Heat exchangers and refrigeration systems

Abstract

To provide a compact, low-cost heat exchanger and refrigeration system. [Solution] A heat exchanger according to one aspect of the present invention comprises a fin module having a plurality of fins, each having refrigerant holes and hot brine holes formed at offset positions from each other when viewed from the X direction, with the plurality of fins spaced apart in the X direction; a refrigerant flow path provided in the fin module so as to penetrate each of the refrigerant holes in the X direction, through which the refrigerant flows; and a hot brine flow path provided in the fin module so as to penetrate each of the hot brine holes in the X direction, through which brine at a higher temperature than the refrigerant flows. The outer diameter of the hot brine flow path is smaller than the outer diameter of the refrigerant flow path.

Description

Technical Field

[0001] The present invention relates to a heat exchanger and a refrigeration system.

Background Art

[0002] In a refrigeration system, moisture in a refrigerated warehouse evaporates and adheres to an evaporator as frost. When frost adheres to the evaporator, the heat exchange efficiency decreases due to a reduction in the heat transfer area and an obstruction to the flow of air in the warehouse. Therefore, in a refrigeration system, it is necessary to periodically defrost the frost adhering to the evaporator. For example, in Patent Document 1 below, a configuration for defrosting by supplying heated brine to the evaporator through a brine circuit is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, there is a problem in that providing a brine circuit in the evaporator leads to an increase in the size of the evaporator. Further, in a configuration for defrosting with brine as in the prior art, there is still room for improvement in reducing the filling amount of brine to achieve cost reduction.

[0005] The present invention provides a small and low-cost heat exchanger and a refrigeration system.

Means for Solving the Problems

[0006] To solve the above problems, the present disclosure has adopted the following aspects. A heat exchanger according to one aspect of the present disclosure comprises a fin module having a plurality of fins, each having a first through-hole and a second through-hole formed at offset positions from each other when viewed from a first direction, and the plurality of fins being spaced apart in the first direction; a refrigerant flow path provided in the fin module so as to penetrate the first through-hole of each of the plurality of fins in the first direction, and through which a refrigerant flows; and a warm brine flow path provided in the fin module so as to penetrate the second through-hole of each of the plurality of fins in the first direction, and through which brine at a higher temperature than the refrigerant flows, wherein the outer diameter of the warm brine flow path is smaller than the outer diameter of the refrigerant flow path.

[0007] According to this embodiment, when frost forms on the heat exchanger, brine is flowed through the warm brine channel, and the heat from the brine is transferred to the fins, etc. This melts the frost adhering to the heat exchanger. In particular, in this embodiment, the warm brine channel passes through the second through-hole, so that the outer surface of the warm brine channel contacts the inner edge of the second through-hole. This allows the heat from the warm brine channel (brine) to be efficiently transferred to the fins, etc. As a result, the outer diameter of the warm brine channel can be made smaller than the outer diameter of the refrigerant channel, while still achieving the desired defrosting performance. Furthermore, by making the outer diameter of the warm brine channel smaller than the outer diameter of the refrigerant channel, the flow rate of brine flowing through the warm brine channel can be reduced, thus providing a low-cost evaporator. In addition, by making the outer diameter of the warm brine channel smaller than the outer diameter of the refrigerant channel, the increase in the size of the heat exchanger that would be required to provide the warm brine channel can be suppressed.

[0008] In the heat exchanger according to the above embodiment, it is preferable that in one fin, the first through-holes are arranged in a plurality at intervals in a second direction intersecting the first direction to form a first row of holes, and in one fin, the second through-holes are arranged in a plurality at intervals in the second direction to form a second row of holes, and that the first row of holes and the second row of holes are aligned in a third direction intersecting the second direction when viewed from the first direction. According to this embodiment, the warm brine channel and the refrigerant channel can be brought closer together in a third direction. This allows the refrigerant flowing through the refrigerant channel to be heated by the brine flowing through the warm brine channel during defrosting. In this case, for example, the liquid phase refrigerant flowing through the refrigerant channel can absorb heat from the surroundings as latent heat when it condenses again after initially evaporating. This makes it easier to achieve the desired defrosting performance while keeping the brine temperature relatively low. As a result, evaporation of moisture present around the evaporator due to the heat of the warm brine channel is suppressed, and frost formation in locations other than the heat exchanger can be suppressed.

[0009] In the heat exchanger according to the above embodiment, it is preferable that the number of second through-holes constituting the second row of holes is less than the number of first through-holes constituting the first row of holes. According to this embodiment, the flow rate of brine flowing through the warm brine channel can be reduced, and the evaporator can be further miniaturized.

[0010] In the heat exchanger according to the above embodiment, it is preferable that each of the first through-holes constituting the first row of holes adjacent in the third direction is provided on both sides in the second direction with respect to one of the second through-holes constituting the second row of holes. In this embodiment, the refrigerant flow path is arranged around the warm brine flow path. This allows the refrigerant flowing through the refrigerant flow path to be heated by the brine flowing through the warm brine flow path during defrosting. In this case, for example, the liquid phase refrigerant flowing through the refrigerant flow path can absorb heat from the fins, etc., as latent heat when it condenses again after initially evaporating. This makes it easier to achieve the desired defrosting performance while keeping the brine temperature relatively low. As a result, evaporation of moisture present around the evaporator due to the heat of the warm brine flow path is suppressed, and frost formation in locations other than the heat exchanger can be suppressed.

[0011] A refrigeration system according to one aspect of the present invention includes a heat exchanger according to the above aspect. According to this embodiment, a compact and low-cost refrigeration system 1 can be provided because it is equipped with the heat exchanger described above. [Effects of the Invention]

[0012] According to each of the above embodiments, a compact and low-cost heat exchanger and refrigeration system can be provided. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the refrigeration system according to the embodiment. [Figure 2] This is a front view of the evaporator according to the embodiment. [Figure 3] This is a cross-sectional view of the evaporator corresponding to line III-III in Figure 2. [Figure 4] This is a diagram showing the configuration of an evaporator and a gas-liquid separator according to an embodiment. [Modes for carrying out the invention]

[0014] Next, embodiments of the present invention will be described with reference to the drawings. In the embodiments and modifications described below, corresponding components may be denoted by the same reference numerals and their descriptions omitted. In the following description, expressions indicating relative or absolute arrangements such as "parallel," "orthogonal," "center," and "coaxial" will not only strictly represent such arrangements, but will also represent states in which the surfaces are relatively displaced by an angle or distance that allows for tolerances or the same function to be obtained. Furthermore, in this embodiment, "facing each other" is not limited to cases where the orthogonal directions (normal directions) of the two surfaces coincide with each other, but also includes cases where the orthogonal directions intersect.

[0015] [Freezing System 1] Figure 1 is a schematic diagram of the refrigeration system 1. The freezing system 1 shown in Figure 1 is an ultra-low temperature freezing system used for storing fish such as tuna and bonito (hereinafter referred to as "items to be frozen"). The freezing system 1 comprises a cold storage warehouse 10, a freezing device 11, a defrosting device 12, and a control unit 13.

[0016] <Chilled warehouse 10> The chilled warehouse 10 allows frozen objects to be carried in and out through an entrance / exit (not shown), and stores the carried-in frozen objects in a predetermined temperature range. In this embodiment, it is preferable that the inside of the chilled warehouse 10 be maintained at an ultra-low temperature (below -50°C).

[0017] <Refrigeration device 11> The refrigeration device 11 cools the inside of the chilled warehouse 10 by exchanging heat between the refrigerant and the air inside the chilled warehouse 10. In this embodiment, carbon dioxide (CO2) is used as the refrigerant. However, other refrigerants (e.g., ammonia (NH3), alternative Freon, etc.) may be used for the refrigeration device 11.

[0018] The refrigeration device 11 includes a refrigeration unit 20, an evaporator 21, a gas-liquid separator 22, and an oil separator 23. The refrigeration unit 20, the evaporator 21, and the gas-liquid separator 22 are provided in order in the refrigerant main flow path 25 in the flow direction of the refrigerant.

[0019] The refrigeration unit 20 is a so-called direct expansion type condensing unit. The refrigeration unit 20 returns mainly the gaseous-phase refrigerant among the gas-liquid two-phase refrigerant that has passed through the evaporator 21, and generates a high-pressure liquid-phase refrigerant by compressing and heat-exchanging (condensing) the gaseous-phase refrigerant. The upstream end of the feed line 30 is connected to the outlet portion of the refrigeration unit 20. The feed line 30 forms a part of the refrigerant main flow path 25. The liquid-phase refrigerant generated by the refrigeration unit 20 flows toward the evaporator 21 in the feed line 30. An expansion valve 31 is provided in the feed line 30.

[0020] The refrigerant discharged from the refrigeration unit 20 contains lubricating oil (refrigeration oil). The lubricating oil is used to lubricate the compressor (not shown) installed in the refrigeration unit 20. In other words, the main refrigerant flow path 25 contains the lubricating oil that flows out with the refrigerant when it is discharged from the compressor's outlet. The lubricating oil used has a lower specific gravity than the refrigerant and is incompatible with the refrigerant, however, if it separates in the evaporator 21 or the gas-liquid separator 22 and accumulates at the top, a compatible lubricating oil may be used.

[0021] The evaporator 21 cools the air inside the storage unit by exchanging heat between the liquid-phase refrigerant supplied from the refrigeration unit 20 and the air inside the storage unit. The downstream end of the supply line 30 is connected to the inlet of the evaporator 21. In other words, the liquid-phase refrigerant is supplied directly to the evaporator 21 through the supply line 30 without passing through the gas-liquid separator 22. When carbon dioxide is used as the refrigerant, the temperature of the refrigerant at the inlet of the evaporator 21 is set to a temperature near the triple point of carbon dioxide (for example, -55°C), but not below the triple point (-56.6°C).

[0022] The upstream end of the gas-liquid two-phase line 32 is connected to the outlet of the evaporator 21. The gas-liquid two-phase line 32 constitutes part of the refrigerant main flow path 25. The gas-liquid two-phase refrigerant used to cool the air inside the chamber in the evaporator 21 flows through the outlet of the evaporator 21 to the gas-liquid separator 22 via the gas-liquid two-phase line 32. The detailed configuration of the evaporator 21 will be described later.

[0023] The gas-liquid separator 22 is located at the downstream end of the gas-liquid two-phase line 32. The gas-liquid separator 22 separates the gas-liquid two-phase refrigerant discharged from the evaporator 21 into a gas phase refrigerant and a liquid phase refrigerant. A first gas return line 35 is connected to the gas-liquid separator 22. The first gas return line 35 constitutes part of the refrigerant main flow path 25 and connects the gas-liquid separator 22 to the refrigeration unit 20. Of the gas-liquid two-phase refrigerant that flows into the gas-liquid separator 22, the gas phase refrigerant flows towards the inlet of the refrigeration unit 20 (compressor suction port) through the first gas return line 35.

[0024] A liquid return line 36 is connected to the gas-liquid separator 22. The liquid return line 36 connects the portion of the supply line 30 located between the expansion valve 31 and the evaporator 21 to the gas-liquid separator 22. In this embodiment, the liquid return line 36 keeps the evaporator 21 and the gas-liquid separator 22 in constant communication. Of the refrigerant that flows into the gas-liquid separator 22, the liquid phase refrigerant flows towards the supply line 30 through the liquid return line 36. That is, the liquid phase refrigerant flowing through the liquid return line 36 merges with the liquid phase refrigerant flowing through the supply line 30 and is then supplied back to the evaporator 21. Furthermore, because the evaporator 21 and the gas-liquid separator 22 are constantly in communication through the supply line 30 and the liquid return line 36, a flow of liquid phase refrigerant from the evaporator 21 to the gas-liquid separator 22 is also possible. The detailed configuration of the gas-liquid separator 22 will be described later.

[0025] The oil separator 23 stores the lubricating oil contained in the refrigerant. The oil separator 23 is formed as a cylinder with its vertical direction as the axial direction, and comprises a container with both its upper and lower ends closed. The oil separator 23 is positioned below the gas-liquid separator 22.

[0026] The oil separator 23 is connected to an oil recovery line 40, an oil return line 42, and a second gas return line 43.

[0027] The oil recovery line 40 connects the gas-liquid separator 22 and the oil separator 23. Specifically, the upstream end of the oil recovery line 40 is connected to a portion of the gas-liquid separator 22 that is below the connection portion of the gas-liquid two-phase line 32 and above the connection portion of the liquid return line 36. The downstream end of the oil recovery line 40 is connected to the upper part of the oil separator 23. The oil separator 23 is located below the connection portion of the gas-liquid separator 22 with the oil recovery line 40. Therefore, the lubricating oil present in the gas-liquid separator 22 flows towards the oil separator 23 in the oil recovery line 40 due to its own gravity (head difference between the gas-liquid separator 22 and the oil separator 23).

[0028] An oil recovery valve 51 is provided in the oil recovery line 40. The oil recovery valve 51 switches between communication and disconnection between the gas-liquid separator 22 and the oil separator 23 through the oil recovery line 40. A check valve 50 (non-return valve) is provided in the portion of the oil recovery line 40 located downstream of the oil recovery valve 51. The check valve 50 allows the flow of fluid (mainly lubricating oil) from the gas-liquid separator 22 to the oil separator 23 and suppresses the flow of fluid from the oil separator 23 to the gas-liquid separator 22.

[0029] The oil return line 42 connects the oil separator 23 and the first gas return line 35. Specifically, the upstream end of the oil return line 42 is connected to the portion of the oil separator 23 located below the connection portion of the oil recovery line 40. In the illustrated example, the upstream end of the oil return line 42 is connected to the bottom wall portion of the oil separator 23. The downstream end of the oil return line 42 is connected to the first gas return line 35. The oil return line 42 is provided with an oil return valve 52. The oil return valve 52 switches between communication and disconnection between the oil separator 23 and the first gas return line 35 through the oil return line 42. The oil return line 42 may also be provided with a temperature sensor 54 for detecting the temperature inside the oil return line 42.

[0030] The second gas return line 43 connects the oil separator 23 and the first gas return line 35. Specifically, the upstream end of the second gas return line 43 is connected to the portion of the oil separator 23 located above the connection portion of the oil recovery line 40. In the illustrated example, the upstream end of the second gas return line 43 is connected to the top wall portion of the oil separator 23. The downstream end of the second gas return line 43 is connected to the portion of the first gas return line 35 located upstream of the connection portion with the oil return line 42. The gaseous refrigerant present in the oil separator 23 flows through the second gas return line 43 toward the first gas return line 35. The second gas return line 43 is provided with a gas return valve 53. The gas return valve 53 switches between communication and disconnection between the oil separator 23 and the first gas return line 35 through the second gas return line 43.

[0031] A heater 55 is provided on the outer surface of the oil separator 23 and the oil return line 42. The heater 55 heats the inside of the oil separator 23 and the oil return line 42, making it easier to vaporize the liquid phase refrigerant contained in the lubricating oil.

[0032] <Evaporator 21> Figure 2 is a front view of the evaporator 21. Figure 3 is a cross-sectional view corresponding to line III-III in Figure 2. As shown in Figures 2 and 3, the evaporator 21 comprises a fin module 80, a refrigerant flow path 81, and a warm brine flow path 82. In this embodiment, the evaporator 21 is a so-called full-liquid type evaporator 21. A full-liquid type evaporator 21 is one in which heat exchange is performed between the liquid phase refrigerant and the air inside the chamber when a predetermined amount of liquid phase refrigerant is filled in the refrigerant flow path 81.

[0033] The fin module 80 is equipped with multiple fins 90. Each fin 90 is made of a material with excellent thermal conductivity, such as aluminum. Each fin 90 is formed in a thin plate shape with the thickness direction being the direction that intersects the vertical direction (hereinafter referred to as the X direction). Each fin 90 is arranged with spacing in the X direction. Air inside the chamber can pass between adjacent fins 90.

[0034] As shown in Figure 3, each fin 90 has a first refrigerant pore row 91, a second refrigerant pore row 92, and a warm brine pore row 93. In each fin 90, the corresponding refrigerant pore rows 91 and 92 and the warm brine pore rows 93 overlap each other when viewed from the X direction. Therefore, in the following description, the details of the refrigerant pore rows 91 and 92 and the warm brine pore row 93 will be explained using one fin 90 as an example.

[0035] The first refrigerant hole rows 91 and the second refrigerant hole rows 92 are arranged alternately with a gap between them in a direction that intersects the X direction when viewed from above (hereinafter referred to as the Y direction). Adjacent first refrigerant hole rows 91 and second refrigerant hole rows 92 constitute a pair of refrigerant hole sets 94. Therefore, in this embodiment, multiple refrigerant hole sets 94 are arranged in the Y direction.

[0036] The row of holes 93 for warm brine is provided between adjacent rows of holes 91 and 92 for refrigerant that constitute a single row of holes 94 for refrigerant. In this case, the row of holes 93 for warm brine is not provided between adjacent rows of holes 94 for refrigerant. However, the row of holes 93 for warm brine may be provided alternately for all rows of holes 91 and 92 for refrigerant.

[0037] The first refrigerant hole row 91 comprises a plurality of first refrigerant holes 95. The plurality of first refrigerant holes 95 are arranged in a straight line with spacing in the vertical direction. Each first refrigerant hole 95 penetrates the fin 90 in the X direction. Each first refrigerant hole 95 is a round hole formed with the same diameter D1. The plurality of first refrigerant holes 95 constituting the first refrigerant hole row 91 are arranged at equal intervals.

[0038] The second refrigerant hole row 92 comprises a plurality of second refrigerant holes 96. The plurality of second refrigerant holes 96 are arranged in a straight line with spacing in the vertical direction. Each second refrigerant hole 96 penetrates the fin 90 in the X direction. Each second refrigerant hole 96 is a round hole formed with a diameter D1 equivalent to that of each first refrigerant hole 95. The plurality of second refrigerant holes 96 constituting the second refrigerant hole row 92 are arranged at equal intervals. Note that the shape of each refrigerant hole 95,96 is not limited to a perfect circle, but can be changed as appropriate to an elliptical shape, etc.

[0039] In the first row of refrigerant holes 91 and the second row of refrigerant holes 92 that constitute a single refrigerant hole set 94, the first refrigerant holes 95 and the second refrigerant holes 96 are arranged with a half-pitch offset in the vertical direction. Specifically, the arrangement pitch of the first refrigerant holes 95 (the distance between adjacent first refrigerant holes 95 in the vertical direction) and the arrangement pitch of the second refrigerant holes 96 (the distance between adjacent second refrigerant holes 96 in the vertical direction) are equal. Furthermore, in the first row of refrigerant holes 91 and the second row of refrigerant holes 92 that constitute a single refrigerant hole set 94, the first refrigerant holes 95 and the second refrigerant holes 96 are arranged in a staggered (alternating) pattern when viewed from the X direction. However, the arrangement pitch of the multiple refrigerant holes 95 and 96 that constitute each refrigerant hole set 91 and 92 can be changed as appropriate.

[0040] The row of warm brine holes 93 comprises a plurality of warm brine holes 105. The plurality of warm brine holes 105 are arranged in a straight line with spacing in the vertical direction. Each warm brine hole 105 penetrates the fin 90 in the X direction. Each warm brine hole 105 is a round hole formed with a diameter D2 smaller than the diameter D1 of the refrigerant holes 95, 96. In this embodiment, the diameter D1 is set to, for example, 15.88 mm, and the diameter D2 is set to 12.70 mm. It is preferable that both diameters D1 and D2 are set in the range of 9 mm to 16 mm. The shape of the warm brine hole 105 is not limited to a perfect circle, but can be changed as appropriate to an elliptical shape, etc. In this case, it is sufficient that the opening area of ​​the warm brine hole 105 is smaller than the opening area of ​​the refrigerant holes 95, 96. Also, the warm brine hole 105 and the refrigerant holes 95, 96 do not necessarily have similar shapes.

[0041] Each of the warm brine holes 105 constituting a row of warm brine holes 93 is arranged at equal intervals. In this embodiment, the arrangement pitch of each warm brine hole 105 is greater than the arrangement pitch of the refrigerant holes 95 and 96. That is, the number of warm brine holes 105 constituting the row of warm brine holes 93 is less than the number of refrigerant holes 95 and 96 constituting the rows of refrigerant holes 91 and 92. In the illustrated example, the warm brine holes 105 are located between vertically adjacent first refrigerant holes 95 in the first row of refrigerant holes 91, and between vertically adjacent second refrigerant holes 96 in the second row of refrigerant holes 92. Therefore, each warm brine hole 105 is surrounded by four refrigerant holes 95 and 96.

[0042] As shown in Figures 2 and 3, the refrigerant flow path 81 constitutes a part of the main refrigerant flow path 25. The refrigerant flow path 81 is connected to the downstream end of the supply line 30 via an inlet header (not shown). On the other hand, the refrigerant flow path 81 is connected to the upstream end of the gas-liquid two-phase line 32 via an outlet header (not shown). The refrigerant flow path 81 is equipped with two coils (first coil 110 and second coil 111) for each row of refrigerant holes 91 and 92. Each coil 110 and 111 is a tubular material (heat transfer tube) having an outer diameter that can be pressed into each refrigerant hole 95 and 96. That is, the outer diameter of each coil 110 and 111 is formed to be equivalent to the diameter D1 of each refrigerant hole 95 and 96. In the following, the coils 110 and 111 provided in the first row of refrigerant holes 91 will be used as an example to explain the details of the coils 110 and 111, and the second row of refrigerant holes 92 will be given the same reference numerals as the coils 110 and 111 provided in the first row of refrigerant holes 91, and its explanation will be omitted.

[0043] Each coil 110, 111 penetrates the refrigerant holes 95 facing each other in the X direction between adjacent fins 90, and extends upward in a meandering manner in the X direction by being folded back on both sides in the X direction relative to the fin module 80. The lower end of each coil 110, 111 is connected to the inlet header. The upper end of each coil 110, 111 is connected to the outlet header. Each coil 110, 111 extends parallel to the same first row of refrigerant holes 91, forming a so-called double-circuit structure (parallel structure).

[0044] As shown in Figure 2, the first coil 110 comprises a first straight section 110a, a second straight section 110b, a first folded section 110c, and a second folded section 110d. The second coil 111 includes a third straight section 111a, a fourth straight section 111b, a third folded section 111c, and a fourth folded section 111d.

[0045] The first straight section 110a is assembled in a state where it is in contact with the inner periphery of the first through-hole 95a by being press-fitted into the first through-hole 95a of the first refrigerant hole 95. The first straight section 110a is provided between adjacent fins 90 so as to penetrate each of the first through-holes 95a that are facing each other in the X direction. The second straight section 110b is assembled in a state where it is in contact with the inner periphery of the second through-hole 95b by press-fitting it into the second through-hole 95b which is adjacent to the first through-hole 95a above the first refrigerant hole 95. The second straight section 110b is provided so as to penetrate each of the second through-holes 95b that are facing each other in the X direction between adjacent fins 90.

[0046] The third straight section 111a is assembled in a state where it is in contact with the inner periphery of the third through-hole 95c by press-fitting it into the third through-hole 95c, which is adjacent to the second through-hole 95b above the first refrigerant hole 95. The third straight section 111a is provided between adjacent fins 90 so as to penetrate each of the third through-holes 95c that are facing each other in the X direction. The fourth straight section 111b is assembled in a state where it is in contact with the inner periphery of the fourth through-hole 95d by press-fitting it into the fourth through-hole 95d, which is adjacent to the third through-hole 95c above among the first refrigerant holes 95. The fourth straight section 111b is provided so as to penetrate each of the fourth through-holes 95d that are facing each other in the X direction between adjacent fins 90.

[0047] In this embodiment, the first refrigerant holes 95 consist of two through-holes (first through-hole 95a and second through-hole 95b) through which the first coil 110 (first straight section 110a and second straight section 110b) passes, and two through-holes (third through-hole 95c and fourth through-hole 95d) through which the second coil 111 (third straight section 111a and fourth straight section 111b) passes, arranged alternately. In the following description, the first through-hole 95a and second through-hole 95b will be referred to as the first hole set 115, and the third through-hole 95c and fourth through-hole 95d will be referred to as the second hole set 116. In this case, the first refrigerant hole row 91 will consist of the first hole set 115 and the second hole set 116 arranged alternately in the vertical direction.

[0048] The first folded portion 110c is provided on one side (-X side) in the X direction relative to the fin module 80. The first folded portion 110c connects the X-direction ends of the first straight portion 110a and the second straight portion 110b, which are provided in the same first hole set 115. The second folded portion 110d is provided on the other side (+X side) in the X direction relative to the fin module 80. The second folded portion 110d connects the other end in the X direction of the second straight portion 110b provided in one first hole set 115 and the first straight portion 110a provided in another first hole set 115 located, for example, above the first first hole set 115.

[0049] The third folded portion 111c is provided on one side in the X direction relative to the fin module 80. The third folded portion 111c connects the X-side ends of the third straight portion 111a provided in one second hole set 116 and the fourth straight portion 111b provided in another second hole set 116 located, for example, below the first second hole set 116. In the illustrated example, the third folded portion 111c wraps around the outside of the first folded portion 110c. The fourth folded portion 111d is provided on the other side in the X direction relative to the fin module 80. The fourth folded portion 111d connects the other ends in the X direction of the third straight portion 111a and the fourth straight portion 111b, which are provided in the same second hole set 116. In the illustrated example, the second folded portion 110c wraps around the outside of the fourth folded portion 111d.

[0050] Brine (antifreeze) used for defrosting the evaporator 21 flows through the warm brine channel 82. In this embodiment, the brine used is a material with a freezing point lower than the triple point of carbon dioxide, such as an HCFO-based brine.

[0051] The warm brine channel 82 is a tubular material (heat transfer tube) having an outer diameter that can be pressed into the warm brine hole 105. That is, the outer diameter of the warm brine channel 82 is equivalent to the diameter D2 of the warm brine hole 105 and smaller than the outer diameter of each coil 110, 111. The warm brine channel 82 penetrates the warm brine holes 105 facing each other in the X direction between adjacent fins 90, and extends upward in a meandering manner in the X direction by being folded back on both sides in the X direction relative to the fin module 80. Specifically, the warm brine channel 82 comprises a straight section 82a, a folded section 82b on one side, and a folded section 82c on the other side.

[0052] The straight section 82a is assembled in contact with the inner periphery of the warm brine hole 105 by press-fitting it into the warm brine hole 105 or the like. The straight section 82a is provided between adjacent fins 90 so as to penetrate the warm brine holes 105 that are opposite each other in the X direction. The one-sided folded portion 82b is provided on one side in the X direction relative to the fin module 80. The one-sided folded portion 82b connects the one-sided ends in the X direction of one straight portion 82a and a straight portion 82a located above the first straight portion 82a. In the illustrated example, the one-sided folded portion 82b is provided so as to straddle the second hole set 116 in the vertical direction. The other-side folded portion 82c is provided on the other side in the X direction relative to the fin module 80. The one-side folded portion 82c connects the other end in the X direction of one straight portion 82a and a straight portion 82a located, for example, below the first straight portion 82a. In the illustrated example, the other-side folded portion 82c is provided so as to straddle the first hole set 115 in the vertical direction.

[0053] Figure 4 is a configuration diagram showing the evaporator 21 and the gas-liquid separator 22. In Figure 4, the gas-liquid separator 22 is shown in cross-section. As shown in Figure 4, the evaporator 21 of this embodiment is positioned within a height range that includes at least a first height T1 and a second height T2 set lower than the first height T1. The first height T1 is the height from the lower end Ta of the refrigerant flow path 81, and is the height at which the liquid phase refrigerant sufficiently fills the refrigerant flow path 81 in the evaporator 21. In this embodiment, the first height T1 is set to, for example, 80% of the total vertical dimension of the refrigerant flow path 81 (dimension from the lower end Ta to the upper end Tb) from the lower end Ta of the refrigerant flow path 81.

[0054] In this case, it is preferable that the first height T1 be 90% or less, in that a predetermined amount of liquid-phase refrigerant can be filled into the refrigerant flow path 81 (in that it is possible to suppress the flow of more than a predetermined amount of liquid-phase refrigerant into the gas-liquid separator 22 and the return of the liquid-phase refrigerant to the compressor).

[0055] The second height T2 is the height from the lower end Ta of the refrigerant flow path 81, and is the height (lower limit height) at which the evaporator 21 is filled with the liquid phase refrigerant necessary to perform the predetermined cooling. In this embodiment, the second height T2 is set to, for example, 70% of the overall vertical dimension of the refrigerant flow path 81 from the lower end Ta of the refrigerant flow path 81. In this case, it is preferable that the second height T2 be 60% or more in order to secure the effective area of ​​the refrigerant flow path 81. However, the first height T1 and the second height T2 can be changed as appropriate.

[0056] <Gas-liquid separator 22> The gas-liquid separator 22 includes a housing 120, an inlet passage 121, a gas discharge passage 122, a liquid discharge opening 123, an oil discharge opening 124, a baffle plate 125, a first liquid level sensor 126, and a second liquid level sensor 127. The housing 120 is a container for separating the gaseous-liquid two-phase refrigerant and lubricating oil that have passed through the evaporator 21. That is, the housing 120 stores two layers of liquid, with the liquid phase refrigerant separated from the gaseous-liquid two-phase refrigerant as the lower layer and the lubricating oil as the upper layer. The housing 120 is positioned adjacent to the evaporator 21 in the horizontal direction. The housing 120 is positioned within a range that includes at least a first height T1 and a second height T2 in the vertical direction. In this embodiment, the housing 120 is positioned so as to straddle the first height T1 and the second height T2 in the vertical direction.

[0057] The housing 120 comprises a cylindrical portion 120a, a bottom wall 120b, and a top wall 120c. The cylindrical portion 120a is formed as a cylinder with its vertical direction as the axial direction. The bottom wall 120b closes the lower end opening of the cylindrical portion 120a. The bottom wall 120b is located between the lower end Ta of the refrigerant flow path 81 and the second height T2. The top wall 120c closes the upper end opening of the cylindrical portion 120a. The top wall 120c is located above the upper end Tb of the refrigerant flow path 81. However, the top wall 120c may be located below the upper end Tb of the refrigerant flow path 81, as long as it is located above at least the first height T1.

[0058] The inflow channel 121 constitutes the downstream end of the gas-liquid two-phase line 32. In other words, the inflow channel 121 is part of the refrigerant main channel 25. In cross-sectional view, the inflow channel 121 is formed in a downward L-shape. The inflow channel 121 comprises an inflow penetration portion 121a, a hanging portion 121b, and a closing portion 121c.

[0059] The inlet penetration 121a penetrates the upper end of the cylindrical portion 120a. Specifically, the inlet penetration 121a extends along the upper end Tb of the refrigerant flow path 81. However, the inlet penetration 121a only needs to be provided in the portion of the cylindrical portion 120a that is located above the first height T1. The tip of the inlet penetration 121a is located on the axis O of the housing 120.

[0060] The hanging portion 121b extends downward along axis O from the tip of the inlet penetration portion 121a within the housing 120. The lower end of the hanging portion 121b is located below the second height T2. In the illustrated example, the lower end of the hanging portion 121b reaches the lower end of the cylindrical portion 120a. Multiple inlets 129 are formed at the lower part of the hanging portion 121b, connecting the inside and outside of the hanging portion 121b. The inlets 129 allow the gas-liquid two-phase refrigerant flowing through the inlet channel 121 to flow into the housing 120. Multiple inlets 129 are arranged at intervals in the vertical direction and in the circumferential direction of the hanging portion 121b.

[0061] In this embodiment, at least a portion of the hanging portion 121b is immersed in the liquid phase refrigerant stored in the housing 120. That is, at least some of the inlets 129 formed in the hanging portion 121b open into the liquid phase refrigerant stored in the housing 120. In the illustrated example, the uppermost inlet 129 is located below the first height T1. The lowermost inlet 129 is located below the second height T2. However, it is sufficient that any of the multiple inlets 129 are located below the first height T1.

[0062] The occluding portion 121c closes the lower end opening of the hanging portion 121b. Therefore, the inflow channel 121 does not open in a position facing the bottom wall 120b. The occluding portion 121c is positioned away from the bottom wall 120b and faces the liquid discharge opening 123.

[0063] The gas discharge passage 122 constitutes the upstream end of the first gas return line 35. In other words, the gas discharge passage 122 is part of the refrigerant main passage 25. In cross-sectional view, the gas discharge passage 122 is formed in an L-shape. The gas discharge passage 122 comprises a discharge penetration portion 122a and an upright portion 122b.

[0064] The discharge penetration 122a penetrates the cylindrical portion 120a at a position opposite the inlet penetration 121a. The tip of the discharge penetration 122a is located inside the housing 120. The upright portion 122b extends upward from the tip of the discharge penetration portion 122a. The upper end opening of the upright portion 122b opens upward above the inflow passage 121. That is, the upper end opening of the upright portion 122b opens above the upper end Tb of the refrigerant passage 81. The gaseous refrigerant present in the housing 120 flows into the gas discharge passage 122 through the upper end opening of the upright portion 122b. The opening position of the gas discharge passage 122 can be changed as appropriate, as long as it is above the first height T1. In this case, it is preferable that the opening position of the gas discharge passage 122 is above the first height T1 and above the baffle plate 125.

[0065] The liquid discharge opening 123 constitutes the upstream end of the liquid return line 36. The liquid discharge opening 123 penetrates the bottom wall 120b in the vertical direction. The upper end opening of the liquid discharge opening 123 opens upward at the lower end inside the housing 120. That is, the upper end opening of the liquid discharge opening 123 opens in a portion located below the second height T2. Liquid phase refrigerant from the refrigerant present inside the housing 120 flows into the liquid discharge opening 123 due to its own gravity (head difference between the gas-liquid separator 22 and the inlet portion of the refrigerant flow path 81).

[0066] The oil discharge opening 124 constitutes the upstream end of the oil recovery line 40. The oil discharge opening 124 is provided by penetrating the portion of the cylindrical section 120a that is located below the portion connected to the inflow passage 121. The oil discharge opening 124 is located in the vertical center of the cylindrical section 120a. Specifically, the oil discharge opening 124 opens into the housing 120 at a position of first height T1. In other words, the oil discharge opening 124 opens into the housing 120 at a portion located above the uppermost inlet 129 among the multiple inlets 129. Lubricating oil that remains as the supernatant of the liquid phase refrigerant inside the housing 120 flows into the oil discharge opening 124. The lubricating oil that flows into the oil discharge opening 124 flows into the oil separator 23 due to its own weight (head difference between the gas-liquid separator 22 and the oil separator 23). The oil discharge opening 124 only needs to be formed at a position higher than the second height T2.

[0067] The baffle plate 125 has the function of preventing liquid-phase refrigerant flowing into the housing 120 through the inlet 129 from reaching the gas discharge passage 122. In this embodiment, a plurality of baffle plates 125 are provided at vertically spaced intervals at the upper end of the hanging portion 121b (the portion located above the inlet 129). The gas discharge passage 122 described above opens above the baffle plates 125 within the housing 120. Each baffle plate 125 is formed in a skirt shape (conical shape) with an outer diameter that gradually increases towards the bottom. The baffle plates 125 are attached to the hanging portion 121b so as to partition the inside of the housing 120 in the vertical direction.

[0068] The baffle plate 125 has multiple through holes (not shown) that penetrate it vertically. Each through hole connects the space below and above the baffle plate 125 within the housing 120. The through holes in each baffle plate 125 are spaced apart so that they do not overlap each other in a plan view.

[0069] The first liquid level sensor 126 detects that the liquid level (liquid phase refrigerant and lubricating oil) inside the housing 120 is at a first height T1. The second liquid level sensor 127 detects that the liquid level inside the housing 120 is at the second height T2. Each liquid level sensor 126, 127 may be a contact type (float type, electrode type, etc.) or a non-contact type (ultrasonic type, etc.).

[0070] <Defrosting device 12> As shown in Figure 1, the defrosting device 12 circulates brine between itself and the evaporator 21 during defrosting of the evaporator 21. In other words, the refrigeration system 1 of this embodiment can be switched between a cooling mode, in which the inside of the refrigerated warehouse 10 is cooled via the evaporator 21 by the operation of the refrigeration device 11, and a defrosting mode, in which frost accumulated on the evaporator 21 (fin module 80, etc.) is removed when the refrigeration device 11 is stopped. The defrosting mode is performed periodically, for example, after the refrigeration device 11 has been driven in cooling mode for a predetermined time. However, the switch from cooling mode to defrosting mode may be performed manually or based on changes in the internal temperature during cooling mode.

[0071] The defrosting device 12 is connected to the evaporator 21 via a brine supply line 140 and a brine return line 141. Brine, adjusted to a desired temperature by the defrosting device 12, flows through the brine supply line 140 toward the evaporator 21. In this embodiment, so-called warm brine, adjusted to a temperature higher than the refrigerant temperature (for example, around 25°C), can be supplied. The upstream end of the brine supply line 140 is connected to the defrosting device 12. The downstream end of the brine supply line 140 is connected to the lower end (upstream end) of the warm brine flow path 82 via an inlet header (not shown).

[0072] The brine return line 141 carries the brine used for defrosting in the evaporator 21 toward the defrosting device 12. The upstream end of the brine return line 141 is connected to the upper end (downstream end) of the warm brine flow path 82 via an outlet header (not shown). The downstream end of the brine return line 141 is connected to the defrosting device 12.

[0073] <Control Unit 13> The control unit 13 shown in Figure 1 comprehensively controls the operation of the refrigeration system 1. The control unit 13 is realized by a hardware processor such as a CPU executing a computer program (software) stored in a memory unit. The control unit 13 controls the flow of refrigerant and lubricating oil by switching the opening and closing of the oil recovery valve 51, oil return valve 52, and gas return valve 53 according to the operating mode of the refrigeration system 1. In addition, the control unit 13 controls the liquid level of the evaporator 21 (refrigerant flow path 81) by adjusting the opening degree of the expansion valve 31 and the output of the refrigeration unit 20 based on the liquid level of the gas-liquid separator 22 detected by the liquid level sensors 126 and 127.

[0074] <Operation method of refrigeration system 1> Next, the operation method of the refrigeration system 1 described above will be explained. The following explanation will describe the operation in cooling mode, defrost mode, and oil recovery mode, respectively.

[0075] <Cooling Mode> As shown in Figure 1, in cooling mode, the control unit 13 opens the oil recovery valve 51 and the gas return valve 53, and closes the oil return valve 52. That is, in cooling mode, the inside of the gas-liquid separator 22 and the inside of the oil separator 23 are in communication through the oil recovery line 40, and the first gas return line 35 and the inside of the oil separator 23 are in communication through the second gas return line 43. On the other hand, in cooling mode, the communication between the first gas return line 35 and the inside of the oil separator 23 via the oil return line 42 is blocked. When the refrigeration system 11 is operated in this state, the liquid phase refrigerant discharged from the refrigeration unit 20 is supplied directly into the evaporator 21 (refrigerant flow path 81) through the supply line 30. The refrigerant flowing into the refrigerant flow path 81 flows upward while meandering in the X direction. The liquid phase refrigerant flowing into the refrigerant flow path 81 then exchanges heat with the air inside the chamber passing between adjacent fins 90 via the fins 90, etc. In other words, the evaporator 21 cools the area around it by absorbing heat of vaporization from the surroundings as the refrigerant in the refrigerant flow path 81 vaporizes. As a result, the air inside the storage area is cooled, and the inside of the refrigerated storage area 10 is maintained at the desired temperature.

[0076] The refrigerant, after heat exchange with the air inside the chamber, becomes a gas-liquid two-phase system and is discharged from the evaporator 21 into the gas-liquid two-phase line 32, before flowing into the gas-liquid separator 22. Specifically, the refrigerant flowing through the gas-liquid two-phase line 32 passes through the inflow channel 121 and then flows into the gas-liquid separator 22 (housing 120) through the inlet 129. Of the refrigerant that has flowed into the gas-liquid separator 22, the gas phase refrigerant flows into the gas discharge channel 122 through the upper end opening of the upright section 122b and is discharged from the gas-liquid separator 22. The gas phase refrigerant that has flowed into the gas discharge channel 122 flows through the first gas return line 35 and is returned to the refrigeration unit 20. The gas phase refrigerant returned to the refrigeration unit 20 is converted back into liquid phase refrigerant in the refrigeration unit 20 and then supplied to the evaporator 21.

[0077] On the other hand, of the refrigerant that flows into the gas-liquid separator 22, the liquid phase refrigerant is stored in the housing 120. In the refrigeration system 1 of this embodiment, the evaporator 21 and the gas-liquid separator 22 are arranged within a height range including the first height T1 and the second height T2. Furthermore, the evaporator 21 and the gas-liquid separator 22 are constantly in communication with each other through the gas-liquid two-phase line 32 and the liquid return line 36. That is, in cooling mode, the inside of the evaporator 21 (inside the refrigerant flow path 81) and the inside of the gas-liquid separator 22 (inside the housing 120) are maintained at the same pressure. In this case, the liquid phase refrigerant stored in the gas-liquid separator 22 is returned to the evaporator 21 due to the head difference between the gas-liquid separator 22 and the inlet portion of the refrigerant flow path 81. Specifically, the liquid phase refrigerant stored in the gas-liquid separator 22 flows into the liquid discharge opening 123 through the upper end opening of the liquid discharge opening 123. Subsequently, the liquid phase refrigerant is returned to the downstream side of the supply line 30, beyond the expansion valve 31, via the liquid return line 36. The liquid phase refrigerant returned to the supply line 30 merges with the liquid phase refrigerant supplied from the refrigeration unit 20, and is then returned to the evaporator 21.

[0078] In this embodiment of the refrigeration system 1, the inside of the evaporator 21 (inside the refrigerant flow path 81) and the inside of the gas-liquid separator 22 (inside the housing 120) are maintained at the same pressure. Therefore, the liquid level of the liquid phase refrigerant in the refrigerant flow path 81 is equal to the liquid level of the liquid phase refrigerant in the housing 120. In other words, the liquid level in the refrigerant flow path 81 can be determined based on the liquid level in the housing 120. In this embodiment, the liquid level in the refrigerant flow path 81 is adjusted by controlling the opening degree of the expansion valve 31 based on the liquid level in the housing 120.

[0079] Specifically, based on the detection result from the first liquid level sensor 126, the control unit 13 determines that the liquid level in the housing 120 has reached a first height T1, and reduces the opening of the expansion valve 31 and lowers the output of the refrigeration unit 20 (low output mode). In low output mode, the control unit 13 determines that the evaporator 21 is filled with a sufficient amount of liquid-phase refrigerant and reduces the amount of liquid-phase refrigerant supplied to the evaporator 21. On the other hand, based on the detection result from the second liquid level sensor 127, if the control unit 13 determines that the liquid level in the housing 120 is less than the first height T1 and has reached the second height T2, it increases the opening of the expansion valve 31 and increases the output of the refrigeration unit 20 (high output mode). In high output mode, if the control unit 13 determines that there is a risk of insufficient liquid phase refrigerant necessary for normal operation in the evaporator 21, it increases the amount of liquid phase refrigerant supplied to the evaporator 21. In low output mode, the opening of the expansion valve 31 may be set to 0.

[0080] In this way, the control unit 13 adjusts the opening degree of the expansion valve 31 and the output of the refrigeration unit 20 based on the detection results from the liquid level sensors 126 and 127, thereby maintaining the liquid level of the gas-liquid separator 22 between the first height T1 and the second height T2. As a result, the liquid level of the liquid phase refrigerant filling the evaporator 21 is maintained within the desired range (the range between the first height T1 and the second height T2). By maintaining the liquid level of the gas-liquid separator 22 between the first height T1 and the second height T2, during the cooling mode, at least some of the inlets 129 formed in the hanging portion 121b open into the liquid phase refrigerant stored in the housing 120.

[0081] Furthermore, lubricating oil is retained in the gas-liquid separator 22 as the supernatant of the liquid phase refrigerant. In other words, two layers of liquid are stored in the gas-liquid separator 22, with the refrigerant in the lower layer and the oil in the upper layer. In this case, since the oil separator 23 is located below the connection point (oil discharge opening 124) to the oil recovery line 40 of the gas-liquid separator 22, when the oil in the upper layer reaches the same height as the oil discharge opening 124, it is discharged from the gas-liquid separator 22 through the oil discharge opening 124. In cooling mode, since the oil recovery valve 51 is open, the oil discharged from the gas-liquid separator 22 flows towards the oil separator 23 through the oil recovery line 40 due to the head difference between the gas-liquid separator 22 and the oil separator 23. As a result, the lubricating oil contained in the refrigerant is stored in the oil separator 23.

[0082] Furthermore, the lubricating oil flowing into the oil separator 23 may contain refrigerant (mainly liquid-phase refrigerant) that has flowed from the gas-liquid separator 22 along with the lubricating oil. Heaters 55 are provided in the oil separator 23 and the oil return line 42, and the liquid-phase refrigerant contained in the oil separator 23 is heated by the heaters 55 and vaporized, and then discharged from the oil separator 23 through the second gas return line 43. The gaseous refrigerant that flows into the second gas return line 43 merges with the gaseous refrigerant discharged from the gas-liquid separator 22 in the first gas return line 35, and is then returned to the refrigeration unit 20.

[0083] <Defrost Mode> In defrost mode, the defrosting device 12 is operated with the refrigeration unit 20 stopped. In defrost mode, brine adjusted to the desired temperature by the defrosting device 12 passes through the evaporator 21, warming the evaporator 21 and removing frost that has accumulated on it. Specifically, the brine flowing through the brine supply line 140 flows into the upstream end of the warm brine flow path 82 via the inlet header. The brine that flows into the warm brine flow path 82 flows upward while meandering in the X direction. The heat from the brine flowing through the warm brine flow path 82 warms the warm brine flow path 82 and the fins 90, etc. This melts the frost that has accumulated on the warm brine flow path 82 and the fins 90, etc. The water generated from the melted frost falls through the gaps between adjacent fins 90. This removes frost from the evaporator 21. In addition, the defrost mode is performed with the oil recovery valve 51 and gas return valve 53 open and the oil return valve 52 closed, similar to the cooling mode.

[0084] In this embodiment, the row of holes for the warm brine 93 is arranged between the rows of holes for the refrigerant 91 and 92 that constitute the refrigerant hole set 94, so that the warm brine channel 82 and the refrigerant channel 81 are located in close proximity. Therefore, the heat of the brine flowing through the warm brine channel 82 is also transferred to the refrigerant channels 81 which are located on both sides of the warm brine channel 82 in the Y direction. Consequently, the refrigerant flowing through the refrigerant channel 81 is efficiently heated by the brine. In this case, for example, the latent heat of condensation when the liquid phase refrigerant flowing through the refrigerant channel 81 evaporates and then condenses again can heat the refrigerant channel 81 and the fins 90. This makes it possible to melt frost that has accumulated on parts located around the refrigerant channel 81 by utilizing the latent heat of condensation of the refrigerant. As a result, it is easier to achieve the desired defrosting performance while keeping the brine temperature relatively low. Therefore, it is possible to suppress the evaporation of moisture present around the refrigerant channel 81 by the heat of the brine and suppress frost formation in locations other than the evaporator 21. The defrost mode may be terminated after the defrost device 12 has been operating for a predetermined time, or it may be terminated when the refrigerant pressure in the refrigerant flow path 81 is detected and rises to a predetermined pressure.

[0085] <Oil recovery mode> In this embodiment, the oil recovery mode is performed after the defrost mode ends and before the cooling mode starts. In the oil recovery mode, the refrigeration unit 20 is operated to supply liquid phase refrigerant to the evaporator 21, and the lubricating oil stored in the oil separator 23 is returned to the refrigeration unit 20.

[0086] In oil recovery mode, the control unit 13 opens the expansion valve 31 and the oil return valve 52, and closes the oil recovery valve 51 and the gas return valve 53. That is, in oil recovery mode, the first gas return line 35 and the inside of the oil separator 23 are in communication through the oil return line 42. On the other hand, in oil recovery mode, the communication between the inside of the gas-liquid separator 22 and the inside of the oil separator 23 through the oil recovery line 40 is blocked, and the communication between the first gas return line 35 and the inside of the oil separator 23 is blocked through the second gas return line 43. In this state, when the refrigeration system 11 is operated, the liquid phase refrigerant discharged from the refrigeration unit 20 is supplied to the evaporator 21 (refrigerant flow path 81) through the supply line 30, similar to the cooling mode.

[0087] Incidentally, when defrosting is performed using the defrost mode described above, the temperature of the refrigerant present in the refrigerant flow path 81 rises, causing the pressure in the refrigerant main flow path 25 and the oil separator 23 to increase. When the oil recovery mode is performed in this state, the refrigerant in the first gas return line 35 is drawn towards the refrigeration unit 20 (compressor), creating negative pressure in the first gas return line 35, including the connection point with the oil return line 42. Since the pressure in the oil separator 23 has increased due to the effect of the defrost mode, this differential pressure causes the lubricating oil present in the oil separator 23 to flow into the first gas return line 35 through the oil return line 42 during the oil recovery mode. Therefore, the gaseous refrigerant and lubricating oil present in the oil separator 23 are returned to the refrigeration unit 20 together with the gaseous refrigerant flowing through the first gas return line 35.

[0088] The operation time for the oil recovery mode may be a predetermined time based on a timer (not shown). The control unit 13 may also determine whether to switch from the defrost mode to the oil recovery mode based on the detection result of the temperature sensor 54 (temperature in the oil return line 42). That is, the control unit 13 may allow switching from the defrost mode to the oil recovery mode when the temperature in the oil return line 42 is higher than a predetermined temperature (for example, -50°C). If the temperature in the oil return line 42 is lower than the predetermined temperature, there is a possibility that liquid phase refrigerant is present in the oil return line 42. Therefore, by prohibiting switching to the oil recovery mode when the temperature in the oil return line 42 is lower than the predetermined temperature, it is possible to suppress the inflow of liquid phase refrigerant into the first gas return line 35 through the oil return line 42.

[0089] As described above, the evaporator (heat exchanger) 21 of this embodiment has a fin module 80 in which a plurality of fins 90 are formed at positions offset from each other when viewed from the X direction (first direction), with refrigerant holes (first through holes) 95, 96 and warm brine holes (second through holes) 105 formed therein, and the plurality of fins 90 are spaced apart in the X direction; a refrigerant flow path 81 is provided in the fin module 80 so as to penetrate the corresponding refrigerant holes 95, 96 of the plurality of fins 90 in the X direction, and through which refrigerant flows; and a warm brine flow path 82 is provided in the fin module 80 so as to penetrate the corresponding warm brine holes 105 of the plurality of fins 90 in the X direction, and through which brine at a higher temperature than the refrigerant flows. The outer diameter of the warm brine flow path 82 is smaller than the outer diameter of the refrigerant flow path 81. With this configuration, when frost forms on the evaporator 21, brine is passed through the warm brine channel 82, and the heat from the brine is transferred to the fins 90, etc. This melts the frost attached to the evaporator 21. In particular, in this embodiment, the warm brine channel 82 penetrates the warm brine hole 105, so the outer surface of the warm brine channel 82 contacts the inner edge of the warm brine hole 105. This allows the heat from the warm brine channel 82 (brine) to be efficiently transferred to the fins 90. As a result, the outer diameter of the warm brine channel 82 can be made smaller than the outer diameter of the refrigerant channel 81, while still achieving the desired defrosting performance. Furthermore, by making the outer diameter of the warm brine channel 82 (diameter D2 of the warm brine hole 105) smaller than the outer diameter of the refrigerant channel 81 (diameter D1 of the refrigerant holes 95, 96), the flow rate of brine flowing through the warm brine channel 82 can be reduced, thus providing a low-cost evaporator 21. Furthermore, by making the outer diameter of the warm brine channel 82 smaller than the outer diameter of the refrigerant channel 81, the increase in size of the evaporator 21 that would occur with the provision of the warm brine channel 82 can be suppressed.

[0090] In this embodiment, the evaporator 21 has multiple refrigerant holes 95 and 96 arranged at intervals in the vertical direction (second direction) on one fin 90 to form refrigerant hole rows (first hole rows) 91 and 92, and multiple warm brine holes 105 arranged at intervals in the vertical direction to form warm brine hole rows (second hole rows) 93. The refrigerant hole rows 91 and 92 and the warm brine hole row 93 are aligned in the Y direction (third direction). This configuration allows the warm brine channel 82 and the refrigerant channel 81 to be brought closer together in the Y direction. This allows the brine flowing through the warm brine channel 82 to heat the refrigerant flowing through the refrigerant channel 81 during defrosting. In this case, for example, the liquid phase refrigerant flowing through the refrigerant channel 81 evaporates once, and then absorbs heat from the surroundings of the refrigerant channel 81 as latent heat when it condenses again. This makes it easier to achieve the desired defrosting performance while keeping the brine temperature relatively low. As a result, evaporation of moisture present around the evaporator 21 due to the heat of the warm brine channel 82 is suppressed, and frost formation in locations other than the evaporator 21 can be suppressed.

[0091] In the evaporator 21 of this embodiment, the number of hot brine holes 105 constituting the hot brine hole row 93 is less than the number of refrigerant holes 95 and 96 constituting the refrigerant hole rows 91 and 92. This configuration allows for a reduction in the flow rate of brine through the warm brine channel 82, and also enables further miniaturization of the evaporator 21.

[0092] In the evaporator 21 of this embodiment, the refrigerant holes 95 and 96 that constitute adjacent refrigerant hole rows 91 and 92 in the Y direction are provided on both sides in the vertical direction relative to one warm brine hole 105 that constitutes a warm brine hole row 93. In this configuration, the refrigerant flow path 81 is arranged around the warm brine flow path 82. This allows the brine flowing through the warm brine flow path 82 to heat the refrigerant flowing through the refrigerant flow path 81 during defrosting. In this case, for example, the liquid phase refrigerant flowing through the refrigerant flow path 81 evaporates once, and then absorbs heat from the fins 90, etc., as latent heat when it condenses again. This makes it easier to achieve the desired defrosting performance while keeping the brine temperature relatively low. As a result, evaporation of moisture present around the evaporator 21 due to the heat of the warm brine flow path 82 is suppressed, and frost formation in locations other than the evaporator 21 can be suppressed.

[0093] Since the refrigeration system 1 of this embodiment is equipped with the evaporator 21 described above, it is possible to provide a compact and low-cost refrigeration system 1.

[0094] (Other variations) While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the appended claims. In the embodiment described above, a configuration was described in which the refrigerant holes 95, 96 and the warm brine holes 105 are arranged alternately in the vertical direction, but the configuration is not limited to this. The refrigerant holes 95, 96 and the warm brine holes 105 may be arranged at the same position in the vertical direction. In the embodiment described above, the refrigerant holes 95, 96 and the warm brine holes 105 were arranged vertically at different positions in the Y direction, but the configuration is not limited to this. The refrigerant holes 95, 96 and the warm brine holes 105 may be arranged alternately, for example, vertically at the same position in the Y direction. In the embodiments described above, the heat exchanger of the present invention was explained using the evaporator 21 as an example, but the present invention is not limited to this configuration. The configuration of the present invention can be applied to various heat exchangers.

[0095] In the embodiment described above, the second direction was described as the vertical direction, but the configuration is not limited to this. The evaporator 21 may also be installed with the first or third direction being the vertical direction. In the embodiment described above, an evaporator 21 with a so-called double-circuit structure, in which two coils 110 and 111 extend in parallel to one row of refrigerant holes 91 and 92, was used as an example, but the configuration is not limited to this. The evaporator 21 may have a configuration in which one coil extends to one row of refrigerant holes 91 and 92, or a configuration in which three or more coils extend. However, compared to a configuration in which one coil extends, a configuration in which multiple coils 110 and 111 extend to one row of refrigerant holes 91 and 92, such as a double-circuit structure, makes it easier to reduce pressure loss because the length of each coil 110 and 111 can be reduced and the number of places where folded sections are formed can be reduced.

[0096] In the above-described embodiment, the refrigerant flow path 81 and the warm brine flow path 82 are assembled into the corresponding holes by press-fitting or the like, resulting in a configuration in which they directly contact the inner periphery of each hole. However, the configuration is not limited to this. The refrigerant flow path 81 and the warm brine flow path 82 may contact the inner periphery of the corresponding hole via an intermediate member such as an adhesive. Alternatively, the refrigerant flow path 81 and the warm brine flow path 82 only need to contact at least a portion of the inner periphery of the corresponding hole. The refrigerant flow path 81 (coils 110, 111) only needs to have a smaller diameter than the warm brine flow path 82, at least at the penetration portion.

[0097] In the embodiments described above, a configuration in which the gas-liquid separator 22 is provided with an oil discharge opening 124 was described, but the configuration is not limited to this. The gas-liquid separator 22 may also be configured without an oil discharge opening 124. In the above-described embodiment, a configuration was explained in which the refrigerant supplied to the evaporator 21 is adjusted based on the liquid level of the liquid phase refrigerant in the gas-liquid separator 22 (inside the housing 120), but the configuration is not limited to this. The evaporator 21 may also be supplied with refrigerant using a separate refrigerant pump or the like. In this case, the layout of the gas-liquid separator 22 relative to the evaporator 21 can be changed as appropriate.

[0098] In the embodiment described above, a configuration was described in which the lubricating oil present in the oil separator 23 is returned to the first gas return line 35 through the oil return line 42, but the configuration is not limited to this. The lubricating oil present in the oil separator 23 may be returned to the refrigeration unit 20 by another method. In the embodiment described above, a configuration was described in which the supply line 30 is connected to the evaporator 21 without going through the gas-liquid separator 22, but the configuration is not limited to this. The supply line 30 may also be connected to the evaporator 21 via a surge tank such as a gas-liquid separator. In this case, the liquid phase refrigerant supplied from the refrigeration unit 20 is temporarily stored in the surge tank before being supplied to the evaporator 21.

[0099] Furthermore, without departing from the spirit of the present invention, the components in the embodiments described above can be replaced with well-known components as appropriate, and the modifications described above can be combined as appropriate. [Explanation of Symbols]

[0100] 1: Refrigeration system 21: Evaporator (heat exchanger) 80: Fin Module 81: Refrigerant flow path 82: Warm brine channel 90: Finn 91: 1st refrigerant hole row (1st hole row) 92: 2nd refrigerant hole row (1st hole row) 93: Warm brine hole row (second hole row) 95: First refrigerant hole (first through hole) 96: Second refrigerant hole (first through hole) 105: Warm brine hole (second through hole)

Claims

1. A fin module having a plurality of fins, each having a first through-hole and a second through-hole formed at positions offset from each other when viewed from a first direction, and the plurality of fins being arranged with spacing in the first direction, Of the plurality of fins, each of the first through-holes is provided in the fin module so as to penetrate in the first direction, and a refrigerant flow path is provided through which the refrigerant flows, The fin module is provided with a warm brine channel through which brine at a temperature higher than the refrigerant flows, with each of the plurality of fins having a second through-hole that penetrates in the first direction, A heat exchanger in which the outer diameter of the hot brine channel is smaller than the outer diameter of the refrigerant channel.

2. In one of the fins, the first through-holes are arranged in a plurality of positions with spacing between them in a second direction intersecting the first direction, forming a first row of holes. In one of the fins, the second through-holes are arranged in a plurality at intervals in the second direction to form a second row of holes. The heat exchanger according to claim 1, wherein the first row of holes and the second row of holes are arranged in a third direction that intersects the second direction when viewed from the first direction.

3. The heat exchanger according to claim 2, wherein the number of second through-holes constituting the second row of holes is less than the number of first through-holes constituting the first row of holes.

4. The heat exchanger according to claim 2 or claim 3, wherein each of the first through holes constituting the first row of holes adjacent in the third direction is provided on both sides in the second direction with respect to one of the second through holes constituting the second row of holes.

5. A refrigeration system comprising a heat exchanger according to any one of claims 1 to 3.

Images