Refrigeration device and container for transportation

Abstract

In a reheating pipe (33) of a refrigerant circuit (30), a fifth expansion valve (EV5) is provided downstream of a reheating heat exchanger (58). In a dehumidifying operation, an inner heat exchanger (57) cools and dehumidifies air. In the dehumidifying operation, a refrigerant discharged from a compressor (50) is supplied to the reheating heat exchanger (58). The reheating heat exchanger (58) heats the air dehumidified in the inner heat exchanger (57). When a controller (90) changes the opening degree of the fifth expansion valve (EV5), the flow rate of the refrigerant in the reheating heat exchanger (58) changes, and the temperature of the air having passed through the reheating heat exchanger (58) changes.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a refrigeration apparatus and a transportation container.BACKGROUND ART

[0002] Patent Document 1 discloses a container refrigeration apparatus, which is one of refrigeration apparatuses. The container refrigeration apparatus includes an evaporator and a reheat heat exchanger (a reheating heat exchanger), and performs a dehumidifying operation.

[0003] In the dehumidifying operation, the air is cooled and dehumidified by the evaporator. In the dehumidifying operation, the refrigerant discharged from a compressor is supplied to the reheat heat exchanger through a reheat circuit. In the reheat heat exchanger, the air cooled and dehumidified when passing through the evaporator is heated by the refrigerant.

[0004] In the dehumidifying operation performed by the container refrigeration apparatus of Patent Document 1, the air cooled and dehumidified by the evaporator is heated by the reheat heat exchanger, and then is supplied to an internal space. In this manner, the container refrigeration apparatus of Patent Document 1 decreases the humidity of the inside air while reducing a temperature decrease in the inside air.CITATION LISTPATENT DOCUMENT

[0005] Patent Document 1: Japanese Unexamined Patent Publication No. 2013-122333SUMMARY OF THE INVENTIONTECHNICAL PROBLEM

[0006] In the reheat circuit of the container refrigeration apparatus of Patent Document 1, an on-off valve is provided upstream of the reheat heat exchanger, and a capillary tube is provided downstream of the reheat heat exchanger. Thus, the flow rate of the refrigerant in the reheat heat exchanger may not be appropriately adjusted during the dehumidifying operation, and the temperature of the air blown into the internal space through the reheat heat exchanger may not be appropriately controlled.

[0007] An object of the present disclosure is to provide a refrigeration apparatus that performs a dehumidifying operation in which the temperature of the air blown by a refrigeration apparatus is appropriately adjusted.SOLUTION TO THE PROBLEM

[0008] A first aspect of the present disclosure is directed to a refrigeration apparatus (10) which includes a refrigerant circuit (30) having a compressor (50), a heat-source-side heat exchanger (56), an expansion valve (65), and a utilization-side heat exchanger (57), and which is configured to condition air in a target space (5). The refrigerant circuit (30) has a reheating heat exchanger (58) configured to exchange heat between air having passed through the utilization-side heat exchanger (57) and a refrigerant, a reheating passage (33) configured to send a refrigerant discharged by the compressor (50) to the reheating heat exchanger (58), and a regulating valve (EV5) of which an opening degree is variable and which is provided downstream of the reheating heat exchanger (58) in the reheating passage (33). The refrigeration apparatus (10) performs a dehumidifying operation to perform a refrigeration cycle in which the heat-source-side heat exchanger (56) functions as a radiator and the utilization-side heat exchanger (57) functions as an evaporator; cool and dehumidify air in the utilization-side heat exchanger (57); heat the air having passed through the utilization-side heat exchanger (57) in the reheating heat exchanger (58); and blow the air heated in the reheating heat exchanger (58) into the target space (5), and the refrigeration apparatus (10) includes a controller (90) that controls the opening degree of the regulating valve (EV5) in the dehumidifying operation.

[0009] The refrigeration apparatus (10) of the first aspect performs the dehumidifying operation. In the dehumidifying operation, the utilization-side heat exchanger (57) functioning as the evaporator cools and dehumidifies air. In the dehumidifying operation, the refrigerant discharged from the compressor (50) is sent to the reheating heat exchanger (58) through the reheating passage (33). The reheating heat exchanger (58) heats the air dehumidified in the utilization-side heat exchanger (57) by the refrigerant. In the dehumidifying operation, the air dehumidified in the utilization-side heat exchanger (57) and then heated in the reheating heat exchanger (58) is blown into the target space (5).

[0010] In the dehumidifying operation, the controller (90) of the first aspect controls the opening degree of the regulating valve (EV5). When the opening degree of the regulating valve (EV5) changes, the flow rate of the refrigerant in the reheating heat exchanger (58) changes, and then the amount of heat applied to the air in the reheating heat exchanger (58) changes. As a result, the temperature of the air blown into the target space (5) after passing through the reheating heat exchanger (58) changes. Thus, by the controller (90) controlling the opening degree of the regulating valve (EV5), it is possible to control the temperature of the air blown into the target space (5) by the refrigeration apparatus (10) in the dehumidifying operation.

[0011] A second aspect of the present disclosure is an embodiment of the first aspect. In the second aspect, in the dehumidifying operation, a pressure of the refrigerant supplied to the reheating heat exchanger (58) through the reheating passage (33) is higher than or equal to a critical pressure of the refrigerant.

[0012] In the defrosting operation performed by the refrigeration apparatus (10) of the second aspect, the refrigerant having a pressure higher than or equal to the critical pressure exchanges heat with the air in the reheating heat exchanger (58). In the course of dissipating heat, the refrigerant having a pressure higher than or equal to the critical pressure undergoes a sensible heat change. Thus, in the defrosting operation performed by the refrigeration apparatus (10) of this aspect, the refrigerant dissipates heat at a substantially uniform rate in the entire part of the reheating heat exchanger (58). As a result, the temperature of the air blown by the refrigeration apparatus (10) in the dehumidifying operation is made uniform.

[0013] A third aspect of the present disclosure is an embodiment of the second aspect. In the third aspect, in the dehumidifying operation, the controller (90) controls an opening degree of the expansion valve (65) so that a pressure of the refrigerant discharged by the compressor (50) can become higher than or equal to a critical pressure of the refrigerant.

[0014] In the refrigeration apparatus (10) of the third aspect, the controller (90) controls the opening degree of the expansion valve (65), whereby the pressure of the refrigerant discharged from the compressor (50) can become higher than or equal to the critical pressure of the refrigerant.

[0015] A fourth aspect of the present disclosure is an embodiment of any one of the first to third aspects. In the fourth aspect, in the dehumidifying operation, the controller (90) controls an opening degree of the regulating valve (EV5) based on a temperature of the air having passed through the reheating heat exchanger (58).

[0016] In the dehumidifying operation, the controller (90) of the fourth aspect controls an opening degree of the regulating valve (EV5) based on a temperature of the air having passed through the reheating heat exchanger (58).

[0017] A fifth aspect of the present disclosure is an embodiment of any one of the first to third aspects. In the fifth aspect, in the dehumidifying operation, the controller (90) controls an opening degree of the regulating valve (EV5) based on a temperature of the refrigerant having flowed out from the reheating heat exchanger (58).

[0018] In the dehumidifying operation, the controller (90) of the fifth aspect controls an opening degree of the regulating valve (EV5) based on a temperature of the refrigerant having passed through the reheating heat exchanger (58).

[0019] A sixth aspect of the present disclosure is an embodiment of any one of the first to fifth aspects. In the sixth aspect, in the dehumidifying operation, the controller (90) controls a rotational speed of the compressor (50) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

[0020] In the dehumidifying operation, when the rotational speed of the compressor (50) changes, the evaporation temperature of the refrigerant in the utilization-side heat exchanger (57) changes. Thus, the controller (90) of the sixth aspect controls a rotational speed of the compressor (50) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

[0021] A seventh aspect of the present disclosure is an embodiment of any one of the first to fifth aspects. In the seventh aspect, the refrigerant circuit (30) has a receiver (62) disposed between the heat-source-side heat exchanger (56) and the utilization-side heat exchanger (57). The expansion valve (65) includes a first expansion valve (EV1) disposed between the heat-source-side heat exchanger (56) and the receiver (62), and a second expansion valve (EV2) disposed between the receiver (62) and the utilization-side heat exchanger (57). In the dehumidifying operation, the controller (90) controls the opening degree of the first expansion valve (EV1) so that the pressure of refrigerant discharged by the compressor (50) can become higher than or equal to the critical pressure of the refrigerant, and controls an opening degree of the second expansion valve (EV2) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

[0022] In the dehumidifying operation, the controller (90) of the seventh aspect controls the opening degree of the first expansion valve (EV1) and the opening degree of the second expansion valve (EV2). When the opening degree of the first expansion valve (EV1) changes, the pressure of the refrigerant discharged by the compressor (50) changes. Thus, the controller (90) controls the opening degree of the first expansion valve (EV1) so that the pressure of refrigerant discharged by the compressor (50) can become higher than or equal to the critical pressure of the refrigerant. When the opening degree of the second expansion valve (EV2) changes, the evaporation temperature of the refrigerant in the utilization-side heat exchanger (57) changes. Thus, the controller (90) controls an opening degree of the second expansion valve (EV2) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

[0023] An eighth aspect of the present disclosure is an embodiment of the sixth or seventh aspect. In the eighth aspect, in the dehumidifying operation, the controller (90) sets the control target value based on a humidity of air flowing into the utilization-side heat exchanger (57) from the target space (5) or a humidity of air blown into the target space (5).

[0024] In the dehumidifying operation, the controller (90) of the eighth aspect sets the control target value based on a humidity of air flowing into the utilization-side heat exchanger (57) from the target space (5) or a humidity of air blown into the target space (5).

[0025] A ninth aspect of the present disclosure is an embodiment of any one of the first to eighth aspects. In the ninth aspect, the compressor (50) includes a low-stage compressor (51) configured to suck a refrigerant having passed through the utilization-side heat exchanger (57), and a high-stage compressor (52) configured to suck a refrigerant discharged by the low-stage compressor (51), and in the dehumidifying operation, the refrigeration apparatus (10) selectively performs a single-stage compressing operation in which one of the low-stage compressor (51) or the high-stage compressor (52) is operated and the other is stopped, and a two-stage compressing operation in which both the low-stage compressor (51) and the high-stage compressor (52) are operated.

[0026] The refrigeration apparatus (10) of the ninth aspect selectively performs the single-stage compressing operation and the two-stage compressing operation in the dehumidifying operation.

[0027] A tenth aspect of the present disclosure is an embodiment of any one of the first to ninth aspects. In the tenth aspect, in the dehumidifying operation, the controller (90) expands the opening degree of the regulating valve (EV5) if a temperature non-uniformity condition indicating that a temperature of the air having passed through the reheating heat exchanger (58) is not uniform is satisfied.

[0028] The controller (90) of the tenth aspect determines whether the temperature non-uniformity condition is satisfied. If the temperature non-uniformity condition is satisfied, it is highly likely that the temperature of the air having passed through the reheating heat exchanger (58) is not uniform. The main cause that makes the temperature of the air having passed through the reheating heat exchanger (58) not uniform is that the amount of heat transferred to the air at each part of the reheating heat exchanger (58) is not uniform. Thus, the controller (90) expands the opening degree of the regulating valve (EV5) if the temperature non-uniformity condition is satisfied. When the opening degree of the regulating valve (EV5) expands, the flow rate of the refrigerant in the reheating heat exchanger (58) increases, and the amount of heat transferred to the air at each part of the reheating heat exchanger (58) is made uniform.

[0029] An eleventh aspect of the present disclosure is an embodiment of any one of the first to tenth aspects. In the eleventh aspect, the reheating passage (33) sends the refrigerant having passed through the reheating heat exchanger (58) to the utilization-side heat exchanger (57).

[0030] In the refrigeration apparatus (10) of the eleventh aspect, the refrigerant having passed through the reheating heat exchanger (58) during the dehumidifying operation passes through the regulating valve (EV5) and then flows into the utilization-side heat exchanger (57).

[0031] A twelfth aspect of the present disclosure is an embodiment of any one of the first to eleventh aspects. In the twelfth aspect, the refrigerant circuit (30) is filled with carbon dioxide as a refrigerant.

[0032] The refrigerant circuit (30) of the twelfth aspect circulates carbon dioxide as the refrigerant to perform the refrigeration cycle.

[0033] A thirteenth aspect of the present disclosure is directed to a transportation container (1) including: the refrigeration apparatus (10) of any one of the first to twelfth aspects; and a container body (2) forming the target space (5) in which the air is conditioned by the refrigeration apparatus (10).

[0034] The transportation container (1) of the thirteenth aspect includes the refrigeration apparatus (10) and the container body (2). The container body (2) forms the target space (5). The refrigeration apparatus (10) conditions the air in the target space (5).BRIEF DESCRIPTION OF THE DRAWINGS

[0035] [FIG. 1] FIG. 1 is a schematic perspective view of a refrigeration apparatus of a first embodiment. [FIG. 2] FIG. 2 is a schematic sectional view of a transportation container of the first embodiment. [FIG. 3] FIG. 3 is a piping diagram which shows the configuration of the refrigeration apparatus of the first embodiment. [FIG. 4] FIG. 4 is a block diagram which shows the configuration of a controller of the first embodiment. [FIG. 5] FIG. 5 is a piping diagram which corresponds to FIG. 3 and which shows the flow of a refrigerant in a cooling operation. [FIG. 6] FIG. 6 is a piping diagram which corresponds to FIG. 3 and which shows the flow of a refrigerant in a two-stage compressing operation of a dehumidifying operation. [FIG. 7] FIG. 7 is a piping diagram which corresponds to FIG. 3 and which shows the flow of a refrigerant in a single-stage compressing operation of a dehumidifying operation. [FIG. 8] FIG. 8 is a piping diagram which corresponds to FIG. 3 and which shows the flow of a refrigerant in a defrosting operation. [FIG. 9] FIG. 9 is a state transition diagram which shows operation of a controller in the dehumidifying operation. [FIG. 10] FIG. 10 is a flowchart of a humidity control operation of the controller. [FIG. 11] FIG. 11 is a flowchart of a temperature control operation of the controller. [FIG. 12] FIG. 12 is a flowchart of a high-pressure control operation of the controller. [FIG. 13] FIG. 13 is a piping diagram which shows the configuration of the refrigeration apparatus of the second embodiment. [FIG. 14] FIG. 14 is a piping diagram which shows the configuration of the refrigeration apparatus of the third embodiment. [FIG. 15] FIG. 15 is a piping diagram which shows the configuration of a refrigeration apparatus of a first variation of other embodiments. DESCRIPTION OF EMBODIMENTS<<First Embodiment>>

[0036] The first embodiment will be described. This embodiment is a transportation container (1) including a refrigeration apparatus (10).-Transportation Container-

[0037] As shown in FIG. 1, the transportation container (1) includes a container body (2) and the refrigeration apparatus (10). The transportation container (1) is a reefer container capable of controlling a temperature in the container.

[0038] The transportation container (1) of this embodiment is used mainly for marine transportation. The transportation container (1) is loaded onto a ship or the like and transported. Usage of the transportation container (1) is not limited to marine transportation. The transportation container (1) may be used for land transportation. In this case, the transportation container (1) is transported by an automobile such as a truck or by rail.-Container Body-

[0039] As shown in FIG. 2, the container body (2) is formed in a hollow box shape. The container body (2) is horizontally long. The container body (2) has an opening at one end in the longitudinal direction. The opening of the container body (2) is blocked by the refrigeration apparatus (10). The container body (2) forms an internal space (5) for housing cargos. The internal space (5) is a target space to be air-conditioned by the refrigeration apparatus.-Refrigeration Apparatus-

[0040] As shown in FIG. 2, the refrigeration apparatus (10) is attached to the opening of the container body (2). The refrigeration apparatus (10) of this embodiment is a refrigeration apparatus for transportation. The refrigeration apparatus (10) includes a casing (11), a refrigerant circuit (30), and a controller (80). The refrigeration apparatus (10) adjusts the temperature of the air (the inside air) in the internal space (5).<Casing>

[0041] The casing (11) includes a division wall (12) and a partition plate (15).

[0042] An internal flow path (20) is formed inside the division wall (12). An external chamber (23) is formed outside the division wall (12). The internal flow path (20) and the external chamber (23) are partitioned by the division wall (12).

[0043] The division wall (12) includes an external wall (13) and an internal wall (14). The external wall (13) is located outside the container body (2). The internal wall (14) is located inside the container body (2).

[0044] The external wall (13) closes the opening of the container body (2). The external wall (13) is attached to a peripheral portion of the opening of the container body (2). A lower part of the external wall (13) bulges toward the inside of the container body (2). The external chamber (23) is formed by the lower portion of the external wall (13).

[0045] The internal wall (14) faces the external wall (13). The internal wall (14) has a shape conforming to the external wall (13). The internal wall (14) is spaced apart from the external wall (13). A thermal insulator (16) is provided between the internal wall (14) and the external wall (13).

[0046] The partition plate (15) is disposed further inward of the container body (2) than the internal wall (14). The internal flow path (20) is formed between the division wall (12) and the partition plate (15). An air inlet port (21) is formed between the upper end of the partition plate (15) and a top panel of the container body (2). An air outlet port (22) is formed between the lower end of the partition plate (15) and the lower end of the division wall (12). The internal flow path (20) is formed from the air inlet port (21) to the air outlet port (22).<Refrigerant Circuit>

[0047] The refrigerant circuit (30) is a closed circuit filled with a refrigerant. The refrigerant circuit (30) circulates a refrigerant to perform a vapor compression refrigeration cycle. The refrigerant circuit (30) includes an outer heat exchanger (56), an inner heat exchanger (57), and a reheating heat exchanger (58). The refrigerant circuit (30) will be described in detail later.

[0048] Each of the outer heat exchanger (56), the inner heat exchanger (57), and the reheating heat exchanger (58) is a fin-and-tube heat exchanger that exchanges heat between the refrigerant and air.

[0049] The outer heat exchanger (56) is disposed in an upper portion in the external chamber (23). The outer heat exchanger (56) is a heat-source-side heat exchanger that exchanges heat between a refrigerant and outside air. The outer heat exchanger (56) has a substantially rectangular tubular shape.

[0050] The inner heat exchanger (57) is disposed in the internal flow path (20). The inner heat exchanger (57) is a utilization-side heat exchanger that exchanges heat between the refrigerant and the inside air.

[0051] The reheating heat exchanger (58) is disposed downstream of the inner heat exchanger (57) in the internal flow path (20). The reheating heat exchanger (58) is a heat exchanger that exchanges heat between a refrigerant and inside air.

[0052] Although not shown, a drain pan is provided below the inner heat exchanger (57). The drain pan receives drain water generated in the inner heat exchanger (57). The drain water having dropped into the drain pan is discharged to the outside of the container.<External Fan>

[0053] The refrigeration apparatus (10) includes an external fan (26). The external fan (26) is a propeller fan. The external fan (26) is disposed in the external chamber (23). The external fan (26) is disposed inside the outer heat exchanger (56) having a tubular shape. The external fan (26) sends the outside air to the outer heat exchanger (56).<Internal Fan>

[0054] The refrigeration apparatus (10) includes an internal fan (27). The internal fan (27) is a propeller fan. The internal fan (27) is disposed in the internal flow path (20). The internal fan (27) is disposed above the inner heat exchanger (57). The internal fan (27) sends the inside air to the inner heat exchanger (57).<Sensor>

[0055] The refrigeration apparatus (10) includes a first air temperature sensor (86), a second air temperature sensor (87), and a humidity sensor (88).

[0056] The first air temperature sensor (86) is disposed upstream of the internal fan (27) in the internal flow path (20). The first air temperature sensor (86) measures the temperature of the air having flowed into the internal flow path (20) through the air inlet port (21).

[0057] The second air temperature sensor (87) and the humidity sensor (88) are disposed downstream of the reheating heat exchanger (58) in the internal flow path (20). The second air temperature sensor (87) measures the temperature of the air having passed through the reheating heat exchanger (58). The humidity sensor (88) measures the relative humidity of the air having passed through the reheating heat exchanger (58).<Electric Component Box>

[0058] As shown in FIG. 1, the refrigeration apparatus (10) includes an electric component box (28). The electric component box (28) is disposed in an upper portion in the external chamber (23). The electric component box (28) houses electric components such as an inverter board and a control board.-Refrigerant Circuit-

[0059] As shown in FIG. 3, the refrigerant circuit (30) is a closed circuit filled with a refrigerant. The refrigerant in the refrigerant circuit (30) of this embodiment is carbon dioxide.

[0060] The refrigerant circuit (30) includes a main circuit (31), a defrosting pipe (32), and a reheating pipe (33). The refrigerant circuit (30) further includes a gas-side connection pipe (41), a liquid-side connection pipe (42), an intermediate connection pipe (43), a low-stage connection pipe (44), and a high-stage connection pipe (45).<Main Circuit>

[0061] The main circuit (31) includes a low-stage compressor (51), a high-stage compressor (52), the outer heat exchanger (56), a receiver (62), and the inner heat exchanger (57). In the main circuit (31), the low-stage compressor (51), the high-stage compressor (52), the outer heat exchanger (56), the receiver (62), and the inner heat exchanger (57) are connected in this order through pipes.

[0062] A discharge pipe of the low-stage compressor (51) is connected to a suction pipe of the high-stage compressor (52). A pipe that connects the discharge pipe of the low-stage compressor (51) and the suction pipe of the high-stage compressor (52) is provided with a first check valve (CV1) and a first electric valve (MV1). The first electric valve (MV1) is disposed downstream of the first check valve (CV1). The first check valve (CV1) allows the refrigerant to flow in a direction in which the refrigerant flows out of the low-stage compressor (51), and prevents the refrigerant from flowing in the opposite direction.

[0063] A discharge pipe of the high-stage compressor (52) is connected to one end of the outer heat exchanger (56). A pipe that connects the discharge pipe of the high-stage compressor (52) and one end of the outer heat exchanger (56) is provided with a second check valve (CV2) and a second electric valve (MV2). The second electric valve (MV2) is disposed downstream of the second check valve (CV2). The second check valve (CV2) allows the refrigerant to flow in a direction in which the refrigerant flows out of the high-stage compressor (52), and prevents the refrigerant from flowing in the opposite direction.

[0064] The other end of the outer heat exchanger (56) is connected to an inflow port of the receiver (62). A pipe that connects the other end of the outer heat exchanger (56) and the inflow port of the receiver (62) is provided with a first flow path (61a) of an internal heat exchanger (61) and a first expansion valve (EV1). The first expansion valve (EV1) is disposed downstream of the internal heat exchanger (61).

[0065] A liquid outflow port of the receiver (62) is connected to one end of the inner heat exchanger (57). A pipe that connects the liquid outflow port of the receiver (62) and one end of the inner heat exchanger (57) is provided with a first electromagnetic valve (SV1) and a second expansion valve (EV2). The second expansion valve (EV2) is disposed downstream of the first electromagnetic valve (SV1).

[0066] The other end of the inner heat exchanger (57) is connected to a suction pipe of the low-stage compressor (51).

[0067] In the main circuit (31), the first expansion valve (EV1) is disposed upstream of the receiver (62), and the second expansion valve (EV2) is disposed downstream of the receiver (62). The first expansion valve (EV1) and the second expansion valve (EV2) are expansion valves (65) of the refrigerant circuit (30).<Gas-Side Connection Pipe>

[0068] One end of the gas-side connection pipe (41) is connected to a gas outflow port of the receiver (62). The other end of the gas-side connection pipe (41) is connected to one end of the intermediate connection pipe (43). The gas-side connection pipe (41) is provided with a second electromagnetic valve (SV2) and a second flow path (61b) of the internal heat exchanger (61). The second flow path (61b) of the internal heat exchanger (61) is disposed downstream of the second electromagnetic valve (SV2).<Liquid-Side Connection Pipe>

[0069] One end of the liquid-side connection pipe (42) is connected to a portion of the main circuit (31) between the first electromagnetic valve (SV1) and the second expansion valve (EV2). The other end of the liquid-side connection pipe (42) is connected to one end of the intermediate connection pipe (43). The liquid-side connection pipe (42) is provided with a third expansion valve (EV3).<Intermediate Connection Pipe>

[0070] As described above, one end of the intermediate connection pipe (43) is connected with the other end of the gas-side connection pipe (41) and the other end of the liquid-side connection pipe (42). The other end of the intermediate connection pipe (43) is connected to part of the main circuit (31) that is between the first electric valve (MV1) and the high-stage compressor (52). The intermediate connection pipe (43) is provided with a third check valve (CV3). The third check valve (CV3) allows a refrigerant to flow from one end to the other end of the intermediate connection pipe (43), and prevents a refrigerant from flowing in the opposite direction.<Low-Stage Connection Pipe>

[0071] The low-stage connection pipe (44) is a pipe that allows a refrigerant to flow while bypassing the low-stage compressor (51). One end of the low-stage connection pipe (44) is connected to part of the main circuit (31) that is between the suction pipe of the low-stage compressor (51) and the inner heat exchanger (57). The other end of the low-stage connection pipe (44) is connected to part of the main circuit (31) that is between the first check valve (CV1) and the first electric valve (MV1). The low-stage connection pipe (44) is provided with a fourth check valve (CV4). The fourth check valve (CV4) allows a refrigerant to flow from one end to the other end of the low-stage connection pipe (44), and prevents a refrigerant from flowing in the opposite direction.<High-Stage Connection Pipe>

[0072] The high-stage connection pipe (45) is a pipe that allows a refrigerant to flow while bypassing the high-stage compressor (52). One end of the high-stage connection pipe (45) is connected to part of the main circuit (31) that is between the first check valve (CV1) and the first electric valve (MV1). The other end of the high-stage connection pipe (45) is connected to part of the main circuit (31) that is between the second check valve (CV2) and the second electric valve (MV2). The high-stage connection pipe (45) is provided with a fifth check valve (CV5). The fifth check valve (CV5) allows a refrigerant to flow from one end to the other end of the high-stage connection pipe (45), and prevents a refrigerant from flowing in the opposite direction.<Defrosting Pipe>

[0073] One end of the defrosting pipe (32) is connected to part of the main circuit (31) that is between the second check valve (CV2) and the second electric valve (MV2). In the main circuit (31), one end of the defrosting pipe (32) is located downstream of the other end of the high-stage connection pipe (45). The other end of the defrosting pipe (32) is connected to part of the main circuit (31) that is between the second expansion valve (EV2) and the inner heat exchanger (57).

[0074] The defrosting pipe (32) is provided with a fourth expansion valve (EV4). The fourth expansion valve (EV4) is a decompression valve of which the opening degree is variable and which decompresses the refrigerant flowing in the defrosting pipe (32).<Reheating Pipe>

[0075] One end of the reheating pipe (33) is connected to part of the main circuit (31) that is between the second check valve (CV2) and the second electric valve (MV2). In the main circuit (31), one end of the reheating pipe (33) is located downstream of the other end of the high-stage connection pipe (45). The other end of the reheating pipe (33) is connected to part of the main circuit (31) that is between the second expansion valve (EV2) and the inner heat exchanger (57). The reheating pipe (33) forms a reheating passage. The reheating pipe (33) sends the refrigerant discharged by the compressor (50) to the inner heat exchanger (57) while bypassing the outer heat exchanger (56) and the expansion valve (65).

[0076] The reheating pipe (33) is provided with a third electromagnetic valve (SV3), the reheating heat exchanger (58), and a fifth expansion valve (EV5). The reheating heat exchanger (58) is disposed downstream of the third electromagnetic valve (SV3). The fifth expansion valve (EV5) is disposed downstream of the reheating heat exchanger (58).<Expansion Valve>

[0077] Each of the first expansion valve (EV1), the second expansion valve (EV2), the third expansion valve (EV3), the fourth expansion valve (EV4), and the fifth expansion valve (EV5) is a so-called electronic expansion valve. Each of the expansion valves (EV1 to EV5) includes a valve body and a stepping motor that drives the valve body. When the valve body is moved by the stepping motor, the opening degree of the expansion valve (EV1 to EV5) changes continuously.<Electric Valve>

[0078] Each of the first electric valve (MV1) and the second electric valve (MV2) is a valve of which the opening degree is variable. Each of the electric valves (MV1, MV2) includes a valve body and a stepping motor that drives the valve body. When the valve body is moved by the stepping motor, the opening degree of the electric valve (MV1, MV2) changes continuously.<Electromagnetic Valve>

[0079] Each of the first electromagnetic valve (SV1), the second electromagnetic valve (SV2), and the third electromagnetic valve (SV3) is an on-off valve. Each of the electromagnetic valves (SV1 to SV3) includes a valve body and a solenoid that drives the valve body. When the valve body is moved by the solenoid, the electromagnetic valve (SV1 to SV3) is turned on or off.<Low-Stage Compressor and High-Stage Compressor>

[0080] Each of the low-stage compressor (51) and the high-stage compressor (52) is a hermetic scroll compressor. Although not shown, each of the low-stage compressor (51) and the high-stage compressor (52) includes a compression mechanism, an electric motor that drives the compression mechanism, and a casing that houses the compression mechanism and the electric motor. The compression mechanism is a scroll type fluid machine, and sucks and compresses a refrigerant.

[0081] The suction pipe of the low-stage compressor (51) is provided with an accumulator (51a). The suction pipe of the high-stage compressor (52) is provided with an accumulator (52a). Each of the low-stage compressor (51) and the high-stage compressor (52) compresses the refrigerant sucked from the suction pipe, and discharges the compressed refrigerant from the discharge pipe. The low-stage compressor (51) and the high-stage compressor (52) are the compressors (50) provided in the refrigerant circuit (30).

[0082] Each of the low-stage compressor (51) and the high-stage compressor (52) is not limited to a scroll compressor. Each of the low-stage compressor (51) and the high-stage compressor (52) may be, for example, a rotary compressor or may be a reciprocating compressor.<Outer Heat Exchanger and Inner Heat Exchanger>

[0083] As described above, each of the outer heat exchanger (56), the inner heat exchanger (57), and the reheating heat exchanger (58) is a fin-and-tube heat exchanger that exchanges heat between a refrigerant and air. The outer heat exchanger (56) exchanges heat between a refrigerant and outside air (external air). Each of the inner heat exchanger (57) and the reheating heat exchanger (58) exchanges heat between a refrigerant and inside air.<Internal Heat Exchanger>

[0084] The internal heat exchanger (61) is a heat exchanger that exchanges heat between a refrigerant and a refrigerant. The internal heat exchanger (61) of this embodiment is a plate-type heat exchanger. The internal heat exchanger (61) has the first flow path (61a) and the second flow path (61b). The first flow path (61a) of the internal heat exchanger (61) is disposed in part of the main circuit (31) that is between the outer heat exchanger (56) and the first expansion valve (EV1). The second flow path (61b) of the internal heat exchanger (61) is disposed downstream of the second electromagnetic valve (SV2) in the gas-side connection pipe (41). The internal heat exchanger (61) exchanges heat between the refrigerant flowing in the first flow path (61a) and the refrigerant flowing in the second flow path (61b).<Receiver>

[0085] The receiver (62) is a container member that stores a refrigerant. The receiver (62) also functions as a gas-liquid separator. The receiver (62) separates the refrigerant in a gas-liquid two-phase state having flowed from the inflow port into a liquid refrigerant and a gas refrigerant. In the receiver (62), the liquid refrigerant is accumulated in a lower part in the receiver (62), and then flows out through the liquid outflow port formed in a bottom part of the receiver (62). In the receiver (62), the gas refrigerant is accumulated in an upper part in the receiver (62), and then flows out through the gas outflow port formed in an upper part of the receiver (62).<Sensors for Low-Stage Compressor>

[0086] In the main circuit (31), a pipe connected to the suction pipe of the low-stage compressor (51) is provided with a low-stage suction temperature sensor (70) and a low-stage suction pressure sensor (75). The low-stage suction temperature sensor (70) measures the temperature of the refrigerant sucked by the low-stage compressor (51). The low-stage suction pressure sensor (75) measures the pressure of the refrigerant sucked by the low-stage compressor (51).

[0087] In the main circuit (31), a pipe between the discharge pipe of the low-stage compressor (51) and the first check valve (CV1) is provided with a low-stage discharge temperature sensor (71) and a low-stage discharge pressure sensor (76). The low-stage discharge temperature sensor (71) measures the temperature of the refrigerant discharged by the low-stage compressor (51). The low-stage discharge pressure sensor (76) measures the pressure of the refrigerant discharged by the low-stage compressor (51).<Sensors for High-Stage Compressor>

[0088] In the main circuit (31), a pipe between the suction pipe of the high-stage compressor (52) and the first electric valve (MV1) is provided with a high-stage suction temperature sensor (72) and a high-stage suction pressure sensor (77). The high-stage suction temperature sensor (72) measures the temperature of the refrigerant sucked by the high-stage compressor (52). The high-stage suction pressure sensor (77) measures the pressure of the refrigerant sucked by the high-stage compressor (52).

[0089] In the main circuit (31), a pipe between the discharge pipe of the high-stage compressor (52) and the second check valve (CV2) is provided with a high-stage discharge temperature sensor (73) and a high-stage discharge pressure sensor (78). The high-stage discharge temperature sensor (73) measures the temperature of the refrigerant discharged by the high-stage compressor (52). The high-stage discharge pressure sensor (78) measures the pressure of the refrigerant discharged by the high-stage compressor (52).<Other Sensors>

[0090] The refrigerant circuit (30) is provided with a receiver pressure sensor (79), first to fourth refrigerant temperature sensors (81 to 84), and a heat exchanger temperature sensor (85).

[0091] The receiver pressure sensor (79) is connected to part of the gas-side connection pipe (41) that is between the receiver (62) and the second electromagnetic valve (SV2). The receiver pressure sensor (79) measures the pressure of the refrigerant stored in the receiver (62).

[0092] The first refrigerant temperature sensor (81) is provided in a pipe of the main circuit (31) that is between the outer heat exchanger (56) and the internal heat exchanger (61). The first refrigerant temperature sensor (81) measures the temperature of the refrigerant flowing into the first flow path (61a) of the internal heat exchanger (61).

[0093] The second refrigerant temperature sensor (82) is provided in a pipe of the main circuit (31) that is between the receiver (62) and the first electromagnetic valve (SV1). The second refrigerant temperature sensor (82) measures the temperature of the refrigerant having flowed out from the liquid outflow port of the receiver (62).

[0094] The third refrigerant temperature sensor (83) is provided in a pipe of the main circuit (31) that is between the second expansion valve (EV2) and the inner heat exchanger (57). The third refrigerant temperature sensor (83) is disposed near one end of the inner heat exchanger (57). The third refrigerant temperature sensor (83) measures the temperature of the refrigerant at the inlet of the inner heat exchanger (57).

[0095] The fourth refrigerant temperature sensor (84) is provided in a pipe of the main circuit (31) that is between the inner heat exchanger (57) and the low-stage compressor (51). The fourth refrigerant temperature sensor (84) is disposed near the other end of the inner heat exchanger (57). The fourth refrigerant temperature sensor (84) measures the temperature of the refrigerant at the outlet of the inner heat exchanger (57).

[0096] The heat exchanger temperature sensor (85) is attached to the inner heat exchanger (57). The heat exchanger temperature sensor (85) measures the temperature of the inner heat exchanger (57).-Controller-

[0097] As shown in FIG. 4, the controller (90) includes a microcomputer (91) and a memory device (92). The memory device (92) is a semiconductor memory. The memory device (92) stores software for operating the microcomputer (91). The controller (90) is housed in the electric component box (28).

[0098] The controller (90) receives measurement values of the sensors provided in the refrigeration apparatus (10). The controller (90) controls the devices provided in the refrigeration apparatus (10) based on the received measurement values of the sensors. For example, the controller (90) controls the rotational speed of the low-stage compressor (51), the rotational speed of the high-stage compressor (52), the opening degrees of the first to fifth expansion valves (EV1 to EV5), the opening degrees of the first and second electric valves (MV1, MV2), the rotational speed of the external fan (26), the rotational speed of the internal fan (27), and the like.-Operation of Refrigeration Apparatus-

[0099] The operation of the refrigeration apparatus (10) will be described. The refrigeration apparatus (10) performs a cooling operation, a dehumidifying operation, and a defrosting operation.<Cooling Operation>

[0100] The cooling operation is an operation to cool the inside air. In the cooling operation, the refrigeration apparatus (10) blows the air cooled in the inner heat exchanger (57) into the internal space (5).

[0101] When the refrigeration apparatus (10) performs the cooling operation, the refrigerant circuit (30) performs a refrigeration cycle. In the cooling operation, the refrigerant circulates in the main circuit (31) of the refrigerant circuit (30), the outer heat exchanger (56) functions as a radiator, and the inner heat exchanger (57) functions as an evaporator. The inner heat exchanger (57) cools the air flowing in the internal flow path (20). In the cooling operation, the refrigerant flows in the gas-side connection pipe (41) and the intermediate connection pipe (43).

[0102] When the refrigeration apparatus (10) performs the cooling operation, the controller (90) operates the external fan (26) and the internal fan (27). In the transportation container (1), the air circulates between the internal flow path (20) of the refrigeration apparatus (10) and the internal space (5) of the container body (2). The inside air of the internal space (5) flows into the internal flow path (20) through the air inlet port (21). The inside air flowing in the internal flow path (20) is cooled by the inner heat exchanger (57). The inside air cooled by the inner heat exchanger (57) is supplied to the internal space (5) through the air outlet port (22).

[0103] In the cooling operation, the controller (90) controls the rotational speed of the compressor (50) and the like so that the temperature of the air blown into the internal space (5) through the air outlet port (22) (specifically, the measurement value of the second air temperature sensor (87)) can reach a set temperature.

[0104] In the cooling operation, the refrigeration apparatus (10) selectively performs a two-stage compressing operation and a single-stage compressing operation. In the two-stage compressing operation, both the low-stage compressor (51) and the high-stage compressor (52) are operated, and a two-stage compression refrigeration cycle is created in the refrigerant circuit (30). In the single-stage compressing operation, the low-stage compressor (51) is stopped and the high-stage compressor (52) is operated, and a single-stage compression refrigeration cycle is created in the refrigerant circuit (30). In the cooling operation, the refrigeration apparatus (10) performs the two-stage compressing operation in an operating state in which the difference between the high pressure and the low pressure of the refrigeration cycle performed by the refrigerant circuit (30) is relatively large, and performs the single-stage compressing operation in an operating state in which the difference is relatively small.(Two-Stage Compressing Operation of Cooling Operation)

[0105] The two-stage compressing operation of the cooling operation will be described with reference to FIG. 5.

[0106] In the two-stage compressing operation of the cooling operation, the controller (90) controls the rotational speeds of the low-stage compressor (51) and the high-stage compressor (52). Further, the controller (90) controls the opening degrees of the first expansion valve (EV1) and the second expansion valve (EV2), and holds the third expansion valve (EV3), the fourth expansion valve (EV4), and the fifth expansion valve (EV5) in a fully-closed state. Further, the controller (90) holds the first electric valve (MV1) and the second electric valve (MV2) in a fully-open state, holds the first electromagnetic valve (SV1) and the second electromagnetic valve (SV2) in an open state, and holds third electromagnetic valve (SV3) in a closed state.

[0107] The high-stage compressor (52) compresses the sucked refrigerant to a pressure higher than the critical pressure of the refrigerant and discharges the compressed refrigerant. The refrigerant having discharged from the high-stage compressor (52) exchanges heat with the external air in the outer heat exchanger (56), and dissipates heat to the external air. The refrigerant having passed through the outer heat exchanger (56) flows into the first flow path (61a) of the internal heat exchanger (61), and is cooled by exchanging heat with the refrigerant flowing in the second flow path (61b) of the internal heat exchanger (61). The refrigerant having passed through the first flow path (61a) of the internal heat exchanger (61) is decompressed when passing through the first expansion valve (EV1) and is brought into a gas-liquid two-phase state. Then, the refrigerant flows into the receiver (62), and is separated into a liquid refrigerant and a gas refrigerant.

[0108] The liquid refrigerant having flowed out from the receiver (62) is decompressed when passing through the second expansion valve (EV2), and then flows into the inner heat exchanger (57). The refrigerant having flowed into the inner heat exchanger (57) absorbs heat from the air passing through the inner heat exchanger (57) and then is evaporated. The refrigerant having flowed out from the inner heat exchanger (57) is sucked into the low-stage compressor (51). The low-stage compressor (51) compresses and discharges the sucked refrigerant. The refrigerant having discharged from the low-stage compressor (51) is sucked into the high-stage compressor (52).

[0109] The gas refrigerant having flowed out from the receiver (62) flows in the gas-side connection pipe (41), then flows into the second flow path (61b) of the internal heat exchanger (61), and then absorbs heat from the refrigerant flowing in the first flow path (61a) of the internal heat exchanger (61). The refrigerant having flowed out from the second flow path (61b) of the internal heat exchanger (61) passes through the intermediate connection pipe (43), and is sucked into the high-stage compressor (52) together with the refrigerant having discharged from the low-stage compressor (51).(Single-Stage Compressing Operation of Cooling Operation)

[0110] The single-stage compressing operation of the cooling operation will be described.

[0111] In the single-stage compressing operation of the cooling operation, the controller (90) holds the low-stage compressor (51) in a stop state. The difference between the single-stage compressing operation and the two-stage compressing operation of the cooling operation is that the low-stage compressor (51) is held in a stop state.

[0112] In the refrigerant circuit (30), the refrigerant having flowed out from the inner heat exchanger (57) is sucked into the high-stage compressor (52) through the low-stage connection pipe (44). In the single-stage compressing operation, the refrigerant flowing in the refrigerant circuit (30) flows while bypassing the low-stage compressor (51), and is compressed only by the high-stage compressor (52). Except that the refrigerant having flowed out from the inner heat exchanger (57) flows in the low-stage connection pipe (44), the flow path of the refrigerant in the refrigerant circuit (30) during the single-stage compressing operation is the same as the flow path of the refrigerant in the refrigerant circuit (30) during the two-stage compressing operation.<Dehumidifying Operation>

[0113] The dehumidifying operation is an operation to dehumidify the inside air while maintaining the temperature of the air in the internal space (5). In the dehumidifying operation, the refrigeration apparatus (10) blows the air dehumidified in the inner heat exchanger (57) and then heated in the reheating heat exchanger (58) into the internal space (5).

[0114] The refrigeration apparatus (10) performs the defrosting operation in a situation in which the temperature of the air in the internal space (5) is stable. Specifically, in the refrigeration apparatus (10), the controller (90) determines whether a temperature stabilization condition is satisfied. The temperature stabilization condition is a condition indicating that the temperature of the air in the internal space (5) is stable. An example of the temperature stabilization condition is the condition that "the state in which the measurement value of the second air temperature sensor (87) falls within ±0.5°C of the set temperature continues for five minutes". If the controller (90) determines that the temperature stabilization condition is satisfied, the controller (90) instructs the refrigeration apparatus (10) to perform the dehumidifying operation.

[0115] In the dehumidifying operation of the refrigeration apparatus (10), similarly to the cooling operation, the controller (90) operates the external fan (26) and the internal fan (27). In the transportation container (1), the air circulates between the internal flow path (20) of the refrigeration apparatus (10) and the internal space (5) of the container body (2). The inside air of the internal space (5) flows into the internal flow path (20) through the air inlet port (21). The inside air flowing in the internal flow path (20) passes through the inner heat exchanger (57) and the reheating heat exchanger (58) in sequence, and then is supplied to the internal space (5) through the air outlet port (22).

[0116] In the dehumidifying operation as well as the cooling operation, the refrigeration apparatus (10) selectively performs the two-stage compressing operation and the single-stage compressing operation. In the two-stage compressing operation, both the low-stage compressor (51) and the high-stage compressor (52) are operated, and a two-stage compression refrigeration cycle is created in the refrigerant circuit (30). In the single-stage compressing operation, the low-stage compressor (51) is stopped and the high-stage compressor (52) is operated, and a single-stage compression refrigeration cycle is created in the refrigerant circuit (30). In the dehumidifying operation, the refrigeration apparatus (10) performs the two-stage compressing operation in an operating state in which the difference between the high pressure and the low pressure of the refrigeration cycle performed by the refrigerant circuit (30) is relatively large, and performs the single-stage compressing operation in an operating state in which the difference is relatively small.(Two-Stage Compressing Operation of Dehumidifying Operation)

[0117] The two-stage compressing operation of the dehumidifying operation will be described with reference to FIG. 6.

[0118] In the two-stage compressing operation of the dehumidifying operation, the controller (90) controls the rotational speeds of the low-stage compressor (51) and the high-stage compressor (52). Further, the controller (90) controls the opening degrees of the first expansion valve (EV1), the second expansion valve (EV2), and the fifth expansion valve (EV5), and holds the third expansion valve (EV3) and the fourth expansion valve (EV4) in a fully-closed state. Further, the controller (90) holds the first electric valve (MV1) and the second electric valve (MV2) in a fully-open state, and holds the first electromagnetic valve (SV1), the second electromagnetic valve (SV2), and the third electromagnetic valve (SV3) in an open state.

[0119] The two-stage compressing operation of dehumidifying operation is different from the cooling operation in that the controller (90) controls the opening degree of the fifth expansion valve (EV5) and holds the third electromagnetic valve (SV3) in an open state. Further, the two-stage compressing operation of the dehumidifying operation is different from the cooling operation in that the refrigerant flows in the reheating pipe (33) as well as the main circuit (31), the gas-side connection pipe (41), and the intermediate connection pipe (43).

[0120] In the two-stage compressing operation of the dehumidifying operation of the refrigeration apparatus (10), the refrigerant circuit (30) performs a refrigeration cycle. In the two-stage compressing operation of the dehumidifying operation, similarly to the cooling operation, the refrigerant circulates in the main circuit (31) of the refrigerant circuit (30), the outer heat exchanger (56) functions as a radiator, and the inner heat exchanger (57) functions as an evaporator. The inner heat exchanger (57) cools the air flowing in the internal flow path (20).

[0121] In the dehumidifying operation, the evaporation temperature of the refrigerant in the inner heat exchanger (57) is set to a value lower than the dew point temperature of the air flowing into the inner heat exchanger (57). Thus, in the inner heat exchanger (57), the moisture contained in the air is condensed into drain water. The drain water generated in the inner heat exchanger (57) flows down into the drain pan, and then is discharged to the outside of the container. Thus, each of the temperature and absolute humidity of the air flowing in the internal flow path (20) is reduced when the air passes through the inner heat exchanger (57).

[0122] In the dehumidifying operation, similarly to the cooling operation, the refrigerant flows in the gas-side connection pipe (41) and the intermediate connection pipe (43). The gas refrigerant having flowed out from the receiver (62) passes through the gas-side connection pipe (41) and the intermediate connection pipe (43) in sequence, and then is sucked into the high-stage compressor (52) together with the refrigerant having discharged from the low-stage compressor (51).

[0123] In the dehumidifying operation, part of the refrigerant having discharged from the high-stage compressor (52) is supplied to the reheating heat exchanger (58) through the reheating pipe (33). In the reheating heat exchanger (58), the air having passed through the inner heat exchanger (57) is heated by the refrigerant. The refrigerant having dissipated heat in the reheating heat exchanger (58) is decompressed when passing through the fifth expansion valve (EV5). The refrigerant having passed through the fifth expansion valve (EV5) flows into the main circuit (31), and then flows into the inner heat exchanger (57) together with the refrigerant having passed through the second expansion valve (EV2).(Single-Stage Compressing Operation of Dehumidifying Operation)

[0124] The single-stage compressing operation of the dehumidifying operation will be described with reference to FIG. 7.

[0125] In the single-stage compressing operation of the dehumidifying operation, the controller (90) holds the low-stage compressor (51) in a stop state. The difference between the single-stage compressing operation and the two-stage compressing operation of the dehumidifying operation is that the low-stage compressor (51) is held in a stop state.

[0126] In the refrigerant circuit (30), the refrigerant having flowed out from the inner heat exchanger (57) is sucked into the high-stage compressor (52) through the low-stage connection pipe (44). In the single-stage compressing operation, the refrigerant flowing in the refrigerant circuit (30) flows while bypassing the low-stage compressor (51), and is compressed only by the high-stage compressor (52). Except that the refrigerant having flowed out from the inner heat exchanger (57) flows in the low-stage connection pipe (44), the flow path of the refrigerant in the refrigerant circuit (30) during the single-stage compressing operation is the same as the flow path of the refrigerant in the refrigerant circuit (30) during the two-stage compressing operation.<Defrosting Operation>

[0127] The defrosting operation is an operation to melt the frost on the inner heat exchanger (57) in the cooling operation.

[0128] In the cooling operation, the evaporation temperature of the refrigerant in the inner heat exchanger (57) may be lower than 0°C. In this case, the moisture in the air is frozen into frost, and the frost adheres to the inner heat exchanger (57). When the frost adheres to the inner heat exchanger (57), the frost blocks the flow of the air passing through the inner heat exchanger (57), and blocks heat exchange between the refrigerant and the air.

[0129] Thus, if the defrosting start condition is satisfied during the cooling operation, the refrigeration apparatus (10) temporarily stops the cooling operation and performs the defrosting operation. For example, the defrosting start condition is the condition that "the cumulative value of the execution time of the cooling operation in which the evaporation temperature of the refrigerant in the internal heat exchanger is lower than 0°C has reached a predetermined time (for example, 2 hours)".

[0130] If the defrosting end condition is satisfied during the defrosting operation, the refrigeration apparatus (10) ends the defrosting operation, and restarts the cooling operation. For example, the defrosting end condition is the condition that "the temperature of the inner heat exchanger (57) (specifically, the measurement value of the heat exchanger temperature sensor (85)) has reached a predetermined temperature (for example, 10°C)".

[0131] The defrosting operation will be described with reference to FIG. 8.

[0132] In the defrosting operation, the controller (90) holds the external fan (26) and the internal fan (27) in a stop state. Further, the controller (90) holds the low-stage compressor (51) in a stop state, and controls the rotational speed of the high-stage compressor (52). Further, the controller (90) holds the first expansion valve (EV1) in an open state, holds the second expansion valve (EV2), the third expansion valve (EV3), and the fifth expansion valve (EV5) in a closed state, and controls the opening degree of the fourth expansion valve (EV4). Further, the controller (90) holds the first electric valve (MV1) in a fully-open state, holds the second electric valve (MV2) in a fully-closed state, and holds the first electromagnetic valve (SV1), the second electromagnetic valve (SV2), and the third electromagnetic valve (SV3) in a closed state.

[0133] In the refrigerant circuit (30) that is performing the defrosting operation, the refrigerant circulates between the high-stage compressor (52) and the inner heat exchanger (57) without passing through the outer heat exchanger (56). The refrigerant having discharged from the high-stage compressor (52) flows in the defrosting pipe (32), and then is decompressed when passing through the fourth expansion valve (EV4). The refrigerant having passed through the fourth expansion valve (EV4) flows into the inner heat exchanger (57). In the inner heat exchanger (57), the refrigerant heats and melts the frost. The refrigerant having flowed out from the inner heat exchanger (57) is sucked into the high-stage compressor (52) through the low-stage connection pipe (44). The high-stage compressor (52) compresses and discharges the sucked refrigerant.-Operation of Controller in Dehumidifying Operation-

[0134] Operation performed by the controller (90) in the dehumidifying operation will be described.

[0135] As shown in FIG. 9, in the dehumidifying operation, the controller (90) repeats a humidity control operation, a temperature control operation, and a high-pressure control operation in sequence. Further, the controller (90) switches between the humidity control operation, the temperature control operation, and the high-pressure control operation at regular time intervals (for example, every five seconds). The sequence of execution of the humidity control operation, the temperature control operation, and the high-pressure control operation is not limited to the sequence shown in FIG. 9. The order shown in FIG. 9 is merely an example.<Humidity Control Operation>

[0136] The humidity control operation will be described with reference to FIG. 10. In the humidity control operation, the controller (90) controls the evaporation temperature of the refrigerant in the inner heat exchanger (57) so that the humidity of the air blown from the air outlet port (22) by the refrigeration apparatus (10) during the dehumidifying operation can reach a set humidity. In order to control the evaporation temperature of the refrigerant in the inner heat exchanger (57), the controller (90) sets a target evaporation temperature, and uses the set target evaporation temperature to control the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2).(Setting of Target Evaporation Temperature)

[0137] The controller (90) sets the target evaporation temperature based on the measurement value of the humidity sensor (88) and the set value (the set humidity) of the humidity of the inside air in the internal space (5). The target evaporation temperature is a target value of the evaporation temperature of the refrigerant in the inner heat exchanger (57).

[0138] The controller (90) conducts the processes of step ST11 to step ST15 in FIG. 10 as the operation to set the target evaporation temperature. The controller (90) compares a measurement value RH of the humidity sensor (88) with a set humidity range including the set humidity (for example, a range within ±5% of the set humidity), and sets the target evaporation temperature based on the comparison result.

[0139] In the process of step ST11, the controller (90) compares the measurement value RH of the humidity sensor (88) with the maximum value of the set humidity range. If the condition that "the measurement value RH of the humidity sensor (88) is higher than the maximum value of the set humidity range" is satisfied, the controller (90) conducts the process of step ST12. In the process of step ST12, the controller (90) decreases the target evaporation temperature. On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST13.

[0140] In the process of step ST13, the controller (90) compares the measurement value RH of the humidity sensor (88) with the minimum value of the set humidity range. If the condition that "the measurement value RH of the humidity sensor (88) is lower than the minimum value of the set humidity range" is satisfied, the process of step ST14 is conducted. In the process of step ST14, the controller (90) decreases the target evaporation temperature. On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST15.

[0141] If the condition in the process of step ST13 is not satisfied, the measurement value RH of the humidity sensor (88) falls within the set humidity range. Thus, in the process of step ST15, the controller (90) does not change but maintains the target evaporation temperature. After ending the process of step ST12, step ST14, or step ST15, the controller (90) conducts the process of step ST16.(Control of Compressor and Second Expansion Valve)

[0142] The controller (90) controls the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2) so that a measurement value Tr3 of the third refrigerant temperature sensor (83) can fall within a target evaporation temperature range including the target evaporation temperature (for example, a range within ±0.5°C of the target evaporation temperature).

[0143] The third refrigerant temperature sensor (83) measures the temperature of the refrigerant flowing into the inner heat exchanger (57) through the second expansion valve (EV2). The refrigerant having passed through the second expansion valve (EV2) is in a gas-liquid two-phase state. Thus, the temperature of the refrigerant flowing into the inner heat exchanger (57) is substantially equal to the evaporation temperature of the refrigerant in the inner heat exchanger (57). Thus, the temperature of the refrigerant flowing into the inner heat exchanger (57) is a physical quantity that correlates with the evaporation temperature of the refrigerant in the inner heat exchanger (57).(Selection of Control Target)

[0144] The controller (90) selectively controls the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2).

[0145] The process of step ST16 in FIG. 10 is the process for selecting a control target. In the process of step ST16, the controller (90) determines whether a selection condition is satisfied.

[0146] The selection condition is the condition that "the first condition is satisfied and at least one of the second condition or the third condition is satisfied". The first condition is the condition that "the target degree of superheat is the lower limit degree of superheat". The lower limit degree of superheat is the minimum value of the numerical range which can be set as the target degree of superheat. The second condition is the condition that "the rotational speed of the compressor (50) is lower than a reference speed". The third condition is the condition that "the measurement value Tr3 of the third refrigerant temperature sensor (83) is lower than the minimum value of the target evaporation temperature range".

[0147] If the selection condition is satisfied in the process of step ST16, the controller (90) conducts the process of step ST17 to start controlling the rotational speed of the compressor (50). On the other hand, if the selection condition is not satisfied, the controller (90) conducts the process of step ST22 to start controlling the opening degree of the second expansion valve (EV2).(Control of Rotational Speed of Compressor)

[0148] The control of the rotational speed of the compressor (50) by the controller (90) will be described.

[0149] Based on the measurement value of the third refrigerant temperature sensor (83), the controller (90) controls the rotational speed of the compressor (50) which sucks the refrigerant having flowed out from the inner heat exchanger (57) during the dehumidifying operation. In the two-stage compressing operation of the dehumidifying operation, the controller (90) controls the rotational speed of the low-stage compressor (51) based on the measurement value of the third refrigerant temperature sensor (83). In the single-stage compressing operation of the dehumidifying operation, the controller (90) controls the rotational speed of the high-stage compressor (52) based on the measurement value of the third refrigerant temperature sensor (83).

[0150] The controller (90) conducts the processes of step ST17 to step ST21 in FIG. 10 as the operation to control the rotational speed of the compressor (50). The controller (90) compares the measurement value Tr3 of the third refrigerant temperature sensor (83) with the target evaporation temperature range, and controls the rotational speed of the compressor (50) based on the comparison result.

[0151] In the process of step ST17, the controller (90) compares the measurement value Tr3 of the third refrigerant temperature sensor (83) with the maximum value of the target evaporation temperature range. If the condition that "the measurement value Tr3 of the third refrigerant temperature sensor (83) is higher than the maximum value of the target evaporation temperature range" is satisfied, the controller (90) conducts the process of step ST18. In the process of step ST18, the controller (90) increases the rotational speed of the compressor (50). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST19.

[0152] In the process of step ST19, the controller (90) compares the measurement value Tr3 of the third refrigerant temperature sensor (83) with the minimum value of the target evaporation temperature range. If the condition that "the measurement value Tr3 of the third refrigerant temperature sensor (83) is lower than the minimum value of the target evaporation temperature range" is satisfied, the controller (90) conducts the process of step ST20. In the process of step ST20, the controller (90) decreases the rotational speed of the compressor (50). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST21.

[0153] If the condition in the process of step ST19 is not satisfied, the measurement value Tr3 of the third refrigerant temperature sensor (83) falls within the target evaporation temperature range. Thus, in the process of step ST21, the controller (90) does not change but maintains the rotational speed of the compressor (50). After ending the process of step ST18, step ST20, or step ST21, the controller (90) ends the humidity control operation.

[0154] In the two-stage compressing operation of the dehumidifying operation, the controller (90) controls the rotational speed of the high-stage compressor (52) based on the measurement value of the high-stage suction pressure sensor (77). The controller (90) controls the rotational speed of the high-stage compressor (52) so that the measurement value of the high-stage suction pressure sensor (77) can reach a target intermediate pressure. The controller (90) sets the target intermediate pressure based on the low pressure of the refrigeration cycle (specifically, the measurement value of the low-stage suction pressure sensor (75)) and the high pressure of the refrigeration cycle (specifically, the measurement value of the high-stage discharge pressure sensor (78)).(Control of Opening Degree of Second Expansion Valve)

[0155] The control of the opening degree of the second expansion valve (EV2) by the controller (90) will be described.

[0156] The controller (90) controls the opening degree of the second expansion valve (EV2) based on the degree of superheat of the refrigerant at the outlet of the inner heat exchanger (57). When the evaporation temperature of the refrigerant in the inner heat exchanger (57) (in other words, the saturation temperature) changes, the degree of superheat of the refrigerant at the outlet of the inner heat exchanger (57) changes. Thus, the degree of superheat of the refrigerant at the outlet of the inner heat exchanger (57) is a physical quantity that correlates with the evaporation temperature of the refrigerant in the inner heat exchanger (57).

[0157] The controller (90) controls the opening degree of the second expansion valve (EV2) so that the degree of superheat SH of the refrigerant at the outlet of the inner heat exchanger (57) can fall within a target superheat degree range including the target degree of superheat (for example, a range within ±1°C of the target degree of superheat). The controller (90) regards the value obtained by subtracting the measurement value Tr3 of the third refrigerant temperature sensor (83) from the measurement value Tr4 of the fourth refrigerant temperature sensor (84) as the degree of superheat SH of the refrigerant at the outlet of the inner heat exchanger (57) (SH = Tr4 - Tr3).

[0158] The controller (90) conducts the processes of step ST22 to step ST26 in FIG. 10 as the operation to control the opening degree of the second expansion valve (EV2). The controller (90) adjusts the target degree of superheat based on the evaporation temperature of the refrigerant in the inner heat exchanger (57). Specifically, the controller (90) adjusts the target degree of superheat based on the measurement value of the third refrigerant temperature sensor (83) and the target evaporation temperature range. When the target degree of superheat changes, the opening degree of the second expansion valve (EV2) changes accordingly.

[0159] In the process of step ST22, the controller (90) compares the measurement value Tr3 of the third refrigerant temperature sensor (83) with the maximum value of the target evaporation temperature range. If the condition that "the measurement value Tr3 of the third refrigerant temperature sensor (83) is higher than the maximum value of the target evaporation temperature range" is satisfied, the controller (90) conducts the process of step ST23. In the process of step ST23, the controller (90) increases the target degree of superheat. When the target degree of superheat increases, the controller (90) reduces the opening degree of the second expansion valve (EV2) in order to increase the degree of superheat SH of the refrigerant at the outlet of the inner heat exchanger (57). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST24.

[0160] In the process of step ST24, the controller (90) compares the measurement value Tr3 of the third refrigerant temperature sensor (83) with the minimum value of the target evaporation temperature range. If the condition that "the measurement value Tr3 of the third refrigerant temperature sensor (83) is lower than the minimum value of the target evaporation temperature range" is satisfied, the controller (90) conducts the process of step ST25. In the process of step ST25, the controller (90) decreases the target degree of superheat. When the target degree of superheat decreases, the controller (90) expands the opening degree of the second expansion valve (EV2) in order to decrease the degree of superheat SH of the refrigerant at the outlet of the inner heat exchanger (57). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST26.

[0161] If the condition in the process of step ST24 is not satisfied, the measurement value Tr3 of the third refrigerant temperature sensor (83) falls within the target evaporation temperature range. Thus, in the process of step ST26, the controller (90) does not change but maintains the target degree of superheat. If the target degree of superheat does not change, the controller (90) does not change but maintains the opening degree of the second expansion valve (EV2). After ending the process of step ST23, step ST25, or step ST26, the controller (90) ends the humidity control operation.<Temperature Control Operation>

[0162] The temperature control operation will be described with reference to FIG. 11. In the temperature control operation, the controller (90) controls the flow rate of the refrigerant in the reheating heat exchanger (58) so that the temperature of the air blown from the air outlet port (22) by the refrigeration apparatus (10) during the dehumidifying operation can reach a set air temperature. In order to control the flow rate of the refrigerant in the reheating heat exchanger (58), the controller (90) controls the opening degree of the fifth expansion valve (EV5) based on the measurement value of the second air temperature sensor (87).

[0163] The controller (90) controls the opening degree of the fifth expansion valve (EV5) so that the measurement value of the second air temperature sensor (87) can fall within a set air temperature range including the set air temperature (for example, a range within ±0.5°C of the set air temperature).

[0164] In the process of step ST31, the controller (90) compares the measurement value Ta2 of the second air temperature sensor (87) with the maximum value of the set air temperature range. If the condition that "the measurement value Ta2 of the second air temperature sensor (87) is higher than the maximum value of the set air temperature range" is satisfied, the controller (90) conducts the process of step ST32. In the process of step ST32, the controller (90) reduces the opening degree of the fifth expansion valve (EV5) in order to decrease the flow rate of the refrigerant in the reheating heat exchanger (58). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST33.

[0165] In the process of step ST33, the controller (90) compares the measurement value Ta2 of the second air temperature sensor (87) with the minimum value of the set air temperature range. If the condition that "the measurement value Ta2 of the second air temperature sensor (87) is lower than the minimum value of the set air temperature range" is satisfied, the controller (90) conducts the process of step ST34. In the process of step ST34, the controller (90) expands the opening degree of the fifth expansion valve (EV5) in order to increase the flow rate of the refrigerant in the reheating heat exchanger (58). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST35.

[0166] If the condition in the process of step ST33 is not satisfied, the measurement value Ta2 of the second air temperature sensor (87) falls within the set air temperature range. Thus, in the process of step ST35, the controller (90) does not change but maintains the opening degree of the fifth expansion valve (EV5). After ending the process of step ST32, step ST34, or step ST35, the controller (90) ends the temperature control operation.<High-Pressure Control Operation>

[0167] The high-pressure control operation will be described with reference to FIG. 12. In the high-pressure control operation, the controller (90) controls the opening degree of the first expansion valve (EV1) so that the pressure of the refrigerant supplied to the reheating heat exchanger (58) during the dehumidifying operation can be held relatively high. The controller (90) controls the opening degree of the first expansion valve (EV1) based on the measurement value of the high-stage discharge pressure sensor (78) in order to control the pressure of the refrigerant discharged from the high-stage compressor (52).

[0168] The controller (90) controls the opening degree of the first expansion valve (EV1) so that the measurement value of the high-stage discharge pressure sensor (78) can fall within a target pressure range (for example, a range within 10±1 MPa). In the controller (90) of this embodiment, the minimum value of the target pressure range is 8 MPa or more, and the maximum value of the target pressure range is 15 MPa or less.

[0169] In the process of step ST41, the controller (90) compares the measurement value Pdh of the high-stage discharge pressure sensor (78) with the maximum value of the target pressure range. If the condition that "the measurement value Pdh of the high-stage discharge pressure sensor (78) is higher than the maximum value of the target pressure range" is satisfied, the controller (90) conducts the process of step ST42. In the process of step ST42, the controller (90) expands the opening degree of the first expansion valve (EV1) in order to decrease the pressure of the refrigerant discharged by the high-stage compressor (52). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST43.

[0170] In the process of step ST43, the controller (90) compares the measurement value Pdh of the high-stage discharge pressure sensor (78) with the minimum value of the target pressure range. If the condition that "the measurement value Pdh of the high-stage discharge pressure sensor (78) is lower than the minimum value of the target pressure range" is satisfied, the controller (90) conducts the process of step ST44. In the process of step ST44, the controller (90) reduces the opening degree of the first expansion valve (EV1) in order to increase the pressure of the refrigerant discharged by the high-stage compressor (52). On the other hand, if the condition is not satisfied, the controller (90) conducts the process of step ST45.

[0171] If the condition in the process of step ST45 is not satisfied, the measurement value Pdh of the high-stage discharge pressure sensor (78) falls within the target pressure range. Thus, in the process of step ST45, the controller (90) does not change but maintains the opening degree of the first expansion valve (EV1). After ending the process of step ST42, step ST44, or step ST45, the controller (90) ends the high-pressure control operation.

[0172] The refrigerant in the refrigerant circuit (30) of this embodiment is carbon dioxide. The critical pressure of carbon dioxide is 7.38 MPa. On the other hand, the target pressure range of this embodiment is within a range of 8 MPa or more and 15 MPa or less. Thus, the controller (90) of this embodiment controls the opening degree of the first expansion valve (EV1) so that the pressure of the refrigerant discharged by the high-stage compressor (52) can become higher than or equal to the critical pressure of the refrigerant (carbon dioxide).-Feature (1) of First Embodiment-

[0173] The refrigeration apparatus (10) of this embodiment performs the dehumidifying operation. In the dehumidifying operation, the temperature and absolute humidity of the air flowing in the internal flow path (20) decrease in the course of passing through the inner heat exchanger (57), and the temperature of the air increases in the course of passing through the reheating heat exchanger (58). Thus, by the refrigeration apparatus (10) performing the dehumidifying operation, it is possible to decrease the humidity of the inside air while maintaining the temperature of the air in the internal space (5).

[0174] In the dehumidifying operation, the controller (90) of this embodiment controls the opening degree of the regulating valve (EV5). When the opening degree of the regulating valve (EV5) changes, the flow rate of the refrigerant in the reheating heat exchanger (58) changes, and then the amount of heat applied to the air in the reheating heat exchanger (58) changes. As a result, the temperature of the air blown into the internal space (5) after passing through the reheating heat exchanger (58) changes. Thus, by the controller (90) controlling the opening degree of the fifth expansion valve (EV5), it is possible to control the temperature of the air blown into the internal space (5) by the refrigeration apparatus (10) in the dehumidifying operation.-Feature (2) of First Embodiment-

[0175] In the two-stage compressing operation of the defrosting operation performed by the refrigeration apparatus (10) of this embodiment, the refrigerant having a pressure higher than or equal to the critical pressure exchanges heat with the air in the reheating heat exchanger (58). In the course of dissipating heat, the refrigerant having a pressure higher than or equal to the critical pressure is not condensed but undergoes a sensible heat change.

[0176] In a state in which the refrigerant having a pressure higher than or equal to the critical pressure flows in the reheating heat exchanger (58), the heat transfer coefficient between the refrigerant and the air is substantially uniform in the entire part of the reheating heat exchanger (58). Thus, in the two-stage compressing operation of the defrosting operation performed by the refrigeration apparatus (10) of this embodiment, the refrigerant dissipates heat at a substantially uniform rate in the entire part of the reheating heat exchanger (58), and as a result, the temperature of the air blown from the air outlet port (22) by the refrigeration apparatus (10) in the dehumidifying operation is made uniform.-Feature (3) of First Embodiment-

[0177] In the refrigeration apparatus (10) of this embodiment, the controller (90) performs the humidity control operation and the temperature control operation.

[0178] In the humidity control operation, the controller (90) sets the target evaporation temperature based on the measurement value of the humidity sensor (88). Then based on the target evaporation temperature, the controller (90) controls the rotational speed of the compressor (50) that sucks the refrigerant having flowed out from the inner heat exchanger (57) during the dehumidifying operation. Thus, the refrigeration apparatus (10) of this embodiment can appropriately control the humidity of the air blown into the internal space (5) by the refrigeration apparatus (10) during the dehumidifying operation.

[0179] In the temperature control operation, the controller (90) controls the opening degree of the fifth expansion valve (EV5) based on the measurement value of the second air temperature sensor (87). Thus, the refrigeration apparatus (10) of this embodiment can appropriately control the temperature of the air blown into the internal space (5) by the refrigeration apparatus (10) during the dehumidifying operation.<<Second Embodiment>>

[0180] The second embodiment will be described. The transportation container (1) of this embodiment is the transportation container (1) of the first embodiment that includes a modified version of the refrigeration apparatus (10).

[0181] The refrigeration apparatus (10) of this embodiment is different in the configuration of the refrigerant circuit (30) from the refrigeration apparatus (10) of the first embodiment. Here, regarding the refrigerant circuit (30) of this embodiment, the differences from the refrigerant circuit (30) of the first embodiment will be described.

[0182] As shown in FIG. 13, in the refrigerant circuit (30) of this embodiment, the defrosting pipe (32) is provided with a drain pan heater (63). In the defrosting pipe (32), the drain pan heater (63) is disposed downstream of the fourth expansion valve (EV4). The drain pan heater (63) is a pipe attached to the drain pan. The drain pan heater (63) heats the drain pan by the refrigerant flowing therein.-Defrosting Operation of Refrigeration Apparatus-

[0183] In the defrosting operation performed by the refrigeration apparatus (10) of this embodiment, similarly to the defrosting operation performed by the refrigeration apparatus (10) of the first embodiment, part of the refrigerant discharged from the high-stage compressor (52) flows into the defrosting pipe (32). In the defrosting operation performed by the refrigeration apparatus (10) of this embodiment, the refrigerant having flowed into the defrosting pipe (32) dissipates heat to the drain pan while passing through the drain pan heater (63), and then flows into the inner heat exchanger (57).

[0184] During the defrosting operation, the frost separated from the inner heat exchanger (57) may drop into the drain pan. In the defrosting operation performed by the refrigeration apparatus (10) of this embodiment, the drain pan is warmed by the refrigerant flowing in the drain pan heater (63). Thus, the frost having dropped from the inner heat exchanger (57) to the drain pan is warmed and melted by the drain pan, and then is discharged as drain water to the external space.<<Third Embodiment>>

[0185] The third embodiment will be described. The transportation container (1) of this embodiment is the transportation container (1) of the second embodiment that includes a modified version of the refrigeration apparatus (10).

[0186] The refrigeration apparatus (10) of this embodiment is different in the configuration of the refrigerant circuit (30) from the refrigeration apparatus (10) of the second embodiment. Here, regarding the refrigerant circuit (30) of this embodiment, the differences from the refrigerant circuit (30) of the second embodiment will be described.

[0187] As shown in FIG. 14, in the refrigerant circuit (30) of this embodiment, the reheating pipe (33) is provided with a drain pan heater (63), and the defrosting pipe (32) and the fourth expansion valve (EV4) are not provided. In the refrigerant circuit (30) of this embodiment, the reheating pipe (33) also serves as the defrosting pipe (32) that sends the refrigerant to the internal heat exchanger in the defrosting operation. In the reheating pipe (33) of this embodiment, the drain pan heater (63) is disposed between the third electromagnetic valve (SV3) and the reheating heat exchanger (58).-Operation of Controller-

[0188] In the refrigeration apparatus of this embodiment, the controller (90) controls the opening degree of the fifth expansion valve (EV5) in both the defrosting operation and the dehumidifying operation. In the defrosting operation, the controller (90) of this embodiment controls the opening degree of the fifth expansion valve (EV5) in the way the controllers (90) of the first and second embodiments control the opening degree of the fourth expansion valve (EV4). In the dehumidifying operation, the controller (90) of this embodiment controls the opening degree of the fifth expansion valve (EV5) similarly to the controllers (90) of the first and second embodiments.<<Other Embodiments>>

[0189] The refrigeration apparatuses (10) of the above embodiments may be modified as follows. The following variations may be combined or replaced as necessary only if the functions of the refrigeration apparatus (10) are not impaired.-First Variation-

[0190] The refrigeration apparatus (10) of each of the first to third embodiments may be configured to perform only a single-stage compression refrigeration cycle. Here, regarding this variation applied to the refrigeration apparatus (10) of the third embodiment, the differences from the refrigeration apparatus (10) of the third embodiment will be described.

[0191] As shown in FIG. 15, the refrigerant circuit (30) of the refrigeration apparatus (10) of this variation is not provided with the low-stage compressor (51), the low-stage connection pipe (44), and the high-stage connection pipe (45). The refrigerant circuit (30) of this variation is provided with one compressor (52) that corresponds to the high-stage compressor of the refrigerant circuit (30) of the third embodiment.

[0192] In the main circuit (31) of the refrigerant circuit (30) of this variation, the other end of the inner heat exchanger (57) is connected to the suction pipe of the compressor (52). The first electric valve (MV1) is provided in part of the main circuit (31) that is between the inner heat exchanger (57) and the suction pipe of the compressor (52). The other end of the intermediate connection pipe (43) is connected to part of the main circuit (31) that is between the first electric valve (MV1) and the compressor (52).

[0193] In the cooling operation of the refrigeration apparatus (10) of this variation, the refrigerant circuit (30) performs the single-stage compression refrigeration cycle. In the refrigerant circuit (30), the compressor (52) operates to circulate the refrigerant in the main circuit (31). The refrigerant discharged by the compressor (52) dissipates heat to the external air in the outer heat exchanger (56). The refrigerant having flowed out from the outer heat exchanger (56) passes through the first flow path (61a) of the internal heat exchanger (61), the first expansion valve (EV1), the receiver (62), the first electromagnetic valve (SV1), and the second expansion valve (EV2) in sequence, and then flows into the inner heat exchanger (57). The refrigerant having flowed into the inner heat exchanger (57) absorbs heat from the air flowing in the internal flow path (20) and then evaporates. The refrigerant having evaporated in the inner heat exchanger (57) is sucked into the compressor (52). The compressor (52) compresses and discharges the sucked refrigerant.-Second Variation-

[0194] In the humidity control operation, the controller (90) of the refrigeration apparatus (10) of each of the first to third embodiments uses the measurement value of the third refrigerant temperature sensor (83) as the evaporation temperature of the refrigerant in the inner heat exchanger (57) in order to control the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2).

[0195] Alternatively, the controller (90) of each of the first to third embodiments may use the saturation temperature of the refrigerant corresponding to the measurement value of the low-stage suction pressure sensor (75) as the evaporation temperature of the refrigerant in the inner heat exchanger (57). In this case, the controller (90) calculates the saturation temperature of the refrigerant corresponding to the measurement value of the low-stage suction pressure sensor (75), and then controls the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2) so that the calculated saturation temperature falls within the target evaporation temperature range.

[0196] The controller (90) of each of the first to third embodiments may set the target evaporation pressure range corresponding to the target evaporation temperature range, and then may control the rotational speed of the compressor (50) and the opening degree of the second expansion valve (EV2) so that the measurement value of the low-stage suction pressure sensor (75) falls within the target evaporation pressure range. The minimum value of the target evaporation pressure range is the saturation pressure of the refrigerant corresponding to the minimum value of the target evaporation temperature range. The maximum value of the target evaporation pressure range is the saturation pressure of the refrigerant corresponding to the maximum value of the target evaporation temperature range.

[0197] The low-stage suction pressure sensor (75) measures the pressure of the refrigerant in the suction pipe of the low-stage compressor (51). The pressure of the refrigerant in the suction pipe of the low-stage compressor (51) is substantially equal to the pressure of the refrigerant having flowed out from the inner heat exchanger (57). The pressure of the refrigerant having flowed out from the inner heat exchanger (57) is substantially equal to the evaporation pressure of the refrigerant in the inner heat exchanger (57). The evaporation temperature of the refrigerant is the saturation temperature corresponding to the evaporation pressure of the refrigerant. Thus, the pressure of the refrigerant in the suction pipe of the low-stage compressor (51) is the physical quantity correlating with the evaporation temperature of the refrigerant in the inner heat exchanger (57).-Third Variation-

[0198] In the dehumidifying operation of the refrigeration apparatus (10), the controller (90) of each of the first to third embodiments may perform an operation of controlling the opening degree of the fifth expansion valve (EV5) depending on whether a temperature non-uniformity condition is satisfied. The temperature non-uniformity condition is the condition indicating that the temperature of the air having passed through the reheating heat exchanger (58) is not uniform in some locations. Examples of the temperature non-uniformity condition include a first temperature non-uniformity condition and a second temperature non-uniformity condition described below. The controller (90) of this variation may determine whether only one of the first temperature non-uniformity condition or the second temperature non-uniformity condition is satisfied, or may determine whether both of the first temperature non-uniformity condition and the second temperature non-uniformity condition are satisfied.<First Temperature Unevenness Condition>

[0199] The first temperature non-uniformity condition is the condition that "the measurement value of the second air temperature sensor (87) is higher than the measurement value of the first air temperature sensor (86)".

[0200] If the first temperature non-uniformity condition is satisfied, it is highly likely that the amount of heating at part of the reheating heat exchanger (58) that is located upstream of the second air temperature sensor (87) is larger than the amount of heating at the other part. In a state in which the amount of heating at each part of the reheating heat exchanger (58) is not uniform, the temperature of the air having passed through the reheating heat exchanger (58) is not uniform in some locations. The "amount of heating" in this description is the amount of heat applied to the air by the reheating heat exchanger (58).

[0201] Thus, the controller (90) of this variation expands the opening degree of the fifth expansion valve (EV5) if the first temperature non-uniformity condition is satisfied. When the opening degree of the fifth expansion valve (EV5) expands, the flow rate of the refrigerant in the reheating heat exchanger (58) increases. When the flow rate of the refrigerant in the reheating heat exchanger (58) increases in a state in which the refrigerant having a pressure higher than or equal to the critical pressure flows in the reheating heat exchanger (58), the amount of decrease in the temperature of the refrigerant in the course of passing through the reheating heat exchanger (58) decreases. Thus, the amount of heating at each part of the reheating heat exchanger (58) is made uniform, and as a result, the temperature of the air having passed through the reheating heat exchanger (58) is made uniform in any location.<Second Temperature Unevenness Condition>

[0202] The second temperature non-uniformity condition is the condition that "the degree of superheat of the refrigerant at the outlet of the inner heat exchanger (57) is higher than the determination reference value (for example, 10°C)".

[0203] Here, the heat exchanger functioning as the evaporator is divided into a gas-liquid two-phase region in which the refrigerant in a gas-liquid two-phase state exchanges heat with the air and a superheat region in which the refrigerant in a gas single-phase state exchanges heat with the air. The heat transfer coefficient between the refrigerant and the air in the superheat region is lower than the heat transfer coefficient between the refrigerant and the air in the gas-liquid two-phase region. Thus, in the heat exchanger functioning as the evaporator, it is highly likely that "the temperature of the air having passed through the superheat region" is higher than "the temperature of the air having passed through the gas-liquid two-phase region".

[0204] If the second temperature non-uniformity condition is satisfied, it is highly likely that the superheat region is relatively large in the inner heat exchanger (57) functioning as the evaporator. Thus, it is highly likely that the temperature of the air having passed through the inner heat exchanger (57) is not uniform in some locations. When the temperature of the air having passed through the inner heat exchanger (57) is not uniform in some locations, the temperature of the air flowing into the reheating heat exchanger (58) is not uniform in some locations, and as a result, the temperature of the air having passed through the reheating heat exchanger (58) is not uniform in some locations.

[0205] Thus, the controller (90) of this variation expands the opening degree of the fifth expansion valve (EV5) if the second temperature non-uniformity condition is satisfied. When the opening degree of the fifth expansion valve (EV5) expands, the flow rate of the refrigerant in the reheating pipe (33) increases, and as a result, the flow rate of the refrigerant in the inner heat exchanger (57) increases. When the flow rate of the refrigerant in the inner heat exchanger (57) increases, the superheat region of the inner heat exchanger (57) decreases, and the temperature of the air having passed through the inner heat exchanger (57) is made uniform in any location. As a result, the temperature of the air having passed through the reheating heat exchanger (58) is made uniform in any location.-Fourth Variation-

[0206] In the temperature control operation, the controller (90) of the refrigeration apparatus (10) of each of the first to third embodiments may control the opening degree of the fifth expansion valve (EV5) based on the temperature of the refrigerant at the outlet of the reheating heat exchanger (58).

[0207] In the refrigeration apparatus (10) of this variation, a fifth refrigerant temperature sensor is provided in part of the reheating pipe (33) that is between the reheating heat exchanger (58) and the fifth expansion valve (EV5). The fifth refrigerant temperature sensor is provided near the other end of the reheating heat exchanger (58), and measures the temperature of the refrigerant at the outlet of the reheating heat exchanger (58). The controller (90) of this variation controls the opening degree of the fifth expansion valve (EV5) based on the measurement value of the fifth refrigerant temperature sensor.

[0208] The temperature of the refrigerant at the outlet of the reheating heat exchanger (58) correlates with the temperature of the air having passed through the reheating heat exchanger (58). Thus, by controlling the opening degree of the fifth expansion valve (EV5) based on the temperature of the refrigerant at the outlet of the reheating heat exchanger (58), it is possible to make the temperature of the air having passed through the reheating heat exchanger (58) within the target temperature range.-Fifth Variation-

[0209] In the refrigeration apparatus (10) of each of the first to third embodiments, the humidity sensor (88) may be provided upstream of the inner heat exchanger (57) in the internal flow path (20). The humidity sensor (88) of this variation measures the relative humidity of the air having flowed into the internal flow path (20) from the internal space (5) at a location upstream of the inner heat exchanger (57). The controller (90) of this variation performs the humidity control operation by using the measurement value of the humidity sensor (88) disposed upstream of the inner heat exchanger (57).-Sixth Variation-

[0210] Usage of the refrigeration apparatus (10) of each of the first to third embodiments is not limited to the air conditioning of the internal space (5) of the transportation container (1). The refrigeration apparatus (10) of each of the first to third embodiments may be used for air conditioning of an internal space of a stationary refrigerator or a cold storage warehouse, for example.

[0211] While the embodiments and variations thereof have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the claims. The elements according to the embodiments, the variations thereof, and the other embodiments may be combined and replaced with each other. In addition, the expressions of "first", "second", "third", ... , in the specification and claims are used to distinguish the terms to which these expressions are given, and do not limit the number and order of the terms.INDUSTRIAL APPLICABILITY

[0212] As described above, the present disclosure is useful for a refrigeration apparatus and a transportation container.DESCRIPTION OF REFERENCE CHARACTERS

[0213] 1Transportation Container 2Container Body 5Internal Space (Target Space) 10Refrigeration Apparatus 30Refrigerant Circuit 33Reheating Pipe (Reheating Passage) 50Compressor 51Low-Stage Compressor 52High-Stage Compressor 56Outer Heat Exchanger (Heat-Source-Side Heat Exchanger) 57Inner Heat Exchanger (Utilization-Side Heat Exchanger) 58Reheating Heat Exchanger 62Receiver 65Expansion Valve 90Controller EV1First Expansion Valve EV2Second Expansion Valve EV5Fifth Expansion Valve (Regulating Valve)

Claims

1. A refrigeration apparatus (10) which includes a refrigerant circuit (30) having a compressor (50), a heat-source-side heat exchanger (56), an expansion valve (65), and a utilization-side heat exchanger (57), and which is configured to condition air in a target space (5), wherein the refrigerant circuit (30) has a reheating heat exchanger (58) configured to exchange heat between air having passed through the utilization-side heat exchanger (57) and a refrigerant, a reheating passage (33) configured to send a refrigerant discharged by the compressor (50) to the reheating heat exchanger (58), and a regulating valve (EV5) of which an opening degree is variable and which is provided downstream of the reheating heat exchanger (58) in the reheating passage (33), The refrigeration apparatus (10) performs a dehumidifying operation to perform a refrigeration cycle in which the heat-source-side heat exchanger (56) functions as a radiator and the utilization-side heat exchanger (57) functions as an evaporator; cool and dehumidify air in the utilization-side heat exchanger (57); heat the air having passed through the utilization-side heat exchanger (57) in the reheating heat exchanger (58); and blow the air heated in the reheating heat exchanger (58) into the target space (5), and the refrigeration apparatus (10) includes a controller (90) that controls the opening degree of the regulating valve (EV5) in the dehumidifying operation.

2. The refrigeration apparatus of claim 1, wherein in the dehumidifying operation, a pressure of the refrigerant supplied to the reheating heat exchanger (58) through the reheating passage (33) is higher than or equal to a critical pressure of the refrigerant.

3. The refrigeration apparatus of claim 2, wherein in the dehumidifying operation, the controller (90) controls an opening degree of the expansion valve (65) so that a pressure of the refrigerant discharged by the compressor (50) can become higher than or equal to a critical pressure of the refrigerant.

4. The refrigeration apparatus of any one of claims 1 to 3, wherein in the dehumidifying operation, the controller (90) controls an opening degree of the regulating valve (EV5) based on a temperature of the air having passed through the reheating heat exchanger (58).

5. The refrigeration apparatus of any one of claims 1 to 3, wherein in the dehumidifying operation, the controller (90) controls an opening degree of the regulating valve (EV5) based on a temperature of the refrigerant having flowed out from the reheating heat exchanger (58).

6. The refrigeration apparatus of any one of claims 1 to 5, wherein in the dehumidifying operation, the controller (90) controls a rotational speed of the compressor (50) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

7. The refrigeration apparatus of any one of claims 1 to 5, wherein the refrigerant circuit (30) has a receiver (62) disposed between the heat-source-side heat exchanger (56) and the utilization-side heat exchanger (57), the expansion valve (65) includes a first expansion valve (EV1) disposed between the heat-source-side heat exchanger (56) and the receiver (62), and a second expansion valve (EV2) disposed between the receiver (62) and the utilization-side heat exchanger (57), and in the dehumidifying operation, the controller (90) controls the opening degree of the first expansion valve (EV1) so that the pressure of refrigerant discharged by the compressor (50) can become higher than or equal to the critical pressure of the refrigerant, and controls an opening degree of the second expansion valve (EV2) so that a physical quantity correlating with an evaporation temperature of a refrigerant in the utilization-side heat exchanger (57) can reach a control target value.

8. The refrigeration apparatus of claim 6 or 7, wherein in the dehumidifying operation, the controller (90) sets the control target value based on a humidity of air flowing into the utilization-side heat exchanger (57) from the target space (5) or a humidity of air blown into the target space (5).

9. The refrigeration apparatus of any one of claims 1 to 8, wherein the compressor (50) includes a low-stage compressor (51) configured to suck a refrigerant having passed through the utilization-side heat exchanger (57), and a high-stage compressor (52) configured to suck a refrigerant discharged by the low-stage compressor (51), and in the dehumidifying operation, the refrigeration apparatus (10) selectively performs a single-stage compressing operation in which one of the low-stage compressor (51) or the high-stage compressor (52) is operated and the other is stopped, and a two-stage compressing operation in which both the low-stage compressor (51) and the high-stage compressor (52) are operated.

10. The refrigeration apparatus of any one of claims 1 to 9, wherein in the dehumidifying operation, the controller (90) expands the opening degree of the regulating valve (EV5) if a temperature non-uniformity condition indicating that a temperature of the air having passed through the reheating heat exchanger (58) is not uniform is satisfied.

11. The refrigeration apparatus of any one of claims 1 to 10, wherein the reheating passage (33) sends the refrigerant having passed through the reheating heat exchanger (58) to the utilization-side heat exchanger (57).

12. The refrigeration apparatus of any one of claims 1 to 11, wherein the refrigerant circuit (30) is filled with carbon dioxide as a refrigerant.

13. A transportation container comprising: the refrigeration apparatus (10) of any one of claims 1 to 12; and a container body (2) forming the target space (5) in which the air is conditioned by the refrigeration apparatus (10).

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