Carbon dioxide cascade refrigeration system with cold carrying loop

Abstract

The utility model discloses a carbon dioxide cascade refrigeration system with a cold carrying loop, which comprises a carbon dioxide refrigeration cycle, an ammonia refrigeration cycle and a carbon dioxide secondary refrigerant cycle, the carbon dioxide refrigeration cycle and the carbon dioxide secondary refrigerant cycle are connected through an evaporative condenser, the carbon dioxide refrigeration cycle comprises a first compressor, a first intercooler, a second compressor and a second intercooler, and the ammonia refrigeration cycle comprises an ammonia storage tank, an ammonia compressor, an ammonia side intercooler and an ammonia side condenser. And the carbon dioxide secondary refrigerant circulation comprises a secondary refrigerant storage tank, a circulating pump, a carbon dioxide air cooler and a carbon dioxide ejector. Buffering components such as the intercooler and the bypass pipeline are added to balance the running temperature and pressure of the system and guarantee the running stability of the system, the drainage ejector is introduced into cold-carrying circulation, the local working medium flow speed is increased, a low-pressure area is formed, the evaporation temperature is further reduced, and the heat exchange efficiency is improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to refrigeration technical field, concretely relates to a carbon dioxide cascade refrigeration system with load cooling loop. BACKGROUND

[0002] With the data center construction development iteration speed accelerates, the cabinet power is increasing, and further requirements are put forward to the refrigeration system. According to the scene needs, cascade system can realize lower refrigeration temperature. The conventional cascade system uses freon and other non-environmentally friendly working medium, which cannot adapt to the requirements of the times, and the system organization lacks buffer components, which is easy to cause system operation instability, affect system operation stability and further cause energy waste.

[0003] Therefore, a carbon dioxide cascade refrigeration system with reasonable design is needed, which can effectively exert the low-temperature advantage of the cascade system, fully consider the buffer system design, and further reduce the system energy consumption by using the load cooling loop design. UTILITY MODEL CONTENTS

[0004] The utility model solves the technical problems in the prior art, provides a carbon dioxide cascade refrigeration system with load cooling loop, which uses natural working medium carbon dioxide and ammonia as circulating working medium, has great development potential and strong environmental friendliness. The intercooler, bypass pipeline and other buffer components are added to balance the system operating temperature and pressure and ensure the system operation stability. The cascade system is used, and the refrigeration temperature range is better than that of a single system. The load cooling cycle is introduced, and carbon dioxide is used as the load cooling working medium, which has low viscosity, large load cooling capacity and is suitable for cold heat transfer under low-temperature conditions, and can further improve the system refrigeration performance. The flow injector is introduced in the load cooling cycle to increase the local working fluid flow rate, form a low-pressure area, further reduce the evaporation temperature and enhance the heat exchange efficiency.

[0005] To solve the above technical problems, the utility model adopts the technical scheme of a carbon dioxide cascade refrigeration system with load cooling loop, characterized by comprising carbon dioxide refrigeration cycle, ammonia refrigeration cycle and carbon dioxide load coolant cycle, the carbon dioxide refrigeration cycle is connected with the ammonia refrigeration cycle through a condenser-evaporator, and the carbon dioxide refrigeration cycle is connected with the carbon dioxide load coolant cycle through an evaporative condenser.

[0006] The carbon dioxide refrigeration cycle comprises a first compressor, a first intercooler, a second compressor and a second intercooler, the inlet of the first intercooler is connected to the outlet of the first compressor, the outlet of the first intercooler is connected to the inlet of the second compressor, the outlet of the second compressor is connected to the inlet of the second intercooler, the outlet of the second intercooler is connected to the carbon dioxide inlet of the condenser evaporator, the carbon dioxide outlet of the condenser evaporator is connected to the carbon dioxide inlet of the evaporative condenser, the carbon dioxide outlet of the evaporative condenser is connected to the carbon dioxide inlet of the carbon dioxide storage tank, and the carbon dioxide inlet of the carbon dioxide storage tank is connected to the inlet of the first compressor.

[0007] The ammonia refrigeration cycle comprises an ammonia storage tank, an ammonia compressor, an ammonia-side intercooler and an ammonia-side condenser, the outlet of the ammonia storage tank is connected to the inlet of the ammonia compressor, the outlet of the ammonia compressor is connected to the inlet of the ammonia-side intercooler, the outlet of the ammonia-side intercooler is connected to the inlet of the ammonia-side condenser, the outlet of the ammonia-side condenser is connected to the ammonia inlet of the condenser evaporator, and the ammonia inlet of the condenser evaporator is connected to the ammonia outlet of the condenser evaporator.

[0008] The carbon dioxide refrigerant cycle comprises a refrigerant storage tank, a circulating pump, a carbon dioxide cooling fan and a carbon dioxide ejector, the inlet of the refrigerant storage tank is connected to the refrigerant outlet of the refrigerant storage tank, the outlet of the refrigerant storage tank is connected to the inlet of the circulating pump, the outlet of the circulating pump is connected to the inlet of the carbon dioxide cooling fan, the outlet of the carbon dioxide cooling fan is connected to the inlet of the carbon dioxide ejector, and the outlet of the carbon dioxide ejector is connected to the carbon dioxide inlet of the evaporative condenser.

[0009] The carbon dioxide cascade refrigeration system with a refrigerant loop, wherein an expander is connected between the carbon dioxide outlet of the condenser evaporator and the carbon dioxide inlet of the evaporative condenser.

[0010] The carbon dioxide cascade refrigeration system with a refrigerant loop, wherein a bypass electromagnetic valve is connected between the expander and the evaporative condenser, and a carbon dioxide bypass branch is connected to the bypass electromagnetic valve.

[0011] The carbon dioxide cascade refrigeration system with a refrigerant loop, wherein the outlet of the first compressor is connected to the inlet of the first intercooler and a carbon dioxide bypass branch through a hot gas bypass valve, and the first compressor is connected to the carbon dioxide inlet of the evaporative condenser through the hot gas bypass valve, the carbon dioxide bypass branch and the bypass electromagnetic valve.

[0012] The carbon dioxide cascade refrigeration system with a refrigerant loop, wherein an ammonia-side electromagnetic bypass valve is connected between the outlet of the ammonia compressor and the inlet of the ammonia-side intercooler, an ammonia-side bypass branch is connected to the ammonia-side electromagnetic bypass valve, and the ammonia-side bypass branch is connected to the ammonia inlet of the condenser evaporator.

[0013] The carbon dioxide cascade refrigeration system with a load cooling loop has the feature that the ammonia inlet of the condenser-evaporator is connected to the outlet of the ammonia bypass branch and the outlet of the ammonia condenser through a throttle valve.

[0014] The carbon dioxide cascade refrigeration system with a load cooling loop has the feature that a drying filter is connected between the carbon dioxide outlet of the evaporative condenser and the inlet of the carbon dioxide storage tank.

[0015] Compared with the prior art, the utility model has the following advantages:

[0016] 1. The first intercooler is connected to the outlet of the first compressor, the second intercooler is connected to the outlet of the second compressor, and the ammonia intercooler is connected to the outlet of the ammonia compressor, so that the intercoolers can be used as buffer components to reduce the temperature and pressure of the refrigeration working medium discharged by the compressors and improve the system efficiency and stability.

[0017] 2. The first compressor, the first intercooler, the second compressor, and the second intercooler are combined together, so that the bipolar intercooling compression action can be performed, the compression process tends to be adiabatic, the system compression energy consumption can be effectively reduced, and the system COP can be improved by more than 10% compared with single-compressor compression.

[0018] 3. The carbon dioxide cold air fan is arranged in the carbon dioxide load refrigerant cycle, the carbon dioxide cold air fan can introduce an auxiliary heat exchange branch, that is, an external heat source is used to assist heat exchange, and the energy consumption level is reduced.

[0019] 4. The carbon dioxide ejector is arranged in the carbon dioxide load refrigerant cycle to inject and spray the working medium generated by the carbon dioxide cold air fan, increase the local working medium flow rate, further form a low-pressure area in the rear end area, assist the carbon dioxide refrigeration cycle to do work, further reduce the evaporation temperature, and enhance the heat exchange efficiency.

[0020] In summary, the utility model uses natural working medium carbon dioxide and ammonia as the circulating working medium, has great development potential and strong environmental friendliness, adds the intercooler and the bypass pipeline and other buffer components to balance the system operating temperature and pressure and ensure the system operating stability, adopts the cascade system to have a better refrigeration temperature range than a single system, introduces the load cooling cycle and uses carbon dioxide as the load refrigerant, the viscosity of carbon dioxide is low, the load cooling capacity is large, the carbon dioxide is suitable for cold and heat transmission under a low-temperature state, and the system refrigeration performance can be further improved, the flow injector is introduced in the load cooling cycle to increase the local working medium flow rate, form a low-pressure area, further reduce the evaporation temperature, and enhance the heat exchange efficiency.

[0021] The technical scheme of the utility model will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the structural schematic diagram of the utility model.

[0023] BRIEF DESCRIPTION OF DRAWINGS

[0024] 1 - first compressor; 2 - first intercooler; 3 - second compressor;

[0025] 4 - second intercooler; 5 - condensing evaporator; 6 - expander;

[0026] 7 - bypass solenoid valve; 8 - hot gas bypass valve; 9 - evaporative condenser;

[0027] 10 - drying filter; 11 - carbon dioxide storage tank; 12 - circulating pump;

[0028] 13 - carbon dioxide ejector; 14 - carbon dioxide cold air machine; 15 - ammonia storage tank;

[0029] 16 - ammonia compressor; 17 - ammonia side electromagnetic bypass valve; 18 - ammonia side intercooler;

[0030] 19 - ammonia side condenser; 20 - throttle valve; 21 - ammonia side bypass branch;

[0031] 22 - carbon dioxide bypass branch; 23 - coolant storage tank. DETAILED DESCRIPTION

[0032] As Figure 1 shown, the utility model includes carbon dioxide refrigeration cycle, ammonia refrigeration cycle and carbon dioxide coolant cycle, the carbon dioxide refrigeration cycle the ammonia refrigeration cycle is connected through condensing evaporator 5 between, the carbon dioxide refrigeration cycle with the carbon dioxide coolant cycle is connected through evaporative condenser 9 between;

[0033] The carbon dioxide refrigeration cycle includes first compressor 1, first intercooler 2, second compressor 3 and second intercooler 4, the import of first intercooler 2 is connected at the export of first compressor 1, the export of first intercooler 2 is connected the import of second compressor 3, the export of second compressor 3 is connected the import of second intercooler 4, the export of second intercooler 4 is connected the carbon dioxide import of condensing evaporator 5, the carbon dioxide export of condensing evaporator 5 is connected the carbon dioxide import of evaporative condenser 9, the carbon dioxide import of evaporative condenser 9 is connected the import of carbon dioxide storage tank 11, the import of carbon dioxide storage tank 11 is connected the import of first compressor 1;

[0034] The ammonia refrigeration cycle comprises an ammonia storage tank 15, an ammonia compressor 16, an ammonia intercooler 18 and an ammonia condenser 19, the outlet of the ammonia storage tank 15 is connected to the inlet of the ammonia compressor 16, the outlet of the ammonia compressor 16 is connected to the inlet of the ammonia intercooler 18, the outlet of the ammonia intercooler 18 is connected to the inlet of the ammonia condenser 19, the outlet of the ammonia condenser 19 is connected to the ammonia inlet of the condensing evaporator 5, and the ammonia outlet of the condensing evaporator 5 is connected to the inlet of the ammonia storage tank 15;

[0035] The carbon dioxide coolant cycle comprises a coolant storage tank 23, a circulating pump 12, a carbon dioxide cooling fan 14 and a carbon dioxide ejector 13, the inlet of the coolant storage tank 23 is connected to the coolant outlet of the coolant storage tank 23, the outlet of the coolant storage tank 23 is connected to the inlet of the circulating pump 12, the outlet of the circulating pump 12 is connected to the inlet of the carbon dioxide cooling fan 14, the outlet of the carbon dioxide cooling fan 14 is connected to the inlet of the carbon dioxide ejector 13, and the outlet of the carbon dioxide ejector 13 is connected to the carbon dioxide inlet of the evaporative condenser 9.

[0036] In actual use, by connecting the first intercooler 2 to the outlet of the first compressor 1, connecting the second intercooler 4 to the outlet of the second compressor 3, and connecting the ammonia intercooler 18 to the outlet of the ammonia compressor 16, the intercoolers can be used as buffer components to reduce the temperature and pressure of the refrigerant discharged by the compressors, thereby improving the efficiency and stability of the system.

[0037] In specific implementation, by combining the first compressor 1, the first intercooler 2, the second compressor 3 and the second intercooler 4 together, a bipolar intercooling compression action can be performed, which is conducive to the adiabatic compression process and can effectively reduce the system compression energy consumption, and the system COP can be increased by more than 10% compared with single compressor compression.

[0038] In particular, by providing the carbon dioxide cooling fan 14 in the carbon dioxide coolant cycle, the carbon dioxide cooling fan 14 can introduce an auxiliary heat exchange branch, i.e., auxiliary heat exchange using an external heat source, to reduce its energy consumption level.

[0039] In addition, by providing the carbon dioxide ejector 13 in the carbon dioxide coolant cycle, the working medium generated by the carbon dioxide cooling fan 14 is injected and ejected, the local working medium flow rate is increased to more than 600 meters per second, a low pressure area is further formed in the rear end area, the carbon dioxide refrigeration cycle is assisted to work, the evaporation temperature is further reduced, and the heat exchange efficiency is enhanced.

[0040] It should be noted that the carbon dioxide refrigeration cycle is used as a low-temperature section cycle, the ammonia side refrigeration cycle is used as a high-temperature section cycle, and the two are connected through the condensing evaporator 5; wherein the low-temperature section heat is transferred to the high-temperature section through the condensing evaporator 5, forming a cascade system heat transfer; the condensing evaporator 5 is regarded as a condenser in the carbon dioxide refrigeration cycle and as an evaporator in the ammonia side refrigeration cycle.

[0041] In specific implementation, the first compressor 1, the second compressor 3 and the ammonia compressor 16 are all magnetic suspension oil-free variable frequency centrifugal compressors, which are oil-free designed, solve the problem of oil film thermal resistance of lubricating oil, improve the heat exchange efficiency of the two devices, do not need to replace the lubricating oil regularly, reduce the maintenance cost, and do not need to consider the oil return problem of the compressor, simplifying the system pipeline design.

[0042] In the embodiment, the carbon dioxide outlet of the condensing evaporator 5 is connected with the carbon dioxide inlet of the evaporative condenser 9 through an expander 6.

[0043] In actual use, the system using carbon dioxide as the circulating working medium can recover more expansion work by using the expander 6 instead of the throttling valve, and the system COP can be improved by more than 20% by setting the expander 6 instead of the throttling valve.

[0044] In the embodiment, the expander 6 is connected with the evaporative condenser 9 through a bypass electromagnetic valve 7, and the bypass electromagnetic valve 7 is connected with a carbon dioxide bypass branch 22.

[0045] In the embodiment, the outlet of the first compressor 1 is connected with the inlet of the first intercooler 2 and the carbon dioxide bypass branch 22 through a hot gas bypass valve 8, and the first compressor 1 is connected with the carbon dioxide inlet of the evaporative condenser 9 through the hot gas bypass valve 8, the carbon dioxide bypass branch 22 and the bypass electromagnetic valve 7.

[0046] In actual use, the carbon dioxide bypass branch 22 is used as a hot gas defrosting branch, and the high-temperature and high-pressure working medium at the outlet of the first compressor 1 is introduced into the carbon dioxide inlet of the evaporative condenser 9, so as to effectively adjust the working medium temperature and pressure range at the inlet end of the evaporative condenser 9, ensure that the system gas return pressure meets the standard, and avoid the condensation and frosting of the evaporator pipe section, thereby ensuring the stable operation of the equipment.

[0047] In the embodiment, the outlet of the ammonia compressor 16 is connected with the inlet of the ammonia side intercooler 18 through an ammonia side electromagnetic bypass valve 17, the ammonia side electromagnetic bypass valve 17 is connected with an ammonia side bypass branch 21, and the ammonia side bypass branch 21 is connected with the ammonia inlet of the condensing evaporator 5.

[0048] In actual use, the ammonia bypass branch 21 is used as a hot gas defrosting branch, and the ammonia working medium at the outlet of the ammonia compressor 16 is introduced into the ammonia inlet of the condensing evaporator 5, so that the temperature and pressure range of the working medium at the inlet of the condensing evaporator 5 is effectively adjusted, the system back pressure is ensured to meet the standard, and the condensing evaporator 5 is prevented from condensing and frosting, so that the equipment is stably operated.

[0049] In the embodiment, the ammonia inlet of the condensing evaporator 5 is connected to the outlet of the ammonia bypass branch 21 and the outlet of the ammonia condenser 19 through the throttle valve 20.

[0050] In actual use, the ammonia condenser 19 can release waste heat through natural heat release or the like, and the ammonia working medium after condensing and heat release enters the throttle valve 20 and then enters the condensing evaporator 5, so that the heat exchange process with the carbon dioxide refrigeration cycle is realized, and finally the ammonia working medium returns to the ammonia storage tank 15, and the ammonia side refrigeration cycle is completed.

[0051] In the embodiment, the carbon dioxide outlet of the evaporative condenser 9 is connected to the inlet of the carbon dioxide storage tank 11 through the drying filter 10.

[0052] In actual use, the drying filter 10 is connected to the carbon dioxide outlet of the evaporative condenser 9, so as to remove impurities and adsorb moisture, and ensure the purity of the medium in the carbon dioxide storage tank 11.

[0053] Further, the evaporative condenser 9 to the carbon dioxide storage tank 11 can be additionally provided with a sight glass, a working medium moisture detection device and the like to optimize the system configuration.

[0054] In actual use of the utility model, the carbon dioxide working medium in the carbon dioxide refrigeration cycle is compressed by the first compressor 1 and enters the first intercooler 2, the temperature of the carbon dioxide working medium is controlled to a rated range by the first intercooler 2, is compressed by the second compressor 3, and then the outlet gas temperature is controlled again by the second intercooler 4; the working medium at the outlet of the second intercooler 4 enters the condensing evaporator 5, and the heat of the carbon dioxide refrigeration cycle is transmitted to the ammonia refrigeration cycle; the working medium at the carbon dioxide outlet of the condensing evaporator 5 enters the evaporative condenser 9 through the expander 6 and the bypass electromagnetic valve 7, at the same time, the carbon dioxide bypass branch 22 can effectively adjust the temperature and pressure range of the working medium at the inlet of the evaporative condenser 9, ensure that the system back pressure meets the standard, and prevent the evaporator pipe section from condensing and frosting, so that the equipment is stably operated; the carbon dioxide at the outlet of the evaporative condenser 9 is returned to the carbon dioxide storage tank 11 after impurities are removed and moisture is adsorbed through the drying filter 10;

[0055] The ammonia refrigeration cycle, the ammonia refrigeration working medium enters the ammonia side intercooler 18 to adjust the temperature and pressure, between the two, there is an ammonia side bypass branch 21 connected by the ammonia side electromagnetic bypass valve 17 to the throttling valve 20, to introduce the high temperature and high pressure side ammonia working medium into the condenser evaporator 5 front pipeline, effectively adjust the condenser evaporator 5 inlet working medium temperature and pressure range, ensure that the system back pressure meets the standard, at the same time avoid the condenser evaporator 5 pipe section condensation frost, so as to ensure the stable operation of the equipment; the ammonia working medium of the ammonia side intercooler 18 outlet is condensed and heat released by the ammonia side condenser 19, then enters the throttling valve 20, and then enters the condenser evaporator 5, realizes the heat exchange process with the carbon dioxide refrigeration cycle, and finally the ammonia side working medium returns to the ammonia storage tank 15, completes the ammonia side refrigeration cycle.

[0056] The carbon dioxide refrigerant cycle is connected with the carbon dioxide refrigeration cycle by the evaporative condenser 9, the carbon dioxide refrigerant is heat exchanged by the evaporative condenser 9, and then enters the refrigerant storage tank 23, and then enters the circulating pump 12, and the circulating power is provided by the circulating pump 12 to enter the carbon dioxide cold air machine 14 to evaporate and exchange heat, wherein the carbon dioxide cold air machine 14 can assist the circulation to transfer heat outside the system, utilize external heat sources, such as high-temperature flue gas, to assist heat exchange, and improve the resource utilization capacity; when the temperature of the heat source of the auxiliary heat exchange branch meets the standard and is stable, the mechanical heat exchange of the carbon dioxide cold air machine 14 can be stopped, and the carbon dioxide ejector 13 is used, the carbon dioxide ejector 13 flows and sprays the high temperature and high pressure working medium generated by the carbon dioxide cold air machine, so that the flow rate is more than 600 meters per second, further forming a pressure zone in the rear end area, assisting the carbon dioxide refrigeration cycle to work; the heat exchange efficiency of the external heat source is enlarged, and the external heat source is used for natural heat exchange; the carbon dioxide refrigerant cycle exchanges heat by phase change, and the heat exchange efficiency is better than that of conventional non-phase change conversion refrigerant under the same conditions. At the same time, based on the carbon dioxide materialization characteristics, the refrigerating capacity is large, and the viscosity is low, which can effectively reduce the pipeline and equipment volume and save land area.

[0057] The above is only a preferred embodiment of the present application, and does not limit the present application, any simple modification, change and equivalent structure change according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical scheme of the present application.

Claims

1. A carbon dioxide cascade refrigeration system with a secondary refrigeration circuit, characterized in that: The carbon dioxide refrigeration cycle, the ammonia refrigeration cycle and the carbon dioxide carrier refrigeration cycle are connected by a condensing evaporator (5) and an evaporative condenser (9); The carbon dioxide refrigeration cycle includes a first compressor (1), a first intercooler (2), a second compressor (3) and a second intercooler (4), the inlet of the first intercooler (2) is connected to the outlet of the first compressor (1), the outlet of the first intercooler (2) is connected to the inlet of the second compressor (3), the outlet of the second compressor (3) is connected to the inlet of the second intercooler (4), the outlet of the second intercooler (4) is connected to the carbon dioxide inlet of the condensing evaporator (5), the carbon dioxide outlet of the condensing evaporator (5) is connected to the carbon dioxide inlet of the evaporative condenser (9), the carbon dioxide outlet of the evaporative condenser (9) is connected to the inlet of a carbon dioxide storage tank (11), and the inlet of the carbon dioxide storage tank (11) is connected to the inlet of the first compressor (1). The ammonia refrigeration cycle includes an ammonia storage tank (15), an ammonia compressor (16), an ammonia side intercooler (18) and an ammonia side condenser (19), the outlet of the ammonia storage tank (15) is connected to the inlet of the ammonia compressor (16), the outlet of the ammonia compressor (16) is connected to the inlet of the ammonia side intercooler (18), the outlet of the ammonia side intercooler (18) is connected to the inlet of the ammonia side condenser (19), the outlet of the ammonia side condenser (19) is connected to the ammonia inlet of the condensing evaporator (5), and the inlet of the ammonia storage tank (15) is connected to the ammonia outlet of the condensing evaporator (5). The carbon dioxide carrier refrigeration cycle includes a carrier refrigerant storage tank (23), a circulating pump (12), a carbon dioxide cooling fan (14) and a carbon dioxide ejector (13), the inlet of the carrier refrigerant storage tank (23) is connected to the carrier refrigerant outlet of the carrier refrigerant storage tank (23), the outlet of the carrier refrigerant storage tank (23) is connected to the inlet of the circulating pump (12), the outlet of the circulating pump (12) is connected to the inlet of the carbon dioxide cooling fan (14), the outlet of the carbon dioxide cooling fan (14) is connected to the inlet of the carbon dioxide ejector (13), and the outlet of the carbon dioxide ejector (13) is connected to the carbon dioxide inlet of the evaporative condenser (9).

2. A carbon dioxide cascade refrigeration system with a subcooling circuit according to claim 1, characterized in that: An expander (6) is connected between the carbon dioxide outlet of the condensing evaporator (5) and the carbon dioxide inlet of the evaporative condenser (9).

3. A carbon dioxide cascade refrigeration system with a subcooling circuit according to claim 2, characterized in that: A bypass electromagnetic valve (7) is connected between the expander (6) and the evaporative condenser (9), and a carbon dioxide bypass branch (22) is connected to the bypass electromagnetic valve (7).

4. A carbon dioxide cascade refrigeration system with a subcooling circuit according to claim 3, characterized in that: The outlet of the first compressor (1) is connected to the inlet of the first intercooler (2) and the carbon dioxide bypass branch (22) through a hot gas bypass valve (8), and the first compressor (1) is connected to the carbon dioxide inlet of the evaporative condenser (9) through the hot gas bypass valve (8), the carbon dioxide bypass branch (22) and the bypass electromagnetic valve (7).

5. A carbon dioxide cascade refrigeration system with a subcooling loop as defined in claim 1, characterized in that: An ammonia side electromagnetic bypass valve (17) is connected between the outlet of the ammonia compressor (16) and the inlet of an ammonia side intercooler (18), and an ammonia side bypass branch (21) is connected to the ammonia side electromagnetic bypass valve (17), with the ammonia side bypass branch (21) being connected to the ammonia inlet of the condensing evaporator (5).

6. A carbon dioxide cascade refrigeration system with a subcooling circuit according to claim 5, characterized in that: The ammonia inlet of the condensing evaporator (5) is connected to the outlet of the ammonia side bypass branch (21) and the outlet of an ammonia side condenser (19) through a throttle valve (20).

7. A carbon dioxide cascade refrigeration system with a subcooling loop as defined in claim 1, characterized in that: A dry filter (10) is connected between the carbon dioxide outlet of the evaporative condenser (9) and the inlet of a carbon dioxide storage tank (11).

Images