CN103438598B - Based on folding type cooling system and the method for just inverse circulation coupling - Google Patents

Abstract

The invention discloses a cascade refrigeration system and method based on forward and reverse cycle coupling, the system includes a power subcycle, an absorption refrigeration subcycle and a compression refrigeration subcycle, wherein the system uses a medium and low temperature heat source to drive the power subcycle Work, the heat removal of the power sub-cycle drives the absorption refrigeration sub-cycle refrigeration, and the work done by the power sub-cycle drives the compression refrigeration sub-cycle refrigeration. The absorption refrigeration sub-cycle and the compression refrigeration sub-cycle constitute a cascade refrigeration system. The evaporative refrigeration subcycle of the absorption refrigeration subcycle in the high temperature region provides cooling load for the condensation process of the compression refrigeration subcycle in the low temperature region. Combined evaporator-condenser. The input energy of the whole system is medium and low temperature heat source, and the product output is low temperature cold.

Description

Cascade refrigeration system and method based on forward and reverse cycle coupling

technical field

The invention relates to the technical field of medium and low temperature heat source refrigeration, in particular to an absorption-compression cascade refrigeration system and method based on forward and reverse cycle coupling.

Background technique

Ammonia water absorption refrigeration technology is a refrigeration technology that can be driven by low-temperature waste heat resources or low-temperature renewable energy such as solar energy and geothermal energy. Smelting and other chemical processes. The evaporation temperature of single-stage ammonia water absorption refrigeration should not be too low, and is suitable for air conditioning, cold storage and some industrial sectors. But there are also some industrial sectors, such as the food processing industry (quick freezing, freeze drying, long-term preservation of food, etc.), some gas (propane, etc.) liquefaction, some low-temperature environmental laboratories, and the production of solid _CO2 (dry ice) etc. It is necessary to use a cooling capacity with a lower temperature (such as lower than -30°C). At this time, the single-stage ammonia water absorption refrigeration is difficult to meet the requirements, and a two-stage process is required. Compared with the single-stage cycle, the thermal coefficient of the two-stage cycle is lower, and the system is complex, with more equipment, larger metal consumption, and more complicated operation. For low-temperature cooling capacity, cascade compression refrigeration cycle can also be used in industry, but the compression refrigeration cycle is used in the high-temperature and low-temperature regions of the cycle, which will consume a lot of work.

Contents of the invention

(1) Technical problems to be solved

In order to overcome the shortcomings of the existing two-stage ammonia water absorption refrigeration system, the present invention provides a cascade refrigeration system and method based on forward and reverse cycle coupling. The ammonia water absorption refrigeration cycle and the compression refrigeration cycle are organically combined to use medium and low temperature heat sources to obtain low temperature cooling capacity.

(2) Technical solution

In order to achieve the above purpose, the present invention provides a cascade refrigeration system based on forward and reverse cycle coupling, which includes a power subcycle, an absorption refrigeration subcycle and a compression refrigeration subcycle, wherein the system is driven by a medium and low temperature heat source The power sub-cycle does work, the heat rejection of the power sub-cycle drives the absorption refrigeration sub-cycle refrigeration, the work done by the power sub-cycle drives the compression refrigeration sub-cycle refrigeration, the absorption refrigeration sub-cycle and the compression refrigeration sub-cycle constitute cascade refrigeration In the system, the absorption refrigeration sub-cycle works in the high-temperature region, and the compression refrigeration sub-cycle works in the low-temperature region; the evaporative refrigeration process of the absorption refrigeration sub-cycle in the high-temperature region provides cooling load for the condensation process of the compression refrigeration sub-cycle in the low-temperature region, The two are combined by an evaporator-condenser.

In the above scheme, the power sub-cycle includes a high-pressure solution pump 1, a steam generator 2, an expander 3, a reboiler 4, and a first condenser 5 that are sequentially connected in a loop, wherein, from the first condenser 5, The solution S1 is pressurized by the high-pressure pump 1 to form S2, enters the steam generator 2, is heated by an external heat source to form superheated steam S3, and then enters the expander 3 to expand and perform work. The exhaust gas S4 of the expander 3 enters the reboiler 4 and the second A condenser 5, which uses the high-temperature part of the condensation heat for the heating process of the solution in the absorption refrigeration sub-cycle, and discharges the low-temperature part of the condensation heat to the environment.

In the above scheme, the high-pressure solution pump 1 is a liquid pressurization device, which is used to increase the liquid pressure; the steam generator 2 and the reboiler 4 are fluid heat exchange devices, which are used for heating and cooling between hot and cold streams. heat exchange; the expander 3 is a device for gas expansion, and the expander 3 uses high-temperature and high-pressure steam to expand and perform work; the first condenser 5 is a condensation device for condensing the steam of the power cycle working medium, and the condensation discharges The heat is dissipated to the environment via the cooling medium.

In the above scheme, the absorption refrigeration sub-cycle includes an absorber 6, a low-pressure solution pump 7, a solution heat exchanger 8, a rectification tower 9, a second condenser 10, a subcooler 11, an ammonia throttle valve 12, an evaporation - condenser 13 and solution throttling valve 14, wherein: the strong solution S6 from absorber 6 enters rectification column 9 after low-pressure solution pump 7 pressurization, solution heat exchanger 8 preheats, is separated into high-purity tower top Ammonia vapor S12 and low-concentration tower kettle dilute solution S9; tower kettle dilute solution S9 first passes through the solution heat exchanger 8 for heat recovery and then throttling and reducing pressure through the solution throttle valve 14, and the formed low-pressure dilute solution S11 enters the absorber 6. The top ammonia vapor S12 enters the second condenser 10 and is condensed into liquid ammonia S13 and then enters the subcooler 11, and after exchanging heat with the low-temperature ammonia vapor S16 from the evaporation-condenser 13, a liquid with a certain degree of subcooling is formed. Ammonia S14 enters the evaporator-condenser 13 after being throttled and reduced by the ammonia throttle valve 12 to evaporate, and the formed low-temperature and low-pressure ammonia vapor S16 is recovered in the subcooler 11 and then enters the absorber 6 to be absorbed by the dilute solution S11 , re-form concentrated solution S6.

In the above scheme, the absorber 6 is a gas-liquid mixed absorption device, which uses an absorbent to absorb the refrigerant vapor, and the heat released during the absorption process is discharged to the environment through the cooling medium; the low-pressure solution pump 7 is a liquid pressurization device for Increase the liquid pressure; the solution heat exchanger 8 and the subcooler 11 are fluid heat exchange equipment for heat exchange between hot and cold streams; the rectification tower 9 is used to realize the separation and separation of mixed working fluid Purification to produce high-purity refrigerant vapor and low-concentration absorbent solution; the second condenser 10 is a condensation device for condensing the refrigerant vapor, and the condensation heat is discharged to the environment through the cooling medium; The ammonia throttling valve 12 and the solution throttling valve 14 are liquid throttling and pressure-reducing devices, which are respectively used to realize the depressurization of the refrigerant ammonia in the high-temperature zone and the tower kettle solution; the evaporation-condenser 13 is an absorption refrigeration sub-cycle The combination point with the compression refrigeration sub-cycle is used to absorb heat and evaporate the refrigerant in the high temperature area to condense the refrigerant vapor in the low temperature area.

In the above scheme, the compression refrigeration sub-cycle includes a compressor 15, _CO throttle valve 16, _CO evaporator 17 and evaporation-condenser 13, wherein: the compressor 15 is driven by the expander 3 of the power sub-cycle Compress the low-pressure refrigerant vapor S21 to form high-pressure refrigerant vapor S18, which enters the evaporator-condenser 13 and condenses into liquid refrigerant CO ₂ , and the heat of condensation in this process is absorbed by the ammonia refrigerant in the absorption refrigeration sub-cycle; the resulting The liquid CO ₂ enters the CO ₂ evaporator 17 for evaporation and refrigeration after being throttled and depressurized by the CO ₂ throttle valve 16, and the obtained low-temperature cooling capacity is the product output of the cascade refrigeration system.

In the above scheme, the compressor 15 is a gas pressurizing device, which is used to compress the low-pressure refrigerant vapor to a high-pressure state. The compressor 15 is connected to the expander 3 through a coupling, and the compression work consumed by the compressor 15 is determined by the expansion machine 3; the _CO2 throttle valve 16 is a liquid throttling and pressure-reducing device for reducing the pressure of the refrigerant _CO2 in the low-temperature region; the _CO2 evaporator 17 is a refrigeration component of the cascade refrigeration system, It is used to absorb heat and evaporate the refrigerant in the low-temperature region to obtain low-temperature cooling capacity; the evaporation-condenser 13 is shared with the absorption refrigeration sub-cycle.

In the above scheme, the energy input of the cascade refrigeration system is medium and low temperature external heat source of industrial waste heat, solar energy or geothermal heat, and the product output is low temperature cooling capacity.

In order to achieve the above object, the present invention also provides a cascade refrigeration method based on the coupling of forward and reverse cycles. The method uses a medium and low temperature heat source to drive the power sub-cycle to do work, and the heat exhaust of the power sub-cycle drives the absorption refrigeration sub-cycle to refrigerate. , the work done by the power sub-cycle drives the compression refrigeration sub-cycle to refrigerate. Wherein, the absorption refrigeration sub-cycle and the compression refrigeration sub-cycle constitute a cascaded refrigeration system, the absorption refrigeration sub-cycle works in a high temperature zone, and the compression refrigeration subcycle works in a low temperature zone; the absorption refrigeration subcycle in a high temperature zone The evaporative refrigeration process of the sub-cycle provides cooling load for the condensation process of the compression refrigeration sub-cycle in the low temperature area, and the two are combined through the evaporation-condenser.

(3) Beneficial effects

From above-mentioned technical scheme, the present invention has following beneficial effect:

1. The cascade refrigeration system and method based on forward and reverse cycle coupling provided by the present invention uses medium and low-grade heat as the heat source, which can be either industrial waste heat or renewable energy sources of medium and low temperature such as solar energy and geothermal heat. In order to achieve the purpose of energy saving and emission reduction; the system uses ammonia-water mixture and CO ₂ as two natural working fluids as the circulating medium, which is environmentally friendly and pollution-free.

2. The cascade refrigeration system and method based on forward and reverse cycle coupling provided by the present invention is based on the power cycle and absorption refrigeration cycle of the ammonia-water mixed working medium, and the heat energy inside and outside the system is used to pass the medium and low temperature heat sources first. The power sub-cycle does work, and the work done drives the compression refrigeration sub-cycle for refrigeration; the heat exhausted by the power sub-cycle is used for absorption refrigeration; the absorption refrigeration sub-cycle and the compression refrigeration sub-cycle constitute a cascade refrigeration cycle, in which the absorption The type cycle works in the high temperature area, and the compression type cycle works in the low temperature area, and the two are combined through the evaporation-condenser. The energy input of the whole system is medium and low temperature heat, and the output is low temperature cooling.

3. In the cascade refrigeration system and method based on forward and reverse cycle coupling provided by the present invention, the power sub-cycle uses ammonia water as the working medium, and the temperature in the evaporation process rises gradually, which can perform good temperature matching with the sensible heat source, reducing The irreversible loss in the evaporation process of the power working medium is reduced; and the exhaust heat temperature of the power sub-cycle expander is relatively high, which can be further utilized in the absorption refrigeration sub-cycle.

4. The cascade refrigeration system and method based on forward and reverse cycle coupling provided by the present invention has a simple process flow, relatively mature technology of each unit, and is convenient for industrialized utilization.

Description of drawings

Fig. 1 is a schematic diagram of an embodiment of a cascade refrigeration system based on forward and reverse cycle coupling provided by the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

As shown in FIG. 1 , FIG. 1 is a schematic diagram of an embodiment of a cascade refrigeration system based on forward and reverse cycle coupling provided by the present invention. Among them, S1 to S21 represent circulating working fluids. S22 and S23 represent heat source media. The system includes a power sub-cycle, an absorption refrigeration sub-cycle and a compression refrigeration sub-cycle. The work done drives the compression refrigeration sub-cycle to refrigerate. The absorption refrigeration sub-cycle and the compression refrigeration sub-cycle constitute a cascade refrigeration system. The absorption refrigeration sub-cycle works in the high temperature area, and the compression refrigeration sub-cycle works in the low temperature area; The evaporative refrigeration process of the absorption refrigeration sub-cycle in the low-temperature zone provides cooling load for the condensation process of the compression refrigeration sub-cycle in the low-temperature zone, and the two are combined through the evaporator-condenser. The energy input of the cascade refrigeration system is medium and low temperature external heat source of industrial waste heat, solar energy or geothermal heat, and the product output is low temperature cooling capacity.

Referring to Fig. 1, the power subcycle includes a high-pressure solution pump 1, a steam generator 2, an expander 3, a reboiler 4 and a first condenser 5 connected in sequence in a loop, wherein the solution S1 from the first condenser 5 After being pressurized by the high-pressure pump 1, S2 is formed, enters the steam generator 2, is heated by an external heat source to form superheated steam S3, and then enters the expander 3 to expand and work, and the exhaust gas S4 of the expander 3 enters the reboiler 4 and the first condensation in turn The device 5 uses the high-temperature part of the condensation heat for the heating process of the solution in the absorption refrigeration sub-cycle, and discharges the low-temperature part of the condensation heat to the environment.

Among them, the high-pressure solution pump 1 is a liquid pressurization device for increasing the liquid pressure; the steam generator 2 and the reboiler 4 are fluid heat exchange devices for heat exchange between hot and cold streams; the expander 3 is Gas expansion work equipment, the expander 3 uses high temperature and high pressure steam to expand and work; the first condenser 5 is a condensation device, used to condense the power cycle working medium steam, and the condensation heat is discharged to the environment through the cooling medium.

Referring to Fig. 1, the absorption refrigeration sub-cycle includes absorber 6, low-pressure solution pump 7, solution heat exchanger 8, rectification column 9, second condenser 10, subcooler 11, ammonia throttle valve 12, evaporation-condensation Device 13 and solution throttling valve 14, wherein: the strong solution S6 from absorber 6 enters rectifying tower 9 after the low-pressure solution pump 7 pressurization, solution heat exchanger 8 preheats, is separated into high-purity tower top ammonia vapor S12 and low-concentration dilute solution S9 in the tower kettle; the dilute solution S9 in the tower kettle first passes through the solution heat exchanger 8 for heat recovery and then throttling and reducing pressure through the solution throttle valve 14, and the formed low-pressure dilute solution S11 enters the absorber 6; The top ammonia vapor S12 enters the second condenser 10 to be condensed into liquid ammonia S13 and then enters the subcooler 11 to exchange heat with the low-temperature ammonia vapor S16 from the evaporator-condenser 13 to form liquid ammonia S14 with a certain degree of supercooling , enter the evaporator-condenser 13 to evaporate after throttling and reducing the pressure of the ammonia throttle valve 12, and the formed low-temperature and low-pressure ammonia vapor S16 is recovered in the subcooler 11 and then enters the absorber 6 to be absorbed by the dilute solution S11 and re- Concentrated solution S6 is formed.

Among them, the absorber 6 is a gas-liquid mixed absorption equipment, which uses an absorbent to absorb refrigerant vapor, and the heat released during the absorption process is discharged to the environment through the cooling medium; the low-pressure solution pump 7 is a liquid pressurization device, which is used to increase the liquid pressure; the solution exchange The heater 8 and the subcooler 11 are fluid heat exchange equipment for heat exchange between hot and cold streams; the rectification tower 9 is used to realize the separation and purification of mixed working fluids to produce high-purity refrigerants steam and low-concentration absorbent solution; the second condenser 10 is a condensing device for condensing the refrigerant vapor, and the condensed heat is discharged to the environment through the cooling medium; the ammonia throttling valve 12 and the solution throttling valve 14 are liquid The throttling and pressure-reducing device is respectively used to reduce the pressure of the refrigerant ammonia in the high-temperature zone and the tower kettle solution; the evaporator-condenser 13 is the combination point of the absorption refrigeration sub-cycle and the compression refrigeration sub-cycle, and is used to refrigerate the high-temperature zone. The refrigerant absorbs heat and evaporates in it to condense the refrigerant vapor in the low temperature region.

With reference to Fig. 1, described compression refrigeration sub-cycle comprises compressor 15, _CO Throttle valve 16, _CO Evaporator 17 and evaporation-condenser 13, wherein: compressor 15 is driven by the expander 3 of power sub-cycle Compress the low-pressure refrigerant vapor S21 to form high-pressure refrigerant vapor S18, which enters the evaporator-condenser 13 and condenses into liquid refrigerant CO ₂ , and the heat of condensation in this process is absorbed by the ammonia refrigerant in the absorption refrigeration sub-cycle; the resulting The liquid CO ₂ enters the CO ₂ evaporator 17 for evaporation and refrigeration after being throttled and depressurized by the CO ₂ belt flow valve 16, and the obtained low-temperature cooling capacity is the product output of the cascade refrigeration system.

Wherein, the compressor 15 is a gas pressurizing device for compressing the low-pressure refrigerant vapor to a high-pressure state, the compressor 15 is connected to the expander 3 through a coupling, and the compression work consumed by the compressor 15 is provided by the expander 3; The _CO2 throttle valve 16 is a liquid throttling and pressure-reducing device, which is used to reduce the pressure of the refrigerant _CO2 in the low-temperature zone; the _CO2 evaporator 17 is the refrigeration component of the cascade refrigeration system, and is used to reduce the pressure of the refrigerant in the low-temperature zone. Wherein heat absorption is evaporated to obtain low-temperature cooling capacity; the evaporation-condenser 13 is shared with the absorption refrigeration sub-cycle.

Referring to Fig. 1 again, the outlet of the high-pressure solution pump 1 is connected to the steam generator 2, the expander 3, the reboiler 4 and the first condenser 5 in sequence; the outlet of the absorber 6 is connected to the low-pressure solution pump 7 and the solution heat exchanger 8 in sequence Connect with rectification tower 9, the outlet of solution at the bottom of rectification tower 9 is connected with reboiler 4, solution heat exchanger 8, solution throttling valve 14 and absorber 6 successively, the tower top steam outlet of rectification tower 9 Connect with the second condenser 10, subcooler 11, throttle valve 12 and evaporator-condenser 13 in turn, the evaporator-condenser 13 is connected with the subcooler 11, and the subcooler 11 is connected with the absorber 6; The compressor 15 is connected to the expander 3 through a coupling, and the high-pressure vapor outlet of the compressor 15 is connected to the evaporator-condenser 13 , the _CO2 throttle valve 16 and the _CO2 evaporator 17 in sequence.

The high-pressure solution pump 1 and the low-pressure solution pump 7 are liquid pressurizing devices for increasing the pressure of the liquid. The steam generator 2, the reboiler 4, the solution heat exchanger 8 and the subcooler 11 are fluid heat exchange equipment for heat exchange between cold and hot streams. The expander 3 and the compressor 15 are gas expansion work and gas pressurization equipment respectively. The expander 3 utilizes the high-temperature and high-pressure vapor to expand and perform work, and the compressor 15 consumes the work generated by the expander 3 to compress the low-pressure refrigerant vapor to a high-pressure state. The first condenser 5 and the second condenser 10 are condensing devices, which are respectively used to condense the power cycle working medium vapor and the refrigerant vapor in the absorption refrigeration sub-cycle, and the condensation heat is discharged to the environment through the cooling medium. The absorber 6 is a gas-liquid mixed absorption device, which uses an absorbent to absorb refrigerant vapor, and the heat released during the absorption process is discharged to the environment through the cooling medium. The rectification column 9 is used to realize the separation and purification of the mixed working medium to produce high-purity refrigerant vapor and low-concentration absorbent solution. Ammonia throttle valve 12, solution throttle valve 14 and _CO2 throttle valve 16 are liquid throttling and pressure-reducing devices, which are respectively used to depressurize refrigerant ammonia in the high temperature zone, tower kettle solution and _CO2 refrigerant in the low temperature zone. The evaporator-condenser 13 is the combination point of the two refrigeration sub-cycles, and is used to absorb heat and evaporate the refrigerant in the high-temperature region so that the refrigerant vapor in the low-temperature region can condense. The CO ₂ evaporator 17 is the refrigeration component of the cascade refrigeration system, and is used to absorb heat and evaporate the refrigerant in the low-temperature region to obtain low-temperature refrigeration.

The cascade refrigeration system is driven by a medium and low temperature heat source, which can be industrial waste heat, solar energy or geothermal heat. In the cascade refrigeration system, the working medium used in the power subcycle and the absorption refrigeration subcycle can be ammonia and water working medium, but not limited to ammonia and water working medium, and can also be other working medium pairs; The working medium used in the compression refrigeration sub-cycle can be CO ₂ , but is not limited to CO ₂ , and can also be other working fluids.

The specific working process of the cascade refrigeration system is:

In the power subcycle, the solution S1 from the first condenser 5 is pressurized by the high-pressure pump 1 to form S2, enters the steam generator 2, is heated by an external heat source to form superheated steam S3, and then enters the expander 3 to expand and perform work. The exhaust gas S4 enters the reboiler 4 and the first condenser 5 sequentially, and the high-temperature part of the condensation heat is used in the heating process of the solution in the absorption refrigeration sub-cycle in turn, and the low-temperature part of the condensation heat is discharged to the environment.

In the absorption refrigeration sub-cycle, the concentrated solution S6 from the absorber 6 is pressurized by the low-pressure solution pump 7 and preheated by the solution heat exchanger 8, and then enters the rectification tower 9, where it is separated into high-purity overhead ammonia vapor S12 and low-concentration ammonia vapor S12. dilute solution S9 in the tower kettle; the dilute solution S9 in the tower kettle first passes through the solution heat exchanger 8 for heat recovery and then throttling and reducing the pressure through the solution throttle valve 14, and the formed low-pressure dilute solution S11 enters the absorber 6; the ammonia vapor at the top of the tower S12 enters the second condenser 10 to condense into liquid ammonia S13 and then enters the subcooler 11. After exchanging heat with the low-temperature ammonia vapor S16 from the evaporator-condenser 13, it forms liquid ammonia S14 with a certain degree of subcooling, and passes through the ammonia section. Throttle valve 12 throttles down and enters evaporator-condenser 13 for evaporation, and the formed low-temperature and low-pressure ammonia vapor S16 is recovered in subcooler 11 and then enters absorber 6 to be absorbed by dilute solution S11 to re-form concentrated solution S6 .

In the compression refrigeration sub-cycle, the compressor 15 is driven by the expander 3 of the power sub-cycle to compress the low-pressure refrigerant vapor S21 to form a high-pressure refrigerant vapor S18, which enters the evaporator-condenser 13 and condenses into liquid refrigerant CO ₂ , the heat of condensation in this process is absorbed by the ammonia refrigerant in the absorption refrigeration sub-cycle; the obtained liquid CO ₂ is throttled and depressurized by the CO ₂ throttle valve 16 and then enters the CO ₂ evaporator 17 for evaporation and refrigeration, and the obtained low-temperature refrigeration The quantity is the product output of the cascade refrigeration system. The compression work consumed by the compressor 15 in the compression refrigeration sub-cycle working in the low temperature region is provided by the expander 3 of the power sub-cycle. The whole system only has medium and low temperature external heat source input, and no input work is required.

Based on the cascade refrigeration system based on forward and reverse cycle coupling shown in FIG. 1 , the present invention also provides a cascade refrigeration method based on forward and reverse cycle coupling, using medium and low temperature waste heat or solar energy as the driving heat source. In the method, a medium-low temperature heat source is used to drive a power sub-cycle to do work, heat rejection of the power sub-cycle drives an absorption refrigeration sub-cycle to refrigerate, and the work done by the power sub-cycle drives a compression-type refrigeration sub-cycle to refrigerate. The absorption refrigeration sub-cycle and the compression refrigeration cycle constitute a cascaded refrigeration system, the absorption refrigeration sub-cycle works in the high-temperature zone, and the compression refrigeration sub-cycle works in the low-temperature zone; the evaporation of the absorption refrigeration sub-cycle in the high-temperature zone The refrigeration process provides the cooling load for the condensation process of the compression refrigeration sub-cycle in the low temperature zone, and the two are combined through the evaporation-condenser. The energy input of the whole system is a medium and low temperature external heat source including waste heat, solar energy or geothermal heat, and the product output is low temperature cooling capacity.

AspenPlus software is used to carry out the simulation calculation of this embodiment. In the simulation, it is assumed that the cooling water temperature is 30°C, the evaporation temperature of liquid ammonia in the absorption refrigeration sub-cycle is -15°C; the heat transfer temperature difference in the evaporator-condenser is 5°C, that is, the CO ₂ condensation temperature in the CO ₂ compression refrigeration sub-cycle It is about -10°C (pressure is 27bar); the refrigeration evaporation temperature in the CO ₂ evaporator is about -63°C (pressure is 3.7bar). Under this pressure ratio condition, the CO ₂ compressor efficiency is 60.6%. The loads of main components of the system and system performance parameters under basic working conditions are shown in Table 1.

project data Heat source temperature, ℃ 350 Flue gas flow, kg/h 3000 Heat source heat, kW 275.5 Cooling medium temperature, ℃ 30 Ammonia evaporation temperature, ℃ -15 _CO2 evaporation temperature, °C -63 Concentration of working fluid ammonia in the power subcycle 0.3 Absorption Refrigeration Subcycle Concentrated Solution Ammonia Concentration 0.37 Steam generator load, kW 159.1 Smoke loss, kW 116.4 Work capacity of expander, kW 24.1 Pump power consumption, kW 2.1 Compressor power consumption, kW twenty two Reboiler load, kw 100.3 First condenser load, kW 35.4 Solution heat exchanger load, kW 153.7 Second condenser load, kw 59.1 Subcooler load, kw 7.3 Evaporator-condenser load, kW 57.9 Absorber load, kw 87.3 _CO2 evaporator load, kW 35.8 Cooling capacity (-63°C), kW 35.8 Compression refrigeration part COP _C 1.63 Overall system COP 0.23 The overall thermal efficiency of the system, % 13

Table 1

Table 1 shows the main component load and system performance parameters of the cascade refrigeration system based on forward and reverse cycle coupling under the basic working conditions.

It can be seen from Table 1 that when the input heat source temperature, cooling water temperature and final refrigeration temperature are 350°C, 30°C and -63°C respectively, the heat contained in the input heat source is 275.5kW, and the ammonia water working medium concentration and When the concentration of the concentrated solution in the absorption refrigeration sub-cycle is 0.3 and 0.37, the exhaust gas temperature of the system is 167.1°C, the heat absorbed by the steam generator is 159.1kW, and the cooling capacity at -63°C is 35.8kW. The power consumption of the compressor in the compression refrigeration sub-cycle is 22kW, the COP _C of the compression refrigeration part is 1.63, and the COP of the overall cascade refrigeration system is 0.23; if the smoke exhaust loss (116.4kW) is considered, the overall thermal efficiency of the system is 13 %. The method does not require additional consumption of work, and only needs to consume medium and low temperature heat to produce cold energy at a lower temperature.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. the folding type cooling system based on just inverse circulation coupling, it is characterized in that, this system comprises power subcycle, absorption refrigeration subcycle and compression-type refrigeration subcycle, wherein in the employing of this system, low-temperature heat source drives power subcycle work done, the heat extraction of power subcycle drives absorption refrigeration subcycle refrigeration, power subcycle institute work drives compression-type refrigeration subcycle refrigeration, absorption refrigeration subcycle and compression-type refrigeration subcycle form folding type cooling system, absorption refrigeration subcycle works in high-temperature region, compression-type refrigeration subcycle works in low-temperature space, the condensation process of the compression-type refrigeration subcycle that the sweat cooling process of the absorption refrigeration subcycle of high-temperature region is low-temperature space provides cooling load, and the two is combined by evaporator-condenser.

2. the folding type cooling system based on just inverse circulation coupling according to claim 1, it is characterized in that, described power subcycle comprises the high-pressure solution pump (1) being in turn connected into loop, steam generator (2), decompressor (3), reboiler (4) and the first condenser (5), wherein, solution S 1 from the first condenser (5) forms S2 after high-pressure solution pump (1) pressurization, enter in steam generator (2), decompressor (3) expansion working is entered after being added thermosetting superheated vapor S3 by external heat source, decompressor (3) exhaust S4 enters reboiler (4) and the first condenser (5) successively, the high-temperature part of condensation heat is used for the heating process of solution in absorption refrigeration subcycle, the low temperature part of condensation heat is discharged to environment.

3. the folding type cooling system based on just inverse circulation coupling according to claim 2, is characterized in that,

Described high-pressure solution pump (1) is liquid pressing equipment, for improving fluid pressure;

Described steam generator (2) and described reboiler (4) are fluid heat transfer equipment, for the exchange heat between cold and hot logistics;

Described decompressor (3) is gas expansion work done equipment, and decompressor (3) utilizes high pressure high temperature vapor expansion working;

Described first condenser (5) is condensing plant, for power cycle refrigerant vapor is carried out condensation, condensation heat release by cooling medium discharged to environment.

4. the folding type cooling system based on just inverse circulation coupling according to claim 1, it is characterized in that, described absorption refrigeration subcycle comprises absorber (6), hypotonic solution pump (7), solution heat exchanger (8), rectifying column (9), the second condenser (10), subcooler (11), ammonia choke valve (12), evaporator-condenser (13) and solution choke valve (14), wherein:

Concentrated solution S6 from absorber (6) enters rectifying column (9) after hypotonic solution pump (7) pressurization, solution heat exchanger (8) preheating, is separated into the tower reactor weak solution S9 of highly purified tower top ammonia steam S12 and low concentration;

Tower reactor weak solution S9 first carries out again through solution choke valve (14) reducing pressure by regulating flow after heat recovery through solution heat exchanger (8), and the low pressure weak solution S11 of formation enters absorber (6);

Tower top ammonia steam S12 enters subcooler (11) after entering and being condensed into liquefied ammonia S13 in the second condenser (10), with from after the low temperature ammonia steam S16 heat exchange of evaporator-condenser (13), form the liquefied ammonia S14 with certain degree of supercooling, evaporator-condenser (13) evaporation is entered after ammonia choke valve (12) reducing pressure by regulating flow, absorber (6) is entered after the low-temp low-pressure ammonia steam S16 formed carries out cold recovery in subcooler (11), absorbed by weak solution S11, again form concentrated solution S6.

5. the folding type cooling system based on just inverse circulation coupling according to claim 4, is characterized in that,

Described absorber (6) is gas-liquid mixed absorption equipment, adopts absorbent absorption refrigeration agent steam, absorption process institute thermal discharge by cooling medium discharged to environment;

Described hypotonic solution pump (7) is liquid pressing equipment, for improving fluid pressure;

Described solution heat exchanger (8) and described subcooler (11) are fluid heat transfer equipment, for the exchange heat between cold and hot logistics;

Described rectifying column (9) for realizing the Separation & Purification of mixed working fluid, with the absorbent solution of obtained highly purified refrigerant vapour and low concentration;

Described second condenser (10) is condensing plant, for refrigerant vapour is carried out condensation, condensation heat release by cooling medium discharged to environment;

Described ammonia choke valve (12) and solution choke valve (14) are liquid throttling dropping equipments, are respectively used to the step-down realizing high-temperature region cold-producing medium ammonia and tower reactor solution;

Described evaporator-condenser (13) is the binding site of absorption refrigeration subcycle and compression-type refrigeration subcycle, for evaporation of being absorbed heat wherein by high-temperature region cold-producing medium, to make the condensation of low-temperature space refrigerant vapour.

6. the folding type cooling system based on just inverse circulation coupling according to claim 1, it is characterized in that, described compression-type refrigeration subcycle comprises compressor (15), CO ₂choke valve (16), CO ₂evaporimeter (17) and evaporator-condenser (13), wherein:

Compressor (15) compresses low-pressure refrigerant vapor S21 under the driving of the decompressor (3) of power subcycle, is formed after high-pressure refrigerant vapor S18, S18 enter evaporator-condenser (13) and is condensed into liquid refrigerant CO ₂, the condensation heat of this process is absorbed by the ammonia refrigerant in absorption refrigeration subcycle; The liquid CO of gained ₂through CO ₂cO is entered after choke valve (16) reducing pressure by regulating flow ₂evaporimeter (17) sweat cooling, the low temperature cold obtained is the output of products of this folding type cooling system.

7. the folding type cooling system based on just inverse circulation coupling according to claim 6, is characterized in that,

Described compressor (15) is gas pressurized equipment, for low-pressure refrigerant vapor compression is reached high pressure conditions, compressor (15) is connected by shaft coupling with decompressor (3), and the work done during compression that compressor (15) consumes is provided by decompressor (3);

Described CO ₂choke valve (16) is liquid throttling dropping equipment, for realizing low-temperature space cold-producing medium CO ₂step-down;

Described CO ₂evaporimeter (17) is the refrigeration part of this cascade refrigeration system, for evaporation of being absorbed heat wherein by low-temperature space cold-producing medium, with obtained low temperature cold;

Described evaporator-condenser (13) shares with described absorption refrigeration subcycle.

8. the folding type cooling system based on just inverse circulation coupling according to claim 1, it is characterized in that, the energy of this folding type cooling system is input as the middle low temperature external heat source of industrial exhaust heat, solar energy or underground heat, and output of products is low temperature cold.

9. the cascade refrigeration method based on just inverse circulation coupling, be applied to the folding type cooling system according to any one of claim 1 to 8, it is characterized in that, during the method adopts, low-temperature heat source drives power subcycle work done, the heat extraction of power subcycle drives absorption refrigeration subcycle refrigeration, and power subcycle institute work drives compression-type refrigeration subcycle to freeze again.

10. the cascade refrigeration method based on just inverse circulation coupling according to claim 9, it is characterized in that, described absorption refrigeration subcycle and described compression-type refrigeration subcycle form folding type cooling system, absorption refrigeration subcycle works in high-temperature region, and compression-type refrigeration subcycle works in low-temperature space; The condensation process of the compression-type refrigeration subcycle that the sweat cooling process of the absorption refrigeration subcycle of high-temperature region is low-temperature space provides cooling load, and the two is combined by evaporator-condenser.