Freon / carbon dioxide cascade skid unit

Abstract

The utility model relates to the field of refrigerating systems, and discloses a Freon / carbon dioxide cascade skid unit which comprises a high-temperature system and a low-temperature system, and the high-temperature system comprises a Freon screw compressor unit skid and a U-Turn type gas-liquid separation condensation evaporation unit skid. The low-temperature system comprises a carbon dioxide piston compressor unit skid and a carbon dioxide barrel pump unit skid, the carbon dioxide piston compressor unit skid and the Freon screw compressor unit skid are arranged in parallel, the unit skid is divided into an upper layer and a lower layer, and a carbon dioxide piston compressor is located at the upper end of the Freon screw compressor. The U-Turn type gas-liquid separation condensation evaporation unit skid is arranged in the width direction of the upper-layer carbon dioxide piston compressor, and the carbon dioxide barrel pump unit skid is arranged at the position close to the tail end evaporator and arranged in the length direction of the Freon screw compressor.

Description

Technical Field

[0001] This application belongs to the field of refrigeration system technology, specifically relating to a Freon / carbon dioxide cascade skid unit. Background Technology

[0002] As people's living standards improve, the quality requirements for food are getting higher and higher, and the processing temperature of food is getting lower and lower. When the high-low pressure compression ratio of the compressor unit, the heart of cold storage, exceeds 8, the efficiency of a single stage is low and the energy consumption is high. Generally, cold storage, low-temperature cold storage, quick-freezing room, and single-freezing machine adopt two-stage compression or cascade refrigeration. In a two-stage refrigeration cycle, the high and low pressure stages use the same refrigerant and the refrigerant is interconnected. The minimum temperature of the high and low pressure stages in a two-stage refrigeration cycle is limited. A cascade refrigeration cycle is usually composed of two (or more) single-stage (or two-stage) refrigeration systems using different refrigerants.

[0003] In existing cold storage refrigeration systems, with the improvement of food quality and the reduction of processing temperature, single-stage refrigeration is too inefficient, and the minimum temperature of high and low pressure in two-stage refrigeration cycles is limited. Ammonia and fluorine refrigeration systems require a large refrigerant charge, making carbon dioxide cascade and secondary cooling systems increasingly popular. Existing carbon dioxide cascade refrigeration systems mostly use dedicated carbon dioxide hot gas defrosting compressors in their top-row pipes. However, the condensation temperature of carbon dioxide in carbon dioxide cascade refrigeration systems is about -10 to -15℃, and the hot gas defrosting condensation temperature is controlled at around 5℃. The carbon dioxide pressure is about 39 kg. As the temperature increases, the pressure inside the refrigeration system increases, which lowers the safety and reliability of the refrigeration system and increases the cost. Summary of the Invention

[0004] This application provides a carbon dioxide cascade skid unit to solve the technical problems of high operating safety and low cost of the refrigeration system when the internal pressure is high.

[0005] The technical solution adopted in this application is as follows:

[0006] A Freon / CO2 cascade skid-mounted chiller unit includes a high-temperature system and a low-temperature system. The high-temperature system includes a Freon screw compressor skid and a U-Turn gas-liquid separation condenser-evaporator skid. The low-temperature system includes a CO2 reciprocating compressor skid and a CO2 tank pump skid. The CO2 reciprocating compressor skid and the Freon screw compressor skid are arranged in parallel. The skids are divided into upper and lower layers. The CO2 reciprocating compressor skid is located at the upper end of the Freon screw compressor skid. The U-Turn gas-liquid separation condenser-evaporator skid is arranged in the width direction of the upper CO2 reciprocating compressor skid. The CO2 tank pump skid is arranged near the end evaporator and in the length direction of the Freon screw compressor skid. The CO2 reciprocating compressor skid is connected to the U-Turn gas-liquid separation condenser-evaporator skid, and the U-Turn gas-liquid separation condenser-evaporator skid is connected to the Freon screw compressor skid.

[0007] Optionally, the carbon dioxide reciprocating compressor unit skid includes a carbon dioxide subcritical reciprocating compressor, an oil separator, a hot gas defrosting oil separator, and a carbon dioxide regenerative heat exchanger. The carbon dioxide reciprocating compressor unit skid is connected to the terminal evaporator in the storage unit via a carbon dioxide barrel pump unit skid, and the exhaust gas from the carbon dioxide subcritical reciprocating compressor is connected to a U-Turn gas-liquid separation condensing evaporator unit skid.

[0008] By adopting the above technical solution, the return gas passes through a carbon dioxide regenerative heat exchanger, effectively increasing the superheat and circulation efficiency of the carbon dioxide return gas. The Freon liquid supply is effectively subcooled, reducing flash gas emissions and improving the overall refrigeration system efficiency by more than 10%. Conventional skid-mounted units are equipped with a separate carbon dioxide reciprocating compressor for hot gas defrosting, which increases investment costs. The carbon dioxide reciprocating compressor configured in this technical solution can be used for both cooling of the refrigeration system and hot gas defrosting. The difference lies in the addition of a pressure regulating valve in the system for switching between hot gas defrosting and refrigeration, reducing manual operation and improving defrosting efficiency by 10%, reducing investment by 15%. The carbon dioxide operates at high pressure, and the reciprocating compressor is more efficient than the screw compressor, reducing high and low pressure cross-flow and improving energy efficiency by more than 15% compared to the parallel carbon dioxide screw unit.

[0009] Optionally, the U-Turn gas-liquid separation condenser-evaporator skid includes a condenser-evaporator and a U-Turn gas-liquid separator, the U-Turn gas-liquid separator being connected to the Freon screw compressor skid.

[0010] Optionally, the condenser-evaporator is a combination of several 200kW Schrupp plate heat exchangers, and the U-Turn gas-liquid separator is a U-shaped tube.

[0011] Optionally, the U-Turn gas-liquid separator is connected to the condenser-evaporator via a gas-liquid separation device, which has an oil return outlet at different liquid levels.

[0012] By adopting the above technical solutions, the U-shaped tube of the U-Turn gas-liquid separator not only ensures the separation effect, reduces liquid slugging in the compressor, and improves compressor efficiency, but also reduces the amount of Freon refrigerant required. The full-liquid gas-liquid separator plate heat exchanger in the U-Turn gas-liquid separation condenser-evaporator skid has two advantages: firstly, the plate heat exchanger uses a full-liquid supply method, which improves the heat exchange efficiency; secondly, the plate heat exchanger replaces the Vardrus plate evaporator, and the brazed plate heat exchanger has high heat exchange efficiency, reducing investment costs by more than 25%. At the same time, Freon and oil are miscible, and the impact of oil on heat exchange efficiency must be considered in low-temperature gas-liquid separators. Since the density of oil is less than that of Freon, three oil return ports are added above the normal liquid level of the U-Turn gas-liquid separator. The oil is heated by the oil return plate heat exchanger and returned to the suction pipe of the Freon screw compressor. This ensures oil return to the compressor, lubrication, and sealing, improving compressor efficiency; and secondly, it improves the heat exchange efficiency of the condenser-evaporator plate heat exchanger.

[0013] Optionally, the Freon screw compressor unit skid includes a screw compressor, an oil separator, and a suction heat exchanger. The Freon screw compressor unit skid is connected to the U-Turn gas-liquid separation condenser-evaporator skid via the suction heat exchanger and is connected to the Freon liquid supply pipeline system via pipelines.

[0014] By adopting the above technical solutions, the added intake heat exchanger, after heat exchange, ensures that the intake is superheated and the liquid supply is subcooled, thus preventing liquid slugging in the compressor. The subcooling of the liquid supply reduces flash gas and improves heat exchange efficiency by more than 15%. The oil separator adopts a high-efficiency 4-stage separation separator, which improves the oil-gas separation effect, reduces the amount of oil charged, and improves the heat exchange efficiency of the low-temperature system by more than 10%.

[0015] Optionally, the carbon dioxide tank pump unit skid includes a horizontal carbon dioxide circulation tank, a canned carbon dioxide pump, an oil return heat exchanger, and a maintenance unit. The canned carbon dioxide pump is connected to the terminal evaporator, the horizontal carbon dioxide circulation tank is connected to the carbon dioxide reciprocating parallel compressor skid through the terminal evaporator, and the oil return heat exchanger is connected to the carbon dioxide reciprocating parallel compressor unit skid.

[0016] Optionally, the shielded carbon dioxide pump in the carbon dioxide tank pump unit skid includes multiple pump heads, which are connected to the terminal evaporators on different floors via pipelines.

[0017] Optionally, the unit is connected to a horizontal carbon dioxide circulation tank via a pressure control device and to a carbon dioxide reciprocating compressor unit skid via a bypass pipe.

[0018] By adopting the above technical solutions, the design of the shielded carbon dioxide pump is matched to different floors and different heat exchange loads, preventing the increase of energy consumption to achieve balanced liquid supply between different floors by adjusting valves. The shielded pump is designed according to the floor and load, saving more than 10% of energy consumption. The maintenance unit reduces the frequent start-up of the compressor in the low-temperature carbon dioxide system, extends the service life of the compressor, and improves the system efficiency by more than 10%. The use of an oil return plate to exchange oil ensures the return of oil to the compressor, lubrication and sealing, and improves the efficiency of the compressor. On the other hand, it improves the heat exchange efficiency of the terminal evaporator.

[0019] Due to the adoption of the above technical solution, the beneficial effects achieved by this application are as follows:

[0020] The entire skid structure is compact, reducing the system's footprint and saving space in the computer room.

[0021] The amount of refrigerant charged was reduced. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0023] Figure 1 This is a schematic diagram of a Freon / carbon dioxide cascade skid unit according to this application;

[0024] Figure 2 for Figure 1 Enlarged view of a portion of point A in the middle;

[0025] Figure 3 for Figure 1 Enlarged view of a section at point B in the middle;

[0026] Figure 4 for Figure 1 Enlarged view of a section at point C;

[0027] Figure 5 for Figure 1 Enlarged view of a section at point D.

[0028] 1. Carbon dioxide reciprocating compressor unit skid; 11. Carbon dioxide subcritical reciprocating compressor; 12. Oil separator; 13. Oil separator for hot gas defrosting; 14. Carbon dioxide regenerative heat exchanger;

[0029] 2. U-Turn type gas-liquid separation condenser-evaporator skid; 21. Condenser-evaporator; 22. U-Turn type gas-liquid separator;

[0030] 3. Freon screw compressor unit skid; 31. Screw compressor; 32. Oil separator; 33. Suction heat exchanger;

[0031] 4. Carbon dioxide tank pump unit skid; 41. Horizontal carbon dioxide circulating tank; 42. Canned carbon dioxide pump; 43. Maintenance unit;

[0032] 5. High-pressure liquid receiver; 6. Oil return plate heat exchanger. Detailed Implementation

[0033] To more clearly illustrate the overall concept of this application, a detailed explanation is provided below with reference to the accompanying drawings.

[0034] Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below. It should be noted that, unless otherwise specified, the embodiments of this application and the features thereof can be combined with each other.

[0035] A Freon / CO2 cascade skid-mounted chiller unit includes a high-temperature system and a low-temperature system. The high-temperature system includes a Freon screw compressor skid 3 and a U-Turn gas-liquid separation condenser-evaporator skid 2. The low-temperature system includes a CO2 reciprocating compressor skid 1 and a CO2 tank pump skid 4. The CO2 reciprocating compressor skid 1 and the Freon screw compressor skid 3 are arranged in parallel. The skids are divided into upper and lower layers. The CO2 reciprocating compressor skid 1 is located at the upper end of the Freon screw compressor skid 3. The U-Turn gas-liquid separation condenser-evaporator skid 2 is arranged in the width direction of the upper CO2 reciprocating compressor skid 1. The CO2 tank pump skid 4 is arranged near the end evaporator and in the length direction of the Freon screw compressor skid 3. The CO2 reciprocating compressor skid 1 is connected to the U-Turn gas-liquid separation condenser-evaporator skid 2, and the U-Turn gas-liquid separation condenser-evaporator skid 2 is connected to the Freon screw compressor skid 3.

[0036] Furthermore, the carbon dioxide reciprocating compressor unit skid 1 includes a carbon dioxide subcritical reciprocating compressor 11, an oil separator 12, a hot gas defrosting oil separator 13, and a carbon dioxide regenerative heat exchanger 14. The carbon dioxide reciprocating compressor unit skid 1 is connected to the end evaporator in the storage room through the carbon dioxide barrel pump unit skid 4. The exhaust gas of the carbon dioxide subcritical reciprocating compressor 11 is connected to the U-Turn gas-liquid separation condensing evaporator unit skid 2.

[0037] Furthermore, the U-Turn gas-liquid separation condenser-evaporator skid 2 includes a condenser-evaporator 21 and a U-Turn gas-liquid separator 22, which is connected to the Freon screw compressor skid 3.

[0038] Furthermore, the condenser-evaporator 21 consists of several 200KW Schrupp plate heat exchangers, and the U-Turn gas-liquid separator 22 is a U-shaped tube.

[0039] Furthermore, the U-Turn gas-liquid separator 22 is connected to the condenser-evaporator 21 via a gas-liquid separation device, and the gas-liquid separation device is equipped with oil return outlets at different liquid levels.

[0040] When using the skid-mounted unit of this application, the low-temperature, low-pressure liquid carbon dioxide refrigerant passes through the terminal evaporator in the warehouse and exchanges heat with the heat load of the goods in the warehouse, becoming a low-temperature, low-pressure gas. After gas-liquid separation in the carbon dioxide drum pump unit skid 4, it passes through the carbon dioxide heat exchanger 14 and is drawn into the carbon dioxide subcritical reciprocating compressor 11. After being pressurized by the reciprocating compressor, it becomes a high-temperature, high-pressure gas. It passes through the oil separator 12 and is condensed into liquid in the condenser 21 in the U-Turn gas-liquid separation condenser evaporator unit skid 2. After being throttled and depressurized by the high-pressure liquid receiver 5, it enters the carbon dioxide drum pump unit skid 4.

[0041] Low-temperature, low-pressure liquid Freon is exchanged with high-temperature, high-pressure carbon dioxide in the low-temperature system through three 200KW Shurepu plate heat exchangers, and then becomes low-temperature, low-pressure gas Freon. After gas-liquid separation by a U-tube, the gas is drawn into the Freon screw parallel compressor unit skid.

[0042] Furthermore, the Freon screw compressor unit skid 3 includes a screw compressor 31, an oil separator 32, and a suction heat exchanger 33. The Freon screw compressor unit skid 3 is connected to the U-Turn gas-liquid separation condenser-evaporator skid 2 through the suction heat exchanger 33, and is connected to the Freon liquid supply pipeline system through pipelines.

[0043] After the U-Turn gas-liquid separation condensing evaporator skid 2 starts working, the Freon gas passes through the suction heat exchanger 33, and after heat exchange, it is drawn into the screw compressor 31. After being pressurized by the compressor, it becomes high-pressure, high-temperature Freon gas. After being separated by the oil separator 32, it is discharged to the evaporative condenser to be cooled and condensed into liquid.

[0044] In this embodiment, the oil separator 32 adopts a high-efficiency 4-stage separation efficiency separator, which improves the oil-gas separation effect, reduces the oil charging amount, and improves the heat exchange efficiency of the low-temperature system by more than 10%.

[0045] Furthermore, the carbon dioxide tank pump unit skid 4 includes a horizontal carbon dioxide circulation tank 41, a canned carbon dioxide pump 42, an oil return plate heat exchanger 6, and a maintenance unit 43. The canned carbon dioxide pump 42 is connected to the terminal evaporator, the horizontal carbon dioxide circulation tank 41 is connected to the carbon dioxide reciprocating parallel compressor skid through the terminal evaporator, and the oil return plate heat exchanger 6 is connected to the carbon dioxide reciprocating parallel compressor unit skid.

[0046] Furthermore, the shielded carbon dioxide pump 42 in the carbon dioxide tank pump unit skid 4 includes multiple pump heads, which are connected to the terminal evaporators on different floors via pipelines.

[0047] Furthermore, the unit 43 is connected to the horizontal carbon dioxide circulation tank 41 via a pressure control device and to the carbon dioxide reciprocating compressor unit skid 1 via a bypass pipe.

[0048] After the carbon dioxide reciprocating compressor unit skid 1 operates, it enters the carbon dioxide horizontal circulation tank 41 after being throttled and depressurized. The shielded carbon dioxide pump 42 pressurizes it and pumps it to the seamless steel pipe top row or terminal evaporator. Since carbon dioxide and oil are also miscible, the return oil plate 6 allows the high-temperature Freon condensate liquid to exchange heat with the low-temperature carbon dioxide oil liquid. The low-pressure, low-temperature carbon dioxide evaporates, and the oil and carbon dioxide gas are sucked away by the carbon dioxide reciprocating parallel compressor unit skid. The unit 43 is maintained to ensure that the carbon dioxide pressure at room temperature is not too high during system shutdown, and to prevent carbon dioxide leakage.

[0049] For any parts not mentioned in this application, existing technologies may be used or referenced.

[0050] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0051] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A freon / carbon dioxide cascade chipping unit comprising a high temperature system and a low temperature system, characterized in that: The high-temperature system comprises a freon screw compressor set pry block (3) and a U-Turn type gas-liquid separation condensation and evaporation set pry block (2), the low-temperature system comprises a carbon dioxide piston compressor set pry block (1) and a carbon dioxide barrel pump set pry block (4), the carbon dioxide piston compressor set pry block (1) and the freon screw compressor set pry block (3) are arranged in parallel, the set pry block is divided into two layers, the carbon dioxide piston compressor set pry block (1) is arranged at the upper end of the freon screw compressor set pry block (3), the U-Turn type gas-liquid separation condensation and evaporation set pry block (2) is arranged in the width direction of the carbon dioxide piston compressor set pry block (1), the carbon dioxide barrel pump set pry block (4) is arranged close to the terminal evaporator and in the length direction of the freon screw compressor set pry block (3), the carbon dioxide piston compressor set pry block (1) is connected with the U-Turn type gas-liquid separation condensation and evaporation set pry block (2), and the U-Turn type gas-liquid separation condensation and evaporation set pry block (2) is connected with the freon screw compressor set pry block (3).

2. A freon / carbon dioxide cascade chiller unit according to claim 1 wherein: The carbon dioxide piston compressor set pry block (1) comprises a carbon dioxide subcritical piston compressor (11), an oil separator (12), a hot gas defrosting special oil separator (13) and a carbon dioxide regenerative heat exchanger (14), the carbon dioxide piston compressor set pry block (1) is connected with the terminal evaporator in the warehouse through the carbon dioxide barrel pump set pry block (4), and the exhaust of the carbon dioxide subcritical piston compressor (11) is connected with the U-Turn type gas-liquid separation condensation and evaporation set pry block (2).

3. A freon / carbon dioxide cascade chiller unit according to claim 1 wherein: The U-Turn type gas-liquid separation condensation and evaporation set pry block (2) comprises a condensation evaporator (21) and a U-Turn type gas-liquid separator (22), and the U-Turn type gas-liquid separator (22) is connected with the freon screw compressor set pry block (3).

4. A freon / carbon dioxide cascade chiller unit according to claim 3 wherein: The condensation evaporator (21) is a plurality of 200KW Surple plate heat exchangers, and the U-Turn type gas-liquid separator (22) is a U-shaped tube.

5. A freon / carbon dioxide cascade chiller unit according to claim 3 wherein: The U-Turn type gas-liquid separator (22) is connected with the condensation evaporator (21) through a gas-liquid separation device, and the gas-liquid separation device is provided with an oil return outlet at different liquid levels.

6. A freon / carbon dioxide cascade chiller unit according to claim 1 wherein: The freon screw compressor set pry block (3) comprises a screw compressor (31), an oil separator (32) and a suction regenerative heat exchanger (33), the freon screw compressor set pry block (3) is connected with the U-Turn type gas-liquid separation condensation and evaporation set pry block (2) through the suction regenerative heat exchanger (33) and connected to a freon liquid supply pipeline system through a pipeline.

7. A freon / carbon dioxide cascade chiller unit according to claim 1 wherein: The carbon dioxide barrel pump unit pry block (4) comprises a carbon dioxide horizontal circulating barrel (41), a shielded carbon dioxide pump (42), an oil return plate exchanger (6) and a maintenance unit (43), the shielded carbon dioxide pump (42) is connected with a terminal evaporator, the carbon dioxide horizontal circulating barrel (41) is connected with a carbon dioxide piston parallel compressor pry block through the terminal evaporator, and the oil return plate exchanger (6) is connected with the carbon dioxide piston parallel compressor unit pry block.

8. A freon / carbon dioxide cascade chiller unit according to claim 7, wherein: The shielded carbon dioxide pump (42) in the carbon dioxide barrel pump unit pry block (4) comprises a plurality of pump heads, and the pump heads are respectively connected with terminal evaporators of different floors through pipelines.

9. A freon / carbon dioxide cascade chiller unit according to claim 7 wherein: The maintenance unit (43) is connected with the carbon dioxide horizontal circulating barrel (41) through a pressure control device and connected with the carbon dioxide piston compressor unit pry block (1) through a bypass pipe.

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