Refrigeration Cycle Equipment

Abstract

To reduce the risk of seizure of a compressor due to dilution of a refrigeration oil progressing by a free cooling operation, in a refrigeration cycle device which performs the free cooling operation.SOLUTION: A refrigerant circuit 10 includes: a compressor 14; a first heat exchanger 11 for performing heat exchange between itself and the outdoor air OA; a decompression device 13 for lowering a pressure of the refrigerant; and a second heat exchanger 12 for performing heat exchange of the refrigerant. A controller 20 executes control for a refrigeration cycle operation, a free cooling operation and an oil recovery operation with respect to the refrigerant circuit 10. The controller 20 controls so that the compressor 14 sucks the refrigerant in a gas state in the refrigeration cycle operation, and controls so that the compressor 14 sucks the refrigerant in a liquid state in the free cooling operation. The controller 20 executes the oil recovery operation when a predetermined condition is satisfied during the free cooling operation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This relates to a refrigeration cycle device capable of free cooling operation. [Background technology]

[0002] A refrigeration cycle refrigeration device that performs free cooling operation using a compressor described in Patent Document 1 (JP Patent Publication 2019-132254 A) as a liquid conveying pump has been proposed. In normal refrigeration cycle operation, the refrigeration cycle device performs a vapor compression refrigeration cycle in which a gaseous refrigerant is sucked into the compressor, compressed, and discharged. For example, when low-temperature outside air can be used as a heat source for cooling, free cooling operation may be performed to reduce power consumption. As described in Patent Document 1, when performing free cooling operation using a compressor, the refrigeration cycle device sucks liquid refrigerant into the compressor and discharges the liquid refrigerant. Summary of the Invention [Problem to be solved by the invention]

[0003] In free cooling operation, where the compressor draws in liquid refrigerant, the refrigeration oil is diluted with the liquid refrigerant. If free cooling operation is continued for a long period of time and the refrigeration oil in the compressor continues to be diluted, the risk of the sliding parts of the compressor seizing up increases.

[0004] A refrigeration cycle device that performs free cooling operation has a problem of reducing the risk of compressor seizure due to dilution of refrigeration oil that progresses during free cooling operation. [Means for solving the problem]

[0005] A refrigeration cycle device according to a first aspect includes a refrigerant circuit and a controller. The refrigerant circuit includes a compressor, a first heat exchanger for exchanging heat with outdoor air, a pressure reducing device for reducing the pressure of the refrigerant, and a second heat exchanger for exchanging heat with the refrigerant. The controller controls the refrigeration cycle operation, the free cooling operation, and an oil recovery operation for recovering refrigeration oil in the compressor, for the refrigeration circuit. In the refrigeration cycle operation, the controller controls the compressor to suck in a gaseous refrigerant, and in the free cooling operation, the controller controls the compressor to suck in a liquid refrigerant. The controller performs the oil recovery operation when a predetermined condition is satisfied during the free cooling operation.

[0006] In the refrigeration cycle apparatus of the first aspect, by performing an oil recovery operation during a free cooling operation, it is possible to suppress a shortage of refrigeration oil during the free cooling operation and reduce the risk of the compressor burning out.

[0007] A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, wherein the refrigerant circuit includes a switching mechanism for switching to a first flow path through which the refrigerant flows in the order of the compressor, the second heat exchanger, the pressure reducing device, and the first heat exchanger, and the controller controls the refrigerant circuit in the free cooling operation so that the refrigerant flows through the first flow path.

[0008] In the refrigeration cycle device of the second aspect, when the refrigerant circulates in the first flow path, refrigeration oil is likely to accumulate between the compressor and the second heat exchanger, and since the refrigeration oil accumulated between the compressor and the second heat exchanger can be easily sucked into the compressor, recovery of the refrigeration oil becomes easy.

[0009] A refrigeration cycle apparatus according to a third aspect is the refrigeration cycle apparatus according to the second aspect, wherein the controller controls the refrigerant circuit so that the refrigerant flows through the first flow path during the oil recovery operation.

[0010] In the refrigeration cycle device of the third aspect, when transitioning from free cooling operation to oil recovery operation, there is no need to switch the flow direction of the refrigerant, thereby eliminating the time required for switching the flow path and shortening the time for oil recovery operation.

[0011] A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to the second aspect, wherein the switching mechanism can switch to a second flow path through which the refrigerant flows in the order of the compressor, the first heat exchanger, the pressure reducing device, and the second heat exchanger. The controller controls the switching mechanism so that the refrigerant flows through the second flow path during the oil recovery operation.

[0012] In the refrigeration cycle apparatus of the fourth aspect, the refrigerant flows from the second heat exchanger toward the compressor during the oil recovery operation, so that refrigeration oil accumulated between the second heat exchanger and the compressor can be easily recovered.

[0013] A refrigeration cycle apparatus of a fifth aspect is the refrigeration cycle apparatus of the first aspect or the second aspect, wherein the controller controls the refrigerant circuit during oil recovery operation so that the refrigerant sucked in and discharged by the compressor is in a gaseous state.

[0014] In the refrigeration cycle apparatus of the fifth aspect, since the compressor can be driven at an operating frequency higher than that in the free cooling operation during the oil recovery operation, the refrigeration oil can be efficiently recovered.

[0015] A refrigeration cycle apparatus of a sixth aspect is the refrigeration cycle apparatus of the first aspect or the second aspect, wherein the controller controls the refrigerant circuit during oil recovery operation so that the refrigerant sucked and discharged by the compressor is in a liquid state.

[0016] In the refrigeration cycle apparatus of the sixth aspect, oil recovery can be performed in the free cooling operation state, and the time required to switch from the free cooling operation to the oil recovery operation can be saved.

[0017] A refrigeration cycle apparatus of a seventh aspect is a refrigeration cycle apparatus of any one of the first aspect to the sixth aspect, in which the controller performs oil recovery operation when an accumulated time obtained by accumulating the compressor driving time during free cooling operation reaches a set time, determining that a specified condition is satisfied.

[0018] In the refrigeration cycle apparatus of the seventh aspect, the oil recovery operation can be performed at an appropriate timing to prevent oil shortage, taking into consideration the outflow of refrigeration oil from the compressor during the free cooling operation.

[0019] A refrigeration cycle apparatus according to an eighth aspect is the refrigeration cycle apparatus according to the seventh aspect, wherein the controller changes the set time depending on an outdoor air temperature or an indoor air temperature.

[0020] In the refrigeration cycle apparatus of the eighth aspect, the oil recovery operation can be performed at an appropriate timing taking into consideration the difference in the dissolution of the refrigeration oil into the refrigerant depending on the air temperature.

[0021] A refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to the seventh or eighth aspect, wherein the controller counts the integrated time by changing the weighting between the refrigeration cycle operation and the free cooling operation.

[0022] In the refrigeration cycle apparatus of the ninth aspect, the oil recovery operation can be performed at an appropriate timing taking into consideration the difference in the ease with which the refrigeration oil flows out during the refrigeration cycle operation and during the free cooling operation.

[0023] A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to any one of the first aspect to the ninth aspect, wherein the controller controls the refrigerant circuit so as to perform an oil recovery operation at the end of the free cooling operation.

[0024] In the refrigeration cycle apparatus of the tenth aspect, when a vapor compression refrigeration cycle operation is performed after the end of the free cooling operation, the risk of the compressor burning out during the refrigeration cycle operation can be reduced.

[0025] A refrigeration cycle apparatus of an eleventh aspect is the refrigeration cycle apparatus of any one of the first aspect to the tenth aspect, wherein the controller controls the operation frequency of the compressor in the free cooling operation to a minimum operation frequency of the compressor.

[0026] In the refrigeration cycle apparatus of the eleventh aspect, the risk of the compressor seizing up during free cooling operation can be significantly reduced.

[0027] A refrigeration cycle apparatus of a twelfth aspect is the refrigeration cycle apparatus of any one of the first aspect to the eleventh aspect, wherein the controller controls to perform an oil recovery operation different from the oil recovery operation during the refrigeration cycle operation.

[0028] In the refrigeration cycle device of the twelfth aspect, the oil recovery operation can be performed according to the compressor in different conditions, that is, refrigeration cycle operation in which the compressor draws in gaseous refrigerant and free cooling operation in which the compressor draws in liquid refrigerant, thereby reducing the risk of compressor malfunction. [Brief description of the drawings]

[0029] [Figure 1] FIG. 4 is a schematic diagram for explaining a refrigeration cycle operation of the refrigeration cycle device in which the refrigerant flows through a second flow path. [Diagram 2] FIG. 2 is a schematic diagram for explaining a free cooling operation of a refrigeration cycle device in which a refrigerant flows through a first flow path. [Diagram 3] FIG. 11 is a schematic diagram for explaining an oil recovery operation of the refrigeration cycle device in which the refrigerant flows through a second flow path. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] First Embodiment (1) Overall structure 1 and 2 show an outline of the configuration of a refrigeration cycle device 1. The refrigeration cycle device 1 includes a refrigerant circuit 10 and a controller 20. The refrigerant circuit 10 includes a first heat exchanger 11, a second heat exchanger 12, a pressure reducing device 13, and a compressor 14. The first heat exchanger 11, the second heat exchanger 12, the pressure reducing device 13, and the compressor 14 are connected by a refrigerant pipe 16 for flowing the refrigerant. In FIG. 1 and FIG. 2, the refrigerant is represented by hatching using diagonal lines and dots. The hatching using diagonal lines indicates a liquid state refrigerant RR, and the hatching using dots indicates a gas state refrigerant GR. The concept of the gas state refrigerant GR includes a refrigerant in which a small amount of liquid state refrigerant is mixed in a gas state refrigerant, and the concept of the liquid state refrigerant RR includes a refrigerant in which a small amount of gas state refrigerant is mixed in a liquid state refrigerant. Fig. 1 shows the refrigerant circuit 10 when the refrigerant flows through the second flow path 200, and Fig. 2 shows the refrigerant circuit 10 when the refrigerant flows through the first flow path 100. The refrigeration cycle device 1 further includes a four-way valve 15 to switch between the first flow path 100 and the second flow path 200. Here, the four-way valve 15 is used as a switching mechanism for switching between the first flow path 100 and the second flow path 200. However, the switching mechanism is not limited to the four-way valve 15. For example, the switching mechanism for switching between the second flow path 200 and the first flow path 100 can also be configured using two three-way valves.

[0031] In the second flow path 200, the refrigerant flows through the compressor 14, the first heat exchanger 11, the pressure reduction device 13, and the second heat exchanger 12 in this order, and then the refrigerant flows from the second heat exchanger 12 to the compressor 14. In other words, the second flow path 200 forms a loop in which the refrigerant flows through the compressor 14, the first heat exchanger 11, the pressure reduction device 13, and the second heat exchanger 12 in this order.

[0032] In the first flow path 100, the refrigerant flows through the compressor 14, the second heat exchanger 12, the pressure reduction device 13, and the first heat exchanger 11 in this order, and then the refrigerant flows from the first heat exchanger 11 to the compressor 14. In other words, the first flow path 100 forms a loop in which the refrigerant flows through the compressor 14, the second heat exchanger 12, the pressure reduction device 13, and the first heat exchanger 11 in this order.

[0033] The first heat exchanger 11 is a heat exchanger for exchanging heat between the refrigerant and the outdoor air OA. In Fig. 1 and Fig. 2, the arrows shown by dashed lines overlapping the first heat exchanger 11 indicate the flow of the outdoor air OA. The second heat exchanger 12 is a heat exchanger for exchanging heat between the refrigerant and the indoor air IA. In Fig. 1 and Fig. 2, the arrows shown by dashed lines overlapping the second heat exchanger 12 indicate the flow of the indoor air IA.

[0034] The pressure reducing device 13 is a device that has a function of reducing the pressure of the refrigerant. The pressure reducing device 13 can reduce the pressure of the refrigerant after passing through the pressure reducing device 13 compared to the refrigerant before passing through the pressure reducing device 13. The pressure reducing device 13 can also be in an open state in which the pressure of the refrigerant passing through is not changed. In other words, when in the open state, the flow path resistance of the pressure reducing device 13 is minimized.

[0035] As shown in Fig. 1, the compressor 14 can suck in the refrigerant GR in a gaseous state, compress the refrigerant GR, and discharge the refrigerant. Also, as shown in Fig. 2, the compressor 14 has a pump function of sucking in and discharging the refrigerant RR in a liquid state. The compressor 14 holds refrigerating machine oil inside. The compressor 14 operates with a mixture of the refrigerant and the refrigerating machine oil, and the refrigerating machine oil lubricates the sliding parts that slide inside the compressor 14, thereby preventing the sliding parts from seizing. The compressor 14 is a compressor whose capacity can be changed by changing the operating frequency.

[0036] When the four-way valve 15 switches the refrigerant circuit 10 so that the refrigerant flows through the second flow path 200, the four-way valve 15 causes the refrigerant discharged from the compressor 14 to flow to the first heat exchanger 11, and causes the refrigerant flowing out of the second heat exchanger 12 to flow to the compressor 14. When the four-way valve 15 switches the refrigerant circuit 10 so that the refrigerant flows through the first flow path 100, the four-way valve 15 causes the refrigerant discharged from the compressor 14 to flow to the second heat exchanger 12, and causes the refrigerant flowing out of the first heat exchanger 11 to flow to the compressor 14.

[0037] The refrigerant circuit 10 is controlled by a controller 20. In detail, the controller 20 controls the degree of pressure reduction by the pressure reducing device 13, the operating frequency and on / off of the compressor 14, and the switching of the four-way valve 15.

[0038] The refrigeration cycle apparatus 1 also has a function of generating an airflow of outdoor air OA in the first heat exchanger 11 and a function of generating an airflow of indoor air IA in the second heat exchanger 12. To achieve this, the refrigeration cycle apparatus 1 includes, for example, a first fan (not shown) for generating an airflow of outdoor air OA in the first heat exchanger 11 and a second fan (not shown) for generating an airflow of indoor air IA in the second heat exchanger 12. In this case, the controller 20 controls the first fan and the second fan.

[0039] (2) Operation of the refrigeration cycle device 1 (2-1) Refrigeration cycle operation The refrigeration cycle device 1 can perform a refrigeration cycle operation that performs a vapor compression refrigeration cycle shown in Fig. 1. By implementing control for the refrigeration cycle operation by the controller 20, the controller 20 controls the refrigerant circuit 10 so that the compressor 14 sucks in and discharges the refrigerant GR in a gas state. In the refrigeration cycle operation, the controller 20 switches the four-way valve 15 so that the refrigerant flows from the compressor 14 to the first heat exchanger 11 via the four-way valve 15, and the refrigerant flows from the second heat exchanger 12 to the compressor 14 via the four-way valve 15. In addition, the controller 20 controls the pressure reducing device 13 so that the pressure reducing device 13 reduces the pressure of the refrigerant passing through.

[0040] In the refrigeration cycle operation, a vapor compression refrigeration cycle is performed in the refrigerant circuit 10. The refrigerant GR discharged from the compressor 14 is sent to the first heat exchanger 11 and exchanges heat with the outdoor air OA in the first heat exchanger 11. The refrigerant GR is cooled by heat exchange that gives heat to the air OA. The liquid refrigerant RR flowing out from the first heat exchanger 11 is a refrigerant generated by condensing the gaseous refrigerant GR through heat exchange in the first heat exchanger 11. The refrigerant RR sent from the first heat exchanger 11 to the pressure reducing device 13 is reduced in pressure reducing device 13 to become a gas-liquid two-phase refrigerant. The refrigerant sent from the pressure reducing device 13 to the second heat exchanger 12 exchanges heat with the indoor air IA in the second heat exchanger 12. The gaseous refrigerant GR, which has been vaporized by removing heat from the air IA through heat exchange in the second heat exchanger 12, is sent from the second heat exchanger 12 to the compressor 14. The refrigeration cycle device 1 can cool the indoor air IA through such a refrigeration cycle operation. The cooled indoor air IA is used, for example, to cool the room.

[0041] (2-2) Free cooling operation The refrigeration cycle device 1 can perform a free cooling operation shown in FIG. 2. The free cooling operation is an operation in which the refrigerant that can remove heat in the second heat exchanger 12 is transported from the first heat exchanger 11 to the second heat exchanger 12 without compressing the refrigerant in a substantial gas state in the compressor 14 by pumping out the refrigerant RR in a liquid state by the pump function of the compressor 14. By implementing control for the free cooling operation by the controller 20, the controller 20 controls the refrigerant circuit 10 so that the refrigerant RR in a liquid state is sucked in and discharged by the compressor 14. In the free cooling operation, the controller 20 switches the four-way valve 15 so that the refrigerant flows from the compressor 14 to the second heat exchanger 12 through the four-way valve 15, and the refrigerant flows from the first heat exchanger 11 to the compressor 14 through the four-way valve 15. In addition, the controller 20 controls the pressure reducing device 13 to be in an open state, thereby reducing the flow resistance of the pressure reducing device 3 to the refrigerant passing through the pressure reducing device 13.

[0042] In the free cooling operation, the refrigerant circuit 10 does not perform a vapor compression refrigeration cycle. The refrigerant RR in a liquid state cooled by heat exchange with the outdoor air OA in the first heat exchanger 11 is drawn into the compressor 14. The refrigerant RR in a liquid state drawn into the compressor 14 is sent to the second heat exchanger 12 by the pump function of the compressor 14. In the second heat exchanger 12, the refrigerant RR cooled in the first heat exchanger 11 exchanges heat with the indoor air IA. In the second heat exchanger 12, the indoor air IA is cooled by the refrigerant RR. The refrigerant RR that removes heat from the air IA is changed, for example, in part or entirely into the gaseous refrigerant GR in the second heat exchanger 12. The refrigerant GR that has completed the heat exchange in the second heat exchanger 12 passes through the pressure reducing device 13 and flows into the first heat exchanger 11. The refrigerant GR that flows into the first heat exchanger 11 is cooled again by heat exchange with the outdoor air OA and becomes a liquid state. The refrigeration cycle apparatus 1 can cool the indoor air IA by such free cooling operation. The cooled indoor air IA can be used to cool the room, for example.

[0043] In the free cooling operation, since the cooling load is low, it is preferable to suppress the operation frequency of the compressor 14 to be lower than the average operation frequency of the compressor 14 during the refrigeration cycle operation. For example, the controller 20 sets the operation frequency of the compressor 14 in the free cooling operation to the minimum operation frequency of the compressor 14. In the free cooling operation, the differential pressure of the refrigerant between the intake and discharge ports of the compressor 14 is smaller than in the refrigeration cycle operation, so the burden on the compressor 14 is smaller. In the free cooling operation, the compressor 14 rotates at a lower speed than the average operating frequency of the compressor 14 in the refrigeration cycle operation, so the burden on the sliding parts of the compressor 14 is smaller. Therefore, in the free cooling operation, even if the dilution of the refrigeration oil progresses, the load on the sliding parts of the compressor 14 is small, so the sliding parts are less likely to seize compared to the refrigeration cycle operation. However, if the free cooling operation is performed and the refrigeration oil is too dilution, and the operation returns to the normal refrigeration cycle operation, the risk of the sliding parts seizing increases. Therefore, the oil recovery operation is performed before the degree of dilution of the refrigeration oil in the free cooling operation increases the risk of the sliding parts seizing. For example, before the dilution of the refrigeration oil progresses too much, the oil recovery operation is performed before returning from the free cooling operation to the refrigeration cycle operation or before returning from the free cooling operation to the refrigeration cycle operation.

[0044] (2-3) Oil recovery operation The controller 20 performs the oil recovery operation when a predetermined condition is satisfied during the free cooling operation. The oil recovery operation is performed by switching to the second flow path 200 shown in Fig. 1 during the free cooling operation. Note that the case where the oil recovery operation is performed at the end of the free cooling operation is also included in the case where the oil recovery operation is performed during the free cooling operation.

[0045] To enter the preparation mode for the oil recovery operation, the controller 20 controls the four-way valve 15 to change the refrigerant circuit 10 from the first flow path 100 to the second flow path 200. In the preparation mode, the controller 20 drives the compressor 14 while keeping the operating frequency (rotation speed) low, and controls the refrigerant circuit 10 so that the compressor 14 draws in the refrigerant GR in a gas state.

[0046] After the compressor 14 is continuously sucked with the refrigerant GR in a gaseous state, the mode shifts from the preparation mode to an oil return mode in which the refrigeration oil is returned to the compressor 14. In the oil return mode of the oil recovery operation during the free cooling operation, the controller 20 does not control the operation frequency (rotation speed) of the compressor 14 to increase to a maximum or a value close to the maximum. In the oil return mode of the oil recovery operation during the free cooling operation, the controller 20 slowly drives the compressor 14 at a lower limit operation frequency at which the oil returns or at an operation frequency that exceeds the lower limit operation frequency but is sufficiently lower than the maximum operation frequency. The lower limit operation frequency at which the oil returns is determined in advance, for example, by an experiment using an actual machine or a simulation.

[0047] In the oil return mode, the compressor 14 draws in the gaseous refrigerant GR from the second heat exchanger 12. The compressor 14 compresses the drawn in refrigerant GR and discharges it to the first heat exchanger 11. The refrigerant that has passed through the first heat exchanger 11 flows into the second heat exchanger 12 via the pressure reducing device 13 in an open state. In the second heat exchanger 12, the gaseous refrigerant GA is generated by heat exchange with the indoor air IA. The oil recovery mode ends in a short time. The short time during which the compressor 14 operates in the oil recovery mode is, for example, about one minute.

[0048] In the oil recovery operation, the controller 20 controls the first fan to be stopped in order to suppress heat exchange in the first heat exchanger 11, so that no airflow of the outdoor air OA is generated in the first heat exchanger 11.

[0049] (2-4) Transition to oil recovery operation A case where a predetermined condition is satisfied during free cooling operation will be described. For example, the predetermined condition can be that the cumulative driving time of the compressor 14 during free cooling operation reaches a set time. For example, when the set time is 12 hours, the controller 20 performs the oil recovery operation again when 12 hours have elapsed after performing the free cooling operation continuously for 12 hours in one day after the oil recovery operation. Then, after the oil recovery operation ends, the controller 20 switches back to the free cooling operation. With the same set time, the controller 20 performs the free cooling operation for 2 hours on the first day after the oil recovery operation and stops it, and performs the oil recovery operation on the second day when the time during which the free cooling operation has been performed reaches 10 hours.

[0050] Also, for example, the end of free cooling operation can be set as the predetermined condition. Such a condition is set in order to prevent an increased risk of seizure occurring in the compressor 14 during normal refrigeration cycle operation that is performed following a state in which the dilution of the refrigeration oil has progressed due to the free cooling operation. More specifically, for example, the predetermined condition can be that the free cooling operation is terminated without performing an oil recovery operation or that the free cooling operation is performed continuously for a predetermined time or more after the oil recovery operation. In the case where the predetermined time is 5 hours, for example, even if the free cooling operation is performed for 8 hours, if an oil recovery operation is performed in the middle and only 4 hours have passed until the end of the free cooling operation, the oil recovery operation will not be performed at the end.

[0051] The controller 20 may have a function of changing the set time and the predetermined time according to the outdoor temperature or the indoor temperature. The lower the outdoor temperature or the indoor temperature, the easier it is for the dilution of the refrigerating machine oil to proceed. Therefore, for example, when the outdoor temperature becomes equal to or lower than a first threshold, the controller 20 changes the set time and the predetermined time to be shorter. Also, for example, when the indoor temperature becomes equal to or lower than a second threshold, the controller 20 changes the set time and the predetermined time to be shorter.

[0052] The controller 20 may change the drive time of the compressor 14 during the oil recovery operation according to the time of the free cooling operation. For example, in a case where the oil recovery operation is performed after 10 hours of free cooling operation and a case where the oil recovery operation is performed after 15 hours of free cooling operation, the drive time of the compressor 14 during the latter oil recovery operation is made longer. Since the longer the free cooling operation is performed, the more the refrigeration oil is diluted, the more the amount of refrigeration oil recovered during the oil recovery operation is adjusted.

[0053] In the case where the predetermined condition is that the cumulative time obtained by accumulating the drive time of the compressor 14 during the free cooling operation reaches a set time, the controller 20 may have a function of changing the predetermined condition according to the refrigeration cycle operation. For example, the controller 20 may count the cumulative time by changing the weighting during the refrigeration cycle operation and during the free cooling operation. During the refrigeration cycle operation, the refrigerant GR in a gas state passes through the compressor 14, whereas during the free cooling operation, the refrigerant RR in a liquid state passes through the compressor 14. Therefore, during the free cooling operation, the dilution of the refrigeration oil proceeds faster than during the refrigeration cycle operation. The weighting is applied so that the cumulative drive time of the compressor 14 during the refrigeration cycle operation becomes lighter, and is added to the cumulative time during the free cooling operation. For example, the controller 20 counts the drive time of the compressor 14 during the refrigeration cycle operation by multiplying it by a coefficient smaller than 1, and counts the drive time of the compressor 14 during the free cooling operation as it is. Also, for example, the controller 20 may be configured to accumulate only the drive time of the compressor 14 during free cooling operation and not count the drive time of the compressor 14 during refrigeration cycle operation as part of the accumulated time. Furthermore, when accumulating the drive time of the compressor 14 during free cooling operation, the controller 20 may be configured to reset the accumulated time not only every time oil recovery operation is performed during free cooling operation, but also every time oil recovery operation is performed during refrigeration cycle operation.

[0054] As already described, when performing a refrigeration cycle operation, another oil recovery operation different from the oil recovery operation during the free cooling operation may be required. In the other oil recovery operation during the refrigeration cycle operation, the controller 20 may, for example, control the operating frequency of the compressor 14 to a maximum value or a value close to the maximum value, control the pressure reducing device 13 to an open state, and switch to the second flow path 200 to cause the refrigerant circuit 10 to perform a vapor compression refrigeration cycle.

[0055] Also, for example, when the outdoor temperature is low, dilution of the refrigeration oil may progress even when the refrigeration cycle device 1 is stopped. The controller 20 may be configured to cause the refrigerant circuit 10 to perform another oil recovery operation when the time during which the outdoor temperature is equal to or lower than a first temperature value (for example, 0°C) is longer than a first time (for example, 12 hours). In this case, the controller 20 may determine the start-up pattern according to the state of the outdoor air temperature. In the oil recovery operation at low outdoor air temperature, the controller 20 slowly starts the compressor 14 at a low start-up frequency at a speed low enough to return the oil. For example, the oil recovery operation at low outdoor air temperature may be performed with the same setting as the oil recovery operation during the free cooling operation. The oil recovery operation at low outdoor air temperature is performed, for example, once every few hours. In the oil recovery operation at low outdoor air temperature, the oil recovery is completed in a short time (for example, about one minute). The start-up frequency of the compressor 14 as described above is determined in advance, for example, by an experiment or simulation using an actual machine.

[0056] (3) Detailed configuration (3-1) First heat exchanger 11 and second heat exchanger 12 The first heat exchanger 11 and the second heat exchanger 12 are heat exchangers that perform heat exchange between a refrigerant and air. For the first heat exchanger 11 and the second heat exchanger 12, for example, a fin-tube type heat exchanger configured with a plurality of heat transfer tubes (not shown) and heat transfer fins (not shown) can be used.

[0057] (3-2) Compressor 14 It is preferable that the compressor 14 is capable of changing the operating frequency by inverter control. For example, a rotary compressor or a scroll compressor can be used as the compressor 14. A compressor having a pump function that draws in and discharges the liquid refrigerant RR is used as the compressor 14.

[0058] (3-3) Pressure reducing device 13 The pressure reducing device 13 has a function of changing the opening degree in order to change the degree of pressure reduction. When the pressure reducing device 13 reduces the opening degree, the pressure of the refrigerant that has passed through the pressure reducing device 13 decreases. When the pressure reducing device 13 is configured to be able to gradually reduce the opening degree, the degree of reduction in the pressure of the refrigerant that has passed through the pressure reducing device 13 gradually increases as the opening degree gradually decreases. When the pressure reducing device 13 is in a fully open state, the pressure of the refrigerant before and after passing through the pressure reducing device 13 is substantially the same. For example, an expansion valve whose opening degree can be changed in response to a signal provided by the controller 20 can be used as the pressure reducing device 13. For example, an electric expansion valve whose opening degree can be changed by a motor can be used as the expansion valve.

[0059] (3-4) Controller 20 The controller 20 is realized by, for example, a computer. The controller 20 includes a control arithmetic device and a storage device. A processor such as a CPU or a GPU can be used for the control arithmetic device. The control arithmetic device reads a program stored in the storage device and performs predetermined image processing and arithmetic processing according to the program. Furthermore, the control arithmetic device can write the calculation result to the storage device and read information stored in the storage device according to the program. The storage device stores a predetermined condition, a set time, a first threshold, a second threshold, a predetermined time, a first time, etc. The controller 20 includes a counter (not shown) for counting an accumulated time.

[0060] The controller 20 is configured to receive data related to temperatures measured by temperature sensors (not shown) provided in each part of the refrigeration cycle device 1. The controller 20 can receive data from the temperature sensors, such as the outdoor air temperature, the indoor air temperature, and the temperature of the refrigerant in each part of the refrigerant circuit 10. In addition, when the rotation speeds of the first fan and the second fan are changeable, the controller 20 controls the rotation speeds of the first fan and the second fan.

[0061] <Second embodiment> (4) Overall structure In the first embodiment, a case has been described in which the oil recovery operation performed during the free cooling operation is performed by implementing a refrigeration cycle operation in the second flow path 200 shown in Fig. 1. However, the oil recovery operation performed during the free cooling operation is not limited to the oil recovery operation described in the first embodiment.

[0062] The oil recovery operation of the second embodiment can be performed with the configuration of the refrigeration cycle apparatus 1 shown in Figures 1 and 2. The configuration of the refrigeration cycle apparatus 1 has been described in the first embodiment, so the description of the configuration of the refrigeration cycle apparatus 1 will be omitted here. In addition, the refrigeration cycle operation and free cooling operation by the refrigeration cycle apparatus 1 are also the same in the second embodiment as in the first embodiment, so the description of the refrigeration cycle operation and free cooling operation will be omitted here.

[0063] Furthermore, as for the transition to oil recovery operation during free cooling operation, the free cooling operation in the first embodiment is the same as that in the second embodiment, so an explanation thereof will be omitted.

[0064] (5) Oil recovery operation In the second embodiment, the controller 20 also performs the oil recovery operation when a predetermined condition is satisfied during the free cooling operation. The oil recovery operation in the second embodiment is performed in a state in which the refrigerant flows through the first flow path 100 shown in Fig. 2, similar to the free cooling operation. In the preparation mode for the oil recovery operation, the controller 20 drives the compressor 14 while keeping the operating frequency (rotation speed) low, and controls the refrigerant circuit 10 so that the compressor 14 is in a state in which it draws in the refrigerant GR in a gas state, as shown in Fig. 3.

[0065] After the compressor 14 is continuously sucked into the refrigerant GR in a gaseous state, the mode shifts from the preparation mode to an oil return mode in which the refrigeration oil is returned to the compressor 14. In the oil return mode of the oil recovery operation during the free cooling operation, the controller 20 does not control the operating frequency (rotation speed) of the compressor 14 to increase to the maximum or a value close to the maximum. In the oil return mode of the oil recovery operation during the free cooling operation, the controller 20 slowly drives the compressor 14 at an operating frequency that is equal to or exceeds the lower limit operating frequency at which the oil returns, or at an operating frequency that is sufficiently lower than the maximum operating frequency while exceeding the lower limit operating frequency.

[0066] In the oil return mode, the compressor 14 draws in the gaseous refrigerant GR from the first heat exchanger 11. The compressor 14 compresses the drawn in refrigerant GR and discharges it to the second heat exchanger 12. The refrigerant that has passed through the second heat exchanger 12 flows into the first heat exchanger 11 via the pressure reducing device 13 in an open state. The gaseous refrigerant GA that has passed through the first heat exchanger 11 is drawn into the compressor 14. The oil recovery mode ends in a short time. The short time during which the compressor 14 operates in the oil recovery mode is, for example, about one minute.

[0067] During oil recovery operation, the controller 20 controls the first fan to stop so as to suppress heat exchange with the cold outdoor air OA in the first heat exchanger 11 and to prevent an airflow of the outdoor air OA from being generated in the first heat exchanger 11.

[0068] <Third embodiment> (6) Overall structure In the first and second embodiments, the oil recovery operation performed during the free cooling operation is described as being performed by the compressor 14 sucking in the gaseous refrigerant GR. However, the oil recovery operation performed during the free cooling operation is not limited to the oil recovery operation in which the compressor sucks in the gaseous refrigerant GR described in the first and second embodiments.

[0069] The oil recovery operation of the third embodiment can be performed with the configuration of the refrigeration cycle apparatus 1 shown in Figures 1 and 2. The configuration of the refrigeration cycle apparatus 1 has been described in the first embodiment, so the description of the configuration of the refrigeration cycle apparatus 1 will be omitted here. In addition, the refrigeration cycle operation and free cooling operation by the refrigeration cycle apparatus 1 are also the same in the third embodiment as in the first embodiment, so the description of the refrigeration cycle operation and free cooling operation will be omitted here.

[0070] Furthermore, as for the transition to oil recovery operation during free cooling operation, the free cooling operation in the first embodiment is the same as that in the third embodiment, so an explanation thereof will be omitted.

[0071] (7) Oil recovery operation In the third embodiment, the controller 20 also performs the oil recovery operation when a predetermined condition is satisfied during the free cooling operation. The oil recovery operation of the third embodiment is performed in a state in which the refrigerant flows through the first flow path 100 shown in FIG. 2, as in the free cooling operation. In the oil recovery operation of the third embodiment, the controller 20 increases the operating frequency of the compressor 14 compared to the free cooling operation. In other words, the controller 20 controls the compressor 14 so that f2>f1, where the operating frequency of the compressor 14 during the free cooling operation is f1 and the operating frequency of the compressor 14 during the oil recovery operation is f2. At the operating frequency f2, the amount of refrigeration oil returning to the compressor 14 is greater than the amount of refrigeration oil leaving the compressor. Conversely, at the operating frequency f1, the amount of refrigeration oil returning to the compressor 14 is less than the amount of refrigeration oil leaving the compressor. In order to reduce the burden on the compressor 14, it is preferable that the operating frequency f2 of the compressor 14 during oil recovery operation be as small as possible within the range that satisfies the condition that the amount of refrigeration oil returning to the compressor 14 is greater than the amount of refrigeration oil leaving the compressor.

[0072] In the oil recovery operation, the liquid refrigerant RR cooled by heat exchange with the outdoor air OA in the first heat exchanger 11 is drawn into the compressor 14. The liquid refrigerant RR drawn into the compressor 14 is sent to the second heat exchanger 12 by the pump function of the compressor 14. The refrigerant that has passed through the second heat exchanger 12 flows into the first heat exchanger 11 via the pressure reducing device 13. The refrigerant GR that has flowed into the first heat exchanger 11 is cooled again by heat exchange with the outdoor air OA. In such an oil recovery operation, the controller 20 stops the second fan to suppress the generation of an airflow of the indoor air IA in the second heat exchanger 12.

[0073] (8) Variations (8-1) Variation A In the first to third embodiments, the refrigeration cycle apparatus 1 cools indoor air IA by free cooling operation. Such a refrigeration cycle apparatus 1 can be applied to, for example, an air conditioner. However, the application of the refrigeration cycle apparatus 1 is not limited to air conditioners. The second heat exchanger 12 may be configured to exchange heat between, for example, water or a heat medium and a refrigerant, instead of between air and a refrigerant. Such a refrigeration cycle apparatus 1 can be applied to, for example, a heat pump chiller or a water cooler that supplies chilled water.

[0074] (8-2) Variation B In the first to third embodiments, the refrigeration cycle apparatus 1 cools the indoor air IA by the free cooling operation. However, the refrigeration cycle apparatus 1 can also be used for heating the room by switching to the first flow path 100 by the four-way valve 15 and implementing a vapor compression refrigeration cycle.

[0075] (9) Features (9-1) The controller 20 of the refrigeration cycle apparatus 1 controls the compressor 14 to draw in the refrigerant GR in a gaseous state during the refrigeration cycle operation, and controls the compressor 14 to draw in the refrigerant RR in a liquid state during the free cooling operation. The controller 20 performs an oil recovery operation when a predetermined condition is satisfied during the free cooling operation. By performing the oil recovery operation during the free cooling operation, the refrigeration cycle apparatus 1 can suppress a shortage of refrigeration oil during the free cooling operation and reduce the risk of the compressor 14 burning out.

[0076] (9-2) The refrigerant circuit 10 includes a four-way valve 15, which is a switching mechanism for switching to a first flow path 100 in which the refrigerant flows through the compressor 14, the second heat exchanger 12, the pressure reducing device 13, and the first heat exchanger 11 in this order. In the free cooling operation, the controller 20 controls the refrigerant circuit 10 so that the refrigerant flows through the first flow path 100. When the refrigerant circulates through the first flow path 100, refrigeration oil is likely to accumulate between the compressor 14 and the second heat exchanger 12. For example, when a refrigeration cycle operation is performed using the second flow path 200 shown in FIG. 1, the refrigeration oil accumulated between the compressor 14 and the second heat exchanger 12 is sucked into the compressor 14. When such a refrigeration cycle operation is performed, the refrigeration oil accumulated outside the compressor 14 can be easily sucked into the compressor 14, making it easy to recover the refrigeration oil.

[0077] (9-3) As in the second and third embodiments, if the controller 20 controls the refrigerant circuit 10 so that the refrigerant flows through the first flow path 100 during the oil recovery operation, there is no need to switch the refrigerant flow direction when transitioning from the free cooling operation to the oil recovery operation. By performing such an oil recovery operation, the time required for switching the flow paths can be eliminated, and the time for the oil recovery operation can be shortened.

[0078] (9-4) 1, the four-way valve 15, which is a switching mechanism, can be switched to the second flow path 200, which allows the refrigerant to flow through the compressor 14, the first heat exchanger 11, the pressure reducing device 13, and the second heat exchanger 12 in this order. As described in the first embodiment, the controller 20 controls the four-way valve 15 so that the refrigerant flows through the second flow path 200 during the oil recovery operation. In such a refrigeration cycle device 1, the refrigerant flows from the second heat exchanger 12 toward the compressor 14 during the oil recovery operation, making it easier to recover refrigeration oil accumulated between the second heat exchanger 12 and the compressor 14.

[0079] (9-5) In the first and second embodiments, the controller 20 controls the refrigerant circuit 10 during the oil recovery operation so that the refrigerant sucked in and discharged by the compressor 14 is in a gaseous state. In such a refrigeration cycle device 1, during the oil recovery operation, the compressor 14 can be driven at a higher operating frequency than during the free cooling operation, so that the refrigeration oil can be efficiently recovered.

[0080] (9-6) The controller 20 of the third embodiment controls the refrigerant circuit 10 so that the refrigerant sucked and discharged by the compressor 14 is in a liquid state during the oil recovery operation. In such a refrigeration cycle device 1, oil recovery can be performed in the free cooling operation state, and the time required to switch from the free cooling operation to the oil recovery operation can be saved.

[0081] (9-7) As described in "(2-4) Transition to oil recovery operation" in the first embodiment, the controller 20 can be configured to perform the oil recovery operation when the accumulated driving time of the compressor 14 during the free cooling operation reaches the set time, assuming that a predetermined condition is satisfied. In such a refrigeration cycle device 1, the oil recovery operation can be performed at an appropriate timing to prevent oil shortage, taking into consideration the outflow of refrigeration oil from the compressor 14 during the free cooling operation.

[0082] (9-8) The controller 20 may have a function of changing the set time depending on the outdoor air temperature or the indoor air temperature. In such a refrigeration cycle device 1, the oil recovery operation can be performed at an appropriate timing considering the difference in the dissolution of the refrigeration oil into the refrigerant depending on the air temperature.

[0083] (9-9) The controller 20 can be configured to count the integrated time by changing the weighting between the refrigeration cycle operation and the free cooling operation when it is determined that the predetermined condition is satisfied when the integrated time reaches the set time. In such a refrigeration cycle device 1, the oil recovery operation can be performed at an appropriate timing considering the difference in the ease with which the refrigeration oil flows out during the refrigeration cycle operation and the free cooling operation.

[0084] (9-10) The controller 20 can be configured to control the refrigerant circuit 10 to perform an oil recovery operation at the end of the free cooling operation. In such a refrigeration cycle device 1, when a refrigeration cycle operation is performed after the free cooling operation, the refrigeration oil is always recovered in the compressor 114. Therefore, the refrigeration cycle device 1 can reduce the risk of the compressor 14 burning out when a vapor compression refrigeration cycle operation is performed after the end of the free cooling operation.

[0085] (9-11) The controller 20 can be configured to set the operating frequency of the compressor 14 during the free cooling operation to the minimum operating frequency of the compressor 14. In such a refrigeration cycle device 1, the risk of the compressor 14 burning out during the free cooling operation can be significantly reduced.

[0086] (9-12) The controller 20 can be configured to control the compressor 14 to perform an oil recovery operation other than the oil recovery operation during the refrigeration cycle operation. The state of the compressor 14 differs between the refrigeration cycle operation in which the compressor 14 draws in the refrigerant GR in a gas state and the free cooling operation in which the compressor 14 draws in the refrigerant RR in a liquid state. Such a refrigeration cycle device 1 can perform an oil recovery operation suited to the compressor 14, whose state differs between the refrigeration cycle operation and the free cooling operation, and can reduce the risk of a malfunction in the compressor 14.

[0087] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in the claims. [Explanation of symbols]

[0088] 1 Refrigeration cycle equipment 10 Refrigerant circuit 11 1st heat exchanger 12 Second heat exchanger 13 Pressure reducing device 14 Compressor 15 Four-way valve (example of switching mechanism) 20 Controller 100 First flow path 200 Second Stream [Prior art documents] [Patent documents]

[0089] [Patent Document 1] JP 2019-132254 A

Claims

1. a refrigerant circuit (10) including a compressor (14), a first heat exchanger (11) for exchanging heat with outdoor air, a pressure reducing device (13) for reducing the pressure of the refrigerant, and a second heat exchanger (12) for exchanging heat with the refrigerant; a controller (20) that controls a refrigeration cycle operation, a free cooling operation, and an oil recovery operation that recovers refrigeration oil in the compressor, for the refrigerant circuit; Equipped with The controller controls the compressor to draw in a gaseous refrigerant in the refrigeration cycle operation, and controls the compressor to draw in a liquid refrigerant in the free cooling operation, The controller performs the oil recovery operation when a predetermined condition is satisfied during the free cooling operation.

2. the refrigerant circuit includes a switching mechanism (15) for switching to a first flow path through which the refrigerant flows in the order of the compressor, the second heat exchanger, the pressure reducing device, and the first heat exchanger; The controller controls the refrigerant circuit in the free cooling operation so that the refrigerant flows through the first flow path. A refrigeration cycle device (1) as claimed in claim 1.

3. The controller controls the refrigerant circuit so that the refrigerant flows through the first flow path (100) during the oil recovery operation. A refrigeration cycle device (1) according to claim 2.

4. The switching mechanism can be switched to a second flow path (200) through which the refrigerant flows in the order of the compressor, the first heat exchanger, the pressure reducing device, and the second heat exchanger, The controller controls the switching mechanism so that the refrigerant flows through the second flow path during the oil recovery operation. A refrigeration cycle device (1) according to claim 2.

5. The controller controls the refrigerant circuit during the oil recovery operation so that the refrigerant sucked and discharged by the compressor is in a gas state. A refrigeration cycle device (1) according to any one of claims 1 to 4.

6. The controller controls the refrigerant circuit during the oil recovery operation so that the refrigerant sucked and discharged by the compressor is in a liquid state. A refrigeration cycle device (1) according to any one of claims 1 to 4.

7. the controller determines that the predetermined condition is satisfied when an accumulated time obtained by accumulating the driving time of the compressor during the free cooling operation reaches a set time, and performs the oil recovery operation. A refrigeration cycle device (1) according to any one of claims 1 to 6.

8. The controller changes the set time depending on an outdoor temperature or an indoor temperature. Refrigeration cycle device (1) according to claim 7.

9. The controller counts the integrated time by changing a weighting during the refrigeration cycle operation and during the free cooling operation. A refrigeration cycle apparatus (1) according to claim 7 or claim 8.

10. The controller controls the refrigerant circuit to perform the oil recovery operation at the end of the free cooling operation. A refrigeration cycle device (1) according to any one of claims 1 to 9.

11. The controller controls the operating frequency of the compressor during the free cooling operation to a minimum operating frequency of the compressor. A refrigeration cycle device (1) according to any one of claims 1 to 10.

12. The controller controls the refrigeration cycle to perform another oil recovery operation different from the oil recovery operation during the refrigeration cycle operation. A refrigeration cycle device (1) according to any one of the preceding claims.

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