Refrigeration unit for crop refrigerator

Abstract

To provide a refrigeration unit for a crop refrigerator which can reduce a possibility that a refrigerant leaks due to corrosion caused by an acid substance contained in air in the crop refrigerator.SOLUTION: A refrigeration unit for a crop refrigerator includes: an evaporator 11 including one heat transfer pipe including a plurality of straight parts extending in parallel to each other and a plurality of U shaped parts each connecting the straight parts with each other at ends and having no seam, and a plurality of fins fixed to the straight parts and each having a surface orthogonal to an extension direction of the straight part, the evaporator 11 having no connection part to be brazed in areas other than both ends of the heat transfer pipe; a heat insulation box 13 enclosing the evaporator 11; a cooling space 132 defined at the inner side of the heat insulation box 13; and a refrigerant pipe which is connected to both ends at the outer side of the cooling space 132 and in which a refrigerant flows.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a refrigeration unit for a crop cold storage.

Background Art

[0002] Patent Document 1 discloses a refrigeration unit for a crop cold storage installed in a crop cold storage for refrigerating crops.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the crop cold storage of Patent Document 1, the air cooled in the evaporator of the refrigeration unit for the crop cold storage flows into the crop cold storage, cools the crops in the cold storage, and then is cooled again in the evaporator of the refrigeration unit for the crop cold storage. Since various crops such as rice, vegetables, and pickles are stored in the crop cold storage, the air that cools these crops may contain acidic substances contained in the crops. When the air containing acidic substances is cooled by the evaporator, moisture containing acidic substances in the air may adhere to the evaporator. As a result, when acidic substances accumulate on the evaporator, corrosion may occur particularly at the brazed connection part, and the refrigerant in the evaporator may leak. If the refrigerant leaks into the atmosphere, it may contribute to global warming.

[0005] An object of the present disclosure is to provide a refrigeration unit for a crop cold storage that can suppress the possibility of refrigerant leakage due to corrosion caused by acidic substances contained in the air in the crop cold storage.

Means for Solving the Problems

[0006] The present disclosure is It has a plurality of straight portions extending in parallel and a plurality of U-shaped portions connecting the plurality of straight portions at their respective ends, and is a single heat transfer tube without joints. A plurality of fins fixed to the straight portion and having a surface orthogonal to the extending direction of the straight portion. An evaporator that is provided and has no brazed connection portion other than both ends of the heat transfer tube. A heat insulation box surrounding the evaporator. A cooling space defined inside the heat insulation box. A refrigerant pipe that is connected to both ends outside the cooling space and through which refrigerant flows. Provided is a refrigeration unit for a crop cold storage.

[0007] According to the refrigeration unit for a crop cold storage of the present disclosure, air that may contain acidic substances circulates inside the cooling space. Since there is no brazed connection portion in the cooling space, it is difficult for acidic substances to accumulate on the brazed portion, and the possibility of refrigerant leakage due to corrosion can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0010] [First Embodiment] FIG. 1 is a perspective view of a crop cold storage 3 and a refrigeration unit 1 for a crop cold storage according to the first embodiment. The refrigeration unit 1 for a crop cold storage is installed above the crop cold storage 3 and is covered with a housing 20. Various crops such as rice, vegetables, and pickles are stored in the crop cold storage 3, and the crops are kept cold by the cold air produced by the refrigeration unit 1 for a crop cold storage.

[0011] FIG. 2 is an exploded perspective view of the refrigeration unit 1 for a crop cold storage with the housing 20 removed. The refrigeration unit 1 for a crop cold storage includes a base plate 10 in the shape of a rectangular flat plate, an evaporator 11 that cools the air in the crop cold storage 3, a cooling fan 12 that circulates the air cooled by the evaporator 11 into the crop cold storage 3, a heat insulation box 13 for thermally insulating the surroundings of the evaporator 11 and the cooling fan 12 from the outside, a compressor 15 that compresses the refrigerant to a high-temperature and high-pressure state and circulates the refrigerant, a capillary tube 16 for decompressing the high-pressure refrigerant, a condenser 17 that exhausts the heat of the high-temperature and high-pressure refrigerant to the outside air, an exhaust heat fan 18 that blows the exhausted air outside the refrigeration unit 1 for a crop cold storage, an evaporation sheet 19 that evaporates the dew water accumulated in the refrigeration unit 1 for a crop cold storage, and a refrigerant pipe 14 that connects between the evaporator 11, the compressor 15, the capillary tube 16, and the condenser 17 respectively and through which the refrigerant flows.

[0012] In this specification, the longitudinal direction of the base plate 10 in FIG. 2 is the left - right direction, the short - hand direction is the front - rear direction, and the direction orthogonal to both the left - right direction and the front - rear direction is the up - down direction. As shown in FIG. 2, the evaporator 11 and the heat - insulating box 13 are arranged on the left side of the base plate 10, and the condenser 17, the compressor 15, and the evaporation sheet 19 are arranged on the right side of the base plate 10. The cooling fan 12 is attached to the right - hand side surface of the evaporator 11. The exhaust - heat fan 18 is attached to the front - side surface of the condenser 17.

[0013] Next, the structure of the evaporator 11 will be described with reference to FIG. 3. The evaporator 11 includes one heat - transfer tube 110 through which the refrigerant flows, a plurality of fins 111 that exchange heat with the refrigerant, and a pair of tube plates 112 for fixing the evaporator 11 to the base plate 10. The heat - transfer tube 110 has a plurality of straight portions 110a extending in parallel (in the front - rear direction in this specification) and a plurality of U - shaped portions 110b connecting the plurality of straight portions 110a at their respective ends, and has no joints. The heat - transfer tube 110 is formed by bending a plurality of straight pipes into a substantially U - shape multiple times. In FIG. 3, both end portions 110c of the heat - transfer tube 110 are arranged on the front side of the evaporator 11 and are connected to the refrigerant pipe 14 (see FIG. 2) by brazing.

[0014] The fins 111 are thin - film metals and have a plurality of hole portions 111a into which the heat - transfer tube 110 is inserted. The fins 111 are fixed to the straight portions 110a and have a surface orthogonal to the extending direction (front - rear direction) of the straight portions 110a. The tube plates 112 are plate - shaped metals and have a plurality of hole portions 112a into which the heat - transfer tube 110 is inserted, similar to the fins 111. After one of the tube plates 112 is inserted into the heat - transfer tube 110 from the rear side, a plurality of fins 111 are inserted from the rear side, and then the other tube plate 112 is inserted from the rear side, so that the fins 111 and the tube plates 112 are mounted on the heat - transfer tube 110. After inserting the fins 111 and the tube plates 112, the heat - transfer tube 110 is expanded, so that the fins 111 and the tube plates 112 are fixed by closely adhering to the heat - transfer tube 110. That is, the evaporator 11 has no connection portion by brazing other than the both end portions 110c.

[0015] The materials of the heat transfer tubes 110, fins 111, and tube sheets 112 that make up the evaporator 11 are aluminum or aluminum alloys. The surface of the evaporator 11 is subjected to a coating treatment with resins such as acrylic, epoxy, and urethane to improve corrosion resistance. For example, cationic electrodeposition coating, which is a coating with an epoxy-based resin, is applied uniformly to the surface of the evaporator 11 by energizing it after placing the evaporator 11 in an electrolyte solution. The heat transfer tubes 110, fins 111, and tube sheets 112 are further subjected to a surface treatment to improve corrosion resistance. Examples of the surface treatment include bauxite treatment, anodizing treatment, and zinc spraying.

[0016] Next, the structures of the heat insulation box 13 and the evaporator 11 will be described with reference to FIG. 4. In FIG. 4, the heat insulation box 13 includes a lower heat insulation box 130 that surrounds the evaporator 11 from below and an upper heat insulation box 131 that surrounds the evaporator 11 from above. The lower heat insulation box 130 and the upper heat insulation box 131 are made of expanded polystyrene. By surrounding the evaporator 11 with the heat insulation box 13, a cooling space 132 is defined inside the heat insulation box 13. As a result, the air cooled by the evaporator 11 is less likely to exit to the outside of the heat insulation box 13. The heat insulation box 13 is provided with a communication port 133 that communicates the cooling space 132 with the space outside the heat insulation box 13. The heat transfer tubes 110 of the evaporator 11 extend outside the heat insulation box 13 through the communication port 133. Therefore, both end portions 110c are arranged outside the cooling space. Further, the cooling space 132 also communicates with the inside of the agricultural product cold storage 3 (see FIG. 5).

[0017] The refrigerants filled in the refrigeration unit 1 for an agricultural product cold storage are R600a, R1234yf, R290, R32, R474A, etc., which have a relatively low global warming potential. These refrigerants are flammable refrigerants and have a specific gravity heavier than air.

[0018] Next, the operation of the refrigeration unit 1 for the agricultural product cold storage and the air flow in the agricultural product cold storage 3 during the operation of the refrigeration unit 1 for the agricultural product cold storage will be described. FIG. 5 is a cross-sectional view of the agricultural product cold storage 3 and the refrigeration unit 1 for the agricultural product cold storage along the cross-section V-V of FIG. 1. The base plate 10 is provided with two openings 100 that communicate the cooling space 132 and the inside of the agricultural product cold storage 3. The refrigerant that has been compressed by the compressor 15 to a high-temperature and high-pressure state is exhausted of heat by exchanging heat with the outside air in the condenser 17, and becomes a low-temperature and low-pressure state by passing through the capillary tube 16. Thereafter, the refrigerant cools the air in the cooling space 132 in the evaporator 11 and circulates again toward the compressor 15.

[0019] When the cooling fan 12 operates, the air in the agricultural product cold storage 3 circulates in the direction f1 of FIG. 5 and is cooled by the evaporator 11 when passing through the cooling space 132. Since various agricultural products such as rice, vegetables, and pickles are stored in the agricultural product cold storage 3, the air in the agricultural product cold storage 3 may contain acidic substances possessed by the agricultural products. When the air containing acidic substances is cooled by the evaporator, the moisture containing acidic substances in the air may adhere to the evaporator as dew water. When the dew water containing acidic substances adhering to the evaporator dries, only the acidic substances accumulate on the evaporator. When these phenomena occur repeatedly, concentrated acidic substances accumulate on the evaporator 11, corroding the evaporator. As the corrosion progresses, defects may occur, and the refrigerant in the piping may leak. Especially in the brazed connection part, since its surface has an uneven shape due to the brazing material, acidic substances are likely to accumulate. Also, when flux is used during brazing, the flux remains in the connection part, and it is difficult for the coating for improving corrosion resistance to adhere to the surface of the flux. Therefore, the brazed connection part is more likely to have inferior corrosion resistance compared to other parts. Furthermore, for example, when dissimilar metals such as copper-aluminum are connected, in addition to corrosion by acidic substances, galvanic corrosion may also occur, so defects are more likely to occur in the connection part.

[0020] In the refrigeration unit 1 for the agricultural product cold storage of the first embodiment, since both end portions 110c of the evaporator 11 are arranged outside the cooling space 132, that is, since there is no connection portion by brazing in the cooling space 132, acidic substances are difficult to accumulate and corrosion is difficult to occur, so that refrigerant leakage can be suppressed. Further, since the materials of the heat transfer tube 110, the fins 111, and the tube sheet 112 constituting the evaporator 11 are aluminum or an aluminum alloy and there is no connection between dissimilar metals in the evaporator 11, refrigerant leakage due to electrolytic corrosion can also be suppressed.

[0021] Next, the arrangement of the condenser 17, the compressor 15, and the evaporation sheet 19 according to the first embodiment will be described with reference to FIG. 6. In FIG. 6, the compressor 15 is arranged in front of the condenser 17, and the evaporation sheet 19 is arranged in front of the compressor 15. When the refrigeration unit 1 for the agricultural product cold storage operates, the exhaust heat fan 18 attached to the condenser 17 blows air forward (in the direction f2 in FIGS. 6 and 7). That is, the compressor 15 is arranged on the downstream side of the condenser 17 in the ventilation direction f2 by the exhaust heat fan 18, and the evaporation sheet 19 is arranged on the downstream side of the compressor 15 in the ventilation direction f2 by the exhaust heat fan 18.

[0022] The evaporation sheet 19 that spreads in a plane parallel to the vertical and front-rear directions is a sheet for evaporating the dew water generated in the evaporator 11 upward, and a plurality of them are arranged side by side in the left-right direction so as to have a plane orthogonal to the flat plate surface of the base plate 10 and parallel to the ventilation direction f2. The evaporation sheet 19 is made of polyester fiber subjected to a hydrophilic treatment in order to improve water absorption, and a porous material having a pore diameter of about 1.7 μm to 3.1 μm is used. For example, UNIVEX / UNIVEKS (registered trademark) manufactured by Unitika Ltd. is used. Further, since antibacterial processing is applied to UNIVEX / UNIVEKS (registered trademark), it is possible to suppress mold generated by long-term retention of dew water and suppress a decrease in the evaporation performance of the evaporation sheet 19 due to aging deterioration. The antibacterial processing is performed by weaving activated carbon fibers that adsorb highly volatile hydrophilic gas into a non-woven fabric.

[0023] Next, the flow of the condensed water will be described with reference to FIG. 7. FIG. 7 is a view showing only the base plate 10 and the evaporation sheet 19 in the refrigeration unit 1 for a crop cold storage. On the base plate 10, a dew receiving tray 101 is provided in the region where the evaporator 11 is arranged. The dew receiving tray 101 is a container for receiving the condensed water generated by the evaporator 11. The base plate 10 is further provided with a water channel 102 for the condensed water to flow from the dew receiving tray 101 toward the evaporation sheet 19. The base plate 10, the dew receiving tray 101, and the water channel 102 may be integrally formed. The dew receiving tray 101 is provided with a plurality of guides 101a for guiding the condensed water to the water channel 102. The condensed water that has fallen onto the dew receiving tray 101 flows through the water channel 102 and toward the evaporation sheet 19 (direction f3 in FIG. 7). The height of the base plate 10 in the region where the water channel 102 is provided is lower than the height of the base plate 10 in the region where the evaporation sheet 19 is arranged. Therefore, the condensed water that has passed through the water channel 102 once does not flow backward and return to the dew receiving tray 101.

[0024] The condensed water adhering to the evaporation sheet 19 evaporates due to the wind from the exhaust heat fan 18, thereby generating an upward airflow f4. When a combustible refrigerant having a specific gravity heavier than air leaks, the upward airflow f4 diffuses the combustible refrigerant staying below the refrigeration unit 1 for a crop cold storage upward, and the concentration of the combustible refrigerant can be suppressed below the lower flammability limit (LFL).

[0025] In addition, since the evaporation sheet 19 is disposed downstream of the ventilation direction f2 by the exhaust heat fan 18 with respect to the compressor 15, the air that has passed through the compressor 15 is applied to the evaporation sheet 19. During the operation of the refrigeration unit 1 for the agricultural product cold storage, the surface temperature of the compressor 15 is about 70 to 80°C. Therefore, since the air applied to the evaporation sheet 19 is heated by the compressor 15 and becomes relatively high temperature, the evaporation of the condensed water adhering to the evaporation sheet 19 is promoted, and the condensed water can be efficiently evaporated. Further, since a plurality of evaporation sheets 19 are arranged side by side in the left-right direction so that the evaporation sheet 19 has a surface orthogonal to the base plate 10 and parallel to the ventilation direction f2, the air can be evenly applied to the plurality of evaporation sheets 19, and the condensed water can be more efficiently evaporated. Note that depending on the size of the compressor 15 in the left-right, front-back direction, the flow direction of the air downstream in the ventilation direction f2 of the compressor 15 may change, and the direction of the surface of the evaporation sheet 19 may be changed according to the flow direction of the air. For example, the surface of the evaporation sheet 19 may be inclined within a range of ±45° with respect to a direction orthogonal to the base plate 10 and parallel to the ventilation direction f2.

[0026] According to the refrigeration unit 1 for the agricultural product cold storage according to the first embodiment, the following effects are achieved.

[0027] (1) It has a plurality of straight portions 110a extending in parallel and a plurality of U-shaped portions 110b connecting the plurality of straight portions 110a at their respective ends, and a single heat transfer tube 110 having no joints, a plurality of fins 111 fixed to the straight portion 110a and having a surface orthogonal to the extending direction of the straight portion, and includes an evaporator 11 having no brazed connection portion other than both end portions 110c of the heat transfer tube 110, a heat insulation box 13 surrounding the evaporator 11, a cooling space 132 defined inside the heat insulation box 13, and a refrigerant pipe 14 connected to both end portions 110c outside the cooling space 132 through which the refrigerant flows. is provided. As a result, the refrigerant pipe 14 is connected to the evaporator 11 outside the cooling space 132, and there is no brazed connection part in the cooling space 132, so it is possible to suppress the occurrence of pipe defects due to corrosion and the leakage of the refrigerant.

[0028] (2) The refrigerant is a flammable refrigerant. As a result, it is possible to suppress the possibility of leakage of the flammable refrigerant.

[0029] (3) The surface of the evaporator 11 is subjected to a painting treatment with acrylic, epoxy, or urethane. As a result, the corrosion resistance of the evaporator 11 can be improved, and the possibility of refrigerant leakage can be suppressed.

[0030] (4) The materials of the heat transfer tubes 110 and the fins 111 are aluminum or an aluminum alloy, and the heat transfer tubes 110 and the fins 111 are subjected to a boehmite treatment, an anodizing treatment, or a zinc spraying. As a result, since the materials of the heat transfer tubes 110 and the fins 111 constituting the evaporator 11 are aluminum or an aluminum alloy, there is no connection part between dissimilar metals in the cooling space 132, and corrosion due to galvanic corrosion is less likely to occur, and the possibility of refrigerant leakage can be suppressed. Further, since the heat transfer tubes 110 and the fins 111 are subjected to a boehmite treatment, an anodizing treatment, or a zinc spraying, the corrosion resistance of the evaporator 11 can be further improved, and the possibility of refrigerant leakage can be suppressed.

[0031] (5) The base plate 10, the condenser 17 disposed on the base plate 10, the exhaust heat fan 18 attached to the condenser 17, and in the base plate 10, the compressor 15 disposed on the downstream side in the ventilation direction f2 by the exhaust heat fan 18 with respect to the condenser 17, In the base plate 10, there is an evaporation sheet 19 which is arranged on the downstream side of the compressor 15 in the ventilation direction f2 and has a surface orthogonal to the base plate 10 and parallel to the ventilation direction f2, and further includes.

[0032] As a result, since the evaporation sheet 19 is arranged on the downstream side of the compressor 15 in the ventilation direction f2, the air heated by the compressor 15 is applied, and the dew water adhering to the evaporation sheet 19 can be efficiently evaporated. Further, since the evaporation sheet 19 has a surface orthogonal to the base plate 10 and parallel to the ventilation direction f2, the air can be evenly applied to the evaporation sheet 19, and the dew water can be more efficiently evaporated. Furthermore, since an upward airflow f4 is generated by the evaporation of the dew water, even if a combustible refrigerant having a specific gravity heavier than that of air leaks, the combustible refrigerant can be diffused upward, and the concentration of the combustible refrigerant can be suppressed below the lower flammability limit (LFL).

[0033] (6) The material of the evaporation sheet 19 is a porous material, and the evaporation sheet 19 is subjected to a hydrophilic treatment. As a result, the evaporation sheet 19 easily absorbs dew water, so that the dew water can be efficiently evaporated.

[0034] (7) The evaporation sheet 19 is subjected to an antibacterial treatment. As a result, the generation of mold due to the dew water adhering to the evaporation sheet 19 can be suppressed, and the deterioration of the evaporation performance of the evaporation sheet 19 can be suppressed.

[0035] [Second Embodiment] FIG. 8 is an exploded perspective view similar to FIG. 6 of the refrigeration unit 2 for a crop cold storage according to the second embodiment. Hereinafter, only the configurations different from those of the first embodiment will be described.

[0036] In FIG. 8, the compressor 15 is disposed downstream of the condenser 17 in the ventilation direction f2 by the exhaust heat fan 18, and the evaporation sheet 19 is disposed between the compressor 15 and the condenser 17. That is, the evaporation sheet 19 is disposed upstream of the compressor 15 in the ventilation direction. For this reason, the evaporation sheet 19 is hit by the wind that has just passed through the exhaust heat fan 18 and has a relatively high flow velocity, so that the evaporation of the condensed water adhering to the evaporation sheet 19 is promoted, and the condensed water can be efficiently evaporated. Further, there may be a guide for guiding the condensed water to the evaporation sheet 19 on the right side of the base plate 10 so that the condensed water flowing from the evaporator 11 can directly reach the evaporation sheet 19.

[0037] According to the refrigeration unit 2 for a crop cold storage according to the second embodiment, the following effects are achieved.

[0038] (8) A base plate 10, A condenser 17 disposed on the base plate 10, An exhaust heat fan 18 attached to the condenser 17, In the base plate 10, a compressor 15 disposed downstream of the condenser 17 in the ventilation direction f2 by the exhaust heat fan 18, In the base plate 10, an evaporation sheet 19 disposed between the compressor 15 and the condenser 17 and having a plane orthogonal to the base plate 10 and parallel to the ventilation direction f2 are further provided.

[0039] As a result, since the evaporation sheet 19 is hit by the wind with a relatively high flow velocity, the condensed water can be efficiently evaporated.

[0040] Note that the refrigeration unit for a crop cold storage according to the present disclosure is not limited to the configuration of the above embodiment, and various modifications are possible.

[0041] [Appendix] The refrigeration unit for a crop cold storage according to the present disclosure provides the following aspects.

[0042] [Aspect 1] It has a plurality of straight portions extending in parallel and a plurality of U-shaped portions connecting the plurality of straight portions at their respective ends, and is a single heat transfer tube without joints, a plurality of fins fixed to the straight portions and having a surface orthogonal to the extending direction of the straight portions, and an evaporator having no brazed connection portions other than both ends of the heat transfer tube, a heat insulation box surrounding the evaporator, a cooling space defined inside the heat insulation box, and a refrigerant pipe connected to both ends outside the cooling space through which refrigerant flows, A refrigeration unit for a crop cold storage.

[0043] [Aspect 2] The refrigerant is a flammable refrigerant, The refrigeration unit for a crop cold storage according to Aspect 1.

[0044] [Aspect 3] The surface of the evaporator is subjected to a painting treatment with acrylic, epoxy, or urethane, The refrigeration unit for a crop cold storage according to Aspect 1 or 2.

[0045] [Aspect 4] The materials of the heat transfer tube and the fins are aluminum or an aluminum alloy, and the heat transfer tube and the fins are subjected to boehmite treatment, anodizing treatment, or zinc spraying, The refrigeration unit for a crop cold storage according to any one of Aspects 1 to 3.

[0046] [Aspect 5] A base plate, a condenser disposed on the base plate, an exhaust heat fan attached to the condenser, and a compressor disposed on the base plate on the downstream side of the ventilation direction by the exhaust heat fan with respect to the condenser, In the base plate, an evaporation sheet is disposed on the downstream side in the ventilation direction with respect to the compressor, and has a surface orthogonal to the base plate and parallel to the ventilation direction The refrigeration unit for a crop cold storage according to any one of Aspects 1 to 4, further comprising

[0047] [Aspect 6] A base plate, A condenser disposed on the base plate, An exhaust heat fan attached to the condenser, In the base plate, a compressor is disposed on the downstream side in the ventilation direction by the exhaust heat fan with respect to the condenser, In the base plate, an evaporation sheet is disposed between the compressor and the condenser, and has a surface orthogonal to the base plate and parallel to the ventilation direction The refrigeration unit for a crop cold storage according to Aspects 1 to 4, further comprising

[0048] [Aspect 7] The material of the evaporation sheet is a porous material, The evaporation sheet is subjected to a hydrophilic treatment The refrigeration unit for a crop cold storage according to Aspect 5 or 6

[0049] [Aspect 8] The evaporation sheet is subjected to an antibacterial treatment The refrigeration unit for a crop cold storage according to any one of Aspects 5 to 7

Explanation of Signs

[0050] 1, 2: Refrigeration unit for crop cold storage 10: Base plate 11: Evaporator 110: Heat transfer tube 110a: Straight part 110b: U-shaped part 110c: Both ends 111: Fin 13: Heat insulation box 132: Cooling space 14: Refrigerant pipe 15: Compressor 17: Condenser 18: Exhaust fan 19: Evaporation sheet f2: Ventilation direction

Claims

1. It has a plurality of straight portions extending in parallel and a plurality of U-shaped portions connecting the plurality of straight portions at their respective ends, and is a single heat transfer tube without joints, A plurality of fins fixed to the straight portion and having a surface orthogonal to the extending direction of the straight portion, An evaporator having no brazed connection portions other than both ends of the heat transfer tube, A heat insulation box surrounding the evaporator, A cooling space defined inside the heat insulation box, A refrigerant pipe connected to both ends on the outside of the cooling space through which refrigerant flows, A refrigeration unit for a crop cold storage comprising the above.

2. The refrigerant is a flammable refrigerant. The refrigeration unit for a crop cold storage according to claim 1.

3. The surface of the evaporator is subjected to a coating treatment with acrylic, epoxy, or urethane. The refrigeration unit for a crop cold storage according to claim 2.

4. The materials of the heat transfer tube and the fins are aluminum or an aluminum alloy, The heat transfer tube and the fins are subjected to boehmite treatment, anodizing treatment, or zinc spraying. The refrigeration unit for a crop cold storage according to claim 2.

5. A base plate, A condenser disposed on the base plate, An exhaust heat fan attached to the condenser, A compressor disposed on the base plate on the downstream side in the ventilation direction by the exhaust heat fan with respect to the condenser, An evaporation sheet disposed on the base plate on the downstream side in the ventilation direction with respect to the compressor and having a surface orthogonal to the base plate and parallel to the ventilation direction, The refrigeration unit for a crop cold storage according to claim 2, further comprising

6. a base plate, a condenser disposed on the base plate, an exhaust heat fan attached to the condenser, a compressor disposed on the base plate on the downstream side in the ventilation direction by the exhaust heat fan with respect to the condenser, an evaporation sheet disposed between the compressor and the condenser on the base plate, having a surface orthogonal to the base plate and parallel to the ventilation direction, The refrigeration unit for a crop cold storage according to claim 2, further comprising

7. The material of the evaporation sheet is a porous material, and the evaporation sheet is subjected to a hydrophilic treatment. The refrigeration unit for a crop cold storage according to claim 5 or 6.

8. The evaporation sheet is subjected to an antibacterial treatment. The refrigeration unit for a crop cold storage according to claim 7.

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