Refrigeration device

Abstract

A refrigeration apparatus includes a refrigerant unit (U) that includes a first refrigerant circuit (R1) configured to perform a refrigeration cycle by using a first refrigerant, which is a highly flammable refrigerant, in which the first refrigerat circuit (R1) includes a first refrigerant pipe (27a) that is configured to connect a first heat exchanger (23) and a decompression mechanism (24) to each other, a second refrigerant pipe (27b) that is configured to connect the decompression mechanism (24) and a second heat exchanger (22) to each other, a third refrigerant pipe (27c) that is configured to connect the second heat exchanger (22) and a compressor (21) to each other, and a fourth refrigerant pipe (27d) that is configured to connect the compressor (21) and the first heat exchanger (23) to each other, and in which the first to fourth refrigerant pipes (27a to 27d) have structures in which a first capacity, which is a sum of a capacity of the first refrigerant pipe (27a) and a capacity of the second refrigerant pipe (27b), is smaller than a second capacity, which is a sum of a capacity of the third refrigerant pipe (27c) and a capacity of the fourth refrigerant pipe (27d).

Description

Technical Field

[0001] The present disclosure relates to a refrigeration apparatus.Background Art

[0002] A hot water supply unit that is disclosed in Patent Literature 1 includes a refrigerant circuit and a tank for hot water supply, the refrigerant circuit including a first heat exchanger and a second heat exchanger. The hot water supply unit stores water heated by a refrigerant of the refrigerant circuit in the tank.Citation ListPatent Literature

[0003] PTL 1: Japanese Unexamined Patent Application Publication No. 2004-132647Summary of InventionTechnical Problem

[0004] When the refrigerant that fills the refrigerant circuit is a flammable refrigerant, in particular, a highly flammable refrigerant, from the viewpoint of, for example, leakage of the refrigerant, it is preferable that the amount of refrigerant that fills the refrigerant circuit be small.

[0005] An object of the present disclosure is to reduce the amount of highly flammable refrigerant that fills a refrigerant circuit.Solution to Problem

[0006] A refrigeration apparatus according to a first aspect includes: a refrigerant unit (U) that includes a first refrigerant circuit (R1) configured to perform a refrigeration cycle by using a first refrigerant, which is a highly flammable refrigerant; and a casing (60) that is configured to accommodate the refrigerant unit (U) and that is disposed in a target space (I), in which to the first refrigerant circuit (R1) are connected in order a compressor unit (CU) that includes a compressor (21), a first heat exchanger (23) that is configured to cause the first refrigerant of the first refrigerant circuit (R1) and a first heat transfer medium that flows in a first heat transfer medium circuit (W) to exchange heat with each other, a decompression mechanism (24), and a second heat exchanger (22) that is configured to cause the first refrigerant of the first refrigerant circuit (R1) and a second heat transfer medium that flows in a second heat transfer medium circuit (R2) to exchange heat with each other, and in which a first refrigerant pipe (27a) that is configured to connect the first heat exchanger (23) and the decompression mechanism (24) to each other, a second refrigerant pipe (27b) that is configured to connect the decompression mechanism (24) and the second heat exchanger (22) to each other, a third refrigerant pipe (27c) that is configured to connect the second heat exchanger (22) and the compressor unit (CU) to each other, and a fourth refrigerant pipe (27d) that is configured to connect the compressor unit (CU) and the first heat exchanger (23) to each other have structures in which a first capacity, which is a sum of a capacity of the first refrigerant pipe (27a) and a capacity of the second refrigerant pipe (27b), is smaller than a second capacity, which is a sum of a capacity of the third refrigerant pipe (27c) and a capacity of the fourth refrigerant pipe (27d).

[0007] When the first refrigerant circuit (R1) performs the refrigeration cycle, the first heat exchanger (23) functions as a radiator, and the second heat exchanger (22) functions as an evaporator. A refrigerant that has been discharged from the compressor unit (CU) flows in the fourth refrigerant pipe (27d), a refrigerant that has radiated heat at the first heat exchanger (23) flows in the first refrigerant pipe (27a), a refrigerant that has been decompressed by the decompression mechanism (24) flows in the second refrigerant pipe (27b), and a refrigerant that has evaporated at the second heat exchanger (22) flows in the third refrigerant pipe (27c). In the first aspect, the first capacity, which is the sum of the capacity of the first refrigerant pipe (27a) and the capacity of the second refrigerant pipe (27b), is made smaller than the second capacity, which is the sum of the capacity of the third refrigerant pipe (27c) and the capacity of the fourth refrigerant pipe (27d). The density of the refrigerant that flows in the first refrigerant pipe (27a) and the density of the refrigerant that flows in the second refrigerant pipe (27b) are higher than the density of the refrigerant that flows in the third refrigerant pipe (27c) and the density of the refrigerant that flows in the fourth refrigerant pipe (27d). Therefore, when the volume of the refrigerant that flows in the first refrigerant pipe (27a) and the volume of the refrigerant that flows in the second refrigerant pipe (27b) are made smaller than the volume of the refrigerant that flows in the third refrigerant pipe (27c) and the volume of the refrigerant that flows in the fourth refrigerant pipe (27d), it is possible to reduce the amount (mass) of the refrigerants, which are the amounts of the refrigerants that each flow in a corresponding one of the first refrigerant pipe (27a) and the second refrigerant pipe (27b), and thus to reduce the amount of refrigerant that fills the first refrigerant circuit (R1).

[0008] A refrigeration apparatus according to a second aspect is the refrigeration apparatus according to the first aspect, in which a sum of a length of the first refrigerant pipe (27a) and a length of the second refrigerant pipe (27b) is smaller than a sum of a length of the third refrigerant pipe (27c) and a length of the fourth refrigerant pipe (27d).

[0009] In the second aspect, when the inside diameter of a tube of the first refrigerant pipe (27a) and the inside diameter of a tube of the second refrigerant pipe (27b) are smaller than the inside diameter of a tube of the third refrigerant pipe (27c) and the inside diameter of a tube of the fourth refrigerant pipe (27d), the first capacity can be reliably made smaller than the second capacity. Even if the inside diameter of the tube of the first refrigerant pipe (27a) and the inside diameter of the tube of the second refrigerant pipe (27b) are equal to the inside diameter of the tube of the third refrigerant pipe (27c) and the inside diameter of the tube of the fourth refrigerant pipe (27d), the first capacity can be made smaller than the second capacity.

[0010] A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the first aspect or the second aspect, in which a length of the first refrigerant pipe (27a) is shorter than a length of the second refrigerant pipe (27b).

[0011] In the third aspect, since the refrigerant in the first refrigerant pipe (27a) has a density that is higher than the density of the refrigerant in the second refrigerant pipe (27b), when the first refrigerant pipe (27a) is made shorter than the second refrigerant pipe (27b), it is possible to further keep down the amount of refrigerant that fills the first refrigerant circuit (R1).

[0012] A refrigeration apparatus according to a fourth aspect is the refrigeration apparatus according to the third aspect, in which the decompression mechanism (24) is an expansion valve whose opening degree is adjustable, and includes an upper connection portion (24a) to which the first refrigerant pipe (27a) is connected, and a lower connection portion (24b) that is disposed below the upper connection portion (24a) and to which the second refrigerant pipe (27b) is connected, and in which, in a direction in which the casing (60) is viewed from a side, the first heat exchanger (23) includes a first refrigerant pipe connection portion (23a) to which the first refrigerant pipe (27a) that extends from the upper connection portion (24a) is connected, the second heat exchanger (22) includes a second refrigerant pipe connection portion (22a) to which the second refrigerant pipe (27b) that extends from the lower connection portion (24b) is connected, and a height position of the first refrigerant pipe connection portion (23a) is higher than a height position of the lower connection portion (24b), and a height position of the second refrigerant pipe connection portion (22a) is lower than the height position of the lower connection portion (24b).

[0013] In the fourth aspect, since, in the decompression mechanism (24), the upper connection portion (24a) is disposed above the lower connection portion (24b), when the height position of the first refrigerant pipe connection portion (23a) is made higher than the height position of the second refrigerant pipe connection portion (22a), the distance from the upper connection portion (24a) to the first refrigerant pipe connection portion (23a) and the distance from the lower connection portion (24b) to the second refrigerant pipe connection portion (22a) can be reduced. In other words, the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) can be reduced.

[0014] A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to the fourth aspect, in which a height position of a bottom surface (23b) of the first heat exchanger (23) is higher than a height position of a bottom surface (22b) of the second heat exchanger (22).

[0015] In the fifth aspect, since the height position of the first refrigerant pipe connection portion (23a) is higher than the height position of the second refrigerant pipe connection portion (22a), the same effects as those of the fourth aspect can be obtained.

[0016] A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to any one of the first aspect to the fourth aspect, in which, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are disposed so as to face each other with the decompression mechanism (24) being interposed therebetween, and in which a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

[0017] In the sixth aspect, when D1 is made less than D2 or D3, the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) can be made smaller than the length of the third refrigerant pipe (27c) or the length of the fourth refrigerant pipe (27d).

[0018] A refrigeration apparatus according to a seventh aspect is the refrigeration apparatus according to any one of the first aspect to the fourth aspect, in which, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are each disposed so as to face the decompression mechanism (24), and the second heat exchanger (22) is disposed closer to one end of the first heat exchanger (23) in a longitudinal direction, and in which a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

[0019] In the seventh aspect, when D1 is made less than D2 or D3, the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) can be smaller than the length of the third refrigerant pipe (27c) or the length of the fourth refrigerant pipe (27d).

[0020] A refrigeration apparatus according to an eighth aspect is the refrigeration apparatus according to any one of the first aspect to the fourth aspect, in which, in a direction in which the casing (60) is viewed from thereabove, a longitudinal direction of the first heat exchanger (23) coincides with a longitudinal direction of the second heat exchanger (22), and the first heat exchanger (23) and the second heat exchanger (22) are disposed adjacent to each other, and in which a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

[0021] In the eighth aspect, when D1 is made less than D2 or D3, the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) can be smaller than the length of the third refrigerant pipe (27c) or the length of the fourth refrigerant pipe (27d).

[0022] A refrigeration apparatus according to a ninth aspect is the refrigeration apparatus according to any one of the first aspect to the eighth aspect, in which the refrigerant unit (U) and the first heat transfer medium circuit (W) are disposed adjacent to each other in a horizontal direction.

[0023] In the ninth aspect, in the horizontal direction, the refrigerant unit (U) and the water circuit (W) can be separately disposed. Therefore, it becomes easier to take out only the refrigerant unit (U).

[0024] A refrigeration apparatus according to a tenth aspect is the refrigeration apparatus according to the ninth aspect, in which the casing (60) is configured to accommodate a third heat exchanger (26) that is connected to the first heat transfer medium circuit (W) and that is configured to cause the first heat transfer medium and the second heat transfer medium to exchange heat with each other, and in which the third heat exchanger (26) is disposed closer to the first heat exchanger (23).

[0025] In the tenth aspect, when the third heat exchanger (26) is disposed closer to the first heat exchanger (23), the pipe length between the first water heat exchanger (23) and the third heat exchanger (26) can be reduced, and the loss of heat that is discharged from water that flows between the first water heat exchanger (23) and the third heat exchanger (26) can be suppressed.

[0026] A refrigeration apparatus according to an eleventh aspect is the refrigeration apparatus according to the tenth aspect, in which, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are disposed toward a first side surface (63) of the casing (60) with respect to a center in the casing (60).

[0027] In the eleventh aspect, when the first heat exchanger (23) and the second heat exchanger (22) are disposed toward one side surface (the first side surface (63)) with respect to the center of the casing (60), a layout that makes it possible for the refrigerant unit (U) to be easily taken out can be realized.

[0028] A refrigeration apparatus according to a twelfth aspect is the refrigeration apparatus according to any one of the first aspect to the eleventh aspect, in which the compressor unit (CU) includes an accumulator (25) that is connected to an intermediate portion of a suction pipe that is provided at the compressor (21).

[0029] In the twelfth aspect, the refrigeration apparatus can include the accumulator (25).

[0030] A refrigeration apparatus according to a thirteenth aspect is the refrigeration apparatus according to any one of the first aspect to the twelfth aspect, in which the first heat transfer medium is water, in which the refrigeration apparatus further includes a tank (41) that is configured to store the first heat transfer medium that has exchanged heat with the first refrigerant, and in which the refrigerant unit (U) and the tank (41) are disposed side by side in an upward direction and a downward direction in the casing (60). Brief Description of Drawings

[0031] [Fig. 1] Fig. 1 is a piping system diagram of a hot water supply system of an embodiment. [Fig. 2] Fig. 2 is an external perspective view illustrating a hot water supply unit. [Fig. 3] Fig. 3 is a plan view schematically illustrating a disposition of devices in a first space. [Fig. 4] Fig. 4 is a plan view of the first space, illustrating relationships of distances between a first water heat exchanger, a refrigerant heat exchanger, and a compressor. [Fig. 5] Fig. 5 is a schematic view illustrating states of connections of the first water heat exchanger, a first expansion valve, and a refrigerant heat exchanger, and a first refrigerant pipe and a second refrigerant pipe in a direction in which a casing is viewed from a side. [Fig. 6] Fig. 6 is a plan view of a first space, illustrating relationships of distances between a first water heat exchanger, a refrigerant heat exchanger, and a compressor of Modification 1. [Fig. 7] Fig. 7 is a plan view of a first space, illustrating relationships of distances between a first water heat exchanger, a refrigerant heat exchanger, and a compressor of Modification 2. [Fig. 8] Fig. 8 is a plan view of a first space, illustrating relationships of distances between a first water heat exchanger, a refrigerant heat exchanger, and a compressor of Modification 3. [Fig. 9] Fig. 9 is a diagram corresponding to Fig. 1 and a piping system diagram of a hot water supply system of Modification 4. [Fig. 10] Fig. 10 is a plan view corresponding to Fig. 3 and schematically illustrates a disposition of devices in a first space. [Fig. 11] Fig. 11 is a schematic view illustrating states of connections of a first water heat exchanger, a first expansion valve, and a refrigerant heat exchanger, and a first refrigerant pipe and a second refrigerant pipe in a direction in which a casing is viewed from a side in another embodiment. Description of Embodiments

[0032] Embodiments of the present disclosure are described in detail below with reference to the drawings. The present disclosure is not limited to the embodiments described below, and can be variously changed within a scope that does not depart from the technical ideas of the present disclosure. Since each figure is provided for conceptually describing the present disclosure, for facilitating understanding, the dimensions, ratios, numbers may be exaggerated or simplified as required.(1) Structure of Hot Water Supply System(1-1) Overall Structure

[0033] A hot water supply system (1) supplies hot water to objects. "Objects" of the present embodiment include a heating device (5) that uses hot water, in addition to objects to which hot water is to be supplied, such as a faucet, a shower, and a bath. The hot water supply system (1) is connected to an object to which hot water is to be supplied and the heating device (5) through a water pipe. The hot water supply system (1) includes an outdoor unit (10) that is disposed outdoors, and a hot water supply unit (20) that is disposed indoors. The hot water supply system (1) is an example of a refrigeration apparatus (1).

[0034] The hot water supply system (1) includes, as a circuit structure, a first refrigerant circuit (R1), a second refrigerant circuit (R2), and a water circuit (W). A highly flammable refrigerant as a first refrigerant fills the first refrigerant circuit (R1). Carbon dioxide as a second refrigerant fills the second refrigerant circuit (R2). The second refrigerant circuit (R2) is an example of a second heat transfer medium circuit, and carbon dioxide is an example of a second heat transfer medium. The water circuit (W) is an example of a first heat transfer medium circuit, and water that flows in the water circuit (W) is an example of a first heat transfer medium.

[0035] The first refrigerant is propane (R290), which is a highly flammable natural refrigerant. The natural refrigerant is a refrigerant whose ozone depletion potential is zero, whose global warming potential is low, and whose load on the environment is small. Propane ignites at 500°C or less. The first refrigerant may be a single refrigerant including one type of refrigerant, or may be a mixture refrigerant including two or more types of refrigerants.

[0036] The hot water supply system (1) includes a refrigerant heat exchanger (22), a first water heat exchanger (23), and a second water heat exchanger (26). The refrigerant heat exchanger (22) is shared by the first refrigerant circuit (R1) and the second refrigerant circuit (R2), the first water heat exchanger (23) is shared by the first refrigerant circuit (R1) and the water circuit (W), and the second water heat exchanger (26) is shared by the second refrigerant circuit (R2) and the water circuit (W). The refrigerant heat exchanger (22) is an example of a second heat exchanger, and the first water heat exchanger (23) is an example of a first heat exchanger. The hot water supply system (1) performs a so-called two-dimensional refrigeration cycle by using the first refrigerant circuit (R1) and the second refrigerant circuit (R2).(1-2) Outdoor Unit

[0037] The outdoor unit (10) is part of the second refrigerant circuit (R2). The outdoor unit (10) includes, as elemental devices of the second refrigerant circuit (R2), a second compressor (11), an outdoor heat exchanger (12), a second expansion valve (13), a four-way switching valve (14), and a second accumulator (15). The outdoor unit (10) includes an outdoor fan (16). The second compressor (11) compresses a sucked refrigerant and discharges the refrigerant that has been compressed. The outdoor heat exchanger (12) causes outdoor air that the outdoor fan (16) conveys and the second refrigerant to exchange heat with each other. The second expansion valve (13) decompresses a refrigerant. The four-way switching valve (14) switches between a first state that is indicated by a solid line in Fig. 1, and a second state that is indicated by a broken line in Fig. 1. The second accumulator (15) accumulates a liquid refrigerant that is a refrigerant before being sucked into the second compressor (11).(1-3) Circuit Structure of Hot Water Supply Unit

[0038] The hot water supply unit (20) is an example of a refrigerant unit (U). The hot water supply unit (20) includes the entire first refrigerant circuit (R1). The hot water supply unit (20) includes, as elemental devices of the first refrigerant circuit (R1), a first compressor (21), the refrigerant heat exchanger (22), the first water heat exchanger (23), a first expansion valve (24), and a first accumulator (25). The first compressor (21) and the first accumulator (25) constitute a compressor unit (CU). The first accumulator (25) is an example of an accumulator of the present disclosure. The first compressor (21) includes a discharge pipe and a suction pipe (not shown). The first compressor (21) compresses a refrigerant that has been sucked in through the suction pipe, and discharges the refrigerant that has been compressed through the discharge pipe. The first compressor (21) is an example of a compressor (21) of the present disclosure.

[0039] The refrigerant heat exchanger (22) includes a first flow path (P1) that communicates with the first refrigerant circuit (R1) and a second flow path (P2) that communicates with the second refrigerant circuit (R2). The refrigerant heat exchanger (22) causes a first refrigerant in the first flow path (P1) at the first refrigerant circuit (R1) and a second refrigerant in the second flow path (P2) at the second refrigerant circuit (R2) to exchange heat with each other. The refrigerant heat exchanger (22) is an example of a second heat exchanger (22).

[0040] The first water heat exchanger (23) includes a third flow path (P3) that communicates with the first refrigerant circuit (R1) and a fourth flow path (P4) that communicates with the water circuit (W). The first water heat exchanger (23) causes a first refrigerant in the third flow path (P3) at the first refrigerant circuit (R1) and water in the fourth flow path (P4) at the water circuit (W) to exchange heat with each other. The first water heat exchanger (23) is an example of a first heat exchanger (23).

[0041] The first expansion valve (24) is an example of a decompression mechanism that decompresses a refrigerant. The first expansion valve (24) has a structure that can adjust an opening degree. The first accumulator (25) accumulates a liquid refrigerant. The first accumulator (25) is connected to an upstream side of the first compressor (21). The first accumulator (25) is disposed at an intermediate portion of a suction pipe. The first accumulator (25) separates a refrigerant that flows in the suction pipe into a gas refrigerant and a liquid refrigerant. The refrigerant heat exchanger (22) and the first water heat exchanger (23) constitute, for example, a plate heat exchanger.

[0042] The first refrigerant circuit (R1) includes a first refrigerant pipe (27a), a second refrigerant pipe (27b), a third refrigerant pipe (27c), and a fourth refrigerant pipe (27d). The first refrigerant pipe (27a) connects the first water heat exchanger (23) and the first expansion valve (24) to each other. The second refrigerant pipe (27b) connects the first expansion valve (24) and the refrigerant heat exchanger (22) to each other. The third refrigerant pipe (27c) connects the refrigerant heat exchanger (22) and the compressor unit (CU) to each other. In the present embodiment, the third refrigerant pipe (27c) connects the refrigerant heat exchanger (22) and the first accumulator (25) to each other. The fourth refrigerant pipe (27d) connects the compressor unit (CU) and the first water heat exchanger (23) to each other. In the present embodiment, the fourth refrigerant pipe (27d) connects the first compressor (21) and the first water heat exchanger (23) to each other.

[0043] The inside diameter of the first refrigerant pipe (27a) and the inside diameter of the second refrigerant pipe (27b) are the same. The inside diameter of the third refrigerant pipe (27c) and the inside diameter of the fourth refrigerant pipe (27d) are the same. The inside diameter of the first refrigerant pipe (27a) and the inside diameter of the second refrigerant pipe (27b) are smaller than the inside diameter of the third refrigerant pipe (27c) and the inside diameter of the fourth refrigerant pipe (27d). The first refrigerant pipe (27a) and the second refrigerant pipe (27b) may together be referred to as "liquid refrigerant pipe (27a, 27b)". The third refrigerant pipe (27c) and the fourth refrigerant pipe (27d) may together be referred to as "gas refrigerant pipe (27c, 27d)".

[0044] The hot water supply unit (20) includes part of the second refrigerant circuit (R2). The hot water supply unit (20) includes, as elemental devices of the second refrigerant circuit (R2), the second water heat exchanger (26) in addition to the above-described first water heat exchanger (23). The second water heat exchanger (26) is an example of a third heat exchanger (26). The second water heat exchanger (26) is connected to the water circuit (W) and causes the second heat transfer medium and water in the water circuit (W) to exchange heat with each other. Specifically, the second water heat exchanger (26) includes a fifth flow path (P5) that communicates with the second refrigerant circuit (R2) and a sixth flow path (P6) that communicates with the water circuit (W). The second water heat exchanger (26) causes a second refrigerant in the fifth flow path (P5) at the second refrigerant circuit (R2) and water in the sixth flow path (P6) at the water circuit (W) to exchange heat with each other. The second water heat exchanger (26) includes, for example, a plate heat exchanger.

[0045] The hot water supply unit (20) includes, as refrigerant pipes that constitute the second refrigerant circuit (R2), a first pipe (31), a second pipe (32), a third pipe (33), and a bypass pipe (34). One end of the first pipe (31) is connected to a gas-side line of the second refrigerant circuit (R2). The other end of the first pipe (31) is connected to one end of the fifth flow path (P5) of the second water heat exchanger (26). One end of the second pipe (32) is connected to the other end of the fifth flow path (P5) of the second water heat exchanger (26). The other end of the second pipe (32) is connected to one end of the second flow path (P2) of the refrigerant heat exchanger (22). One end of the third pipe (33) is connected to the other end of the second flow path (P2) of the refrigerant heat exchanger (22). The other end of the third pipe (33) is connected to a liquid-side line of the second refrigerant circuit (R2). One end of the bypass pipe (34) is connected to a midway portion of the first pipe (31). The other end of the bypass pipe (34) is connected to a midway portion of the second pipe (32). A first on-off valve (35) is provided at the first pipe (31) at a location between the fifth flow path (P5) and a connection portion of the bypass pipe (34). A second on-off valve (36) is provided at the bypass pipe (34).

[0046] The hot water supply unit (20) includes part of the water circuit (W). The hot water supply unit (20) includes, as elemental devices of the water circuit (W), a first pump (40), a tank (41), and an internal heat exchanger (42), in addition to the above-described first water heat exchanger (23) and the above-described second water heat exchanger (26).

[0047] The first pump (40) causes water in the water circuit (W) to circulate. Fig. 1 indicates the directions of the circulation of the water in the water circuit (W) by arrows.

[0048] The tank (41) stores water (strictly speaking, hot water) that is supplied to an object. The tank (41) is a hollow container, and a hot water storage space (41a) is provided therein. A water supply pipe (43) and a hot water discharge pipe (44) are connected to the tank (41). One end of the water supply pipe (43) is connected to a bottom portion of the tank (41), and the other end of the water supply pipe (43) is connected to a water pipe. When the amount of water in the tank (41) decreases, the water supply pipe (43) supplies low-temperature water in the water pipe into the tank (41). One end of the hot water discharge pipe (44) is connected to an upper portion of the tank (41), and the other end of the hot water discharge pipe (44) is connected to a predetermined object to which hot water is to be supplied. The hot water discharge pipe (44) supplies high-temperature water in the tank (41) to the object to which hot water is to be supplied, such as a faucet, a shower, or a bath.

[0049] The internal heat exchanger (42) is disposed in the hot water storage space (41a). The internal heat exchanger (42) of the present embodiment is a spiral heat transfer tube. Hot water heated by the first water heat exchanger (23) and the second water heat exchanger (26) flows in the internal heat exchanger (42). The internal heat exchanger (42) causes the hot water that flows therein and surrounding water thereof to exchange heat with each other. As a result, the water in the hot water storage space (41a) is heated by the internal heat exchanger (42). In this way, the tank (41) of the present embodiment stores water indirectly heated by the first refrigerant of the first water heat exchanger (23).

[0050] The water circuit (W) includes a main flow path (50), a hot-water-supply-side flow path (51), and a heating-side flow path (52). An inflow end of the hot-water-supply-side flow path (51) and an inflow end of the heating-side flow path (52) communicate with an outflow-end of the main flow path (50). A three-way valve (53) is connected to the water circuit (W). The three-way valve (53) switches between a first state in which the main flow path (50) and the hot-water-supply-side flow path (51) communicate with each other and a second state in which the main flow path (50) and the heating-side flow path (52) communicate with each other.

[0051] The first pump (40), the fourth flow path (P4) of the first water heat exchanger (23), and the sixth flow path (P6) of the second water heat exchanger (26) are connected in order to the main flow path (50).

[0052] The hot-water-supply-side flow path (51) includes an inflow pipe (51a) and an outflow pipe (51b). The internal heat exchanger (42) is connected between the inflow pipe (51a) and the outflow pipe (51b).

[0053] A use-side heat exchanger (6) of the heating device (5) is connected to the heating-side flow path (52). The user-side heat exchanger (6) heats air in a target space (indoor space). The use-side heat exchanger (6) includes a fin-and-tube heat exchanger or a radiation panel. The use-side heat exchanger (6) includes an air heat exchanger that directly heats the air in the target space, or a floor-heating heat exchanger that heats the floor in the target space.

[0054] The hot water supply unit (20) includes, as elements of part of the heating-side flow path (52), a supply pipe (52a) and a return pipe (52b). The supply pipe (52a) is a flow path for supplying to the use-side heat exchanger (6) hot water heated by the first water heat exchanger (23) and the second water heat exchanger (26). The return pipe (52b) is a flow path for returning to the main flow path (50) water whose heat has been radiated at the use-side heat exchanger (6).

[0055] The hot water supply unit (20) further includes, as device elements of the water circuit (W), a heater unit (54) and an expansion tank (55). The heater unit (54) is provided in the main flow path (50), and assists in heating the water in the water circuit (W). The expansion tank (55) communicates with the main flow path (50) and mitigates the rising of water pressure of the water circuit (W).(2) Structure of Hot Water Supply Unit

[0056] A structure of the hot water supply unit (20) is described with reference to Figs. 1 to 4. In the description below, the terms up, down, front, back, left, and right are based on the directions of the arrows in Fig. 2.(2-1) Casing

[0057] As shown in Fig. 2, the hot water supply system (1) includes a casing (60) that is disposed in an indoor space (I). The indoor space (I) is a space that is formed inside a building, and includes not only a space of a room, but also a non-room space, such as a space of a hallway, a basement, a storage, or a garage. The casing (60) is set on a floor surface defining the indoor space (I). The indoor space (I) is an example of a target space (I). The casing (60) accommodates, for example, the refrigerant unit (U), the second water heat exchanger (26), and the tank (41).

[0058] The casing (60) has a hollow box shape. The casing (60) has a rectangular parallelepiped external shape. The height of the casing (60) in an upward direction and a downward direction is greater than the length of the casing (60) in a forward direction and a backward direction and the width of the casing (60) in a leftward direction and a rightward direction. The casing (60) includes an upper plate (61), a bottom plate (62), a front plate (63), a back plate (64), a right plate (65), and a left plate (66). The upper plate (61) forms an upper surface of the casing (60), and the bottom plate (62) forms a lower surface of the casing (60). The front plate (63) forms a front surface, which is a first side surface of the casing (60).

[0059] A partition plate (67) is provided in the casing (60). The partition plate (67) divides the inside of the casing (60) into an upper portion and a lower portion. Specifically, the partition plate (67) divides the inside of the casing (60) into a first space (S1) and a second space (S2). The first space (S1) is formed in the lower portion of the casing (60). The second space (S2) is formed from an intermediate portion of the casing (60) to the upper portion thereof. The first space (S1) and the second space (S2) each have a rectangular parallelepiped shape. The height of the second space (S2) is larger than the height of the first space (S1). The tank (41) is disposed in the second space (S2).

[0060] In a set state of the casing (60), a work space (S3) is provided on a forward side of the casing (60). An access port (A) is formed in a lower portion of the front plate (63) of the casing (60). An opening-closing cover (68), which is part of the front plate (63), is attachably and detachably attached to the access port (A). A worker can access the first space (S1) in the casing (60) through the access port (A) from the work space (S3).(2-2) Disposition of Each Device in First Space

[0061] Each device of the above-described hot water supply unit (20) is disposed in the first space (S1). As shown in Fig. 3, the refrigerant unit (U) including the first refrigerant circuit (R1) is disposed in the first space (S1). The refrigerant unit (U) includes the entire first refrigerant circuit (R1) as a closed circuit. The refrigerant unit (U) includes, as elemental devices of the first refrigerant circuit (R1), the first compressor (21), the refrigerant heat exchanger (22), the first expansion valve (24), and the first water heat exchanger (23).

[0062] The refrigerant unit (U) is disposed closer to the front plate (63) than to the back plate (64). The refrigerant unit (U) is disposed closer to the left plate (66) than to the right plate (65). The first compressor (21) is disposed closer to the access port (A). With the opening-closing cover (68) being detached, the first compressor (21) can be seen from the outside of the casing (60) through the access port (A). The refrigerant unit (U) is disposed below the tank (41). In a vertical direction, the refrigerant unit (U) overlaps the tank (41).

[0063] The refrigerant heat exchanger (22) and the first water heat exchanger (23) are disposed behind the first compressor (21). In the present embodiment, the refrigerant heat exchanger (22) is disposed on the right of the first water heat exchanger (23).

[0064] The hot water supply unit (20) includes a support (70) that supports the refrigerant unit (U). The support (70) is positioned below the refrigerant unit (U) and supports the refrigerant unit (U) from therebelow. The support (70) can be drawn out of the access port (A) along the bottom plate (62). It is preferable to provide the bottom plate (62) with a guide member that guides the support (70) in the forward direction and the rearward direction.

[0065] An electric component unit (71) is provided in the first space (S1). The electric component unit (71) is disposed below the tank (41). In the vertical direction, the electric component unit (71) overlaps the tank (41).

[0066] The electric component unit (71) includes a control board for controlling each device of the hot water supply unit (20). The electric component unit (71) is disposed closer to the access port (A). With the opening-closing cover (68) being detached, the electric component unit (71) can be seen from the outside of the casing (60) through the access port (A).

[0067] The second water heat exchanger (26) is disposed behind the electric component unit (71). The first on-off valve (35) and the second on-off valve (36) are disposed between the second water heat exchanger (26) and the electric component unit (71). The first pipe (31) and the third pipe (33), which are refrigerant pipes, are disposed around the second water heat exchanger (26). The first pipe (31) and the third pipe (33) extend through the partition plate (67) and extend in the vertical direction in the first space (S1).

[0068] A connection space (75) is formed behind the electric component unit (71) in the first space (S1). The connection space (75) is formed toward a forward side of the first space (S1). A first connection portion (C1), a second connection portion (C2), a third connection portion (C3), and a fourth connection portion (C4) are disposed in the connection space (75).

[0069] The first connection portion (C1) and the second connection portion (C2) constitute a water-side connection portion that attachably and detachably connects the first water heat exchanger (23) and the water circuit (W). As shown in Fig. 1, the first connection portion (C1) connects the water circuit (W) and a water pipe on an inflow side of the fourth flow path (P4) of the first water heat exchanger (23). The second connection portion (C2) connects the water circuit (W) and a water pipe on an outflow side of the fourth flow path (P4) of the first water heat exchanger (23). The first connection portion (C1) is closer to the front plate (63) than to the back plate (64). The second connection portion (C2) is closer to the front plate (63) than to the back plate (64). The first connection portion (C1) and the second connection portion (C2) are disposed side by side in the leftward direction and the rightward direction along a back surface of the electric component unit (71). In this way, the refrigerant unit (U) is disposed adjacent to the water circuit (W) in a horizontal direction.

[0070] The third connection portion (C3) and the fourth connection portion (C4) constitute a heat-transfer-medium-side connection portion that attachably and detachably connects the refrigerant heat exchanger (22) and the second refrigerant circuit (R2). As shown in Fig. 1, the third connection portion (C3) connects the second refrigerant circuit (R2) and a refrigerant pipe on an upstream side of the second flow path (P2) of the refrigerant heat exchanger (22). The third connection portion (C3) is closer to the front plate (63) than to the back plate (64). The fourth connection portion (C4) is disposed behind the third connection portion (C3). As with the fourth connection portion (C4), the third connection portion (C3) may be disposed closer to the front plate (63) than to the back plate (64).

[0071] In the first space (S1), the elemental devices of the water circuit (W) are disposed behind the refrigerant unit (U) and the connection space (75). A water-circuit-side space (76) is formed. The water-circuit-side space (76) is formed toward a rear side of the first space (S1). The first pump (40), the heater unit (54), the three-way valve (53), and the expansion tank (55) are disposed in the water-circuit-side space (76). As water pipes, the inflow pipe (51a), the outflow pipe (51b), the supply pipe (52a), and the return pipe (52b) are disposed in the water-circuit-side space (76).

[0072] The inflow pipe (51a) and the outflow pipe (51b) extend through the partition plate (67) and are connected to the internal heat exchanger (42) in the tank (41). The supply pipe (52a) and the return pipe (52b) extend through the partition plate (67) and extend in the vertical direction in the first space (S1).

[0073] Although not illustrated, other devices of the water circuit (W) are disposed in the first space (S1). The other devices include a water-discharge valve, a ball valve, a flow-rate sensor, and a filter. It is preferable that the other devices be disposed closer to the front plate (63) than to the back plate (64).(3) Regarding First Refrigerant Circuit

[0074] The first refrigerant circuit (R1) of the present embodiment has a structure in which the capacity in a tube of the liquid refrigerant pipe (27a, 27b) is smaller than the capacity in a tube of the gas refrigerant pipe (27c, 27d). In other words, the first to fourth refrigerant pipes (27a to 27d) that constitute the first refrigerant circuit (R1) have structures in which a first capacity, which is the sum of the capacity of the first refrigerant pipe (27a) and the capacity of the second refrigerant pipe (27b), is smaller than a second capacity, which is the sum of the capacity of the third refrigerant pipe (27c) and the capacity of the fourth refrigerant pipe (27d). In the present embodiment, the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) is smaller than the sum of the length of the third refrigerant pipe (27c) and the length of the fourth refrigerant pipe (27d).

[0075] Specifically, as shown in Fig. 4, in a direction in which the casing (60) is viewed from thereabove, the shortest distance between the refrigerant heat exchanger (22) and the first water heat exchanger (23) is D1, the shortest distance between the first water heat exchanger (23) and the compressor unit (CU) is D2, and the shortest distance between the refrigerant heat exchanger (22) and the compressor unit (CU) is D3. In the present embodiment, D2 is the shortest distance between the first water heat exchanger (23) and the first compressor (21), and D3 is the shortest distance between the refrigerant heat exchanger (22) and the first accumulator (25). In this way, the first compressor (21) and the first accumulator (25) are disposed such that D1 is less than D2 and D3.

[0076] Here, D1 is, in the direction in which the casing (60) is viewed from thereabove, the shortest length of lengths of straight lines connecting a middle point or points near the middle point of the refrigerant heat exchanger (22) in a longitudinal direction and a middle point or points near the middle point of the first water heat exchanger (23) in the longitudinal direction. D2 is, in the direction in which the casing (60) is viewed from thereabove, the shortest length of lengths of straight lines connecting the middle point or the points near the middle point of the first water heat exchanger (23) in the longitudinal direction and a cylindrical shaft center of the first compressor (21). D3 is, in the direction in which the casing (60) is viewed from thereabove, the shortest length of lengths of straight lines connecting the middle point or the points near the middle point of the refrigerant heat exchanger (22) in the longitudinal direction and a cylindrical shaft center of the first accumulator (25). "Points near the middle point" refer to points that are within a range of ±10% from the middle point when the length of the refrigerant heat exchanger (22) in the longitudinal direction or the length of the first water heat exchanger (23) in the longitudinal direction is 100%.

[0077] In the present embodiment, in the direction in which the casing (60) is viewed from thereabove, the refrigerant heat exchanger (22) and the first water heat exchanger (23) are disposed so as to face each other with the first expansion valve (24) being interposed therebetween. The first expansion valve (24) is disposed toward the first water heat exchanger (23) with respect to the refrigerant heat exchanger (22). In other words, the length of the first refrigerant pipe (27a) is shorter than the length of the second refrigerant pipe (27b).(4) Regarding First Refrigerant Pipe and Second Refrigerant Pipe

[0078] As shown in Fig. 5, the first expansion valve (24) includes an upper connection portion (24a) and a lower connection portion (24b). The first refrigerant pipe (27a) is connected to the upper connection portion (24a). The second refrigerant pipe (27b) is connected to the lower connection portion (24b). In the first expansion valve (24), the lower connection portion (24b) is provided below the upper connection portion (24a).

[0079] The first water heat exchanger (23) includes a first refrigerant pipe connection portion (23a) to which the first refrigerant pipe (27a) that extends from the upper connection portion (24a) is connected. The refrigerant heat exchanger (22) includes a second refrigerant pipe connection portion (22a) to which the second refrigerant pipe (27b) that extends from the lower connection portion (24b) is connected. In a direction in which the casing (60) is viewed from a side, the first water heat exchanger (23), the first expansion valve (24), and the refrigerant heat exchanger (22) are disposed side by side in order in the leftward direction and the rightward direction, and the height position of the first refrigerant pipe connection portion (23a) is higher than the height position of the second refrigerant pipe connection portion (22a).

[0080] The position of a bottom surface (22b) of the refrigerant heat exchanger (22) and the position of a bottom surface (23b) of the first water heat exchanger (23) are at the same height. In other words, the refrigerant heat exchanger (22) and the first water heat exchanger (23) are fixed in the casing (60) with the positions of the bottom surfaces (22b, 23b) being at the same height. Even if the height position of the upper connection portion (24a) of the first expansion valve (24) is higher than the height position of the lower connection portion (24b), since the height position of the first refrigerant pipe connection portion (23a) is higher than the height position of the second refrigerant pipe connection portion (22a), it is possible to suppress an increase in the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b).

[0081] Here, when the refrigerant heat exchanger (22) and the first water heat exchanger (23) include a casing, the bottom surface (22b) of the refrigerant heat exchanger (22) and the bottom surface (23b) of the first water heat exchanger (23) each mean the bottom surface of the casing. When the refrigerant heat exchanger (22) and the first water heat exchanger (23) are plate heat exchangers in which a plurality of plates are disposed side by side in a horizontal direction, the bottom surface of the refrigerant heat exchanger (22) and the bottom surface of the first water heat exchanger (23) may each mean a surface that connects lower ends of the respective plates. When the refrigerant heat exchanger (22) and the first water heat exchanger (23) are plate heat exchangers in which a plurality of plates are placed upon each other in a vertical direction, the bottom surface of the refrigerant heat exchanger (22) and the bottom surface of the first water heat exchanger (23) may each be a plate that is disposed at a lower end. When the refrigerant heat exchanger (22) and the first water heat exchanger (23) are fixed to the bottom surface of the casing (60), the bottom surface of the refrigerant heat exchanger (22) and the bottom surface of the first water heat exchanger (23) may each be a portion that is fixed to the bottom surface of the casing. In this case, the bottom surface of the casing may be the support (70). The refrigerant heat exchanger (22) and the first water heat exchanger (23) may be attached to the bottom surface of the casing with an insulation material being interposed therebetween. In this case, the bottom surface of the refrigerant heat exchanger (22) and the bottom surface of the first water heat exchanger (23) may each be an insulation material surface that contacts the bottom surface of the casing or the support (70).(5) Operation

[0082] In an operation of the hot water supply system (1), the second refrigerant circuit (R2) performs a subcritical cycle or a supercritical cycle, and, at the same time, the first refrigerant circuit (R1) performs a subcritical cycle. The second refrigerant circuit (R2) switches between a first operation and a second operation and performs the first operation or the second operation. The water circuit (W) switches between a third operation and a fourth operation and performs the third operation or the fourth operation.

[0083] In the first operation, the four-way switching valve (14) is brought into a first state, the first on-off valve (35) is brought into an open state, and the second on-off valve (36) is brought into a closed state. In the first operation, a refrigerant compressed by the second compressor (11) radiates heat at the second water heat exchanger (26) and the refrigerant heat exchanger (22), is decompressed by the second expansion valve (13), and is evaporated at the outdoor heat exchanger (12).

[0084] In the second operation, the four-way switching valve (14) is brought into the first state, the first on-off valve (35) is brought in a closed state, and the second on-off valve (36) is brought into an open state. In the second operation, a refrigerant compressed by the second compressor (11) bypasses the second water heat exchanger (26), radiates heat at the refrigerant heat exchanger (22), is decompressed by the second expansion valve (13), and is evaporated at the outdoor heat exchanger (12).

[0085] In the first refrigerant circuit (R1), a refrigerant compressed by the first compressor (21) radiates heat at the first water heat exchanger (23), is decompressed by the first expansion valve (24), and is evaporated at the refrigerant heat exchanger (22).

[0086] In the third operation, the three-way valve (53) is brought into a first state. In the third operation, water transported by the first pump (40) is heated by only the first water heat exchanger (23) or by both the second water heat exchanger (26) and the first water heat exchanger (23). The water after being heated radiates heat to water in the hot water storage space (41a) in the internal heat exchanger (42). As a result, hot water is produced in the tank (41).

[0087] In the fourth operation, the three-way valve (53) is brought into a second state. In the fourth operation, water transported by the first pump (40) is heated by only the first water heat exchanger (23) or by both the second water heat exchanger (26) and the first water heat exchanger (23). The water after being heated radiates heat to air in a target space at the use-side heat exchanger (6) of the heating device (5). As a result, the target space is heated.(6) Features(6-1) Feature 1

[0088] The refrigeration apparatus (1) of the present embodiment includes the refrigerant unit (U) and the casing (60), the refrigerant unit (U) including the first refrigerant circuit (R1) that performs a refrigeration cycle by using the first refrigerant, which is a highly flammable refrigerant, the casing (60) accommodating the refrigerant unit (U) and being disposed in the target space (I). The first compressor (21), the first water heat exchanger (23) that causes the first refrigerant of the first refrigerant circuit (R1) and water that flows in the water circuit (W) to exchange heat with each other, the first expansion valve (24), and the refrigerant heat exchanger (22) that causes the first refrigerant of the first refrigerant circuit (R1) and carbon dioxide that flows in the second refrigerant circuit (R2) to exchange heat with each other are connected in order to the first refrigerant circuit (R1). The refrigerant pipes of the first refrigerant circuit (R1) include the first refrigerant pipe (27a) that connects the first water heat exchanger (23) and the first expansion valve (24) to each other, the second refrigerant pipe (27b) that connects the first expansion valve (24) and the refrigerant heat exchanger (22) to each other, the third refrigerant pipe (27c) that connects the refrigerant heat exchanger (22) and the first compressor (21) to each other, and the fourth refrigerant pipe (27d) that connects the first compressor (21) and the first water heat exchanger (23) to each other. The first to fourth refrigerant pipes (27a to 27d) have structures in which the first capacity, which is the sum of the capacity of the first refrigerant pipe (27a) and the capacity of the second refrigerant pipe (27b), is smaller than the second capacity, which is the sum of the capacity of the third refrigerant pipe (27c) and the capacity of the fourth refrigerant pipe (27d).

[0089] Here, when the refrigerants are highly flammable refrigerants, such as propane, from the viewpoint of, for example, leakage of the refrigerants to the indoor space (I), it is preferable to suppress to the extent possible the amount (weight) of refrigerant that fills the first refrigerant circuit (R1). However, when the amount of refrigerant is excessively suppressed, the refrigerating capacity of the first refrigerant circuit (R1) cannot be sufficiently realized.

[0090] Therefore, there is a demand for suppressing the amount of refrigerant that fills the first refrigerant circuit (R1) while ensuring a predetermined refrigerating capacity. Here, the density of the refrigerant in the first refrigerant circuit (R1) is such that the density of the liquid refrigerant is higher than the density of the gas refrigerant. Therefore, when the capacity in the tube of the liquid refrigerant pipe (27a, 27b) of the first refrigerant circuit (R1) increases, the amount of refrigerant that fills the first refrigerant circuit (R1) also increases correspondingly.

[0091] Focusing on such a point, the hot water supply unit of the present embodiment has a structure in which, in the first refrigerant circuit (R1), the first capacity, which is the sum of the capacity of the first refrigerant pipe (27a) and the capacity of the second refrigerant pipe (27b), is smaller than the second capacity, which is the sum of the capacity of the third refrigerant pipe (27c) and the capacity of the fourth refrigerant pipe (27d). Therefore, the volumes of the refrigerants that each flow in a corresponding one of the first refrigerant pipe (27a) and the second refrigerant pipe (27b) can be made smaller than the volumes of the refrigerants that each flow in a corresponding one of the third refrigerant pipe (27c) and the fourth refrigerant pipe (27d). As a result, it is possible to reduce the amount of refrigerant (the weight of the refrigerant) that flows in the liquid refrigerant pipe (27a, 27b) and thus reduce the amount of refrigerant that fills the first refrigerant circuit (R1), and ensure a required refrigerating capacity of the first refrigerant circuit (R1).(6-2) Feature 2

[0092] In the refrigeration apparatus (1) of the present embodiment, the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) is smaller than the sum of the length of the third refrigerant pipe (27c) and the length of the fourth refrigerant pipe (27d). In the present embodiment, since the inside diameter of the tube of the first refrigerant pipe (27a) and the inside diameter of the tube of the second refrigerant pipe (27b) are smaller than the inside diameter of the tube of the third refrigerant pipe (27c) and the inside diameter of the tube of the fourth refrigerant pipe (27d), the first capacity can be reliably made smaller than the second capacity.(6-3) Feature 3

[0093] In the refrigeration apparatus (1) of the present embodiment, the length of the first refrigerant pipe (27a) is shorter than the length of the second refrigerant pipe (27b). During the refrigeration cycle operation of the first refrigerant circuit (R1), the refrigerant that passes through the first refrigerant pipe (27a) is decompressed by the first expansion valve (24) and flows into the second refrigerant pipe (27b). In this way, the density of the refrigerant that flows in the first refrigerant pipe (27a) is higher than the density of the refrigerant that flows in the second refrigerant pipe (27b). Therefore, when the first refrigerant pipe (27a) is made shorter than the second refrigerant pipe (27b), it is possible to reduce the amount of refrigerant that fills the first refrigerant circuit (R1).(6-4) Feature 4

[0094] In the present embodiment, the first expansion valve (24) includes the upper connection portion (24a) to which the first refrigerant pipe (27a) is connected, and the lower connection portion (24b) that is disposed below the upper connection portion (24a) and to which the second refrigerant pipe (27b) is connected. In a direction in which the casing (60) is viewed from a side, the first heat exchanger (23) includes the first refrigerant pipe connection portion (23a) to which the first refrigerant pipe (27a) that extends from the upper connection portion (24a) is connected, and the second heat exchanger (22) includes the second refrigerant pipe connection portion (22a) to which the second refrigerant pipe (27b) that extends from the lower connection portion (24b) is connected. The height position of the first refrigerant pipe connection portion (23a) is higher than the height position of the second refrigerant pipe connection portion (22a).

[0095] Since the upper connection portion (24a) is disposed above the lower connection portion (24b), when the height position of the first refrigerant pipe connection portion (23a) is made higher than the height position of the second refrigerant pipe connection portion (22a), the distance from the upper connection portion (24a) to the first refrigerant pipe connection portion (23a) and the distance from the lower connection portion (24b) to the second refrigerant pipe connection portion (22a) can be reduced. In other words, the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) can be reduced.(6-5) Feature 5

[0096] In the hot water supply system (1) of the present embodiment, when the casing (60) is viewed from thereabove, the first water heat exchanger (23) and the refrigerant heat exchanger (22) are disposed so as to face each other with the first expansion valve (24) being interposed therebetween, and the shortest distance D1 between the first water heat exchanger (23) and the refrigerant heat exchanger (22) is smaller than the shortest distance D2 between the first water heat exchanger (23) and the first compressor (21) of the compressor unit (CU) and the shortest distance D3 between the refrigerant heat exchanger (22) and the first accumulator (25) of the compressor unit (CU).

[0097] In this way, when the first water heat exchanger (23), the first expansion valve (24), and the refrigerant heat exchanger (22) are disposed in order in a lateral direction of the casing (60), and when D1 is made less than D2 and D3, the first capacity can be made smaller than the second capacity.(6-6) Feature 6

[0098] In the hot water supply system (1) of the present embodiment, the refrigerant unit (U) and the water circuit (W) are disposed adjacent to each other in a horizontal direction. In this way, in the horizontal direction, the refrigerant unit (U) and the water circuit (W) can be separately disposed. Due to such a disposition, it becomes possible to take out only the refrigerant unit (U) through the access port (A) so as to draw the refrigerant unit (U) out of the casing (60) in the horizontal direction.(6-7) Feature 7

[0099] The hot water supply system (1) of the present embodiment further includes the tank (41) that stores water that has exchanged heat with the first refrigerant, and the refrigerant unit (U) is disposed side by side and below the tank (41) in the casing (60). When the refrigerant unit (U) is disposed below the tank (41), the center of gravity of the hot water supply unit (20) can be moved downward. Therefore, the hot water supply unit (20) is more stably set.(7) Modifications

[0100] Modifications of the hot water supply system (1) of the above-described embodiment are described. It should be noted that only structures that differ from those of the above-described embodiment are described below.(7-1) Modification 1

[0101] As shown in Fig. 6, in a hot water supply system (1) of Modification 1, in a direction in which a casing (60) is viewed from thereabove, a first water heat exchanger (23) and a refrigerant heat exchanger (22) are each disposed so as to face a first expansion valve (24), and the refrigerant heat exchanger (22) is disposed closer to one end of the first water heat exchanger (23) in a longitudinal direction. A compressor unit (CU) of Modification 1 is also disposed at a position where D1 is less than D2 and D3.

[0102] Specifically, in the direction in which the casing (60) is viewed from thereabove, the first water heat exchanger (23) and the refrigerant heat exchanger (22) are disposed such that a longitudinal direction of the first water heat exchanger (23) and a longitudinal direction of the refrigerant heat exchanger (22) are orthogonal to each other, and such that one end of the first water heat exchanger (23) and one end of the refrigerant heat exchanger (22) are closer to each other. Since the first expansion valve (24) is disposed so as to face both of the first water heat exchanger (23) and the refrigerant heat exchanger (22), a liquid refrigerant pipe (27a, 27b) can be made shorter. "Closer to" means that, in the direction in which the casing (60) is viewed from thereabove, the shortest distance between the one end of the first water heat exchanger (23) in the longitudinal direction and the one end of the refrigerant heat exchanger (22) is smaller than the length of the first water heat exchanger (23) or the length of the refrigerant heat exchanger (22) in the longitudinal direction. In the present modification, the shortest distance between the one end of the first water heat exchanger (23) in the longitudinal direction and the one end of the refrigerant heat exchanger (22) is 5 mm to 10 mm.

[0103] Therefore, even in a hot water supply unit (20) of Modification 1, the liquid refrigerant pipe (27a, 27b) can be made shorter than a gas refrigerant pipe (27c, 27d). As a result, since a first capacity becomes smaller than a second capacity, it is possible to reduce the amount of refrigerant (the weight of the refrigerant) that flows in the liquid refrigerant pipe (27a, 27b), and to ensure a required refrigerating capacity while reducing the amount of refrigerant that fills a first refrigerant circuit (R1).(7-2) Modification 2

[0104] As shown in Fig. 7, in a hot water supply system (1) of Modification 2, in a direction in which a casing (60) is viewed from thereabove, a longitudinal direction of a first water heat exchanger (23) coincides with a longitudinal direction of a refrigerant heat exchanger (22), and the first water heat exchanger (23) and the refrigerant heat exchanger (22) are disposed adjacent to each other. Specifically, a first end portion (23c), which is one end portion of the first water heat exchanger (23) in the longitudinal direction, is disposed so as to face a second end portion (22c), which is one end portion of the refrigerant heat exchanger (22) in the longitudinal direction, when the first end portion (23c) is closer to the second end portion (22c). A compressor unit (CU) of Modification 2 is disposed such that D1 becomes less than D2 and D3.

[0105] Therefore, since the first water heat exchanger (23) and the refrigerant heat exchanger (22) can be disposed so as to be closer to each other, a first refrigerant pipe (27a) and a second refrigerant pipe (27b) can be made relatively short. "Closer to" means that, in the direction in which the casing (60) is viewed from thereabove, the distance between the first end portion (23c) and the second end portion (22c) is smaller than the length of the first water heat exchanger (23) in the longitudinal direction and the length of the refrigerant heat exchanger (22) in the longitudinal direction. Specifically, it is preferable that the distance between the first end portion (23c) and the second end portion (22c) be 5 mm to 10 mm.

[0106] Even in the refrigeration apparatus of Modification 2, since a first capacity can be made smaller than a second capacity, it is possible to reduce the amount of refrigerant (the weight of the refrigerant) that flows in a liquid refrigerant pipe (27a, 27b), and to ensure a required refrigerating capacity while reducing the amount of refrigerant that fills a first refrigerant circuit (R1).(7-3) Modification 3

[0107] As shown in Fig. 8, in a hot water supply system (1) of Modification 3, a second water heat exchanger (26) is disposed closer to a first water heat exchanger (23). Specifically, in a direction in which a casing (60) is viewed from thereabove, the first water heat exchanger (23), the second water heat exchanger (26), and a refrigerant heat exchanger (22) are disposed toward a front plate (63) with respect to a center in the casing (60).

[0108] Here, "closer to" means that, in the direction in which the casing (60) is viewed from thereabove, the shortest distance between the second water heat exchanger (26) and the first water heat exchanger (23) is smaller than the length of the second water heat exchanger (26) in a longitudinal direction or the length of the first water heat exchanger (23) in a longitudinal direction.

[0109] In the refrigeration apparatus (1) of Modification 3, since the first water heat exchanger (23) and the refrigerant heat exchanger (22) are disposed toward a front surface, it is possible to easily take out a refrigerant unit (U) through an access port (A). Since the first water heat exchanger (23) and the second heat exchanger (22) are closer to each other, the length of a pipe between the first water heat exchanger (23) and the second water heat exchanger (26) can be reduced, and loss of heat that is discharged from water that flows between the first water heat exchanger (23) and the second water heat exchanger (26) can be suppressed.(7-4) Modification 4

[0110] As shown in Figs. 9 and 10, a hot water supply system (1) of Modification 4 includes a water source heat pump (WSHP). A second heat transfer medium circuit (R2) of Modification 4 differs from the second refrigerant circuit (R2) of the above embodiment. A second heat exchanger (22) of the second heat transfer medium circuit (R2) of Modification 4 is a water heat exchanger that causes heat to be exchanged between a refrigerant and water. A second heat transfer medium is water. The second heat transfer medium may be brine. In Modification 4, the second heat exchanger (22) is called a third water heat exchanger (22). In the second heat transfer medium circuit (R2), water heated by an external heat source device (not shown) circulates.

[0111] A hot water supply unit (20) of Modification 4 includes a first pipe (81), a second pipe (82), and a second pump (45). The first pipe (81) and the second pipe (82) constitute the second heat transfer medium circuit (R2). The first pipe (81) transports to the second heat exchanger (22) water heated by the heat source device. The first pipe (81) is connected to an inflow side of a second flow path (P2) of the second heat exchanger (22). Specifically, the first pipe (81) is connected to a third connection portion (C3). The second pipe (82) transports toward the heat source device the water that has exchanged heat at the second heat exchanger (22). Specifically, the second pipe (82) is connected to a fourth connection portion (C4). The second pump (45) transports water of the second heat transfer medium circuit (R2). The water circulates in the second heat transfer medium circuit (R2) by the operation of the second pump (45). The second pump (45) is provided at the second pipe (82).

[0112] As shown in Fig. 10, a compressor unit (CU), a first water heat exchanger (23), and the third water heat exchanger (22) are disposed toward a back plate (64) in a casing (60). Specifically, the compressor unit (CU), the first water heat exchanger (23), and the third water heat exchanger (22) are disposed so as to face the back plate (64). The compressor unit (CU) is disposed toward a right end, and the first water heat exchanger (23) and the third water heat exchanger (22) are disposed adjacent to each other in the leftward direction and the rightward direction.(8) Other Embodiments

[0113] As shown in Fig. 11, the height position of a bottom surface (23b) of a first heat exchanger (23) may be higher than the height position of a bottom surface (22b) of a second heat exchanger (22). Since the height position of a first refrigerant pipe connection portion (23a) is higher than the height position of a second refrigerant pipe connection portion (22a), the distance from an upper connection portion (24a) to the first refrigerant pipe connection portion (23a) and the distance from a lower connection portion (24b) to the second refrigerant pipe connection portion (22a) can be reduced.

[0114] The first refrigerant is not limited to propane as long as the first refrigerant is a highly flammable refrigerant.

[0115] The first heat transfer medium need not be water as long as the first heat transfer medium is a heat transfer medium that can exchange heat with the first refrigerant.

[0116] The second heat transfer medium is not limited to carbon dioxide and may be other refrigerants (for example, an HFC refrigerant and an HFO refrigerant). The second heat transfer medium may be water or brine. In this case, the second refrigerant circuit (R2) may have a structure that allows heat exchange with ground heat. Specifically, part of the pipes that constitute the second refrigerant circuit (R2) are disposed in the ground.

[0117] The hot water supply system (1) may be a system that supplies hot water to only the heating device (5) from the tank (41).

[0118] The hot water supply unit (20) need not include a second water heat exchanger (26). In this case, the second refrigerant circuit (R2) does not include a second water heat exchanger (26), a bypass pipe (34), a first on-off valve (35), and a second on-off valve (36).

[0119] The tank (41) may have a structure that directly stores therein water heated by the first water heat exchanger (23). In other words, the tank (41) may store water directly heated by the first refrigerant.

[0120] In the casing (60), the refrigerant unit (U) may be disposed below the tank (41). In other words, in the casing (60), the tank (41) may be disposed above the refrigerant unit (U).

[0121] The refrigeration apparatus (1) may have a structure without an outdoor unit (10).

[0122] The first refrigerant circuit (R1) is to have a structure in which the first capacity is smaller than the second capacity, and the sum of the length of the first refrigerant pipe (27a) and the length of the second refrigerant pipe (27b) may be smaller than or equal to the sum of the length of the third refrigerant pipe (27c) and the length of the fourth refrigerant pipe (27d). The length of the first refrigerant pipe (27a) may be shorter than the length of the second refrigerant pipe (27b).

[0123] The compressor unit (CU) may include another structural element in place of the first accumulator (25). In this case, D3 may be the shortest distance between the other structural element and the first water heat exchanger (23). The compressor unit (CU) may include only the first compressor (21). In this case, D3 is the shortest distance between the first compressor (21) and the first water heat exchanger (23).

[0124] D2 may be the shortest distance between the first accumulator (25) of the compressor unit (CU) and the refrigerant heat exchanger (22). D3 may be the shortest distance between the first compressor (21) of the compressor unit (CU) and the first water heat exchanger (23).

[0125] Although the embodiments and the modifications have been described, it should be understood that various changes can be made in forms and details without departing from the spirit and scope of the claims. As long as functions of objects of the present disclosure are not impaired, any of the above embodiments and modifications may be combined or substituted as appropriate. Added words such as "first", "second", ... above are used to distinguish between terms including such added words, and do not limit the number and order of such terms.Industrial Applicability

[0126] As described above, the present disclosure is useful for a refrigeration apparatus.Reference Signs List

[0127] 1 hot water supply system (refrigeration apparatus) 21 first compressor (compressor) 22 refrigerant heat exchanger (second heat exchanger) 22 third water heat exchanger (second heat exchanger) 23 first water heat exchanger (first heat exchanger) 24 first expansion valve (decompression mechanism) 24a upper connection portion 24b lower connection portion 26 second water heat exchanger (third heat exchanger) 27a first refrigerant pipe 27b second refrigerant pipe 27c third refrigerant pipe 27d fourth refrigerant pipe 41 tank 60 casing 63 front plate (first side surface) CU compressor unit I indoor space (target space) R1 first refrigerant circuit R2 second refrigerant circuit (second heat transfer medium circuit) U refrigerant unit W water circuit (first heat transfer medium circuit)

Claims

1. A refrigeration apparatus comprising: a refrigerant unit (U) that includes a first refrigerant circuit (R1) configured to perform a refrigeration cycle by using a first refrigerant, which is a highly flammable refrigerant; and a casing (60) that is configured to accommodate the refrigerant unit (U) and that is disposed in a target space (I), wherein to the first refrigerant circuit (R1) are connected in order a compressor unit (CU) that includes a compressor (21), a first heat exchanger (23) that is configured to cause the first refrigerant of the first refrigerant circuit (R1) and a first heat transfer medium that flows in a first heat transfer medium circuit (W) to exchange heat with each other, a decompression mechanism (24), and a second heat exchanger (22) that is configured to cause the first refrigerant of the first refrigerant circuit (R1) and a second heat transfer medium that flows in a second heat transfer medium circuit (R2) to exchange heat with each other, and wherein a first refrigerant pipe (27a) that is configured to connect the first heat exchanger (23) and the decompression mechanism (24) to each other, a second refrigerant pipe (27b) that is configured to connect the decompression mechanism (24) and the second heat exchanger (22) to each other, a third refrigerant pipe (27c) that is configured to connect the second heat exchanger (22) and the compressor unit (CU) to each other, and a fourth refrigerant pipe (27d) that is configured to connect the compressor unit (CU) and the first heat exchanger (23) to each other have structures in which a first capacity, which is a sum of a capacity of the first refrigerant pipe (27a) and a capacity of the second refrigerant pipe (27b), is smaller than a second capacity, which is a sum of a capacity of the third refrigerant pipe (27c) and a capacity of the fourth refrigerant pipe (27d).

2. The refrigeration apparatus according to claim 1, wherein a sum of a length of the first refrigerant pipe (27a) and a length of the second refrigerant pipe (27b) is smaller than a sum of a length of the third refrigerant pipe (27c) and a length of the fourth refrigerant pipe (27d).

3. The refrigeration apparatus according to claim 1 or claim 2, wherein a length of the first refrigerant pipe (27a) is shorter than a length of the second refrigerant pipe (27b).

4. The refrigeration apparatus according to claim 3, wherein the decompression mechanism (24) is an expansion valve whose opening degree is adjustable, and includes an upper connection portion (24a) to which the first refrigerant pipe (27a) is connected, and a lower connection portion (24b) that is disposed below the upper connection portion (24a) and to which the second refrigerant pipe (27b) is connected, and wherein, in a direction in which the casing (60) is viewed from a side, the first heat exchanger (23) includes a first refrigerant pipe connection portion (23a) to which the first refrigerant pipe (27a) that extends from the upper connection portion (24a) is connected, the second heat exchanger (22) includes a second refrigerant pipe connection portion (22a) to which the second refrigerant pipe (27b) that extends from the lower connection portion (24b) is connected, and a height position of the first refrigerant pipe connection portion (23a) is higher than a height position of the lower connection portion (24b), and a height position of the second refrigerant pipe connection portion (22a) is lower than the height position of the lower connection portion (24b).

5. The refrigeration apparatus according to claim 4, wherein a height position of a bottom surface (23b) of the first heat exchanger (23) is higher than a height position of a bottom surface (22b) of the second heat exchanger (22).

6. The refrigeration apparatus according to any one of claims 1 to 4, wherein, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are disposed so as to face each other with the decompression mechanism (24) being interposed therebetween, and wherein a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

7. The refrigeration apparatus according to claim 1 or claim 2, wherein, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are each disposed so as to face the decompression mechanism (24), and the second heat exchanger (22) is disposed closer to one end of the first heat exchanger (23) in a longitudinal direction, and wherein a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

8. The refrigeration apparatus according to any one of claims 1 to 4, wherein, in a direction in which the casing (60) is viewed from thereabove, a longitudinal direction of the first heat exchanger (23) coincides with a longitudinal direction of the second heat exchanger (22), and the first heat exchanger (23) and the second heat exchanger (22) are disposed adjacent to each other, and wherein a shortest distance D1 between the first heat exchanger (23) and the second heat exchanger (22) is less than a shortest distance D2 between the first heat exchanger (23) and the compressor unit (CU) or a shortest distance D3 between the second heat exchanger (22) and the compressor unit (CU).

9. The refrigeration apparatus according to any one of claims 1 to 8, wherein the refrigerant unit (U) and the first heat transfer medium circuit (W) are disposed adjacent to each other in a horizontal direction.

10. The refrigeration apparatus according to claim 9, wherein the casing (60) is configured to accommodate a third heat exchanger (26) that is connected to the first heat transfer medium circuit (W) and that is configured to cause the first heat transfer medium and the second heat transfer medium to exchange heat with each other, and wherein the third heat exchanger (26) is disposed closer to the first heat exchanger (23).

11. The refrigeration apparatus according to claim 10, wherein, in a direction in which the casing (60) is viewed from thereabove, the first heat exchanger (23) and the second heat exchanger (22) are disposed toward a first side surface (63) of the casing (60) with respect to a center in the casing (60).

12. The refrigeration apparatus according to any one of claims 1 to 11, wherein the compressor unit (CU) includes an accumulator (25) that is connected to an intermediate portion of a suction pipe that is provided at the compressor (21).

13. The refrigeration apparatus according to any one of claims 1 to 12, wherein the first heat transfer medium is water, wherein the refrigeration apparatus further comprises a tank (41) that is configured to store the first heat transfer medium that has exchanged heat with the first refrigerant, and wherein the refrigerant unit (U) and the tank (41) are disposed side by side in an upward direction and a downward direction in the casing (60).

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