Refrigeration cycle device

Abstract

The purpose of the present invention is to provide a refrigeration cycle device enabling suppression of a decrease in heat collection amount from the ground along with suppression of a decrease in operation efficiency in a heat pump using underground heat and air heat as heat sources. A refrigeration cycle device (1A) comprises air conditioning units (11a, 11b), a heat medium (12), an underground heat exchanger (13), a heat medium circuit (10), and a control device (15A). When a state in which the heat medium (12) flows through the heat medium circuit (10) in the order of an air heat source unit (14), the underground heat exchanger (13), and the air conditioning unit (11a) is defined as a first cycle (CL1), and a state in which the heat medium (12) flows through the heat medium circuit (10) in the order of the underground heat exchanger (13), the air heat source unit (14), and the air conditioning unit (11a) is defined as a second cycle (CL2), the control device (15A) controls a four-way valve (19) to switch the state of flow of the heat medium (12) from either the first cycle (CL1) or the second cycle (CL2) to the other.

Description

Refrigeration cycle apparatus

[0001] The present invention relates to a refrigeration cycle apparatus that uses geothermal heat.

[0002] Among refrigeration cycle apparatuses using geothermal heat, there is known a geothermal utilization apparatus in which a geothermal heat exchanger and a heat source heat pump (air source heat pump) are connected to a circulating water line (for example, Patent Document 1). In this apparatus, a decrease in the operating efficiency (Coefficient of Performance: COP) of the heat pump can be suppressed even when the amount of heat collected from the ground decreases (thermal depletion).

[0003] Japanese Unexamined Patent Publication No. 2009-198102

[0004] Patent Document 1 discloses a first circuit configuration in which a heat medium that has absorbed heat from air flows toward a geothermal heat exchanger, and a second circuit configuration in which a heat medium that has absorbed heat from air flows toward an air conditioning heat pump. The first circuit configuration has a great effect of suppressing underground thermal depletion, but has the problem that the temperature of the heat medium flowing into the air conditioning heat pump cannot be controlled, which may lead to a decrease in operating efficiency. The second circuit configuration has a great effect of improving the operating efficiency on the side of the air conditioning heat pump, but has the problem that the temperature of the heat medium flowing into the geothermal heat exchanger cannot be controlled, so there is a concern that thermal depletion may occur.

[0005] Once thermal depletion occurs, the amount of heat collected from the ground may decrease for a period of one year or more. For this reason, it is necessary to prevent thermal depletion from occurring, but conventional techniques have the problem that it is difficult to achieve both the suppression of a decrease in the operating efficiency of the air conditioning heat pump and the suppression of thermal depletion, that is, the suppression of a decrease in the amount of heat collected from the ground.

[0006] An object of the present invention is to provide a refrigeration cycle apparatus capable of suppressing a decrease in the amount of heat collected from the ground while suppressing a decrease in operating efficiency in a heat pump that uses geothermal heat and air heat as heat sources.

[0007] To achieve the above objective, a refrigeration cycle apparatus according to one aspect of the present invention comprises an air conditioning unit, a heat transfer medium supplied to the air conditioning unit, a geothermal heat exchanger that exchanges heat between the heat transfer medium and soil, an air heat source unit that exchanges heat between the heat transfer medium and outside air, a heat transfer medium circuit through which the heat transfer medium flows, a flow path switching unit provided in the heat transfer medium circuit for switching the flow of the heat transfer medium, and a control device that controls the air conditioning unit, the air heat source unit, and the flow path switching unit. The first cycle is defined as the state in which the heat transfer medium flows through the heat transfer medium circuit in the order of the air heat source unit, the geothermal heat exchanger, and the air conditioning unit, and the second cycle is defined as the state in which the heat transfer medium flows through the heat transfer medium circuit in the order of the geothermal heat exchanger, the air heat source unit, and the air conditioning unit. The control device controls the flow path switching unit to switch the flow state of the heat transfer medium from one of the first cycle and the second cycle to the other.

[0008] According to one aspect of the present invention, in a heat pump that uses geothermal and air heat as heat sources, it is possible to suppress a decrease in the amount of heat extracted from the ground while suppressing a decrease in operating efficiency.

[0009] This is a refrigerant circuit diagram showing an example of the schematic configuration of a refrigeration cycle device according to the first embodiment of the present invention. This is a flowchart showing an example of the operation flow of a refrigeration cycle device according to the first embodiment of the present invention. This is a refrigerant circuit diagram showing an example of the schematic configuration of a refrigeration cycle device according to the second embodiment of the present invention. This is a flowchart showing an example of the operation flow of a refrigeration cycle device according to the second embodiment of the present invention. This is a refrigerant circuit diagram showing an example of the schematic configuration of a refrigeration cycle device according to the third embodiment of the present invention. This is a diagram for explaining a method for obtaining temperature unevenness occurring in the soil. This is a diagram for explaining the state before improvement of temperature unevenness in the soil. This is a graph showing an example of the temporal change in the ratio of the temperature difference at the two inlets and outlets of a geothermal heat exchanger caused by temperature unevenness in the soil. This is a diagram for explaining the state after improvement of temperature unevenness in the soil. This is a flowchart showing an example of the operation flow of a refrigeration cycle device according to the third embodiment of the present invention.

[0010] Each embodiment of the present invention illustrates an apparatus or method for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0011] [First Embodiment] A refrigeration cycle device according to the first embodiment of the present invention will be described with reference to Figures 1 and 2.

[0012] 1-1. Configuration of the Refrigeration Cycle System: First, the configuration of the refrigeration cycle system according to this embodiment will be explained using Figure 1. Figure 1 is a refrigerant circuit diagram showing an example of a schematic configuration of the refrigeration cycle system according to this embodiment.

[0013] As shown in Figure 1, the refrigeration cycle device 1A according to this embodiment includes air conditioning units 11a and 11b, a heat transfer medium 12 supplied to the air conditioning units 11a and 11b, and a geothermal heat exchanger 13 that exchanges heat between the heat transfer medium 12 and the soil 2. The refrigeration cycle device 1A also includes an air heat source unit 14 that exchanges heat between the heat transfer medium 12 and the outside air, a heat transfer medium circuit 10 through which the heat transfer medium 12 flows, a four-way valve 19 (an example of a flow path switching unit) provided in the heat transfer medium circuit 10 to switch the flow of the heat transfer medium 12, and a control device 15A that controls the air conditioning units 11a and 11b, the air heat source unit 14, and the four-way valve 19.

[0014] The refrigeration cycle device 1A includes a heat transfer medium circuit 10 that connects the air conditioning units 11a and 11b, the ground heat exchanger 13, the four-way valve 19, and the air heat source unit 14. In Figure 1, for ease of understanding, the heat transfer medium 12 flowing through the heat transfer medium circuit 10 is illustrated with arrows. Solid arrows indicate the heat transfer medium 12 flowing through the heat transfer medium circuit 10 when switched to the first cycle CL1 state (details described later), and dashed arrows indicate the heat transfer medium 12 flowing through the heat transfer medium circuit 10 when switched to the second cycle CL2 state (details described later). The direction indicated by the solid and dashed arrows represents the direction in which the heat transfer medium 12 flows. As shown in Figure 1, the multiple air conditioning units 11a and 11b are connected in parallel in the direction in which the heat transfer medium 12 flows. In this embodiment, water is used as the heat transfer medium 12, but other heat transfer mediums may be used.

[0015] The heat transfer medium circuit 10 is located between the inlets and outlets 131 and 132 of the underground heat exchanger 13. A four-way valve 19, an air heat source unit 14, and air conditioning units 11a and 11b are provided in the middle of the heat transfer medium circuit 10. The heat transfer medium circuit 10 is configured to branch upstream of the heat exchanger 111 provided in the air conditioning unit 11a and connect to the air conditioning unit 11b, and then merge downstream of the heat exchanger 111. In addition to the four-way valve 19, air heat source unit 14, and air conditioning units 11a and 11b, a circulation pump 17 and three-way valves 18a and 18b are located between the four-way valve 19 and the air heat source unit 14 in the heat transfer medium circuit 10. The circulation pump 17 is controlled, for example, by a control device 15A, and circulates the heat transfer medium 12 in the heat transfer medium circuit 10 and the underground heat exchanger 13.

[0016] The three-way valve 18a has inlets and outlets for the heat transfer medium 12 on the side of the four-way valve 19, the side of the air heat source unit 14, and the side of the three-way valve 18b. The three-way valve 18b has inlets and outlets for the heat transfer medium 12 on the side of the air heat source unit 14, the side of the circulation pump 17, and the side of the three-way valve 18a. When the air heat source unit 14 is not operating, the three-way valve 18a connects the four-way valve 19 and the three-way valve 18b, and the three-way valve 18b connects the three-way valve 18a and the circulation pump 17. As a result, when the air heat source unit 14 is not operating, the heat transfer medium 12 does not flow to the air heat source unit 14 but circulates through the heat transfer medium circuit 10 and the ground heat exchanger 13. Hereinafter, the state in which the three-way valves 18a and 18b are switched so that the three-way valve 18a connects the four-way valve 19 and the three-way valve 18b, and the three-way valve 18b connects the three-way valve 18a and the circulation pump 17 will be referred to as "switched state α".

[0017] On the other hand, when the air heat source unit 14 is operating, the three-way valve 18a connects the four-way valve 19 to the air heat source unit 14, and the three-way valve 18b connects the air heat source unit 14 to the circulation pump 17. As a result, when the air heat source unit 14 is operating, the heat transfer medium 12 flows through the air heat source unit 14 while also flowing through the heat transfer medium circuit 10 and the ground heat exchanger 13. Hereinafter, the state in which the three-way valves 18a and 18b are switched so that the three-way valve 18a connects the four-way valve 19 to the air heat source unit 14, and the three-way valve 18b connects the air heat source unit 14 to the circulation pump 17 will be referred to as "switched state β". The three-way valves 18a and 18b are controlled by the control device 15A.

[0018] The four-way valve 19 switches the direction of flow of the heat transfer medium 12 circulating in the heat transfer circuit 10. When the state in which the heat transfer medium 12 flows through the heat transfer circuit 10 in the order of air heat source unit 14, ground heat exchanger 13, and air conditioning unit 11a is defined as the first cycle CL1, and when the state in which the heat transfer medium 12 flows through the heat transfer circuit 10 in the order of ground heat exchanger 13, air heat source unit 14, and air conditioning unit 11a is defined as the second cycle CL2, the four-way valve 19 switches the flow state of the heat transfer medium 12 from one of the first cycle CL1 and the second cycle CL2 to the other. The four-way valve 19 is controlled by the control device 15A to switch the flow state of the heat transfer medium 12 from the first cycle CL1 to the second cycle CL2 or from the second cycle CL2 to the first cycle CL1. In the first cycle CL1, the heat from the air heat source unit 14 can be directly supplied to the ground heat exchanger 13, thereby suppressing heat depletion of the soil 2. In the second cycle CL2, the heat from the air heat source unit 14 can be directly supplied to the air conditioning unit 11a, thereby contributing to improved operating efficiency of the air conditioning units 11a and 11b. In Figure 1, and in Figures 3 and 5 described later, the first cycle CL1 in the heat transfer medium circuit 10 is shown by a solid thick arrow, and the second cycle CL2 is shown by a dashed thick arrow. The direction indicated by the thick arrow represents the direction of the first cycle CL1 and the second cycle CL2.

[0019] More specifically, the four-way valve 19 is controlled by the control device 15A to connect port a and port b, and port c and port d, and the state in which the heat transfer medium 12 flows is defined as the first cycle CL1. In the first cycle CL1, the heat transfer medium circuit 10 is connected in the following order so that the heat transfer medium 12 (see solid arrows) can flow through: the inlet / outlet 131 of the ground heat exchanger 13, the air conditioning units 11a and 11b, port c, port d, three-way valve 18a, air heat source unit 14, three-way valve 18b, circulation pump 17, port b, port a, and the inlet / outlet 132 of the ground heat exchanger 13.

[0020] Meanwhile, the four-way valve 19 is controlled by the control device 15A to connect ports a and d, and ports c and b, and the state in which the heat transfer medium 12 flows is defined as the second cycle CL2. In the second cycle CL2, the heat transfer medium circuit 10 is connected in the following order so that the heat transfer medium 12 (see dashed arrows) can flow through: the inlet / outlet 132 of the ground heat exchanger 13, port a, port d, three-way valve 18a, air heat source unit 14, three-way valve 18b, circulation pump 17, port b, port c, air conditioning units 11a, 11b, and the inlet / outlet 131 of the ground heat exchanger 13. In this way, the direction in which the heat transfer medium 12 flows to the ground heat exchanger 13 is reversed between the first cycle CL1 and the second cycle CL2.

[0021] The refrigeration cycle device 1A includes a plurality of (two in this embodiment) air conditioning units 11a, 11b, but it may also include one air conditioning unit or three or more air conditioning units.

[0022] Air conditioning units 11a and 11b have the same configuration. Therefore, the configurations of air conditioning units 11a and 11b will be explained using air conditioning unit 11a as an example.

[0023] As shown in Figure 1, the air conditioning unit 11a is capable of both cooling and heating operation. The air conditioning unit 11a includes heat exchangers 111 and 112, a compressor 113, a four-way valve 114, an expansion valve 115, and a room temperature sensor 116. The four-way valve 114 is located on the discharge side of the compressor 113. An accumulator may be located on the suction side of the compressor 113. The air conditioning unit 11a includes a blower (not shown) for supplying air from the room in which the air conditioning unit 11a is located to the heat exchanger 112, and a drive motor (not shown) for driving the blower.

[0024] The heat exchanger 111 is, for example, a plate-type heat exchanger and has a heat transfer medium channel 111a connected to the heat transfer medium circuit 10 and a refrigerant channel 111b through which the refrigerant used for heat exchange in the heat exchanger 111 flows. Therefore, in the heat exchanger 111, heat is exchanged between the heat transfer medium 12 flowing from the heat transfer medium circuit 10 into the heat transfer medium channel 111a and the refrigerant flowing through the refrigerant channel 111b.

[0025] The heat exchanger 111 provided in the air conditioning unit 11b is, for example, a plate-type heat exchanger and has a heat transfer medium flow path 111a connected to the heat transfer medium circuit 10 and a refrigerant flow path 111b through which the refrigerant used for heat exchange in the heat exchanger 111 flows. In the heat exchanger 111 provided in the air conditioning unit 11b, heat exchange occurs between the heat transfer medium 12 flowing from the heat transfer medium circuit 10 into the heat transfer medium flow path 111a and the refrigerant flowing through the refrigerant flow path 111b.

[0026] The room temperature sensor 116 is located inside the air conditioning unit 11a. The room temperature sensor 116 detects the temperature of the indoor air drawn into the air conditioning unit 11a before it passes through the heat exchanger 112.

[0027] The ground heat exchanger 13 is buried in the soil 2 and connected to the heat transfer medium circuit 10 by inlets and outlets 131 and 132. The inlet and outlet 131 of the ground heat exchanger 13 is connected to the air heat source unit 14 via port c of the four-way valve 19, and the inlet and outlet 132 of the ground heat exchanger 13 is connected to the air heat source unit 14 via port a of the four-way valve 19. Therefore, when the three-way valves 18a and 18b are in the switched state β, the air heat source unit 14 is connected in series with the parallel-connected air conditioning units 11a and 11b in the direction in which the heat transfer medium 12 flows into port b, regardless of whether it is the first cycle CL1 or the second cycle CL2.

[0028] The air heat source unit 14 operates together with the ground heat exchanger 13 to heat or cool the heat transfer medium 12. During periods when the air conditioning units 11a and 11b are operating in heating mode (for example, in winter), the air heat source unit 14 performs an operation to heat the heat transfer medium 12 circulating in the heat transfer medium circuit 10. Furthermore, during periods when the air conditioning units 11a and 11b are operating in cooling mode (for example, in summer), the air heat source unit 14 performs an operation to cool the heat transfer medium 12.

[0029] In other words, when the air conditioning units 11a and 11b are operating in heating mode, the air heat source unit 14 absorbs heat from the outside air to heat the heat transfer medium 12. Conversely, when the air conditioning units 11a and 11b are operating in cooling mode, the air heat source unit 14 releases heat to the outside air to cool the heat transfer medium 12.

[0030] The air heat source unit 14 includes heat exchangers 141 and 142, a compressor 143, a four-way valve 144, an expansion valve 145, and an outside temperature sensor 146. The four-way valve 144 is located on the discharge side of the compressor 143. An accumulator may be located on the suction side of the compressor 143. The air heat source unit 14 also includes a blower (not shown) for supplying outside air to the heat exchanger 142, and a drive motor (not shown) for driving the blower.

[0031] The heat exchanger 141 is, for example, a plate-type heat exchanger and has a heat transfer medium channel 141a connected to the heat transfer medium circuit 10 and a refrigerant channel 141b through which the refrigerant used for heat exchange in the air heat source unit 14 flows. Therefore, in the heat exchanger 141, heat is exchanged between the heat transfer medium 12 flowing from the heat transfer medium circuit 10 into the heat transfer medium channel 141a and the refrigerant flowing through the refrigerant channel 141b.

[0032] As shown in Figure 1, the control device 15A has a storage unit 151 and a soil condition acquisition unit 152. The control device 15A is, for example, a computer and is composed of, for example, one or more central processing units (CPUs) or microprocessing units (MPUs). A part of the control device 15A functions as a functional element or functional unit. The control device 15A executes a program for air conditioning control stored in the storage unit 151 as one of the computer programs, so that the part that functions as a functional element or functional unit functions as the soil condition acquisition unit 152.

[0033] The soil condition acquisition unit 152 acquires the state of the soil 2 that exchanges heat with the heat transfer medium 12 in the geothermal heat exchanger 13. The control device 15A controls the four-way valve 19 to enter the first cycle CL1 if the state of the soil 2 acquired by the soil condition acquisition unit 152 is heat depleted, and controls the four-way valve 19 to enter the second cycle CL2 if the state of the soil 2 acquired by the soil condition acquisition unit 152 is not heat depleted.

[0034] Here, "thermal depletion" refers to a state where the soil temperature is such that the operating efficiency (Coefficient of Performance: COP) of the heat pump is lower than that of a heat pump using only an air heat source. In other words, in the refrigeration cycle device 1A, the soil 2 is presumed to be in a state of thermal depletion when the temperature reaches a point where the COP of the heat pump using only the ground heat exchanger 13 is lower than that of the heat pump using only the air heat source unit 14.

[0035] For example, when heating operation is being performed in the air conditioning units 11a and 11b, if the temperature of the heat transfer medium 12 flowing out from the ground heat exchanger 13 is below a predetermined threshold (for example, a value corresponding to the outside temperature detected by the outside temperature sensor 146), it may be determined that the soil 2 is in a state of heat depletion. Alternatively, if the continuous heating operation time in the air conditioning units 11a and 11b is above a predetermined threshold, it may be determined that the soil 2 is in a state of heat depletion. This time threshold may be obtained in advance through testing, or it may be obtained based on past operating data. The obtained threshold is stored, for example, in the storage unit 151.

[0036] The temperature sensor 16a is positioned near the inlet / outlet 131 of the underground heat exchanger 13. The temperature sensor 16a detects the temperature of the heat transfer medium 12 flowing from the heat transfer medium circuit 10 into the underground heat exchanger 13 and the temperature of the heat transfer medium 12 flowing out of the underground heat exchanger 13 into the heat transfer medium circuit 10. The temperature sensor 16a transmits the detected temperature values ​​to the control device 15A.

[0037] The temperature sensor 16b is positioned near the inlet / outlet 132 of the underground heat exchanger 13. The temperature sensor 16b detects the temperature of the heat transfer medium 12 flowing from the underground heat exchanger 13 into the heat transfer medium circuit 10. The temperature sensor 16b transmits the detected temperature information (temperature value) to the control device 15A.

[0038] 1-2. Operation of the Refrigeration Cycle System: The operation of the refrigeration cycle system 1A according to this embodiment will be explained with reference to Figure 1 and using Figure 2. Figure 2 is a flowchart showing an example of the operation flow of the refrigeration cycle system 1A. The operation of the refrigeration cycle system 1A shown in Figure 2 is controlled by the control device 15A.

[0039] In the refrigeration cycle device 1A (see Figure 1), the control device 15A controls the four-way valve 19 so that the flow state of the heat transfer medium 12 becomes the second cycle CL2, and after setting the state of the three-way valves 18a and 18b to the switching state α, it operates the circulation pump 17 to start the operation of the refrigeration cycle device 1A. As shown in Figure 2, when the control device 15A starts the operation of the refrigeration cycle device 1A, first in step ST10 it determines whether or not the operation of the air conditioning units 11a and 11b (see Figure 1) has started. If the control device 15A determines that at least one of the air conditioning units 11a and 11b has started operation (Yes in step ST10), it proceeds to the process of step ST20. On the other hand, if the control device 15A determines that neither of the air conditioning units 11a and 11b has started operation (No in step ST10), it repeats the process of step ST10. The control device 15A repeatedly executes the process of step ST10 at predetermined time intervals unless it proceeds to the process of step ST11.

[0040] For example, when air conditioning units 11a and 11b perform cooling operation, the refrigerant, which has been compressed to high temperature and pressure by the compressor 113 (see Figure 1), flows through the refrigerant flow path 111b (see Figure 1) of the heat exchanger 111 via the four-way valve 114 (see Figure 1). In air conditioning unit 11a, the high temperature and pressure refrigerant flowing through the refrigerant flow path 111b dissipates heat by exchanging heat with the heat transfer medium 12 (see Figure 1) flowing through the heat transfer medium flow path 111a (see Figure 1) of the heat exchanger 111. On the other hand, in air conditioning unit 11b, the high temperature and pressure refrigerant flowing through the heat exchanger 111 dissipates heat by exchanging heat with the heat transfer medium 12 (see Figure 1) flowing through the heat transfer medium flow path 111a.

[0041] The refrigerant that has dissipated heat by passing through the heat exchanger 111 is depressurized by the expansion valve 115 (see Figure 1). The depressurized refrigerant then flows through the heat exchanger 112. The heat exchanger 112 functions as an evaporator, and the refrigerant flowing through the heat exchanger 112 exchanges heat with the room air blown by a fan (not shown) and absorbs heat. The room air that has absorbed heat from the refrigerant flowing through the heat exchanger 112 is cooled. The heat-absorbing refrigerant returns to the compressor 113 and is compressed again to high temperature and high pressure. In other words, the air conditioning units 11a and 11b are configured with a refrigerant circuit in which, in cooling operation, the refrigerant flows in the following order: compressor 113, four-way valve 114, heat exchanger 111 (which functions as a condenser), expansion valve 115, heat exchanger 112 (which functions as an evaporator), and compressor 113.

[0042] When the air conditioning units 11a and 11b perform heating operation, the refrigerant flows in the opposite direction to the cooling operation due to the four-way valve 114. During heating operation, the refrigerant, which has been compressed to high temperature and pressure by the compressor 113, flows through the heat exchanger 112 via the four-way valve 114. The heat exchanger 112 functions as a condenser, and the high temperature and pressure refrigerant flowing through the heat exchanger 112 releases heat by exchanging heat with the indoor air blown by the fan, and the indoor air that has exchanged heat with the high temperature and pressure refrigerant is warmed. The refrigerant that has released heat after passing through the heat exchanger 112 is depressurized by the expansion valve 115. The depressurized refrigerant flows through the refrigerant flow path 111b of the heat exchanger 111. In the air conditioning unit 11a, the refrigerant flowing through the refrigerant flow path 111b exchanges heat with the heat transfer medium 12 flowing through the heat transfer medium flow path 111a of the heat exchanger 111 and absorbs heat. Meanwhile, in the air conditioning unit 11b, the refrigerant flowing through the refrigerant channel 111b exchanges heat with the heat transfer medium 12 flowing through the heat transfer medium channel 111a of the heat exchanger 111, absorbing heat. The refrigerant that has absorbed heat returns to the compressor 113 and is compressed again to high temperature and high pressure.

[0043] Further, when the air heat source unit 14 operates to cool the heat medium 12 (that is, when the air conditioning units 11a and 11b perform a cooling operation), the refrigerant compressed by the compressor 143 (see FIG. 1) to become high-temperature and high-pressure flows through the heat exchanger 142 (see FIG. 1) via the four-way valve 144 (see FIG. 1). The heat exchanger 142 functions as a condenser, and the high-temperature and high-pressure refrigerant flowing through the heat exchanger 142 dissipates heat by exchanging heat with outside air blown by a blower (not shown). The refrigerant that has passed through the heat exchanger 142 and dissipated heat is decompressed by the expansion valve 145 (see FIG. 1). The decompressed refrigerant flows through the refrigerant channel 141b (see FIG. 1) of the heat exchanger 141. The refrigerant flowing through the refrigerant channel 141b exchanges heat with the heat medium 12 flowing through the heat medium channel 141a (see FIG. 1) of the heat exchanger 141 to absorb heat, thereby cooling the heat medium 12. The refrigerant that has absorbed heat returns to the compressor 143 and is compressed again to become high-temperature and high-pressure.

[0044] When heating the heat medium 12 (that is, when the air conditioning units 11a and 11b perform a heating operation), the refrigerant flows in the opposite direction to that when cooling the heat medium 12 by the four-way valve 144. The refrigerant compressed by the compressor 143 to become high-temperature and high-pressure flows through the refrigerant channel 141b of the heat exchanger 141 via the four-way valve 144. The high-temperature and high-pressure refrigerant flowing through the refrigerant channel 141b exchanges heat with the heat medium 12 flowing through the heat medium channel 141a of the heat exchanger 141 to dissipate heat, thereby heating the heat medium 12. The refrigerant that has passed through the heat exchanger 141 and dissipated heat is decompressed by the expansion valve 145. The decompressed refrigerant flows through the heat exchanger 142. The heat exchanger 142 functions as an evaporator, and the refrigerant flowing through the heat exchanger 142 exchanges heat with outside air blown by a blower to absorb heat. The refrigerant that has absorbed heat returns to the compressor 143 and is compressed again to become high-temperature and high-pressure.

[0045] In step ST20, the soil condition acquisition unit 152 (see Figure 1) provided in the control device 15A acquires the state of the soil 2 and proceeds to the processing in step ST30. To acquire the state of the soil 2, the soil condition acquisition unit 152 acquires, for example, temperature information output from temperature sensors 16a and 16b as the temperature of the heat transfer medium 12 at the inlets and outlets 131 and 132 of the ground heat exchanger 13. The temperature information acquired by the soil condition acquisition unit 152 is stored, for example, in the storage unit 151 (see Figure 1). As mentioned above, the soil condition acquisition unit 152 may also acquire the continuous heating time of the air conditioning units 11a and 11b in order to acquire the state of the soil 2.

[0046] In step ST30, the control device 15A determines whether the soil condition 2 acquired by the soil condition acquisition unit 152 is in a heat-depleted state. During heating operation, if the control device 15A determines that the temperature value acquired in step ST20, detected by one of the temperature sensors 16a and 16b, which is located near the inlet and outlet 131 and 132 of the underground heat exchanger 13 on the side where the heat transfer medium 12 flows out of the heat transfer medium circuit 10, is less than a predetermined heating threshold, then the control device 15A determines that the soil condition 2 is in a heat-depleted state (Yes in step ST30) and proceeds to the process in step ST40. On the other hand, if the control device 15A determines that the temperature value acquired in step ST20 is greater than or equal to a predetermined threshold, then the control device 15A determines that the soil condition 2 is not in a heat-depleted state (No in step ST30) and proceeds to the process in step ST70. Furthermore, during cooling operation, the control device 15A determines that the soil 2 is in a heat-depleted state if it determines that the temperature value obtained in step ST20 exceeds a predetermined cooling threshold. Alternatively, as described above, the control device 15A may also determine that the soil 2 is in a heat-depleted state if the continuous heating operation time of the air conditioning units 11a and 11b is greater than or equal to a predetermined threshold.

[0047] In step ST40, the control device 15A controls the four-way valve 19 such that the flow state of the heat medium 12 becomes the first cycle CL1 (see FIG. 1). Further, the control device 15A controls the three-way valves 18a and 18b to enter the switching state β, and the process proceeds to step ST50.

[0048] In step ST50, the control device 15A determines whether the air conditioning units 11a and 11b have finished operation. When the control device 15A determines that both the air conditioning units 11a and 11b have finished operation (Yes in step ST50), the process proceeds to step ST60. On the other hand, when the control device 15A determines that at least one of the air conditioning units 11a and 11b is in operation (No in step ST50), the process proceeds to step ST20.

[0049] In step ST60, after stopping the circulation pump 17, the control device 15A stops the refrigeration cycle apparatus 1A.

[0050] In step ST70, the control device 15A controls the four-way valve 19 such that the flow state of the heat medium 12 becomes the second cycle CL2. Further, the control device 15A controls the three-way valves 18a and 18b to enter the switching state α, and the process proceeds to step ST50.

[0051] As shown in the flow from step ST30 to step ST40 or step ST70, the control device 15A controls the four-way valve 19 to enter the first cycle CL1 if the soil condition acquisition unit 152 has acquired that the soil 2 is depleted by heat, and controls the four-way valve 19 to enter the second cycle CL2 if the soil condition acquisition unit 152 has acquired that the soil 2 is not depleted by heat. When the soil is depleted by heat, the refrigeration cycle device 1A circulates the heat transfer medium 12 in the first cycle CL1, allowing the heat transfer medium 12 heated by air heat as a heat source to be directly supplied to the ground heat exchanger 13. As a result, the refrigeration cycle device 1A can restore the temperature of the soil 2 and suppress the decrease in the amount of heat extracted from the soil 2. On the other hand, when the soil is not depleted by heat, the heat transfer medium 12 is circulated in the second cycle CL2, allowing the heat transfer medium 12 heated by air heat as a heat source to flow into the air conditioning units 11a and 11b. This allows for a reduction in the compression ratio of the air conditioning units 11a and 11b, thereby improving the operating efficiency of the refrigeration cycle device 1A.

[0052] As described above, the refrigeration cycle device 1A according to this embodiment comprises air conditioning units 11a and 11b, a heat transfer medium 12 supplied to the air conditioning units 11a and 11b, a geothermal heat exchanger 13 that exchanges heat between the heat transfer medium 12 and the soil 2, an air heat source unit 14 that exchanges heat between the heat transfer medium 12 and the outside air, a heat transfer medium circuit 10 through which the heat transfer medium 12 flows, a four-way valve 19 provided in the heat transfer medium circuit 10 to switch the flow of the heat transfer medium 12, and a control device 15A that controls the air conditioning units 11a and 11b, the air heat source unit 14, and the four-way valve 19. When the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of air heat source unit 14, ground heat exchanger 13, and air conditioning unit 11a is defined as the first cycle CL1, and when the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of ground heat exchanger 13, air heat source unit 14, and air conditioning unit 11a is defined as the second cycle CL2, the control device 15A controls the four-way valve 19 to switch the flow state of the heat transfer medium 12 from one of the first cycle CL1 and the second cycle CL2 to the other.

[0053] By having such a configuration, the refrigeration cycle device 1A can suppress a decrease in the amount of heat extracted from the ground while suppressing a decrease in operating efficiency in a heat pump that uses geothermal and air heat as heat sources.

[0054] [Second Embodiment] A refrigeration cycle device according to a second embodiment of the present invention will be described with reference to Figures 3 and 4.

[0055] 2-1. Configuration of the Refrigeration Cycle System: The configuration of the refrigeration cycle system according to this embodiment will be explained with reference to Figure 3. The refrigeration cycle system according to this embodiment has the same configuration as the refrigeration cycle system 1A according to the first embodiment, except that the configuration of the control device is different. For this reason, with respect to the refrigeration cycle system according to this embodiment, the same functions and operations as those of the refrigeration cycle system 1A according to the first embodiment will be given to the same reference numerals, and their explanation will be omitted. Figure 3 is a refrigerant circuit diagram showing an example of the schematic configuration of the refrigeration cycle system according to this embodiment.

[0056] As shown in Figure 3, the refrigeration cycle device 1B according to this embodiment includes a control device 15B that controls the air conditioning units 11a, 11b, the air heat source unit 14, and the four-way valve 19 (an example of a flow path switching unit). The control device 15B has a storage unit 151 and a requested capacity acquisition unit 153. The control device 15B is, for example, a computer and is composed of, for example, one or more CPUs or MPUs. A part of the control device 15B functions as a functional element or functional unit. The control device 15B executes an air conditioning control program stored in the storage unit 151 as one of the computer programs, so that the part that functions as a functional element or functional unit functions as the requested capacity acquisition unit 153.

[0057] The required capacity acquisition unit 153 acquires the magnitude of the required capacity, which is the capacity required for the air conditioning units 11a and 11b to perform the desired air conditioning operation. The control device 15B controls the four-way valve 19 to enter the first cycle CL1 if the magnitude of the required capacity is less than a predetermined required capacity threshold (an example of a first threshold), and controls the four-way valve 19 to enter the second cycle CL2 if the magnitude of the required capacity is equal to or greater than the required capacity threshold.

[0058] Here, the required capacity of the air conditioning unit (hereinafter sometimes referred to as "indoor required capacity") is the absolute value of the difference between the room temperature in the room where the air conditioning unit is installed and the set temperature set for the air conditioning unit during air conditioning operation, and is a value corresponding to the indoor air conditioning load. The required underground capacity, which is the capacity required of the ground heat exchanger for air conditioning operation by the air conditioning unit, is determined based on the indoor required capacity of each air conditioning unit. Specifically, the required underground capacity is set to a value higher than the indoor required capacity, taking into account the heat loss in the heat transfer medium circuit 10 and the air conditioning units 11a and 11b. If the required underground capacity of the ground heat exchanger exceeds the underground capacity design value (e.g., 4 kW), which is the required underground capacity determined during the design of the ground heat exchanger, the soil is prone to heat depletion. The upper limit of the total indoor required capacity of the air conditioning units when the required underground capacity of the ground heat exchanger does not exceed the underground capacity design value of the ground heat exchanger is set as the required capacity threshold.

[0059] For example, the design value for underground capacity is estimated from the apparent effective thermal conductivity [W / (m·K)] obtained in a soil thermal response test (TRT) conducted before the installation of the underground heat exchanger. The amount of heat exchanged per unit length is calculated using the apparent effective thermal conductivity [W / (m·K)], and the amount of heat exchanged over a predetermined length of underground heat exchanger is set as the design value for underground capacity (see Figure 1 on page 2 of "Technical Manual for Constant Heating and Hot Water Circulation Thermal Response Test (TRT) | Geothermal Energy Utilization Promotion Association (https: / / www.geohpaj.org / project / document / document01) "Technical Manual for Constant Heating and Hot Water Circulation Thermal Response Test (TRT) August 2018 Edition (PDF file)").

[0060] Since the refrigeration cycle device 1B is equipped with air conditioning units 11a and 11b, the required capacity is the sum of the required capacity of air conditioning unit 11a and the required capacity of air conditioning unit 11b. When the required capacity of air conditioning units 11a and 11b is high, the compression ratio of air conditioning units 11a and 11b can be reduced by circulating the heat transfer medium 12 in the second cycle CL2, thereby improving the operating efficiency of the refrigeration cycle device 1B.

[0061] 2-2. Operation of the Refrigeration Cycle System: The operation of the refrigeration cycle system 1B according to this embodiment will be explained with reference to Figure 3 and using Figure 4. Figure 4 is a flowchart showing an example of the operation flow of the refrigeration cycle system 1B. The operation of the refrigeration cycle system 1B shown in Figure 4 is controlled by the control device 15B. Regarding the operation of the refrigeration cycle system 1B in this embodiment, processes that are the same as those in the operation of the refrigeration cycle system 1A according to the first embodiment described above will be given the same step numbers and their explanations will be omitted.

[0062] In the refrigeration cycle device 1B (see Figure 3), the control device 15B controls the four-way valve 19 so that the flow state of the heat transfer medium 12 becomes the second cycle CL2, and after setting the state of the three-way valves 18a and 18b to the switching state α, it operates the circulation pump 17 to start the operation of the refrigeration cycle device 1B. The processing of the first step ST10 after the operation of the refrigeration cycle device 1B has started is the same as the processing of step ST10 of the operation of the refrigeration cycle device 1A according to the first embodiment described above, so the explanation is omitted.

[0063] In the next step ST21 following step ST10, the request capacity acquisition unit 153 (see Figure 3) provided in the control device 15B acquires the request capacity of each of the air conditioning units 11a and 11b and proceeds to the processing of step ST31. In order to calculate the request capacity of the air conditioning units 11a and 11b, the request capacity acquisition unit 153 acquires, for example, the temperature information output from the respective room temperature sensors 116 of the air conditioning units 11a and 11b, and the set temperatures set for the air conditioning units 11a and 11b. For each of the air conditioning units 11a and 11b, the request capacity acquisition unit 153 calculates the request capacity by subtracting the set temperature from the acquired temperature. The request capacity acquisition unit 153 acquires the sum of the request capacity of air conditioning unit 11a and the request capacity of air conditioning unit 11b as the total request capacity of air conditioning units 11a and 11b and stores it in the storage unit 151.

[0064] In step ST31, the control device 15B compares the magnitude of the requested capability acquired by the requested capability acquisition unit 153 with the threshold value for the requested capability pre-stored in the storage unit 151. If the control device 15B determines that the magnitude of the requested capability is less than the threshold value for the requested capability (Yes in step ST31), it proceeds to the process in step ST40. On the other hand, if the control device 15B determines that the magnitude of the requested capability is greater than or equal to the threshold value for the requested capability (No in step ST31), it proceeds to the process in step ST70.

[0065] The processes in steps ST50, ST60, and ST70 are the same as those in the operation of the refrigeration cycle device 1A according to the first embodiment described above, so their explanation is omitted. If, in step ST50, it is determined that at least one of the air conditioning units 11a and 11b has not finished operation (No. in step ST50), the process proceeds to step ST21.

[0066] As shown in the flow from step ST31 to step ST40 or step ST70, the control device 15B controls the four-way valve 19 to enter the first cycle CL1 if the magnitude of the required capacity acquired by the required capacity acquisition unit 153 is less than a predetermined threshold for required capacity (Yes in step ST31), and controls the four-way valve 19 to enter the second cycle CL2 if the required capacity acquired by the required capacity acquisition unit 153 is equal to or greater than the threshold for required capacity (No in step ST31). In this way, the refrigeration cycle device 1B can reduce the compression ratio of the air conditioning units 11a and 11b by circulating the heat transfer medium 12 in the heat transfer medium circuit 10 in the second cycle CL2 when the required capacity of the air conditioning units 11a and 11b is high. As a result, the refrigeration cycle device 1B can improve its operating efficiency.

[0067] As described above, the refrigeration cycle device 1B according to this embodiment comprises air conditioning units 11a and 11b, a heat transfer medium 12 supplied to the air conditioning units 11a and 11b, a geothermal heat exchanger 13 that exchanges heat between the heat transfer medium 12 and the soil 2, an air heat source unit 14 that exchanges heat between the heat transfer medium 12 and the outside air, a heat transfer medium circuit 10 through which the heat transfer medium 12 flows, a four-way valve 19 provided in the heat transfer medium circuit 10 to switch the flow of the heat transfer medium 12, and a control device 15B that controls the air conditioning units 11a and 11b, the air heat source unit 14, and the four-way valve 19. When the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of air heat source unit 14, ground heat exchanger 13, and air conditioning unit 11a is defined as the first cycle CL1, and when the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of ground heat exchanger 13, air heat source unit 14, and air conditioning unit 11a is defined as the second cycle CL2, the control device 15B controls the four-way valve 19 to switch the flow state of the heat transfer medium 12 from one of the first cycle CL1 and the second cycle CL2 to the other.

[0068] By having such a configuration, the refrigeration cycle device 1B can suppress a decrease in the amount of heat extracted from the ground while suppressing a decrease in operating efficiency in a heat pump that uses geothermal and air heat as heat sources.

[0069] [Third Embodiment] A refrigeration cycle device according to the third embodiment of the present invention will be described with reference to Figures 5 to 10.

[0070] 3-1. Configuration of the Refrigeration Cycle System: The configuration of the refrigeration cycle system according to this embodiment will be explained with reference to Figure 5. The refrigeration cycle system according to this embodiment has the same configuration as the refrigeration cycle system 1A according to the first embodiment, except that the configuration of the control device is different. For this reason, with respect to the refrigeration cycle system according to this embodiment, the same functions and operations as those of the refrigeration cycle system 1A according to the first embodiment will be given to the same components, and their descriptions will be omitted. Figure 5 is a refrigerant circuit diagram showing an example of the schematic configuration of the refrigeration cycle system according to this embodiment.

[0071] As shown in Figure 5, the refrigeration cycle device 1C according to this embodiment includes a control device 15C that controls the air conditioning units 11a, 11b, the air heat source unit 14, and the four-way valve 19 (an example of a flow path switching unit). The control device 15C has a storage unit 151 and a temperature unevenness acquisition unit 154. The control device 15C is, for example, a computer and is composed of, for example, one or more CPUs or MPUs. A part of the control device 15C functions as a functional element or functional unit. The control device 15C executes an air conditioning control program stored in the storage unit 151 as one of the computer programs, so that the part that functions as a functional element or functional unit functions as the temperature unevenness acquisition unit 154.

[0072] The temperature unevenness acquisition unit 154 acquires the magnitude of temperature unevenness in the geothermal heat exchanger 13. If the magnitude of temperature unevenness acquired by the temperature unevenness acquisition unit 154 is greater than or equal to a predetermined temperature unevenness threshold (an example of a second threshold), the four-way valve 19 is controlled to switch from one of the first cycle CL1 and the second cycle CL2 to the other. If there is temperature unevenness (temperature difference) between the inlet / outlet 131 and the inlet / outlet 132 of the geothermal heat exchanger 13, the amount of heat exchanged between the soil 2 and the heat transfer medium 12 will decrease. Therefore, if the magnitude of temperature unevenness occurring in the geothermal heat exchanger 13 exceeds the temperature unevenness threshold, the refrigeration cycle device 1C can suppress the decrease in the amount of heat exchanged in the geothermal heat exchanger 13 by reversing the flow direction of the heat transfer medium 12.

[0073] Temperature unevenness is the difference between the soil temperature at one of the two inlets / outlets of the geothermal heat exchanger and the soil temperature at the other inlet / outlet. Here, the method for obtaining temperature unevenness will be explained using Figures 6 to 8. In this embodiment, the following method is used to obtain temperature unevenness.

[0074] In this acquisition method, temperature unevenness is acquired based on the temperature elements of the two inlets and outlets of the ground heat exchanger. Figure 6 is a schematic diagram showing an example of the soil temperature distribution near the ground heat exchanger. In Figure 6, "TC0" shows the soil temperature distribution before operation of the refrigeration cycle device, and "TC1" and "TC2" in Figure 6 show the soil temperature distribution when the refrigeration cycle device is operated continuously for a predetermined time without changing the direction of flow of the heat transfer medium. Temperature distribution TC2 shows the temperature distribution when the operation time of the refrigeration cycle device is longer than that of temperature distribution TC1. In Figure 6, "Inlet / Outlet A" and "Inlet / Outlet B" show the vicinity of the inlets and outlets of the heat transfer medium of the ground heat exchanger (corresponding to inlets and outlets 131 and 132 of the ground heat exchanger 13). In the diagram in Figure 6, the horizontal axis shows the position of the soil along the ground heat exchanger, and the vertical axis shows the temperature.

[0075] In this acquisition method, the ratio of the temperature difference in the soil near the inlet / outlet A of the geothermal heat exchanger before and after operation of the refrigeration cycle system to the temperature difference in the soil near the inlet / outlet B of the geothermal heat exchanger before and after operation is acquired as the magnitude of temperature unevenness. The acquired ratio of temperature differences is compared with a threshold temperature difference ratio set as a threshold for temperature unevenness to determine the magnitude of temperature unevenness occurring in the geothermal heat exchanger.

[0076] As shown in Figure 6, in temperature distribution TC1, the ratio W2 / W1 of the temperature difference W1 at inlet / outlet A and the temperature difference W2 at inlet / outlet B, compared to the temperature distribution TC0 before operation of the refrigeration cycle, represents the magnitude of temperature unevenness. Similarly, in temperature distribution TC2, the ratio W4 / W3 of the temperature difference W3 at inlet / outlet A and the temperature difference W4 at inlet / outlet B, compared to the temperature distribution TC0 before operation of the refrigeration cycle, represents the magnitude of temperature unevenness.

[0077] Figure 7 schematically shows an example of the soil temperature distribution along a geothermal heat exchanger when the refrigeration cycle system is in continuous operation. Figure 7 illustrates the temperature distribution when the direction of flow of the heat transfer medium is not changed. Figure 8 is a graph showing an example of the temporal change in the ratio of the temperature difference at each of the two inlets and outlets of the geothermal heat exchanger. Figure 9 schematically shows an example of the soil temperature distribution along a geothermal heat exchanger when the refrigeration cycle system is in continuous operation. Figure 9 illustrates the temperature distribution when the direction of flow of the heat transfer medium is changed.

[0078] In Figures 7 and 9, "TC0," "TC1," "TC2," "Inlet / Outlet A," and "Inlet / Outlet B" represent the same content as "TC0," "TC1," "TC2," "Inlet / Outlet A," and "Inlet / Outlet B" in Figure 6. In Figure 9, "TC3" shows the soil temperature distribution when the heat transfer medium flows through the geothermal heat exchanger in the opposite direction to the case of temperature distribution TC1. In Figures 7 and 9, the horizontal axis shows the position of the soil along the geothermal heat exchanger, and the vertical axis shows the temperature. In Figure 8, "Inlet / Outlet A" and "Inlet / Outlet B" represent the same content as "Inlet / Outlet A" and "Inlet / Outlet B" in Figure 6. In Figure 8, "W1" shows the temperature difference before and after operation of the refrigeration cycle at Inlet / Outlet A, and "W2" shows the temperature difference before and after operation of the refrigeration cycle at Inlet / Outlet B. In the graph shown in Figure 8, the horizontal axis represents time, and the vertical axis represents the ratio of temperature differences W1 and W2.

[0079] In Figures 7 and 9, temperature distribution TC1 represents the soil temperature distribution when the refrigeration cycle device is operated continuously for, for example, 3 hours, while temperature distribution TC2 in Figure 7 and temperature distribution TC3 in Figure 9 represent the soil temperature distribution when the refrigeration cycle device is operated continuously for, for example, 6 hours. Furthermore, the ratio of the soil temperature difference near inlets A and B obtained from temperature distribution TC1 is above the threshold temperature, indicating that temperature unevenness has occurred in the soil to the extent that it is necessary to change the direction of flow of the heat transfer medium.

[0080] When a refrigeration cycle system operates in heating mode, the heat transfer medium absorbs heat from the soil. Therefore, if the heat transfer medium continues to flow from inlet / outlet A to inlet / outlet B, as shown in the temperature distributions TC0, TC1, and TC2 in Figure 7, the soil temperature near inlet / outlet A will be lower than that near inlet / outlet B, and the temperature difference between the soil near inlet / outlet A and B will be larger. In this way, if the direction in which the heat transfer medium flows into the geothermal heat exchanger is not changed, the temperature unevenness in the soil will continue to increase, and the amount of heat exchanged in the geothermal heat exchanger will decrease.

[0081] As shown in Figure 8, at the start of operation of the refrigeration cycle system, there is no difference between the temperature difference W1 and the temperature difference W2, so the ratio (W2 / W1) = 1.0. When heating operation continues, the heat transfer medium, which has absorbed heat from the refrigerant in the heat exchanger that functions as the evaporator of the air conditioning unit and is now colder than the soil temperature, flows into the geothermal heat exchanger. As the heat transfer medium passes through the geothermal heat exchanger, it absorbs heat from the soil, so its temperature rises from inlet / outlet A to inlet / outlet B. That is, the temperature difference between the temperature of the heat transfer medium and the soil temperature is greater on the inlet / outlet A side than on the inlet / outlet B side. Therefore, the ratio (W2 / W1) gradually increases. If heating operation continues further, the soil temperature on the inlet / outlet A side decreases, and the temperature difference with the heat transfer medium becomes smaller. Therefore, the heat transfer medium passes through the inlet / outlet B side without its temperature rising much after flowing into the geothermal heat exchanger. At this time, the amount of temperature decrease per unit time is greater on the inlet / outlet B side than on the inlet / outlet A side. As a result, the slope θ of the change in the ratio (W2 / W1) changes from positive to negative at the timing indicated by the vertical dashed line in Figure 8.

[0082] A negative slope θ in the change of the ratio W2 / W1 indicates that sufficient heat exchange is not occurring between the heat transfer medium and the soil on the inlet / outlet A side, and that the entire geothermal heat exchanger is not being utilized effectively. Therefore, if the change in the ratio W2 / W1 falls below a predetermined threshold change (e.g., 0), it is determined that there is significant temperature unevenness.

[0083] If the direction of the heat transfer medium flowing to the ground heat exchanger is changed based on the change in the ratio W2 / W1, and it is determined that the temperature unevenness is large, then, as shown in the temperature distribution TC3 in Figure 9, even if the refrigeration cycle system is operated continuously for, for example, 6 hours, the ratio of the temperature difference of the soil near each of the inlet / outlet A and B will be approximately the same as the ratio of the temperature difference when the refrigeration cycle system is operated continuously for, for example, 3 hours (see temperature distribution TC2 shown in Figure 9). This suppresses the decrease in the amount of heat exchanged in the ground heat exchanger. When the refrigeration cycle system is performing cooling operation, the ratio of the temperature difference W1 at inlet / outlet A to the temperature difference W2 at inlet / outlet B when the heat transfer medium continues to flow from inlet / outlet A to inlet / outlet B is defined as W1 / W2.

[0084] 3-2. Operation of the Refrigeration Cycle System: The operation of the refrigeration cycle system 1C according to this embodiment will be explained using Figure 10 with reference to Figure 5. Figure 10 is a flowchart showing an example of the operation flow of the refrigeration cycle system 1C. The operation of the refrigeration cycle system 1C shown in Figure 10 is controlled by the control device 15C. Regarding the operation of the refrigeration cycle system 1C in this embodiment, processes that are the same as those in the operation of the refrigeration cycle system 1A according to the first embodiment described above will be given the same step numbers and their explanations will be omitted.

[0085] In the refrigeration cycle device 1C (see Figure 5), the control device 15C controls the four-way valve 19 so that the flow state of the heat transfer medium 12 becomes the second cycle CL2, and after setting the state of the three-way valves 18a and 18b to the switching state α, it operates the circulation pump 17 to start the operation of the refrigeration cycle device 1C. The processing of the first step ST10 after the operation of the refrigeration cycle device 1C has started is the same as the processing of step ST10 of the operation of the refrigeration cycle device 1A according to the first embodiment described above, so the explanation is omitted.

[0086] In the next step ST22 following step ST10, the temperature unevenness acquisition unit 154 (see Figure 5) provided in the control device 15C acquires the temperature unevenness in the soil 2 and proceeds to the processing in step ST32. The temperature unevenness acquisition unit 154 acquires the temperature unevenness using the method of acquiring temperature unevenness described with reference to Figure 6. When the temperature unevenness acquisition unit 154 acquires the temperature unevenness using the acquisition method described above, for example, it constantly detects the temperature information input from temperature sensors 16a and 16b as the temperature of the soil 2 near the inlets and outlets 131 and 132 of the geothermal heat exchanger 13. The temperature unevenness acquisition unit 154 uses the detected temperature to calculate the ratio of the temperature difference described above, and further calculates the amount of change in the ratio of the temperature difference per unit time. This amount of change in the ratio of the temperature difference is used as an indicator of temperature unevenness. The temperature unevenness acquisition unit 154 stores the acquired magnitude of temperature unevenness in the storage unit 151 (see Figure 5).

[0087] In step ST32, the control device 15C compares the magnitude of the temperature unevenness acquired by the temperature unevenness acquisition unit 154 with the temperature unevenness threshold (for example, the threshold change amount described above) that is stored in the storage unit 151 beforehand. If the control device 15C determines that the magnitude of the temperature unevenness is greater than or equal to the temperature unevenness threshold (Yes in step ST32), it proceeds to the process in step ST41. On the other hand, if the control device 15C determines that the magnitude of the temperature unevenness is less than the temperature unevenness threshold (No in step ST32), it proceeds to the process in step ST50.

[0088] In step ST41, the control device 15C switches the flow direction of the heat transfer medium 12 and proceeds to the process in step ST50. If the current flow state of the heat transfer medium 12 is the first cycle CL1 (see Figure 5), the control device 15C controls the four-way valve 19 to become the second cycle CL2 (see Figure 5). On the other hand, if the current flow state of the heat transfer medium 12 is the second cycle CL2, the control device 15C controls the four-way valve 19 to become the first cycle CL1.

[0089] The processes in steps ST50 and ST60 are the same as those in steps ST50 and ST60 in the operation of the refrigeration cycle device 1A according to the first embodiment described above, so their explanation will be omitted. If, in step ST50, it is determined that at least one of the air conditioning units 11a and 11b has not finished operation (Yes in step ST50), the process proceeds to step ST22.

[0090] As shown in the flow from step ST32 to step ST41, the control device 15C controls the four-way valve 19 to switch from one of the first cycle CL1 and the second cycle CL2 to the other if the magnitude of the temperature unevenness acquired by the temperature unevenness acquisition unit 154 is greater than or equal to a predetermined temperature unevenness threshold (Yes in step ST32). As a result, the refrigeration cycle device 1C can suppress the increase in temperature unevenness in the ground heat exchanger 13 and suppress the decrease in the amount of heat exchanged in the ground heat exchanger 13.

[0091] As described above, the refrigeration cycle device 1C according to this embodiment comprises air conditioning units 11a and 11b, a heat transfer medium 12 supplied to the air conditioning units 11a and 11b, a geothermal heat exchanger 13 that exchanges heat between the heat transfer medium 12 and the soil 2, an air heat source unit 14 that exchanges heat between the heat transfer medium 12 and the outside air, a heat transfer medium circuit 10 through which the heat transfer medium 12 flows, a four-way valve 19 provided in the heat transfer medium circuit 10 to switch the flow of the heat transfer medium 12, and a control device 15C that controls the air conditioning units 11a and 11b, the air heat source unit 14, and the four-way valve 19. When the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of air heat source unit 14, ground heat exchanger 13, and air conditioning unit 11a is defined as the first cycle CL1, and when the state in which the heat transfer medium 12 flows through the heat transfer medium circuit 10 in the order of ground heat exchanger 13, air heat source unit 14, and air conditioning unit 11a is defined as the second cycle CL2, the control device 15C controls the four-way valve 19 to switch the flow state of the heat transfer medium 12 from one of the first cycle CL1 and the second cycle CL2 to the other.

[0092] By having such a configuration, the refrigeration cycle device 1C can suppress a decrease in the amount of heat extracted from the ground while suppressing a decrease in operating efficiency in a heat pump that uses geothermal and air heat as heat sources.

[0093] 1A, 1B, 1C Refrigeration cycle device 2 Soil 10 Heat transfer fluid circuit 11a, 11b Air conditioning unit 12 Heat transfer fluid 13 Geothermal heat exchanger 14 Air heat source unit 15A, 15B, 15C Control device 16a, 16b Temperature sensor 17 Circulation pump 18a, 18b Three-way valve 19, 114, 144 Four-way valve 111, 112, 141, 142 Heat exchanger 111a, 141a Heat transfer fluid flow path 111b, 141b Refrigerant flow path 113, 143 Compressor 115, 145 Expansion valve 116 Room temperature sensor 131, 132 Inlet / Outlet 146 Outdoor temperature sensor 151 Memory unit 152 Soil condition acquisition unit 153 Required capacity acquisition unit 154 Temperature unevenness acquisition unit

Claims

1. A refrigeration cycle device comprising: an air conditioning unit; a heat transfer medium supplied to the air conditioning unit; a geothermal heat exchanger for exchanging heat between the heat transfer medium and soil; an air heat source unit for exchanging heat between the heat transfer medium and outside air; a heat transfer medium circuit through which the heat transfer medium flows; a flow path switching unit provided in the heat transfer medium circuit for switching the flow of the heat transfer medium; and a control device for controlling the air conditioning unit, the air heat source unit, and the flow path switching unit, wherein the state in which the heat transfer medium flows through the heat transfer medium circuit in the order of the air heat source unit, the geothermal heat exchanger, and the air conditioning unit is defined as the first cycle, and the state in which the heat transfer medium flows through the heat transfer medium circuit in the order of the geothermal heat exchanger, the air heat source unit, and the air conditioning unit is defined as the second cycle, the control device controls the flow path switching unit to switch the flow state of the heat transfer medium from one of the first cycle and the second cycle to the other.

2. The refrigeration cycle apparatus according to claim 1, wherein the control device has a soil condition acquisition unit that acquires the state of the soil that exchanges heat with the heat medium in the ground heat exchanger, and controls the flow path switching unit to enter the first cycle when the state of the soil acquired by the soil condition acquisition unit is heat depleted, and controls the flow path switching unit to enter the second cycle when the state of the soil acquired by the soil condition acquisition unit is not heat depleted.

3. The refrigeration cycle apparatus according to claim 1, wherein the control device has a required capacity acquisition unit that acquires the magnitude of the required capacity, which is the capacity required of the air conditioning unit to perform the desired air conditioning operation, and controls the flow path switching unit to perform the first cycle when the magnitude of the required capacity is less than a predetermined first threshold, and controls the flow path switching unit to perform the second cycle when the magnitude of the required capacity is equal to or greater than the first threshold.

4. The refrigeration cycle apparatus according to claim 1, wherein the control device has a temperature unevenness acquisition unit that acquires the magnitude of temperature unevenness in the ground heat exchanger, and when the magnitude of the temperature unevenness acquired by the temperature unevenness acquisition unit is equal to or greater than a predetermined second threshold, the control device controls the flow path switching unit to switch from one of the first cycle and the second cycle to the other.

5. The refrigeration cycle apparatus according to any one of claims 1 to 4, comprising a plurality of the air conditioning units, wherein each of the plurality of air conditioning units is connected in parallel to the air heat source unit.

Images