Refrigeration system for fishing vessels

Abstract

This invention provides a refrigeration system for fishing vessels that simplifies the configuration and reduces installation space, even when using refrigerants such as ammonia. [Solution] The system comprises multiple oil-cooled single-stage screw compressors 4-6, a first fish hold 2 cooled by the multiple oil-cooled single-stage screw compressors 4-6, and at least one second fish hold 3. The first fish hold 2 and the second fish hold 3 each have different cooling temperature ranges. The first fish hold 2 is cooled by operating each of the multiple oil-cooled single-stage screw compressors 4-6 in parallel in a single-stage compression system, while the second fish hold 3 is cooled by operating the multiple oil-cooled single-stage screw compressors 4-6 in series, combining them as the lower and upper stages of a two-stage compression system.

Description

Technical Field

[0001] The present invention relates to a refrigeration system for fishing vessels.

Background Art

[0002] For example, in a refrigeration system for fishing vessels mounted on ocean fishing vessels, in order to maintain the freshness of fish, brine freezing of fish is performed at about -20°C. Further, the fish storage for storing fish is cooled to about -50°C to perform cold storage treatment of fish. For generating different temperature ranges for each of these processes, for example, a two-stage reciprocating compressor having a low-stage side and a high-stage side is used. This type of reciprocating compressor can be switched between single-stage compression operation or two-stage compression operation. Thus, by operating the reciprocating compressor in the single-stage compression mode, brine freezing treatment is performed. Also, by operating the reciprocating compressor in the two-stage compression mode, cold storage treatment is performed.

[0003] Here, in recent years, due to considerations for the global environment, the use of ammonia, a natural refrigerant, as a refrigerant used in refrigeration systems has been increasing. When ammonia is used as a refrigerant, the discharge temperature in the compression process becomes higher compared to other refrigerants. In order to prevent deterioration of the refrigeration oil due to this high discharge temperature, various techniques have been proposed.

[0004] For example, a refrigeration system (refrigeration device) has been proposed, which is composed of a main refrigeration device including at least a two-stage compressor, a condenser, an expansion valve, and an evaporator, and a sub-refrigeration device including at least a single-stage compressor, a condenser, an expansion valve, and an evaporator. As the compressor, a reciprocating compressor is used (for example, see Patent Document 1). According to this, by supplying the condenser cooling water cooled by the evaporator of the sub-refrigeration device to the condenser of the main refrigeration device via a circulation pump, the condensation temperature of the refrigerant gas can be lowered compared to the case where it is condensed by normal-temperature cooling water.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-214611 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the conventional technology described above has the drawback of requiring a secondary refrigeration unit to cool the cooling water, which complicates the refrigeration system's configuration and increases the installation space required. In particular, since installation space is limited in refrigeration systems installed on fishing vessels, the conventional technology described above is difficult to install on some fishing vessels. Furthermore, if ammonia is used as a refrigerant, for example, the discharge temperature of a reciprocating compressor becomes high. In such cases, the refrigerant oil can carbonize, potentially clogging components such as strainers, leading to malfunctions in the refrigeration system, inefficient operation, and even compressor failures.

[0007] Therefore, the present invention provides a refrigeration system for fishing vessels that can simplify the configuration even when using a refrigerant such as ammonia, reduce installation space, and suppress the rise in discharge temperature, thereby preventing malfunctions in the compressor. [Means for solving the problem]

[0008] To solve the above problems, the refrigeration system for fishing vessels according to the present invention comprises a plurality of oil-cooled single-stage screw compressors, a first fish hold cooled by the plurality of oil-cooled single-stage screw compressors, and at least one second fish hold, wherein the first fish hold and the second fish hold have different cooling temperature ranges, the first fish hold is cooled by operating each of the plurality of oil-cooled single-stage screw compressors in parallel in a single-stage compression method, and the second fish hold is cooled by operating the plurality of oil-cooled single-stage screw compressors in series, combining them as the lower stage and upper stage of a two-stage compression method.

[0009] Thus, by using an oil-cooled single-stage screw compressor, the rise in discharge temperature can be suppressed compared to a reciprocating compressor, even when ammonia is used as the refrigerant. This helps to prevent compressor malfunctions. Furthermore, in the cooling of the first fish hold, multiple oil-cooled single-stage screw compressors are operated in parallel using a single-stage compression method, while in the cooling of the second fish hold, multiple oil-cooled single-stage screw compressors are combined as the lower and upper stages of a two-stage compression method and operated in series. In this way, by switching the operating method of the oil-cooled single-stage screw compressors, each fish hold can be kept in a different cooling temperature range. In other words, it becomes possible to perform brine freezing and cooling treatments for fish while suppressing the rise in discharge temperature of each oil-cooled single-stage screw compressor. Therefore, since a device for cooling the cooling water, as in conventional systems, is no longer necessary, the configuration of the refrigeration system for fishing vessels can be simplified, even when using refrigerants such as ammonia, and the installation space can be reduced.

[0010] In the above configuration, the temperature range of the second fish hold is lower than the temperature range of the first fish hold.

[0011] This configuration allows for operation in a single-stage or two-stage compression mode using each oil-cooled single-stage screw compressor appropriately, depending on the temperature range required for refrigeration. More specifically, the first fish hold can be used for, for example, brine freezing of fish. The second fish hold can be used for refrigeration of fish. This improves the operating efficiency of the refrigeration system 1 for fishing vessels.

[0012] In the above configuration, a two-stage compression connecting passage connects the discharge side of at least one oil-cooled single-stage screw compressor to the suction side of at least one oil-cooled single-stage screw compressor, and a first valve is provided in the two-stage compression connecting passage for opening and closing the two-stage compression connecting passage. When operating in parallel in a single-stage compression system, the two-stage compression connecting passage is closed by the first valve, and when operating in a two-stage compression system, the two-stage compression connecting passage is opened by the first valve.

[0013] This configuration allows for a simple yet reliable operation of either a single-stage or two-stage compression system using a separate oil-cooled single-stage screw compressor for each fish hold.

[0014] In the above configuration, a second valve is provided on the discharge side of the oil-cooled single-stage screw compressor, which is the lower stage in the two-stage compression system, and is used to open and close the discharge side of the oil-cooled single-stage screw compressor. When operating in parallel in the single-stage compression system, the discharge side of the oil-cooled single-stage screw compressor is opened, and when operating in the two-stage compression system, the discharge side of the oil-cooled single-stage screw compressor is closed.

[0015] This configuration allows for more reliable operation of each oil-cooled single-stage screw compressor in either a single-stage or two-stage compression configuration for each fish hold. [Effects of the Invention]

[0016] According to the present invention, even when using refrigerants such as ammonia, the configuration of the refrigeration system for fishing vessels can be simplified, installation space can be reduced, and the rise in discharge temperature can be suppressed, thereby preventing malfunctions in the compressor. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram of a refrigeration system for fishing vessels according to an embodiment of the present invention. [Figure 2] This is an explanatory diagram illustrating the cooling of brine in the first fish hold according to an embodiment of the present invention. [Figure 3] This is an explanatory diagram illustrating the cooling of the inside of the second fish storage compartment in an embodiment of the present invention. [Modes for carrying out the invention]

[0018] Next, embodiments of the present invention will be described with reference to the drawings.

[0019] <Refrigeration systems for fishing vessels> Figure 1 is a schematic configuration diagram of the fishing boat refrigeration system 1. The fishing boat refrigeration system 1 is provided on a fishing boat not shown. As shown in Figure 1, the fishing boat refrigeration system 1 includes two fish holds 2 and 3 (the first fish hold 2 and the second fish hold 3) where fish not shown are stored, and three oil-cooled single-stage screw compressors 4, 5, and 6 (the first oil-cooled single-stage screw compressor 4, the second oil-cooled single-stage screw compressor 5, the third oil-cooled single-stage screw compressor 6; hereinafter simply referred to as the first compressor 4, the second compressor 5, and the third compressor 6) connected to the two fish holds 2 and 3, and a condenser 7 provided between each fish hold 2 and each compressor 4 to 6. In the fishing boat refrigeration system 1, a refrigerant such as ammonia (hereinafter simply referred to as the refrigerant) flows. Hereinafter, when referring to the downstream side, the upstream side, etc. based on the flow direction of the refrigerant.

[0020] Of the two fish holds 2 and 3, the first fish hold 2 freeze fish not shown with brine. The cold preservation temperature range of the brine is maintained at about -10°C to -20°C by each compressor 4, 5, and 6. Of the two fish holds 2 and 3, the second fish hold 3 further preserves the fish frozen in the first fish hold 2 at a lower temperature. The cold preservation temperature range inside the second fish hold 3 is maintained at about -40°C to -60°C by each compressor 4, 5, and 6.

[0021] The suction ports 4a to 6a of each of the three compressors 4 to 6 are connected in parallel to the first fish hold 2 and the second fish hold 3 via the first connection path 8. On the side of each fish hold 2 and 3 of the first connection path 8, the first fish hold outflow path 9a extending from the first fish hold 2 and the second fish hold outflow path 9b extending from the second fish hold 3 merge. On the side of each compressor 4 to 6 of the first connection path 8, three branched suction paths 10a, 10b, and 10c (the first suction path 10a, the second suction path 10b, the third suction path 10c) are provided.

[0022] Of the three intake passages 10a to 10c, the first intake passage 10a is connected to the intake port 4a of the first compressor 4. Of the three intake passages 10a to 10c, the second intake passage 10b is connected to the intake port 5a of the second compressor 5. Of the three intake passages 10a to 10c, the third intake passage 10c is connected to the intake port 6a of the third compressor 6. An intake valve 11 is provided in the first intake passage 10a. The intake valve 11 opens and closes the first intake passage 10a.

[0023] The first discharge passage 12a is connected to the discharge port 4b of the first compressor 4. The second discharge passage 12b is connected to the discharge port 5b of the second compressor 5. The third discharge passage 12c is connected to the discharge port 6b of the third compressor 6. Of the three discharge passages 12a to 12c, the second discharge passage 12b and the third discharge passage 12c are each provided with a discharge valve (an example of the second valve in the claim) 16. Each discharge valve 16 opens and closes the corresponding discharge passages 12b and 12c.

[0024] Between the second discharge passage 12b and the third discharge passage 12c and the first suction passage 10a, a two-stage compression connecting passage 20 is provided to connect these discharge passages 12b, 12c and the suction passage 10a. The two-stage compression connecting passage 20 includes a first low-stage passage 20a connected between the second compressor 5 and the discharge valve 16 in the second discharge passage 12b, a second low-stage passage 20b connected between the third compressor 6 and the discharge valve 16 in the third discharge passage 12c, and a confluence passage 20c into which the first low-stage passage 20a and the second low-stage passage 20b merge.

[0025] The downstream side of the confluence passage 20c is connected to the first intake passage 10a between the first compressor 4 and the intake valve 11. Each low-stage passage 20a, 20b is provided with a low-stage discharge valve (an example of the first valve in the claim) 22. Each low-stage discharge valve 22 opens and closes the corresponding low-stage passages 20a, 20b. In other words, each low-stage discharge valve 22 opens and closes the two-stage compression connecting passage 20.

[0026] Each discharge passage 12a to 12c is consolidated and connected to each fish hold 2 and 3 via a second connecting passage 13. A condenser 7 is provided in the second connecting passage 13. On each of the fish holds 2 and 3 sides of the second connecting passage 13, branched first fish hold inflow passages 14a and 2 fish hold inflow passages 14b are provided. The first fish hold inflow passage 14a is connected to the first fish hold 2. The second fish hold inflow passage 14b is connected to the second fish hold 3.

[0027] The first fish hold inlet passage 14a is equipped with a first fish hold valve 15a. The second fish hold inlet passage 14b is equipped with a second fish hold valve 15b. These fish hold valves 15a and 15b open and close the corresponding fish hold inlet passages 14a and 14b, respectively. In addition, the fish hold valves 15a and 15b function as expansion valves.

[0028] <Operating Instructions for Refrigeration Systems on Fishing Vessels> Next, the operation method of the fishing vessel refrigeration system 1 will be explained based on Figures 2 and 3. The fishing vessel refrigeration system 1 operates differently depending on whether it is cooling the brine in the first fish hold 2 or the contents of the second fish hold 3. Therefore, we will first explain the operation when cooling the brine in the first fish hold 2.

[0029] Figure 2 is an explanatory diagram for the cooling of brine in the first fish hold 2. Figure 2 corresponds to the aforementioned Figure 1. As shown in Figure 2, when cooling the brine in the first fish hold 2, the intake valve 11, the discharge valve 16, and the first fish hold valve 15a are opened. On the other hand, the second fish hold valve 15b and the low-stage discharge valve 22 are closed. As a result, a parallel refrigerant flow path 31 (see the thick line in Figure 2) is formed in parallel with respect to the first fish hold 2 by the connection passages 8, 13, the discharge passages 12a to 12c, and the first fish hold inlet passage 14a, with the three compressors 4 to 6 connected in parallel, and the two-stage compression connection passage 20 is blocked.

[0030] In the parallel refrigerant flow path 31, each of the compressors 4 to 6 operates in parallel using a single-stage compression method, allowing refrigerant to flow (see arrows in Figure 2). As a result, the brine in the first fish hold 2 is cooled via a heat exchanger (evaporator) not shown. The cooled brine then freezes the fish brought into the first fish hold 2.

[0031] Next, we will explain the case of cooling the inside of the second fish hold 3. Figure 3 is an explanatory diagram for the cooling of the interior of the second fish hold 3. Figure 3 corresponds to Figure 1 mentioned above. As shown in Figure 3, when cooling the second fish hold 3, the intake valve 11, the discharge valve 16, and the first fish hold valve 15a are closed. On the other hand, the second fish hold valve 15b and the low-stage discharge valve 22 are opened. As a result, a series refrigerant flow path 32 (see the thick line in Figure 3) is formed in relation to the second fish hold 3, with the first compressor 4, the second compressor 5, and the third compressor 6 connected in series by the respective connection passages 8, 13, the respective discharge passages 12a to 12c, the two-stage compression connection passage 20, and the second fish hold inlet passage 14b.

[0032] In other words, in the series refrigerant flow path 32, the two-stage compression connection path 20 is opened, and the compressors 4 to 6 are combined in a two-stage compression system. More specifically, the second compressor 5 and the third compressor 6 function as the lower stage, and the first compressor 4 functions as the higher stage. The compressors 4 to 6, combined in this way, are operated in series in a two-stage compression system, and refrigerant flows through the series refrigerant flow path 32 (see arrow in Figure 3). As a result, the air inside the second fish hold 3 is cooled by a heat exchanger (evaporator) (not shown) installed inside the hold, and the fish are kept cold.

[0033] As described above, the fishing vessel refrigeration system 1 includes three compressors 4-6 and two fish holds 2 and 3 with different temperature ranges. The three compressors 4-6 are oil-cooled single-stage screw compressors. Oil-cooled single-stage screw compressors cool the refrigerant by supplying oil to the compression space when the refrigerant is compressed. Therefore, even when ammonia is used as the refrigerant, the rise in discharge temperature can be suppressed compared to a reciprocating compressor, and malfunctions in compressors 4-6 can be prevented.

[0034] Unlike reciprocating compressors, screw compressors 4-6 cannot be compounded (they cannot switch between single-stage and double-stage compression operation individually). Using these compressors 4-6, the fish holds 2 and 3 are cooled by switching between single-stage and double-stage compression operation. More specifically, the first fish hold 2 is cooled by operating compressors 4-6 in parallel in single-stage compression mode. The second fish hold 3 is cooled by directly operating the second compressor 5 and third compressor 6 as the lower stage of a double-stage compression system, and the first compressor 4 as the higher stage of a double-stage compression system. In this way, by switching the operation mode of each compressor 4-6, the cooling temperature range of the first fish hold 2 and the second fish hold 3 can be made different. That is, it becomes possible to perform brine freezing and cooling treatment of fish while suppressing the rise in discharge temperature of each compressor 4-6. Therefore, since a device for cooling the cooling water, as in conventional systems, is no longer necessary, the configuration of the fishing vessel refrigeration system 1 can be simplified and the installation space can be reduced, even when using a refrigerant such as ammonia.

[0035] Of the two fish holds 2 and 3, the first fish hold 2, which has a higher temperature range, is cooled by operating compressors 4 to 6 in parallel using a single-stage compression method. Of the two fish holds 2 and 3, the second fish hold 3, which has a lower temperature range, is cooled by operating compressors 4 to 6 in series using a two-stage compression method. In this way, by operating compressors 4 to 6 appropriately according to the temperature range, the operating efficiency of the fishing vessel refrigeration system 1 can be improved.

[0036] The fishing vessel refrigeration system 1 includes a two-stage compression connection passage 20 and a low-stage discharge valve 22 for opening and closing the two-stage compression connection passage 20. By closing the low-stage discharge valve 22, the two-stage compression connection passage 20 is closed, forming a parallel refrigerant flow path 31, and each of the compressors 4 to 6 is operated in parallel using a single-stage compression method. On the other hand, by opening the low-stage discharge valve 22, the two-stage compression connection passage 20 is opened, forming a series refrigerant flow path 32, and the compressors 4 to 6 are operated using a two-stage compression method. In this way, it is possible to operate the compressors 4 to 6 in a single-stage compression method or a two-stage compression method for each of the fish holds 2 and 3 with a simple structure and with reliable reliability.

[0037] The fishing vessel refrigeration system 1 is equipped with discharge valves 16 that open and close the discharge passages 12b and 12c of the second compressor 5 and third compressor 6, which are on the lower side in the two-stage compression system. By opening these discharge valves 16, a parallel refrigerant flow path 31 is formed, and the compressors 4 to 6 are operated in parallel in a single-stage compression system. On the other hand, by closing the discharge valves 16, a series refrigerant flow path 32 is formed, and the compressors 4 to 6 are operated in a two-stage compression system. In this way, it is possible to operate each of the fish holds 2 and 3 using compressors 4 to 6 in either a single-stage compression system or a two-stage compression system with a simple structure and with greater reliability.

[0038] The present invention is not limited to the embodiments described above, but includes various modifications to the embodiments described above, without departing from the spirit of the invention.

[0039] For example, in the above embodiment, the case in which the refrigeration system 1 for fishing vessels is equipped with three compressors 4 to 6 was described. However, it is not limited to this, and the number of compressors can be two or more. Even if there are four or more compressors, when cooling the second fish hold 3, each compressor can be used in series operation as the lower and upper stages of a two-stage compression system.

[0040] In the above-described embodiment, the first fish storage 2 was described in which fish are brine-frozen by cooling the brine. The second fish storage 3 was described in which fish are kept cool by cooling the inside of the storage shed. However, the method of freezing fish in each fish storage shed 2 and 3 can be arbitrarily selected. For example, the inside of the first fish storage shed 2 may be cooled and the fish may be brine-frozen in the second fish storage shed 3. It is sufficient that the cooling temperature ranges of each fish storage shed 2 and 3 are different.

[0041] In the embodiments described above, the case in which the suction valve 11 is provided in the first suction passage 10a was explained. The case in which the discharge valve 16 is provided in the second discharge passage 12b and the third discharge passage 12c was explained. However, the invention is not limited to these cases, and an suction valve 11 may be provided in each of the suction passages 10a to 10c.

[0042] When operating in a two-stage compression system using compressors 4-6, it is sufficient to use one of the compressors 4-6 with the suction valve 11 closed as the higher stage. In other words, by opening and closing the discharge valve 16, it is possible to allow or block the intake of refrigerant by each of the compressors 4-6. On the other hand, the discharge valve 16 only needs to be provided in at least two of the discharge passages 12a to 12c connected to the compressors 4 to 6 used on the lower stage. It is also possible to provide a discharge valve 16 in each of the discharge passages 12a to 12c.

[0043] In the above embodiment, the case in which each of the three compressors 4 to 6 is operated to cool the brine in the first fish hold 2 was described. However, it is not limited to this, and it is also possible to increase or decrease the number of compressors 4 to 6 that are operated depending on the cooling temperature range of the first fish hold 2.

[0044] In the above-described embodiment, the fishing vessel refrigeration system 1 was described in a case where it is equipped with one first fish hold 2 and one second fish hold 3. However, it is not limited to this, and there may be two or more second fish holds 3. It is sufficient that the refrigeration temperature range of the first fish hold 2 and the refrigeration temperature range of the second fish hold 3 are different. It is also possible to increase or decrease the number of compressors 4 to 6 according to the number of second fish holds 3. [Explanation of Symbols]

[0045] 1… Refrigeration system for fishing vessels 2…First Uokura 3…Second Uokura 4…First oil-cooled single-stage screw compressor (oil-cooled single-stage screw compressor) 4a, 5a, 6a…Suction port (suction side) 4b,5b,6b…Discharge port (discharge side) 5…Second oil-cooled single-stage screw compressor (oil-cooled single-stage screw compressor) 6…Third oil-cooled single-stage screw compressor (oil-cooled single-stage screw compressor) 16…Discharge valve (second valve) 20…Connecting path for two-stage compression 22... Low-stage discharge valve (1st valve) 31…Parallel refrigerant flow path 32…Series refrigerant flow path

Claims

1. Multiple oil-cooled single-stage screw compressors, A first fish hold cooled by the aforementioned plurality of oil-cooled single-stage screw compressors, and at least one second fish hold, Equipped with, The first fish hold and the second fish hold each have different temperature zones for maintaining their temperature. The first fish hold is cooled by operating each of the plurality of oil-cooled single-stage screw compressors in parallel in a single-stage compression system, and the second fish hold is cooled by operating the plurality of oil-cooled single-stage screw compressors in series, combining them as the lower and upper stages of a two-stage compression system. A refrigeration system for fishing vessels characterized by the following features.

2. The temperature range of the second fish warehouse is lower than the temperature range of the first fish warehouse. The refrigeration system for fishing vessels according to claim 1.

3. A two-stage compression connecting passage connecting the discharge side of at least one oil-cooled single-stage screw compressor to the suction side of at least one oil-cooled single-stage screw compressor, A first valve is provided in the aforementioned two-stage compression connection path, which opens and closes the aforementioned two-stage compression connection path. Equipped with, When operating in parallel in a single-stage compression system, the first valve blocks the two-stage compression connection path, and when operating in a two-stage compression system, the first valve opens the two-stage compression connection path. A refrigeration system for fishing vessels according to claim 1 or 2, characterized by the features described herein.

4. In a two-stage compression system, a second valve is provided on the discharge side of the oil-cooled single-stage screw compressor, which is the lower stage, and is used to open and close the discharge side of the oil-cooled single-stage screw compressor. When operating in parallel in a single-stage compression system, the discharge side of the oil-cooled single-stage screw compressor is opened, and when operating in a two-stage compression system, the discharge side of the oil-cooled single-stage screw compressor is shut off. The refrigeration system for fishing vessels according to claim 3.

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