of the second steam trap 43 to the inlet side of the feed pump 30.
(D) As shown with a broken-line region on the lower side in FIG. 30, a drain from the second steam trap 43 and/or a drain from the discharge valve 45 are/is stored once in the feed tank 44, and then the water in this feed tank 44 is supplied to the inlet side of the feed pump 30. The feed tank 44 may be supplied with pure water or soft water as appropriate in addition to the drain from the steam-utilizing facility 29.
(E) At least two configurations of (A) to (D) above may be combined. In this case, at least two supply channels are merged to feed water to the steam-generating heat exchanger (5, 14). When the feed channels have different inner pressures, the feed pump 30 is not provided on the downstream side of the merged portion, but may be provided on each of the feed channels on the upstream side of the merged portion.
A first sensor 48 which is a pressure sensor is provided at a position where the pressure of a mixture of steam from the steam-generating heat exchanger (5, 14) and steam from the boiler 28 can be detected. Moreover, a second sensor 49 which is a pressure sensor or a temperature sensor is provided so as to be capable of detecting the pressure or temperature of the fluid passed through the heat-drawing heat exchanger (8, 17, 12, 15). The steam generation system 1 is controlled on the basis of values detected by one of or both the first sensor 48 and the second sensor 49.
For example, the compressor of the uppermost heat pump (the compressor 4 of the first heat pump) may be controlled on the basis of the pressure detected by the first sensor 48. In addition, the compressor of each heat pump lower than the uppermost heat pump (the compressor 9 of the second heat pump 3) may be controlled on the basis of the pressure of the refrigerant in the condenser 10 on the relevant heat pump or the evaporator 7, 8 of the heat pump which is upper by one stage than the relevant heat pump.
Alternatively, the compressor of the lowermost heat pump (the compressor 9 of the second heat pump 3) may be controlled on the basis of the pressure or temperature detected by the second sensor 49. In addition, the compressor of each heat pump upper than the lowermost heat pump (the compressor 4 of the first heat pump 2) may be controlled on the basis of the pressure or temperature of the refrigerant in the evaporator 7, 8 of the relevant heat pump or the condenser 10 of the heat pump which is lower by one stage than the relevant heat pump.
FIG. 31 is a schematic diagram illustrating a modification example of the steam system 27 illustrated in FIG. 30. The steam system 27 in FIG. 31 is basically similar to that in FIG. 30. In the following, therefore, differences between FIG. 31 and FIG. 30 will be mainly described with the corresponding components denoted with the same reference sign.
In this modification example, the drain from the steam-utilizing facility 29 is once stored in a buffer tank 50 serving as a drain reservoir. The drain in the buffer tank 50 can be supplied to the heat-drawing heat exchanger (8, 17, 12, 15) via the first channel 41, and can be discharged via a third channel 51 without being passed through the heat-drawing heat exchanger (8, 17, 12, 15).
Specifically, the buffer tank 50 has a lower part connected to the first channel 41 and an upper part connected to the third channel 51. On the first channel 41, an introduction valve 52, the heat-drawing heat exchanger (8, 17, 12, 15), and the second steam trap 43 are provided in sequence from the side of the buffer tank 50. The introduction valve 52 is a self-operated decompression valve (secondary pressure-regulating valve) in this modification example.
Because of the configuration described above, the drain from the steam-utilizing facility 29 is discharged under a low pressure by the introduction valve 52, and then is passed through the heat-drawing heat exchanger (8, 17, 12, 15). Thereafter, the drain is discharged under a lower pressure (typically, under the atmospheric pressure) by the second steam trap 43. The drain from the second steam trap 43 may be disposed as it is, may be supplied to the feed tank 44 for the boiler 28 and/or the steam-generating heat exchanger (5, 14), or may be used as feed water to the steam-generating heat exchanger (5, 14) without being passed through the feed tank 44.
On the other hand, a third steam trap 53 is provided on the third channel 51. The third channel 51 is connected to the buffer tank 50 on the upstream side of the first channel 41, so that the drain overflown from the buffer tank 50 is discharged from the third channel 51. Then, the drain is discharged by way of the third steam trap 53. Then, the drain from the third steam trap 53 may be disposed as it is, may be supplied to the feed tank 44 for the boiler 28 and/or the steam-generating heat exchanger (5, 14), or may be used as feed water to the steam-generating heat exchanger (5, 14) without being passed through the feed tank 44.
For the use in emergency and power failure, preferably, a normally-closed type electromagnetic valve 46 is provided between the introduction valve 52 and the buffer tank 50 on the first channel 41. In this case, normally, the electromagnetic valve 46 on the first channel 41 is kept open. At the time of emergency or power failure, the electromagnetic valve 46 on the first channel 41 is closed. Therefore, the drain from the steam-utilizing facility 29 is discharged via the third channel 51 without being passed through the heat-drawing heat exchanger (8, 17, 12, 15).
Also in the case of this modification example, the steam-generating heat exchanger (5, 14) is supplied with pure water or soft water, the drain from the steam-utilizing facility, or mixed water of the drain with the pure water or soft water. A water feed system therefor is not particularly limited, but may configured as follows, as in the case illustrated in FIG. 30.
(A) As shown with a chain double-dashed line A, the drain from the buffer tank 50 is supplied from the upstream side of the introduction valve 52 (any of the upstream side or the downstream side of the introduction valve 52 in the case where electromagnetic valve 46 is provided) to the inlet side of the feed pump 30.
(B) As shown with a chain double-dashed line B, a drain passed through the heat-drawing heat exchanger (8, 17, 12, 15) is supplied from the upstream side of the second steam trap 43 to the inlet side of the feed pump 30. The heat-drawing heat exchanger (8, 17, 12, 15) includes a plurality of heat exchangers. As shown with a chain double-dashed line B′, however, the drain passed through some of the heat exchangers may be branched off, and then may be supplied to the inlet side of the feed pump 30.
(C) As shown with a chain double-dashed line C, a drain passed through the heat-drawing heat exchanger (8, 17, 12, 15) is supplied from the downstream side of the second steam trap 43 to the inlet side of the feed pump 30.
(D) As shown with a broken-line region on the lower side in FIG. 31, a drain from the second steam trap 43 and/or a drain from the third steam trap 53 are/is stored once in the feed tank 44, and then the water in this feed tank 44 is supplied to the inlet side of the feed pump 30. The feed tank 44 may be supplied with pure water or soft water as appropriate in addition to the drain from the steam-utilizing facility 29. As in the case illustrated in FIG. 30, the feed tank 44 may store the drain at a pressure exceeding the atmospheric pressure without being opened upward.
(E) At least two configurations of (A) to (D) above may be combined. In this case, at least two supply channels are merged to feed water to the steam-generating heat exchanger (5, 14). When the feed channels have different inner pressures, the feed pump 30 is not provided on the downstream side of the merged portion, but may be provided on each of the feed channels on the upstream side of the merged portion.
The steam generation system 1 according to the present invention is not limited to the configurations in the foregoing embodiments and can be changed as appropriate. For example, the steam generation system 1 is applied to the steam system 27 illustrated in FIGS. 30 and 31. It goes without saying that the steam generation system 1 is applicable to other systems. In the above description, moreover, the drain from the steam-utilizing facility 29 is used as the heat source of the steam generation system 1; however, the example is not limited to the drain. It is possible to use, for example, exhaust gas from a boiler or the like, water used to cool the exhaust gas, a hot drain discharged from a factory or the like, water used to cool a compressor, water used as cooling water in an oil cooler for an engine (a drive unit such as a compressor), or water used to cool an engine jacket.
Further, the steam generation system 1 is not limited to the case of generating steam using heat while reducing the temperature of the heat source fluid. For example, the exhaust steam from the steam-utilizing facility 29 may be used as the heat source fluid. In this case, the exhaust steam is passed through the fourth sub-heat exchanger 17 and the second evaporator 2 in the first heat pump 2 illustrated in FIG. 1. After being passed through the second evaporator 8, the exhaust steam may be decompressed by a steam trap, an orifice or a decompressing valve, and then may be passed through the second sub-heat exchanger 15 and the evaporator 12 in the second heat pump 3. On an exhaust steam channel, a steam trap or the like may be or may not be provided on the outlet side of the evaporator 12 of the second heat pump 3. In other words, the steam passed through the evaporator 12 of the second heat pump 3 may be in a state exceeding the atmospheric pressure or in the atmospheric state. It goes without saying that one of or both the fourth sub-heat exchanger 17 and the second sub-heat exchanger 15 may be eliminated.

Claims

1. A steam generation system comprising:

a single-stage or multiple-stage first heat pump in which at least the lowermost heat pump includes a first evaporator and a second evaporator; and

a single-stage or multiple-stage second heat pump connected to the first heat pump via a condenser of the uppermost heat pump, the condenser serving as the first evaporator of the lowermost heat pump, wherein

a heat source fluid is passed through the second evaporator of the first heat pump and an evaporator of the lowermost heat pump in the second heat pump in sequence, and

steam is generated by application of heat to water in a condenser of the uppermost heat pump in the first heat pump.

2. The steam generation system of claim 1, wherein

the second heat pump is a single-stage heat pump,

heat is drawn from the heat source fluid passed through the second evaporator of the first heat pump and the evaporator of the lowermost heat pump in the second heat pump in sequence, and

steam is generated by application of the heat to water in the condenser of the uppermost heat pump in the first heat pump.

3. The steam generation system of claim 1, wherein

the first heat pump is a multiple-stage heat pump in which some of or all of the heat pumps each include the first evaporator and the second evaporator as an evaporator,

each of the first evaporators connects between the vertically adjoining heat pumps, and

the heat source fluid is passed through the respective second evaporators in sequence from the upper heat pump toward the tower heat pump.

4. The steam generation system of claim 3, wherein

the heat pumps in the multiple-stage first heat pump each include the first evaporator and the second evaporator as an evaporator.

5. The steam generation system of claim 1, wherein

in the heat pump including the first and second evaporators in the single-stage or multiple-stage first heat pump, the first evaporator and the second evaporator are provided in series or in parallel on a refrigerant channel from an expansion valve to a compressor, or a first expansion valve and the first evaporator are provided in parallel with a second expansion valve and the second evaporator on a refrigerant channel from a condenser to a compressor.

6. The steam generation system of claim 1, wherein

the first heat pump and the second heat pump are connected in accordance with one of the following relations (a) to (c):

(a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange without mixing both the refrigerants, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump;

(b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump; and

(c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the second heat pump and a refrigerant from an expansion valve of the first heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the first heat pump to the expansion valve of the second heat pump without being passed through the expansion valve, and serves as the condenser of the second heat pump and the first evaporator of the first heat pump.

7. The steam generation system of claim 1, wherein

when the first heat pump and/or the second heat pump are/is a multiple-stage heat pump, the adjoining heat pumps are connected in accordance with one of the following relations (a) to (c):

(a) an indirect heat exchanger is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange without mixing both the refrigerants, and serves as a condenser of the lower heat pump and an evaporator of the upper heat pump;

(b) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump; and

(c) an intermediate cooler is provided for receiving a refrigerant from a compressor of the lower heat pump and a refrigerant from an expansion valve of the upper heat pump to perform heat exchange by bringing both the refrigerants into direct contact with each other and also to perform heat exchange without mixing both the refrigerants with a refrigerant to be supplied from the condenser of the upper heat pump to the expansion valve of the lower heat pump without being passed through the expansion valve, and serves as the condenser of the lower heat pump and the evaporator of the upper heat pump.

8. The steam generation system of claim 6, wherein

when the first heat pump and the second heat pump are connected in accordance with the relation (b) in claim 6, the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor, in place of or in addition to the supply to the intermediate cooler.

9. The steam generation system of claim 6, wherein

when the first heat pump and the second heat pump are connected in accordance with the relation (c) in claim 6, the refrigerant from the compressor of the second heat pump is supplied to a refrigerant channel from the intermediate cooler to the compressor in the first heat pump, or a refrigerant channel from the expansion valve to the intermediate cooler or compressor, in place of or in addition to the supply to the intermediate cooler.

10. The steam generation system of claim 6, further comprising:

a separator for separating the refrigerant from the expansion valve of the first heat pump into a vapor phase and a liquid phase when the first heat pump and the second heat pump are connected in accordance with the relation (c) in claim 6, wherein

the vapor-phase refrigerant separated by the separator is supplied to a refrigerant channel from the second evaporator to the compressor.

11. The steam generation system of claim 1, further comprising at least one of:

(a) a first sub-heat exchanger for performing heat exchange between the water and the refrigerant from the condenser to the expansion valve in the uppermost heat pump of the first heat pump;

(b) a second sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the evaporator to the compressor in the lowermost heat pump of the second heat pump;

(c) a third sub-heat exchanger for performing heat exchange between the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump and the refrigerant from the compressor to the first evaporator in the second heat pump, in a case where the first evaporator is an indirect heat exchanger; and

(d) a fourth sub-heat exchanger for performing heat exchange between the heat source fluid and the refrigerant from the expansion valve to the compressor in the lowermost heat pump of the first heat pump, wherein

with regard to order of distribution of the water and steam to the condenser of the uppermost heat pump in the first heat pump, and the first sub-heat exchanger in the case where the first sub-heat exchanger is provided, the first sub-heat exchanger is provided on the upstream side in the case where the first sub-heat exchanger is provided,

with regard to order of distribution of the heat source fluid to the second evaporator of the first heat pump, the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump, and the second sub-heat exchanger in the case where the second sub-heat exchanger is provided, the evaporator of the lowermost heat pump in the second heat pump is provided on the downstream side, and

with regard to order of distribution of the refrigerant to the first evaporator of the first heat pump, the third sub-heat exchanger in the case where the third sub-heat exchanger is provided, the second evaporator of the first heat pump, and the fourth sub-heat exchanger in the case where the fourth sub-heat exchanger is provided, the first evaporator and the second evaporator are provided on the upstream side of the third sub-heat exchanger and the fourth sub-heat exchanger.

12. The steam generation system of claim 1, wherein

the heat source fluid is a drain from a steam-utilizing facility.