Cascade cryogenic freezing system

Abstract

The application discloses a cascade deep-freezing system, which comprises a high-temperature stage circulating loop, a low-temperature stage circulating loop and an evaporative condenser connecting the high-temperature stage circulating loop with the low-temperature stage circulating loop, the evaporative condenser comprises a low-temperature stage condenser on one side and a high-temperature stage evaporator on the other side, the low-temperature stage condenser is connected in the low-temperature stage circulating loop, the high-temperature stage evaporator is connected in the high-temperature stage circulating loop, a spraying loop and a low-temperature freezing loop are further connected to the low-temperature stage circulating loop, and the spraying loop and the low-temperature freezing loop are both in heat exchange with refrigerant in the low-temperature stage circulating loop through unfreezing liquid. Different from the single-step quick-freezing process of the traditional device, the freezing system provided by the application can carry out a two-step freezing process of'spraying initial freezing-low-temperature freezing', so that the loss and volatilization of water can be effectively reduced, and the freshness of food can be locked to the maximum extent.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration technology, specifically relating to a cascade deep cryo-junction system. Background Technology

[0002] Currently, refrigeration units are generally divided into two categories: single-system and cascade refrigeration systems. Cascade refrigeration systems are often used when lower temperatures are required. Cascade refrigeration systems are widely used in commercial food processing, transportation, and storage, playing a crucial role in food preservation and quality maintenance. A cascade refrigeration system typically includes a high-temperature stage circulation loop, a low-temperature stage circulation loop, and an evaporator-condenser connecting the high-temperature and low-temperature stage circulation loops. This evaporator-condenser functions as both the evaporator in the high-temperature stage and the condenser in the low-temperature stage. In the low-temperature stage, the refrigerant absorbs heat from the object being cooled (i.e., generates cooling capacity) within the heat exchanger. During the low-temperature stage circulation, this heat is transferred to the refrigerant in the high-temperature stage through the evaporator-condenser, and then the refrigerant in the high-temperature stage transfers the heat to the external environment.

[0003] In processing fresh food, traditional methods often prioritize shorter freezing times to prevent heat-induced spoilage, directly using refrigerant in a low-temperature circulating loop for rapid freezing. However, rapidly frozen food often lacks freshness and doesn't taste as good as its uncold counterparts. The inventors, through research and experimentation, discovered that this problem arises because rapid freezing causes most of the water molecules in the food to freeze into larger ice crystals, damaging the food's cellular and tissue structure. This leads to nutrient loss and a decline in freshness and taste. Summary of the Invention

[0004] To address the above problems, the present invention provides a cascaded deep cryo-junction system.

[0005] The present invention adopts the following technical solution:

[0006] A cascade cryogenic system includes a high-temperature stage circulation loop, a low-temperature stage circulation loop, and an evaporator-condenser connecting the high-temperature stage circulation loop and the low-temperature stage circulation loop. The evaporator-condenser includes a low-temperature stage condenser on one side and a high-temperature stage evaporator on the other side. The low-temperature stage condenser is connected in the low-temperature stage circulation loop, and the high-temperature stage evaporator is connected in the high-temperature stage circulation loop. A spray circuit and a cryogenic freezing circuit are also connected to the low-temperature stage circulation loop. Both the spray circuit and the cryogenic freezing circuit exchange heat with the refrigerant in the low-temperature stage circulation loop through antifreeze.

[0007] In some embodiments, the cryogenic stage circulation loop includes a cryogenic stage compressor, a first oil separator, the evaporator-condenser, a liquid receiver, a first dryer filter, a first expansion valve, a cryogenic stage heat exchanger, and a first gas-liquid separator connected in sequence.

[0008] In some embodiments, the spray circuit includes a first housing and a spray device connected by a circulation pipeline. The first housing contains food-grade antifreeze liquid, and the first housing is also connected to a cold energy recovery coil disposed inside the first gas-liquid separator.

[0009] In some embodiments, the cryogenic freezing circuit includes a second chamber and a cryogenic evaporator connected by a circulation pipeline, the second chamber containing antifreeze and also connected to the cryogenic stage heat exchanger.

[0010] In some embodiments, an air-cooled condenser is further provided between the first oil separator and the evaporator-condenser.

[0011] In some embodiments, the high-temperature stage circulation loop includes a high-temperature stage compressor, a second oil separator, a high-temperature stage condenser, a second dryer filter, a second expansion valve, the evaporator-condenser, and the second gas-liquid separator connected in sequence.

[0012] In some embodiments, the evaporator-condenser is a plate heat exchanger, a tube-and-shell heat exchanger, or a shell-and-tube heat exchanger.

[0013] In some embodiments, the cryogenic stage circulation loop uses environmentally friendly refrigerants such as R23, R13, or R508B.

[0014] In some embodiments, the high-temperature stage circulation loop uses environmentally friendly refrigerants such as R507A, R404A, or R448A.

[0015] The beneficial effects of this invention are:

[0016] 1. The addition of a spray circuit can not only recover and utilize the cold energy in the gas-liquid separator in the low-temperature circulating circuit, but also spray the food to be frozen for initial freezing, quickly forming an ice layer on the surface of the food, reducing the loss and evaporation of moisture, and in conjunction with the subsequent low-temperature freezing processing, "locking in" the freshness of the food to the greatest extent.

[0017] 2. In the cryogenic freezing loop, pure liquid antifreeze is used instead of traditional gaseous or gas-liquid mixed refrigerant because the thermal conductivity of liquid medium is higher than that of gaseous / gas-liquid medium. Under the premise of the same heat transfer performance, the amount of antifreeze required in the cryogenic freezing loop is much smaller than that of traditional refrigerant, which can be compatible with smaller loop pipes and greatly save the space occupied by the equipment.

[0018] 3. Both the spray circuit and the cryogenic freezing circuit are connected to the main equipment through antifreeze pipes. Even if a leak occurs, it will not have the same significant impact on the environment or personnel as traditional refrigerants such as Freon and ammonia. Therefore, the pipes can be directly installed outdoors for easy installation, disassembly, or maintenance. Attached Figure Description

[0019] Figure 1 This is a system schematic diagram of one embodiment of the present invention;

[0020] Figure 2 These are electron microscope images of the cell and tissue state of fresh shrimp before freezing;

[0021] Figure 3 These are electron microscope images of the cell tissue state of shrimp feed after it has undergone traditional quick-freezing process.

[0022] Figure 4 These are electron micrographs of the cell tissue state of shrimp feed after being frozen in stages according to embodiments of the present invention;

[0023] Figure 1 middle:

[0024] 10 Low-temperature stage circulation loop, 11 Low-temperature stage compressor, 12 First oil separator, 13 Air-cooled condenser, 14 Liquid receiver, 15 First dryer filter, 16 First expansion valve, 17 Low-temperature stage heat exchanger, 18 First gas-liquid separator.

[0025] 20 High-temperature stage circulation loop, 21 High-temperature stage compressor, 22 Second oil separator, 23 High-temperature stage condenser, 24 Second dryer filter, 25 Second expansion valve, 26 Second gas-liquid separator;

[0026] 30 Evaporator-condenser, 31 Low-temperature stage condenser, 32 High-temperature stage evaporator;

[0027] 40 Spray circuit, 41 First housing, 42 Spray device, 43 Cold energy recovery coil;

[0028] 50 Low-temperature freezing circuit, 51 Second chamber, 52 Low-temperature evaporator. Detailed Implementation

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] The cascade cryogenic system provided by this invention includes a high-temperature stage system and a low-temperature stage system. The high-temperature stage system is used to cool and liquefy the refrigerant in the low-temperature stage system. It does not come into contact with the outside world and is a separate closed-loop system.

[0031] When the cascade cryogenic refrigeration system is in operation, the required temperature can be set according to the operating conditions. This allows the high-temperature stage system to liquefy the refrigerant in the low-temperature system under optimal energy-saving operating conditions. The liquefied refrigerant flows into the receiver using the high and low pressure difference, and then vaporizes through the expansion valve to generate cooling capacity. The low-temperature stage system can also adjust the vaporization rate according to the refrigeration conditions, thereby cooling the external environment under optimal energy-saving conditions and achieving a high level of energy efficiency.

[0032] The following is a detailed explanation.

[0033] like Figure 1 As shown, this embodiment provides a cascaded deep cryogenic system, including a high-temperature stage circulation loop 20, a low-temperature stage circulation loop 10, and an evaporator-condenser 30 connecting the high-temperature stage circulation loop 20 and the low-temperature stage circulation loop 10. The evaporator-condenser 30 includes a low-temperature stage condenser 31 located on one side and a high-temperature stage evaporator 32 located on the other side. The low-temperature stage condenser 31 is connected to the low-temperature stage circulation loop 10, and the high-temperature stage evaporator 32 is connected to the high-temperature stage circulation loop 20. The low-temperature stage circulation loop 10 is also connected to a spray loop 40 and a low-temperature freezing loop 50. Both the spray loop 40 and the low-temperature freezing loop 50 exchange heat with the refrigerant in the low-temperature stage circulation loop 10 through antifreeze.

[0034] Specifically, the high-temperature stage circulation loop 20 includes a high-temperature stage compressor 21, a second oil separator 22, a high-temperature stage condenser 23, a second dryer filter 24, a second expansion valve 25, an evaporator condenser 30, and a second gas-liquid separator 26 connected in sequence.

[0035] The working process of the high-temperature stage circulation loop 20 is as follows: After the refrigerant (R507A, R404A or R448A, preferably R507A) is compressed by the high-temperature stage compressor 21, it becomes a high-temperature and high-pressure state. After oil-gas separation by the second oil separator 22, the liquid refrigerant enters the high-temperature stage condenser 23 (which is connected to an external cooling tower). After cooling, it passes through the second dryer filter 24 and the second expansion valve 25. The refrigerant, after expansion and cooling, enters the evaporator condenser 30 to cool the refrigerant in the low-temperature stage circulation loop 10. Finally, it enters the second gas-liquid separator 26 for separation. The gaseous refrigerant re-enters the high-temperature stage compressor 21, thus completing one refrigeration cycle.

[0036] Overall, the high-temperature circulating loop 20 is not much different from the prior art. The main technical improvement of the embodiment of the present invention lies in the low-temperature circulating loop 10.

[0037] Specifically, the low-temperature stage circulation loop 10 includes a low-temperature stage compressor 11, a first oil separator 12, an evaporator-condenser 30, a liquid receiver 14, a first dryer filter 15, a first expansion valve 16, a low-temperature stage heat exchanger 17, and a first gas-liquid separator 18 connected in sequence.

[0038] The working process of the low-temperature stage circulation loop 10 is as follows: After the refrigerant (R23, R13 or R508B, preferably R23) is compressed by the low-temperature stage compressor 11, it becomes a high-temperature and high-pressure state. After oil-gas separation by the first oil separator 12, it enters the evaporator-condenser 30, cools down and becomes liquid, and enters the liquid receiver 14. Then it is dried by the first dryer filter 15, expands through the first expansion valve 16, enters the low-temperature stage heat exchanger 17 for cooling, and provides cooling capacity for the low-temperature freezing loop 50. Finally, it enters the first gas-liquid separator 18. After gas-liquid separation, the gaseous refrigerant re-enters the low-temperature stage compressor 11, thus completing one refrigeration cycle.

[0039] The spray circuit 40 includes a first housing 41 and a spray device 42 connected by a circulation pipeline. The first housing 41 contains food-grade antifreeze liquid and is also connected to a cold energy recovery coil 43 located inside the first gas-liquid separator 18. After the refrigerant passes through the low-temperature heat exchanger 17, some of the refrigerant's cold energy is not completely exchanged. In the prior art, this portion of cold energy is wasted after being carried into the first gas-liquid separator 18. In this embodiment, by setting a cold energy recovery coil 43 in the first gas-liquid separator 18, the food-grade antifreeze flows through the cold energy recovery coil 43, which can effectively absorb the remaining cold energy of the refrigerant, keeping the antifreeze itself at around -15°C; then, the food is sprayed by the spray device 41, causing the surface temperature of the food to drop rapidly. Under the condition that the internal temperature of the food is 5°C, a layer of ice at -10°C is formed on its surface. With the help of this ice layer, the loss of moisture is reduced, so that the moisture in the food is not easily evaporated in the next freezing process, achieving the effect of zero dry loss.

[0040] The cryogenic freezing circuit 50 includes a second housing 51 and a cryogenic evaporator 52 connected by a circulation pipeline. The second housing 51 contains antifreeze and is connected to the cryogenic stage heat exchanger 52. After the refrigerant expands through the first expansion valve 16, it enters the cryogenic stage heat exchanger 17 and exchanges heat with the antifreeze, providing cooling capacity to the cryogenic freezing circuit 50. Because the thermal conductivity of liquid media is higher than that of general gaseous or gas-liquid mixed media, under the same heat transfer performance conditions, the amount of antifreeze required in the cryogenic freezing circuit 50 is much smaller than that of traditional refrigerants, allowing for the use of smaller circuit pipes and significantly saving space. The antifreeze, having absorbed the refrigerant's cooling capacity, then enters the cryogenic evaporator 52 to provide cooling capacity to the outside, which in this embodiment is the cooling and freezing of food. Food that has undergone initial freezing by spraying is now subjected to low-temperature freezing, causing its internal temperature to drop rapidly to below -18°C. At this point, the ice crystals formed by the freezing of water inside the food are small and uniform in size, and will not damage the cell structure, thus maximizing the preservation of the food's freshness.

[0041] Combination Figure 2-4 It can be seen that after traditional quick-freezing, large ice crystals appear in the cell tissue of shrimp, damaging the cell and tissue structure. However, in the shrimp processed by the two-step freezing method in this embodiment, the ice crystals in the cell tissue are smaller and evenly distributed, without affecting the cell and tissue structure. This avoids the loss of nutrients and makes the shrimp taste fresher after cooking.

[0042] Those skilled in the art will appreciate that various modifications to the above embodiments can be made without departing from the overall spirit and concept of the present invention. All such modifications fall within the protection scope of the present invention. The protection scheme of the present invention is defined by the appended claims.

Claims

1. A cascade cryogenic freezing system comprising a low temperature stage cycle circuit (10), a high temperature stage cycle circuit (20) and an evaporative condenser (30) connecting the high temperature stage cycle circuit (20) with the low temperature stage cycle circuit (10), the evaporative condenser (30) comprising a low temperature stage condenser (31) on one side and a high temperature stage evaporator (32) on the other side, the low temperature stage condenser (31) being connected in the low temperature stage cycle circuit (10) and the high temperature stage evaporator (32) being connected in the high temperature stage cycle circuit (20), characterized in that, A spraying circuit (40) and a low-temperature freezing circuit (50) are further connected to the low-temperature stage circulation circuit (10), and the spraying circuit (40) and the low-temperature freezing circuit (50) exchange heat with the refrigerant in the low-temperature stage circulation circuit (10) through the non-freezing liquid; The low-temperature stage circulation circuit (10) comprises, in sequence, a low-temperature stage compressor (11), a first oil separator (12), the evaporative condenser (30), a liquid accumulator (14), a first dry filter (15), a first expansion valve (16), a low-temperature stage heat exchanger (17) and a first gas-liquid separator (18). The spraying circuit (40) comprises a first tank (41) and a spraying device (42) connected through a circulating pipeline, the first tank (41) is filled with food-grade non-freezing liquid, and the first tank (41) is further connected with a cold energy recovery coil (43) which is arranged in the first gas-liquid separator (18). The low-temperature freezing circuit (50) comprises a second tank (51) and a low-temperature evaporator (52) connected through a circulating pipeline, the second tank (51) is filled with non-freezing liquid, and the second tank (51) is further connected with the low-temperature stage heat exchanger (17). The low-temperature freezing circuit (50) is used for low-temperature freezing of food, and the spraying circuit (40) is used for initial freezing of the food by spraying.

2. The cascade cryogenic freezing system of claim 1, wherein, A wind-cooled condenser (13) is further arranged between the first oil separator (12) and the evaporative condenser (30).

3. The cascade cryogenic freezing system of claim 1, wherein, The high-temperature stage circulation circuit (20) comprises, in sequence, a high-temperature stage compressor (21), a second oil separator (22), a high-temperature stage condenser (23), a second dry filter (24), a second expansion valve (25), the evaporative condenser (30) and a second gas-liquid separator (26).

4. The cascade cryogenic freezing system of claim 1, wherein, The evaporative condenser (30) is a plate heat exchanger, a tube-in-shell heat exchanger or a shell-and-tube heat exchanger.

5. The cascade cryogenic freezing system of claim 1, wherein, The low-temperature stage circulation circuit (10) uses R23, R13 or R508B environmentally-friendly refrigerant.

6. The cascade cryogenic freezing system of claim 1, wherein, The high-temperature stage circulation circuit (20) uses R507A, R404A or R448A environmentally-friendly refrigerant.

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