JP5811498B2 - Water heating system - Google Patents

Description

  The present invention relates to a feed water heating system that heats water using a heat pump.

  Conventionally, as disclosed in Patent Document 1 below, an apparatus for producing steam or hot water using a heat pump is known. Here, when it is going to use the waste water from a factory etc. as a heat source of a heat pump, since the temperature of waste water changes, it must be able to cope with this.

JP 2007-232357 A

  The problem to be solved by the present invention is a heat pump for supplying hot water such as waste water discharged from a factory or the like that produces hot water by producing heat, even if the temperature of the cooled fluid changes. It is in operating a heat pump efficiently, aiming at protection of.

The present invention has been made to solve the above problems, and the invention according to claim 1 is characterized in that a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in an annular manner to circulate a refrigerant, and the condensation A heat pump for producing hot water by exchanging heat between the refrigerant and water in a cooler, and cooling the cooled fluid by exchanging heat between the refrigerant and the fluid to be cooled in the evaporator, and an outlet of the evaporator The fluid to be cooled is supplied to the evaporator so as to control the compressor and maintain the temperature detected by the temperature sensor at a predetermined temperature based on the temperature detected by a temperature sensor provided on the side for detecting the temperature of the fluid to be cooled The feed water heating system is characterized in that the amount is controlled, the compressor is controlled to maintain the temperature detected by the temperature sensor at a set temperature, and the set temperature is set lower than the predetermined temperature. .

  According to the first aspect of the present invention, the amount of fluid to be cooled supplied to the evaporator is controlled so that the temperature of the fluid to be cooled on the outlet side of the evaporator is maintained at a predetermined temperature (third set temperature in the embodiment). At the same time, the compressor is controlled so as to maintain the temperature of the fluid to be cooled on the outlet side of the evaporator at the set temperature (second set temperature in the embodiment). And by setting the said setting temperature lower than the said predetermined temperature, even if the temperature of the to-be-cooled fluid changes, a heat pump can be drive | operated efficiently, aiming at protection of a heat pump.

  According to the present invention, in a feed water heating system that produces hot water by raising the heat of a fluid to be cooled, such as waste water discharged from a factory, the heat pump is protected even if the temperature of the fluid to be cooled changes. However, the heat pump can be operated efficiently.

It is the schematic which shows one Example of the feed water heating system of this invention. In the feed water heating system of FIG. 1, it is the schematic which shows the water temperature from a condenser, and the state of a compressor. It is a figure which shows the modification of FIG. In the feed water heating system of FIG. 1, it is the schematic which shows the water temperature from an evaporator, and the state of a bypass valve and a compressor. It is a figure which shows the modification of FIG. It is the schematic which shows an example of a feed water heating system provided with the multistage heat pump by which the control by a 1st temperature sensor and the control by a 2nd temperature sensor are switched.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a water supply heating system of the present invention.
The feed water heating system 1 of the present embodiment includes a heat pump 2.

  The heat pump 2 is a vapor compression heat pump, and includes a compressor 4, a condenser 5, an expansion valve 6, and an evaporator 7 that are sequentially connected in an annular shape. The compressor 4 compresses the gas refrigerant to a high temperature and a high pressure. The condenser 5 condenses and liquefies the gas refrigerant from the compressor 4. Furthermore, the expansion valve 6 allows the liquid refrigerant from the condenser 5 to pass therethrough, thereby reducing the pressure and temperature of the refrigerant. The evaporator 7 evaporates the refrigerant from the expansion valve 6.

  Therefore, in the heat pump 2, in the evaporator 7, the refrigerant takes heat from the outside and vaporizes, while in the condenser 5, the refrigerant dissipates heat to the outside and condenses. By utilizing this, the heat pump 2 is used in the evaporator 7 with hot water (for example, exhausted hot water discharged from a factory), air (including air having heat such as discharge air from an air compressor), or Heat is drawn up from exhaust gas and the like, and in the condenser 5, water is heated to produce hot water.

  The refrigerant used for the heat pump 2 is not particularly limited, but is a hydrofluorocarbon (HFC) having 4 or more carbon atoms or a mixture obtained by adding water and / or a fire extinguishing liquid, alcohol (for example, ethyl alcohol or methyl alcohol) or water And what added fire extinguishing liquid, or water (for example, pure water or soft water) is used suitably.

  The heat pump 2 is not limited to a single stage and may be a plurality of stages. In the case of a plurality of stages, the evaporator 7 of the lowermost heat pump 2 draws heat from hot water, air, exhaust gas, etc., and the hot water is heated in the condenser 5 of the uppermost heat pump 2 to produce hot water. Hereinafter, unless otherwise specified, when the term “evaporator 7” is used, the term “evaporator 7” refers to the evaporator 7 of the lowermost stage heat pump 2. Is the condenser 5 of the uppermost heat pump 2.

  As long as the condenser 5 is configured to exchange heat without mixing refrigerant and water, the specific configuration thereof is not particularly limited. For example, a plate heat exchanger or a shell and tube heat exchanger is used.

  In the heat pump 2 of a single stage or a part or all of the heat pumps 2 of the plurality of stages, the refrigerant from the condenser 5 to the expansion valve 6 and the refrigerant from the evaporator 7 to the compressor 4 are not mixed. A liquid gas heat exchanger (not shown) for heat exchange may be installed. Thereby, the refrigerant from the evaporator 7 to the compressor 4 is superheated by the refrigerant from the condenser 5 to the expansion valve 6 by the liquid gas heat exchanger. In this way, the coefficient of performance (COP) of the heat pump 2 can be increased by increasing the enthalpy on the inlet side of the compressor 4 and thereby also increasing the enthalpy on the outlet side of the compressor 4. In addition, the disadvantage that the liquid refrigerant is supplied to the compressor 4 can be prevented. However, in the case of a multi-stage heat pump 2, it is preferable that the uppermost heat pump 2 is not provided with a liquid gas heat exchanger. By not providing a liquid gas heat exchanger in the uppermost heat pump 2 that is high temperature and pressure, temperature rise on the outlet side of the compressor 4 can be prevented, and deterioration of the lubricating oil in the compressor 4 can be prevented. Can do.

  In the single-stage heat pump 2 or the uppermost heat pump 2 of the multiple-stage heat pumps 2, a supercooler (not shown) may be provided between the condenser 5 and the expansion valve 6 as desired. The supercooler is an indirect heat exchanger between the refrigerant from the condenser 5 to the expansion valve 6 and the feed water to the condenser 5. The subcooler can supercool the refrigerant from the condenser 5 to the expansion valve 6 by supplying water to the condenser 5 and can supply water to the condenser 5 by using the refrigerant from the condenser 5 to the expansion valve 6. Can be heated. Further, heat exchange between the refrigerant and water can be divided into a supercooler as a heat exchange part by sensible heat and a condenser 5 as a heat exchange part by latent heat, so heat transfer efficiency can be improved.

  The compressor 4 includes a compressor body and a drive device for the compressor, and the drive device includes an engine (typically a gas engine or a diesel engine) and / or a motor. As a specific aspect of the control of the compressor 4, for example, the drive device is on / off controlled. Alternatively, a power transmission device (clutch and / or transmission) from the drive device to the compressor main body is provided between the compressor main body and the drive device, and whether or not power is transmitted from the drive device to the compressor main body, The power transmission device is controlled to change the amount. Or the motor which comprises a drive device is controlled by an inverter, and the rotation speed (it can also be said to be a rotational speed) of a motor is changed. Alternatively, the engine output constituting the drive device is controlled to change the engine output. Alternatively, the compressor main body is controlled in order to mechanically adjust the refrigerant discharge flow rate (including the case where the discharge flow rate is changed by adjusting the suction side) of the compressor main body. Of these, a plurality of them may be combined to control the compressor 4.

  A first temperature sensor 8 is provided in the hot water path 13 from the condenser 5. Based on the temperature detected by the first temperature sensor 8, the heat pump 2, more specifically, the compressor 4 is controlled. Typically, the compressor 4 is controlled to maintain the detected temperature of the first temperature sensor 8 at the first set temperature T1.

  FIG. 2 is a schematic diagram showing the detected temperature of the first temperature sensor 8 and the operating state of the heat pump 2. Here, an example in which the heat pump 2 is turned on / off at the first set temperature T1 will be described.

  When the detected temperature of the first temperature sensor 8 is lower than the first set temperature T1, the compressor 4 of the heat pump 2 is driven. And if it becomes more than 1st preset temperature T1, the compressor 4 will be stopped.

  Needless to say, a differential (operation gap) is set as desired for the first set temperature T1. Further, the compressor 4 may be proportionally controlled or PID-controlled by adjusting the rotational speed, for example, instead of on / off control of driving and stopping thereof.

  This will be described in more detail with reference to FIG. First, the on / off control in which the differential is set to the first set temperature T1 will be described. In this case, the first upper limit temperature T1H and the first lower limit temperature T1L are set for the first set temperature T1, and when the temperature detected by the first temperature sensor 8 exceeds the first upper limit temperature T1H when the temperature rises, the compressor is set. 4 stops and the compressor 4 is driven when the temperature detected by the first temperature sensor 8 falls below the first lower limit temperature T1L.

  Next, an example in the case of proportionally controlling the compressor 4 will be described. In this case, based on the temperature detected by the first temperature sensor 8, the compressor 4 is proportional to the first upper limit temperature T1H and the first lower limit temperature T1L and the first upper limit temperature T1H as a set value (target value). Control. Typically, the rotation speed of the compressor 4 is changed. Here, the compressor 4 stops at the first upper limit temperature T1H or higher, and the compressor 4 operates at full load below the first lower limit temperature T1L. Note that PID control may be performed instead of proportional control.

  In either case, the water temperature on the outlet side of the evaporator 7 is monitored by the second temperature sensor 14 described later, and if this temperature is less than the lower limit value, the desired hot water cannot be obtained even if the heat pump 2 is operated. The compressor 4 may be stopped.

  By the way, the feed water heating system 1 may control the compressor 4 based on the water temperature after passing through the evaporator 7 in addition to controlling the compressor 4 based on the water temperature from the condenser 5. Specifically, in order to detect the water temperature after cooling by the evaporator 7, a second temperature sensor 14 is provided in the evaporator 7 or the drainage passage 15 therefrom, and a detection signal of the second temperature sensor 14 is detected. Based on this, the compressor 4 of the heat pump 2 is controlled. In the case of such a configuration, it is possible to reliably cool the hot water to the desired temperature in the evaporator 7.

  When the compressor 4 is controlled based on the water temperature after passing through the evaporator 7, it is preferable that the water supply / drainage for the evaporator 7 is configured as shown in FIG. 1. That is, the water supply path 16 to the evaporator 7 and the drainage path 15 from the evaporator 7 are connected by the bypass path 17, and the second temperature sensor 14 is upstream of the junction with the bypass path 17. Is provided. The second temperature sensor 14 monitors the water temperature on the outlet side of the evaporator 7.

  Moreover, it is comprised so that adjustment of the bypass flow volume which flows into the drainage channel 15 via the bypass channel 17 without passing through the evaporator 7 is possible. Specifically, in the illustrated example, a bypass valve 18 composed of a three-way valve is provided at a branch portion between the water supply passage 16 and the bypass passage 17. However, instead of installing a three-way valve in the branching section, a valve may be provided in the water supply path 16 and / or the bypass path 17 downstream from the branching section so that the bypass flow rate can be adjusted. In any case, the flow rate through the evaporator 7 is adjusted by adjusting the bypass flow rate.

  FIG. 4 is a schematic diagram showing the detected temperature of the second temperature sensor 14, the open / close state of the bypass valve 18, and the operating state of the compressor 4. Here, an example in which the bypass valve 18 is opened and closed at a predetermined temperature (third set temperature) T3 and the compressor 4 is turned on and off at the second set temperature T2 will be described. When the bypass valve 18 is on / off controlled, when the bypass valve 18 is closed, water supply to the bypass passage 17 is completely stopped, whereas when the bypass valve 18 is opened, water supply to the bypass passage 17 is stopped. Be started. At this time, water may be supplied to the evaporator 7 and the bypass passage 17 at a predetermined rate, or water supply to the evaporator 7 may be stopped.

  If the detected temperature of the second temperature sensor 14 is lower than the second set temperature T2, the compressor 4 is stopped and the bypass valve 18 is closed because the desired hot water cannot be obtained even if the heat pump 2 is operated. Yes. And if it becomes 2nd preset temperature T2 or more, the compressor 4 will act | operate and water supply will be heated in the condenser 5 of the heat pump 2. FIG. When the detected temperature of the second temperature sensor 14 is equal to or higher than the third set temperature T3, the bypass valve 18 is opened, and the heat pump 2 is protected. In addition, when the temperature detected by the second temperature sensor 14 further rises and exceeds the upper limit value TH, the compressor 4 may be forcibly stopped.

  Needless to say, differentials (operation gaps) are set for the third set temperature T3 and the second set temperature T2, respectively, as desired. The compressor 4 and the bypass valve 18 may be proportionally controlled as well as on / off control.

  These cases will be described with reference to FIG. In FIG. 5, the differential (or proportional band) T3H to T3L of the third set temperature T3 and the differential (or proportional band) T2H to T2L of the second set temperature T2 do not overlap, but some You may overlap. That is, the second upper limit temperature T2H may be set higher than the third lower limit temperature T3L.

  First, on / off control in which differentials are respectively set for the third set temperature T3 and the second set temperature T2 will be described. In this case, with respect to the third set temperature T3, the third upper limit temperature T3H and the third lower limit temperature T3L are set, and when the temperature rises, when the temperature detected by the second temperature sensor 14 becomes the third upper limit temperature T3H or more, the bypass valve 18 opens and the bypass valve 18 closes when the temperature detected by the second temperature sensor 14 falls below the third lower limit temperature T3L. As for the second set temperature T2, a second upper limit temperature T2H and a second lower limit temperature T2L are set. When the temperature rises, the compressor 4 operates when the temperature exceeds the second upper limit temperature T2H. When the temperature becomes lower than the second lower limit temperature T2L, the compressor 4 stops.

  Next, an example in the case of proportionally controlling the compressor 4 and the bypass valve 18 will be described. In this case, based on the temperature detected by the second temperature sensor 14, the bypass valve 18 is proportionally set within the range between the third upper limit temperature T3H and the third lower limit temperature T3L and the third lower limit temperature T3L as a set value (target value). Control. Further, based on the temperature detected by the second temperature sensor 14, the compressor 4 is proportionally controlled in the range between the second upper limit temperature T2H and the second lower limit temperature T2L and using the second lower limit temperature T2L as a set value (target value). To do. Here, the bypass valve 18 is fully closed below the third lower limit temperature T3L, and the bypass valve 18 is fully opened above the third upper limit temperature T3H. Moreover, if it is less than 2nd minimum temperature T2L, the compressor 4 will stop, and if it is 2nd upper limit temperature T2H or more, the compressor 4 carries out full load operation. Note that PID control may be performed instead of proportional control.

  In any case, the temperature of the hot water is monitored by the first temperature sensor 8 described above, and the compressor 4 of the heat pump 2 is preferably stopped when the temperature becomes equal to or higher than the upper limit value. Further, the bypass valve 18 may be a self-powered temperature control valve that is opened and closed in the same manner as this control, in addition to being controlled based on the temperature detected by the second temperature sensor 14.

  As described above, the compressor 4 is controlled based on the temperature detected by the first temperature sensor 8 (FIGS. 2 and 3), or alternatively, controlled based on the temperature detected by the second temperature sensor 14. (FIGS. 4 and 5). However, the compressor 4 may be controlled based on both the first temperature sensor 8 and the second temperature sensor 14. One example will be described next. This can be said to be a combination of the control according to FIG. 3 and the control according to FIG.

  First, the compressor 4 can be proportionally controlled based on the temperature detected by the first temperature sensor 8 in a range between the first upper limit temperature T1H and the first lower limit temperature T1L and using the first upper limit temperature T1H as a set value. The Further, the compressor 4 can be proportionally controlled based on the temperature detected by the second temperature sensor 14 in the range between the second upper limit temperature T2H and the second lower limit temperature T2L and using the second lower limit temperature T2L as a set value. The Then, at the set timing (for example, every set time), the first deviation rate η1 and the second deviation rate η2 are obtained by the following equations, and the deviation among the control by the first temperature sensor 8 and the control by the second temperature sensor 14 is obtained. The compressor 4 may be controlled by switching to the control with the smaller rate. Specifically, when the relationship of η1 <η2 is satisfied, the compressor 4 may be proportionally controlled based on the detected temperature of the first temperature sensor 8, and when the relationship of η1> η2 is satisfied, the detection of the second temperature sensor 14 is performed. The compressor 4 may be proportionally controlled based on the temperature. The current temperature TA is a temperature detected by the first temperature sensor 8, and the current temperature TB is a temperature detected by the second temperature sensor 14.

First deviation rate η1 = (first upper limit temperature T1H−current temperature TA) / (first upper limit temperature T1H−first lower limit temperature T1L)
Second deviation rate η2 = (current temperature TB−second lower limit temperature T2L) / (second upper limit temperature T2H−second lower limit temperature T2L)

  The smaller the deviation rate, the closer to the target value, the smaller the operation amount of the compressor 4. If an attempt is made to control the compressor 4 with a larger deviation rate, that is, a larger operation amount, the smaller deviation rate, that is, the smaller operation amount, will soon reach the target value. However, the frequency at which the compressor 4 stops can be reduced by appropriately switching to the control with the smaller deviation rate. Moreover, even if it stops, it can transfer to a stop state gradually. Further, it is not necessary to manually set whether the control is performed by the first temperature sensor 8 or the second temperature sensor 14.

  During this control, the detected temperature of the second temperature sensor 14 becomes less than the lower limit value, the detected temperature of the second temperature sensor 14 becomes more than the upper limit value, or the detected temperature of the first temperature sensor 8 becomes more than the upper limit value. For example, the compressor 4 should be forcibly stopped. Note that PID control may be performed instead of proportional control.

  The control by the first temperature sensor 8 and the control by the second temperature sensor 14 may be switched based on the operation amount of the compressor 4 in addition to switching based on the deviation rate as described above. Also in this case, the compressor 4 is in proportion to the first upper limit temperature T1H and the first lower limit temperature T1L based on the temperature detected by the first temperature sensor 8, and is proportionally controlled with the first upper limit temperature T1H as a set value. PID control is possible. Further, the compressor 4 is in a range between the second upper limit temperature T2H and the second lower limit temperature T2L based on the temperature detected by the second temperature sensor 14, and the proportional control or PID control with the second lower limit temperature T2L as a set value. It is possible. Then, at the set timing (for example, every set time), the operation amount of the compressor 4 in the control by the first temperature sensor 8 and the operation amount of the compressor 4 in the control by the second temperature sensor 14 are obtained, and the first temperature sensor Of the control by 8 and the control by the second temperature sensor 14, the compressor 4 may be controlled by the smaller operation amount. For example, the control by the first temperature sensor 8 requires the operation amount X, while the control by the second temperature sensor 14 requires the operation amount Y. If X <Y, The compressor 4 may be controlled based on the temperature detected by the temperature sensor 8, and if the relationship X> Y, the compressor 4 may be controlled based on the temperature detected by the second temperature sensor 14.

  The feed water warming system 1 of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, the heat pump 2 is not limited to a single stage and can be a plurality of stages. When the heat pump 2 has a plurality of stages, the adjacent heat pumps 2 and 2 may be connected using an indirect heat exchanger or may be connected using a direct heat exchanger (intercooler). Good. In the latter case, an intermediate cooler that receives the refrigerant from the compressor 4 of the lower heat pump and the refrigerant from the expansion valve 6 of the upper heat pump and exchanges heat by directly contacting both refrigerants is provided. It is the condenser 5 of the lower heat pump and the evaporator 7 of the upper heat pump. As described above, the multi-stage (multi-stage) heat pump includes a single-stage multi-stage heat pump, a multi-element (multi-element) heat pump, or a combination thereof.

  When controlling a plurality of stages of heat pumps 2 based on the detected temperature of the first temperature sensor 8, for example, the compressor 4 of the uppermost stage heat pump 2 is controlled based on the detected temperature of the first temperature sensor 8, and the lower stage The compressor 4 of each heat pump 2 may be controlled based on the pressure or temperature of the refrigerant in the condenser 5 of the corresponding heat pump 2 (or the refrigerant in the evaporator 7 of the upper heat pump 2).

  When controlling a plurality of stages of heat pumps 2 based on the temperature detected by the second temperature sensor 14, for example, the compressor 4 of the lowermost stage heat pump 2 is controlled based on the detected temperature of the second temperature sensor 14, and the upper stage of the compressor 4 The compressor 4 of each heat pump 2 may be controlled based on the pressure or temperature of the refrigerant in the evaporator 7 of the heat pump 2 in the corresponding stage (or the refrigerant in the condenser 5 of the heat pump 2 in the lower stage).

  In the case where the control by the first temperature sensor 8 and the control by the second temperature sensor 14 are switched based on the deviation rate or the operation amount, the heat pump 2 may have a plurality of stages as shown in FIG. In FIG. 6, two stages of heat pumps 2X and 2Y are shown, but three or more stages can be similarly controlled. Moreover, in FIG. 6, although a liquid gas heat exchanger, a supercooler, etc. are not provided, it cannot be overemphasized that these may be provided.

  The compressor 4Y of the uppermost heat pump 2Y is in a range between the first upper limit temperature T1H and the first lower limit temperature T1L based on the detected temperature of the first temperature sensor 8, and is proportional to the first upper limit temperature T1H as a set value. Control or PID control is possible. Further, the compressor 4X of the lowermost heat pump 2X is based on the temperature detected by the second temperature sensor 14, and the second lower limit temperature T2L is set within the range between the second upper limit temperature T2H and the second lower limit temperature T2L. Proportional control or PID control is possible.

  As shown by the broken line, when the compressor 4Y of the uppermost heat pump 2Y is controlled based on the temperature detected by the first temperature sensor 8, the compressor 4X of each lower heat pump 2X is connected to the condenser of that stage. Control is performed based on the refrigerant pressure (detected pressure of the refrigerant pressure sensor 20) of the evaporator 7Y of 5X or one upper stage. Further, as indicated by the alternate long and short dash line, when the compressor 4X of the lowermost heat pump 2X is controlled based on the temperature detected by the second temperature sensor 14, the compressor 4Y of each upper heat pump 2Y is evaporated at that stage. It is controlled based on the refrigerant pressure (detected pressure of the refrigerant pressure sensor 20) of the condenser 7Y or the condenser 5X in the lower stage. The refrigerant pressure in the condenser 5 may be detected at any point from the compressor 4 outlet to the expansion valve 6 inlet, and the refrigerant pressure in the evaporator 7 is detected from the expansion valve 6 outlet to the compressor 4 inlet. It may be detected at any point up to.

  When switching control is performed based on the deviation rate, the first deviation rate η1 and the second deviation rate η2 are obtained at the set timing in the same manner as described above, and the control by the first temperature sensor 8 and the second temperature sensor 14 are performed. Of the control, the control may be switched to the control with the smaller deviation rate.

  Alternatively, when switching control is performed based on the operation amount, the operation amount (first operation amount y1) of the uppermost compressor 4Y in the control by the first temperature sensor 8 and the control in the control by the second temperature sensor 14 at the set timing. The value y1 / y2 of the ratio of the first manipulated variable y1 to the second manipulated variable y2 is obtained from the manipulated variable (second manipulated variable y2) of the lower compressor 4X, and if this value is less than a preset constant, While the control by the first temperature sensor 8 is performed, the control by the second temperature sensor 14 may be performed if it is equal to or greater than the constant.

  The single-stage or multiple-stage heat pumps 2 are not limited to the configuration shown in FIG. For example, the evaporator 7 may be installed in parallel, or a set of the expansion valve 6 and the evaporator 7 may be installed in parallel. Further, an oil separator may be installed on the outlet side of the compressor 4, a liquid receiver may be installed on the outlet side of the condenser 5, or an accumulator may be installed on the inlet side of the compressor 4.

  In the above-described embodiment, the heat pump 2 is described as an example in which heat is pumped from warm water to heat the feed water. However, air or exhaust gas may be used as the fluid to be cooled instead of warm water.

  Further, in FIG. 1, a water supply path 16 to the evaporator 7 and a drainage path 15 from the evaporator 7 are connected by a bypass path 17, and a bypass valve 18 provided at a branch portion between the water supply path 16 and the bypass path 17 is used. Although the configuration is such that the amount of water supplied to the evaporator 7 is adjusted, the amount of water passing through the evaporator 7 can be appropriately changed as long as it can be adjusted. For example, a three-way valve is provided in the water supply path 16 to the evaporator 7 to branch a part of the water supply, as in FIG. Or returned to the cooling tower or drained as it is. Alternatively, in FIG. 1, instead of omitting the installation of the bypass passage 17 and the bypass valve 18, a valve may be provided in the water supply passage 16, and the opening / closing or opening degree of the valve may be adjusted. In any case, the drainage from the drainage channel 15 may be discarded as it is, returned to a cooling tower or the like, or may be returned to the facility if it is cooled by the evaporator 7.

DESCRIPTION OF SYMBOLS 1 Feed water heating system 2 Heat pump 4 Compressor 5 Condenser 6 Expansion valve 7 Evaporator 8 1st temperature sensor 13 Warm water path 14 2nd temperature sensor 15 Drainage path 16 Feed water path 17 Bypass path 18 Bypass valve 20 Refrigerant pressure sensor T1 1st One set temperature T1H First upper limit temperature T1L First lower limit temperature T2 Second set temperature T2H Second upper limit temperature T2L Second lower limit temperature T3 Third set temperature T3H Third upper limit temperature T3L Third lower limit temperature TA Current by first temperature sensor Temperature TB Current temperature by the second temperature sensor

Claims (1)

A compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in a ring to circulate the refrigerant, and the heat pump that produces hot water by exchanging heat between the refrigerant and water in the condenser,
In the evaporator, heat exchange is performed between the refrigerant and the fluid to be cooled to cool the fluid to be cooled.
Based on the detected temperature of a temperature sensor provided on the outlet side of the evaporator to detect the temperature of the fluid to be cooled , the compressor is controlled,
The amount of fluid to be cooled supplied to the evaporator is controlled so as to maintain the temperature detected by the temperature sensor at a predetermined temperature,
The compressor is controlled to maintain a temperature detected by the temperature sensor at a set temperature;
The set temperature is set to be lower than the predetermined temperature.

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