JPH0926226A - Refrigeration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the thermal efficiency of a refrigeration apparatus as a whole and save the expenses on fuel by a method wherein an absorption- refrigeration machine is actuated by the exhaust heat from a heat engine and made to produce cold heat at intermediate temperatures, which heat is supplied as an auxiliary cold-heat source to a two-stage compression type cryogenic refrigerating machine. SOLUTION: A heat engine 20 drives an electric generator 21 and the electric generator 21 drives the compressors 1a, 1b of a two-stage compression one-stage expansion refrigeration cycle 10. Between a condenser 2 of the two-stage compression one-stage expansion refrigeration cycle 10 and an indirect heat exchanger 7a a supercooler 5 is connected in a manner of cooling it by a second evaporator 51 of an absorption refrigeration cycle 50. The cylinder of the gas engine 20 is water-cooled by a water-cooling circuit 23 and the exthaust gas 26 is made to heat a vapor generator 25 and then discharged to the outdoors. The steam from the steam generator 25 is supplied to a generator 53 of the absorption-refrigeration machine and utilized as a heat source of the absorption- refrigeration machine. As a result, the flow rate of the refrigerant in the high- pressure-side compressor and the motive power required therefor can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low temperature refrigerator used in a frozen warehouse and various manufacturing industries.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional technique in the case of applying a refrigeration system driven by a gas engine as an example of a heat engine to a refrigerated warehouse. Upon receiving the supply of the fuel gas 30, the gas engine 20 operates and drives the generator 21 to generate electric power, and the compressor 1a of the compression refrigerator,
It is supplied as a power source for 1b.

At this time, in the gas engine 20, the cylinder is cooled by the cooling water circulation circuit 23 and the heat exchanger 27. The exhaust gas is used to reheat the cylinder cooling water in the steam generator 25 to generate low-pressure steam, and is discharged from the flue 22 to the outside air.

The generated steam may be supplied to a heat demand destination for use, or may be simply radiated by an air-cooled or water-cooled condenser 29. FIG. 6 shows the heat balance in the gas engine in that case. 35% of the input heat amount is converted into electric power, but 36% is low-pressure steam, and the remaining 29% is dissipated to the outside as other heat loss.

Therefore, in the conventional gas engine refrigeration system, only 35% of the input energy is used as a power source for refrigeration. Such poor energy efficiency is a major problem in the conventional technology.

The refrigeration system used in FIG.
It is a two-stage compression refrigerator that is often used when obtaining an ultralow temperature of about -30 ° C or less. The lower the freezing temperature, the higher the pressure ratio required by the compressor. In the case of a high pressure ratio in a single-stage compressor, there is a problem that the refrigerant temperature on the outlet side of the compressor rises too much and the compression efficiency deteriorates, resulting in a region exceeding the allowable temperature range of the refrigerant. .

In order to avoid these problems, in the two-stage compression refrigerator, the compressor has two stages, and the intercooler 7 is provided in the middle thereof. In addition, in this method, a part of the generated refrigeration is used for precooling of refrigeration to form a supercooling cycle,
We are trying to improve the refrigeration efficiency.

The principle will be described with reference to FIG. FIG.
Shows a part of the two-stage compression refrigerator in FIG. In this system, for example, R22 is used as the refrigerant.
Is used.

The low-pressure side compressor 1a sucks the low-pressure refrigerant vapor (state g, pressure P ₁ (FIG. 7)) evaporated in the evaporator 4 and compresses it to an intermediate pressure P _m (state a). The pressurized refrigerant gas enters the intercooler 7, directly merges with the low-temperature heat medium that has passed through the expansion valve 3b, is cooled to saturated steam (state b), and then passes through the duct 9 to generate high pressure. Enter the side compressor 1b. The compressor 1b pressurizes the heat medium to P ₂ (state c). Further, the refrigerant enters the condenser 2 and is condensed to a saturated liquid (state d) by air cooling or water cooling.

The refrigerant entering the pipe 11 is divided into both the pipe 12 and the pipe 13. Part of the refrigerant enters the auxiliary cooling line 13 and passes through the expansion valve 3b. The outlet pressure of the expansion valve is equal to the outlet pressure of the low pressure side compressor 1a and is P _m . The expansion valve outlet side state (h) still contains a large amount of liquid,
While being mixed with the gas from the compressor 1a, the refrigerant gas of the main expansion line passing through the pipe 12 undergoes endothermic evaporation for supercooling and becomes a saturated gas (state b) inside the pipe 9. Go.

The refrigerant liquid entering the main expansion line 12 enters the intercooler 7 and is indirectly cooled in the indirect heat exchanger 7a portion by the refrigerant whose temperature has been reduced to the intermediate temperature in the auxiliary cooling line 13. After that, it enters the expansion valve 3a and adiabatically expands to the pressure P ₁ (state f).

Further, when it passes through the evaporator 4, it exerts a refrigerating effect, becomes a saturated gas (state g) at its outlet, and enters the low pressure side compressor 1a again. This series of flows is called a two-stage compression / one-stage expansion refrigeration cycle and is a well-known technique that has already been established and is widely used as an ultra-low temperature refrigeration system. For details, see “Theory and Performance of Refrigerators” (Revised Second Edition) by Ichitaro Gensei (Published by the Japan Refrigeration Association (1990)).

The compressors 1a and 1b in FIG. 4 are both driven by a gas engine. FIG. 7 shows the above changes on the Mollier diagram. g → a is the state change in the low pressure side compressor 1a, a → b is the state change in the intercooler 7, b → c is the state change in the high pressure side compressor 1b, and c → d is the state change in the condenser 2. Are shown respectively.

Further, d → e shows the supercooling process in the main expansion line 12, e → f shows the adiabatic expansion change in the expansion valve 3a, and f → g shows the change in the evaporator 4. Further, d → h represents adiabatic expansion change in the expansion valve 3b of the auxiliary cooling line 13, and h → b represents a process of changing the heat medium in the intercooler 7.

As shown in the flow chart of FIG. 3, in the conventional refrigeration cycle, only the power generation output by the heat engine is input. The heat energy emitted from the heat engine is not effectively used. Moreover, since a part of the generated refrigeration is used for the intercooling of the refrigerant gas and the supercooling of the refrigerant liquid, the efficiency of the refrigeration system is deteriorated.

[0016]

A large amount of waste heat is generated in addition to the generated power in the privately-generated power in which a heat engine such as a gas engine, a diesel engine, or a gas turbine is introduced. In order to increase the total energy efficiency of the heat engine, it is an important issue to effectively use the exhaust heat discharged at the same time.

In the present invention, the absorption refrigerator is operated by the exhaust heat generated in the heat engine to generate cold heat at an intermediate temperature, which is supplied as an auxiliary cold heat source for the two-stage compression ultra-low temperature refrigerator to supply the entire refrigeration system. The purpose is to improve the heat efficiency of the vehicle and reduce fuel consumption.

[0018]

The refrigerating apparatus of the present invention comprises a heat engine: a generator driven by the heat engine: a low pressure side compressor, an intercooler, a high pressure side compressor, a condenser, an indirect heat source. A closed loop is constituted by the exchanger, the first expansion valve and the evaporator; further, a branch pipe is provided which branches from the middle of the condenser and the indirect heat exchanger and joins with the intercooler, and on the branch pipe. A two-stage compression one-stage expansion refrigeration cycle in which a second expansion valve is arranged to cool the indirect heat exchanger in the intercooler: an absorber, a regenerator, a second condenser and a second evaporator. An absorption refrigeration cycle having a closed loop formed by: a refrigeration system comprising: a two-stage compression one-stage expansion refrigeration cycle, which comprises a subcooler between a condenser and an indirect heat exchanger. The cooler is the second evaporator of the absorption refrigeration cycle. The two refrigeration cycles are combined so as to be cooled more; the low pressure side compressor and the high pressure side compressor of the two-stage compression one-stage expansion type refrigeration cycle are driven by the generator; The regenerator uses steam or hot water obtained by recovering the exhaust heat of the heat engine as a heat source.

The low pressure side compressor and the high pressure side compressor are
It is designed to be driven directly by a heat engine. Also, the two-stage compression one-stage expansion refrigeration cycle includes a second indirect heat exchanger between the low pressure side compressor and the intercooler; the second indirect heat exchanger is the first indirect heat exchanger of the absorption refrigeration cycle. It is designed to be cooled by the two evaporators.

Here, the heat engine includes a gas engine, a diesel engine, a gas turbine and the like. And
The heat engine drives the generator, and the resulting electricity drives the compressor of the two-stage compression refrigerator. Alternatively, the heat engine and the compressor are directly connected to drive the compressor.

The absorption refrigerator is operated by the exhaust heat of the heat engine to generate intermediate cold heat. A supercooler for the refrigerant is provided after the condenser of the two-stage compression refrigerator, and the refrigerant is supercooled by the intermediate temperature cold heat obtained in the absorption refrigerator. This enhances the net refrigeration capacity of the refrigeration system.

Further, a second indirect heat exchanger is provided on the outlet side of the low pressure side compressor to cool the refrigerant by the intermediate temperature cold heat obtained by the absorption refrigerator. This enhances the net refrigeration capacity of the refrigeration system.

As the absorption refrigerator used here, a system using lithium bromide / water as a medium is in a practical stage and is used in various fields. Here, FIG.
The single-effect absorption refrigerating machine shown in Figure 1 will be outlined. This technology itself can use the existing technology.

In FIG. 5, the evaporator 51 is a cold heat generating portion, and the pump 6 is provided on the tube surface of the evaporation heat exchanger 68.
4. Water is sprayed by the refrigerant spray nozzle 65. In the absorber 52, a concentrated solution of lithium bromide is sprayed by the nozzle 66 onto the tube surface of the absorption heat exchanger 69. This time,
By the vapor pressure difference between water and a concentrated aqueous solution of lithium bromide,
The water on the surface of the evaporative heat exchanger 68 evaporates, and this vapor is absorbed by the concentrated solution of lithium bromide sprayed on the surface of the absorption heat exchanger 69 tube.

At this time, cold heat corresponding to the latent heat of evaporation of water is generated on the evaporation heat exchanger 68, and if water or another refrigerant is flown through the heat exchanger 68, cold water or a refrigerant of about 5 ° C. is usually obtained. To be On the other hand, the condensation heat of water vapor is generated on the surface of the absorption heat exchanger 69, and therefore cooling water is normally flowed inside the heat exchanger 69 to remove heat.

The diluted solution of lithium bromide which has absorbed water vapor is regenerated by the pump 63 and the solution spraying nozzle 67.
3 is sprayed on the tube surface of the regenerative heat exchanger 70 and heated by the high temperature heat source flowing in this heat exchanger, a part of water is evaporated, and it is returned to the absorber 52 again as a concentrated solution. The heat exchanger 55 is for recovering the heat of solution and improving the efficiency of the refrigeration cycle.

On the other hand, the water vapor evaporated in the regenerator 53 enters the condenser 54, through which the cooling water flows and the condensation heat exchanger 62.
It cools and condenses on the surface of the tube. This water is again
Water is supplied to the evaporator 51.

As described above, the conventional absorption refrigerator has been used to supply a high temperature heat source (hot water or steam at 100 to 200 ° C) and cooling water (20 to 30 ° C). It is possible to obtain cold water at about 5 ° C.

In a system using lithium bromide / water,
Since water is used as the refrigerant, the temperature that can be generated is 0 ° C or higher. Usually, the limit is about 5 ° C., so the supercooling temperature is also about this limit.

On the other hand, in the ammonia / water system, since ammonia is used as the refrigerant, the temperature that can be generated can be up to 0 ° C or lower. Therefore, the temperature at which supercooling is possible can be up to 0 ° C or lower.

In the present invention, the type of the absorption refrigerator is not particularly limited, and an appropriate refrigerant and refrigeration system (single-effect, single-effect, depending on the temperature level of exhaust heat obtained from the heat engine, the required temperature level of generation of the refrigeration system, etc. It can be selected and used.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an embodiment of the present invention. A gas engine is used as the heat engine 20. The generator 21 is driven by the gas engine, and the compressors 1a and 1b of the two-stage compression one-stage expansion refrigeration cycle 10 are driven by this generator.

The two-stage compression one-stage expansion refrigeration cycle 10 comprises a low pressure side compressor 1a, an intercooler 7, a high pressure side compressor 1b, a condenser 2, an indirect heat exchanger 7a, a first expansion valve 3a and an evaporator 4. It is configured by forming a closed loop. A branch pipe 13 that branches from the middle of the condenser 2 and the indirect heat exchanger 7a and joins the intercooler 7 is provided,
The second expansion valve 3b is arranged on the branch pipe 13 to cool the indirect heat exchanger 7a in the intercooler 7.

On the other hand, the absorption refrigeration cycle 50 includes an absorber 52, a regenerator 53, a second condenser 54, and a second evaporator 5.
1 to form a closed loop. The two-stage compression one-stage expansion refrigeration cycle 10 is provided with a subcooler 5 between the condenser 2 and the indirect heat exchanger 7a, and this subcooler 5 is provided by the second evaporator 51 of the absorption refrigeration cycle 50. Combined to be cooled.

Further, the regenerator 5 of the absorption refrigeration cycle 50
3 uses steam or hot water obtained by cooling the heat engine 20 as a heat source. The specific configuration and operation will be described below.

Reference numeral 20 is a gas engine, and the cylinder of the engine is water-cooled by a water-cooling circuit 23. The exhaust gas 26 heats the steam generator 25 and then is discharged to the outside air. From the steam generator 25, saturated steam at 120 ° C. is obtained. This vapor is supplied to the regenerator 53 of the absorption refrigerator using lithium bromide / water as a medium, and is used as a heat source of the absorption refrigerator.

The low-pressure steam of 120 ° C. from the gas engine 20 is supplied to the regenerator 53 on the route of 56 → 57, and this operates as a driving heat source. On the other hand, 60 → 6
Cooling water is supplied along the first route. 6 of driving heat source
A 0% size freezing is obtained.

The refrigerant liquid (R22) of the compression refrigerator is passed through the evaporation heat transfer tube 68 in the second evaporator 51.
This corresponds to the supercooler 5 from the viewpoint of the compression refrigerator. R22 of 40 ° C condensed in the condenser 2 of the compression refrigerator flows into the evaporation heat transfer tube 68, and is cooled to 10 ° C and then exits.

The structure and operation of the two-stage compression one-stage expansion refrigeration cycle 10 are as described above with reference to FIG. Specifically, the evaporation temperature is -50 ° C (pressure: 0.66 kg /
cm ² ), condensation temperature is 40 ° C (pressure: 15.78 kg / cm
² ). The outlet pressure (intermediate pressure) of the low-pressure compressor 1a is 3.03 kg / cm ² . The refrigerant is guided to the second evaporator 51 of the absorption refrigerator after the liquid receiver 6, where the temperature is 40 ° C (d
It is supercooled from (point) to 10 ° C (point e '). This is the subcooler 5.

Most of the supercooled refrigerant passes through the intercooler 7 and is further supercooled to 0 ° C. to be in the state e, passes through the expansion valve 3a and is decompressed and cooled to the evaporator 4. Once inside, it absorbs heat from the outside and exerts a freezing effect.

Here, a part of the refrigerant discharged from the subcooler 5 goes to the auxiliary cooling circuit 13, passes through the expansion valve 3b, and is expanded and reduced to an intermediate pressure of 3.03 kg / cm ² and a temperature of -15 ° C. Warm. This refrigerant enters the intercooler 7, supercools the refrigerant in the main expansion line to 0 ° C, and compresses the low pressure side compressor 1a.
For the intercooling of the outlet side refrigerant gas, the gas is directly mixed with the refrigerant, and the combined gas becomes saturated dry vapor (state b) and is sucked into the high pressure side compressor 1b.

When the refrigerant is supercooled from 40 ° C to 10 ° C by the absorption refrigerator as in this embodiment,
This is effective in reducing the amount of refrigerant in the auxiliary cooling line necessary for generating cold heat. In addition, the liquid in the auxiliary cooling line
Since it has already been pre-cooled to 10 ° C before the expansion valve 3b, the amount of refrigeration generated after expansion by the valve 3b (-15 ° C)
Is greater than in the case of the prior art, and in that sense also has the effect of reducing the amount of refrigerant liquid in the auxiliary cooling line.

In this embodiment, the point (A) in the flow chart of FIG. 4 is cooled by the absorption refrigerator, but the point (B) may be changed depending on the refrigerating capacity and the refrigeration temperature obtained by the absorption refrigerator. ), Or supercooling may be performed at the point (C). That is, the refrigerating capacity can be enhanced by supercooling all the positions from the condenser 2 to the position before the expansion valve 3a in the main expansion line 12.

In the embodiment shown in FIG. 1, the gas engine 20 drives the generator 21,
The compressors 1a and 1b of the two-stage compression and one-stage expansion refrigeration cycle 10 are driven by this generator.
b may be directly driven by the gas engine 20.

Next, a second embodiment will be described with reference to FIG. In FIG. 1, the intercooling of the compressed gas is
It is carried out by direct mixing with the intermediate temperature refrigerant in the auxiliary cooling line 13, and this uses a part of the cold heat generated by the refrigerator, thus deteriorating the efficiency of the refrigerator.

Therefore, when there is a margin in the refrigerating capacity of the absorption refrigerator, as shown in FIG. 2, before the intercooler 7,
If the second indirect heat exchanger 19 is provided and cooled by the second evaporator 51 of the absorption refrigerator, the refrigeration efficiency can be further enhanced.

[0047]

The energy saving effect of the present invention will be quantitatively described in comparison with the prior art, with the first embodiment as a representative. The following conditions are set for comparison. Two-stage compression refrigerator (1) Evaporation temperature -50 ° C (Intermediate evaporation temperature -15 ° C) (2) Condensation temperature 40 ° C (3) Compressor Low pressure side compressor inlet pressure: P ₁ 0.66kg / cm ² Outlet pressure: P _m 3.03 kg / cm ² Adiabatic efficiency: η 70% Compression power: Wa 0.0141 kWh / refrigerant 1 kg High pressure side compressor inlet pressure: P _m 3.03 kg / cm ² Outlet pressure: P ₂ 15. 78kg / cm ² Adiabatic efficiency: η 70% Compression power: Wb 0.0159kWh / Refrigerant 1kg (4) Supercooling temperature of main expansion line 0 ° C Absorption refrigerator (1) Working fluid Lithium bromide / water (2) Results Coefficient = Refrigeration amount / Heat supply amount 0.6 (-) Under these conditions, 1 kg of refrigerant passing through the main expansion line
The compressor power required for (generated refrigeration amount = 43.9 kcal) is compared.

In the case of the prior art (1) Main expansion line refrigerant flow rate 1.0 kg (2) Auxiliary cooling line refrigerant flow rate 0.594 kg (3) Compressor required power 1 × 0.0141 + (0.594 + 1.0) × 0.0159 = 0.0394kWh In the case of the present invention (1) Main expansion line refrigerant flow rate 1.0 kg (2) Auxiliary cooling line refrigerant flow rate 0.206 kg (3) Compressor required power 1 x 0.0141 + (0.206 + 1.0) x 0.0159 = 0.0333kWh (= 28.64 kcal) (4) Required supercooling heat quantity of refrigerant (R22) by absorption refrigerator (40 ° C → 10 ° C) 11.3kcal From the heat quantity of low pressure steam of 36% in the balance of FIG. The amount of refrigeration obtained by the absorption refrigerator is 36 x 0.6 = 2
It is 1.6%. At that time, 35% of electric power was obtained at the same time.

Now, assuming that the amount of power generation is 0.0333kWh,
The refrigeration amount of the absorption chiller obtained at that time is 0.0333 × 21.6 / 35.0 × 860 = 17.7 kcal, which is larger than the required supercooling heat amount (11.3 kcal).
Therefore, the first embodiment is possible in terms of heat balance.

Comparing the required power of the two compressors, in the present invention (Embodiment 1), the required power of 15.5% can be saved. This is because the refrigerant flow rate of the auxiliary cooling line is reduced by the amount of supercooling performed by the absorption refrigerator, and as a result, the refrigerant flow rate of the high-pressure side compressor and its required power are reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an overall configuration of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional technique (combination of a gas engine and a two-stage compression refrigerator).

FIG. 4 is an explanatory diagram of a conventional technique (two-stage compression / one-stage expansion refrigerator).

FIG. 5 is an explanatory diagram of a conventional technique (lithium bromide / water absorption refrigerator).

FIG. 6 is an explanatory view of heat balance of the gas engine.

FIG. 7 is a Mollier diagram of a two-stage compression refrigerator.

[Explanation of symbols]

1a ... low pressure side compressor, 1b ... high pressure side compression, 2 ... condenser,
3a, 3b ... Expansion valve, 4 ... Evaporator, 5 ... Supercooler, 7 ...
Intercooler, 7a ... Indirect heat exchanger, 10 ... Two-stage compression / one-stage expansion refrigeration cycle, 20 ... Heat engine, 21 ... Generator, 5
0 ... Absorption type refrigeration cycle, 51 ... Second evaporator, 52 ... Absorber, 53 ... Regenerator, 54 ... Second condenser.

Claims (3)

[Claims] 1. A heat engine: a generator driven by this heat engine: a low-pressure side compressor, an intercooler, a high-pressure side compressor,
A closed loop is constituted by a condenser, an indirect heat exchanger, a first expansion valve and an evaporator; and a branch pipe is provided which branches from the middle of the condenser and the indirect heat exchanger and joins with the intercooler, A two-stage compression one-stage expansion refrigeration cycle in which a second expansion valve is arranged on the branch pipe to cool the indirect heat exchanger in the intercooler: an absorber, a regenerator, a second condenser And an absorption type refrigeration cycle in which a closed loop is constituted by a second evaporator, wherein: the two-stage compression one-stage expansion refrigeration cycle is a subcooler between a condenser and an indirect heat exchanger. And connecting the two refrigeration cycles so that the subcooler is cooled by the second evaporator of the absorption refrigeration cycle; and the low-pressure side compressor of the two-stage compression one-stage expansion refrigeration cycle and The high-pressure side compressor It is driven by electric; regenerator of the absorption refrigerating cycle uses steam or hot water is obtained by recovering the waste heat of the heat engine as heat source; that the refrigeration apparatus according to claim. 2. A heat engine: a low pressure side compressor, an intercooler,
A high-pressure side compressor, a condenser, an indirect heat exchanger, a first expansion valve and an evaporator form a closed loop; and further branch from the middle of the condenser and the indirect heat exchanger to join the intercooler. A two-stage compression / one-stage expansion refrigeration cycle in which a branch pipe is provided, a second expansion valve is arranged on the branch pipe, and the indirect heat exchanger is cooled in the intercooler: an absorber, a regenerator A refrigerating apparatus comprising: an absorption refrigeration cycle in which a closed loop is constituted by a second condenser and a second evaporator; and: the two-stage compression, one-stage expansion refrigeration cycle, comprising a condenser and an indirect heat exchanger. Equipped with a subcooler between
The two refrigeration cycles are combined so that the supercooler is cooled by the second evaporator of the absorption refrigeration cycle; the low pressure side compressor and the high pressure side compression of the two-stage compression one-stage expansion refrigeration cycle. A refrigerating apparatus characterized in that steam generator or hot water obtained by recovering exhaust heat of the heat engine is used as a heat source for the regenerator of the absorption refrigeration cycle by directly driving the machine by the generator. 3. The two-stage compression one-stage expansion refrigeration cycle comprises a second indirect heat exchanger between a low pressure side compressor and an intercooler; the second indirect heat exchanger is the absorption refrigeration system. The refrigeration system according to claim 1 or 2, wherein the refrigeration system is cooled by the second evaporator of the cycle.