Refrigeration cycle device

Abstract

To suppress a high pressure in a refrigerant circuit increasing suddenly caused by a liquid refrigerant accumulating in a water heat exchanger.SOLUTION: A refrigerant circuit (10) includes: a liquid flow passage (33) for connecting a liquid side end part of a water heat exchanger (14) and a liquid side end part of an air heat exchanger (12); a liquid draining flow passage (50) for connecting the liquid flow passage (33) and a suction side of a compressor (11); and opening / closing elements (43, 53) for opening / closing the liquid draining flow passage (50). When a first condition is established in which a high pressure in the refrigerant circuit (10) is larger than a predetermined value and a liquid refrigerant accumulates in the water heat exchanger (14), a controller (100) opens the opening / closing elements (43, 53).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a refrigeration cycle device. [Background technology]

[0002] The refrigeration cycle device disclosed in Patent Document 1 includes a refrigerant circuit having a compressor, an air heat exchanger, an expansion valve, and a plate-type water heat exchanger. During heating operation of the refrigeration cycle device, the refrigerant compressed by the compressor releases heat in the water heat exchanger, is decompressed by the expansion valve, and evaporates in the air heat exchanger. In the water heat exchanger, heat is exchanged between the water in the water flow path and the refrigerant in the refrigerant circuit. As a result, in the water heat exchanger, the refrigerant condenses and the water is heated. The water heated in the water heat exchanger is supplied to a predetermined target. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6873988 Summary of the Invention [Problem to be solved by the invention]

[0004] The internal volume of a plate-type water heat exchanger is smaller than that of an air heat exchanger. Therefore, if excess liquid refrigerant accumulates in the water heat exchanger, which functions as a radiator, the high-pressure will rise rapidly.

[0005] An object of the present disclosure is to suppress a sudden increase in the high-pressure in a refrigerant circuit caused by accumulation of liquid refrigerant in a water heat exchanger. [Means for solving the problem]

[0006] The first aspect relates to a refrigeration cycle apparatus (1). The refrigeration cycle apparatus (1) includes a refrigerant circuit (10) having a compressor (11), a plate-type water heat exchanger (14), an expansion element (13), and an air heat exchanger (12), in which the water heat exchanger (14) functions as a radiator and the air heat exchanger (12) functions as an evaporator, and a controller (100) for controlling the refrigerant circuit (10). The refrigerant circuit (10) includes a liquid flow path (33) connecting a liquid side end of the water heat exchanger (14) to a liquid side end of the air heat exchanger (12), a liquid discharge flow path (50) connecting the liquid flow path (33) to the suction side of the compressor (11), and opening / closing elements (43, 53) for opening and closing the liquid discharge flow path (50). The controller (100) opens the opening / closing elements (43, 53) when a first condition is met, which indicates that the high pressure in the refrigerant circuit (10) is greater than a predetermined value and liquid refrigerant is accumulating in the water heat exchanger (14).

[0007] In the first aspect, when a first condition is met, which indicates that the high-side pressure of the refrigerant circuit (10) is greater than a predetermined value and that liquid refrigerant is accumulating in the water heat exchanger (14), the controller (100) opens the open / close elements (43, 53) of the liquid drain passage (50). This causes the liquid refrigerant in the water heat exchanger (14) to be drawn into the compressor (11) through the liquid passage (33) and the liquid drain passage (50). This eliminates the accumulation of liquid in the water heat exchanger (14). By sending the liquid refrigerant in the water heat exchanger (14) to the suction side of the compressor (11), the internal pressure of the water heat exchanger (14) can be reduced, and the high-side pressure can also be reduced.

[0008] In the second aspect, in the first aspect, the first condition is that the high pressure of the refrigerant circuit (10) is greater than a predetermined value and the degree of subcooling of the refrigerant flowing out of the water heat exchanger (14) is greater than a predetermined value.

[0009] In the second aspect, accumulation of liquid refrigerant in the water heat exchanger (14) can be determined based on the degree of subcooling of the refrigerant on the outlet side of the water heat exchanger (14).

[0010] In a third aspect, in the first or second aspect, the refrigerant circuit (10) includes a first flow path (16a) through which a refrigerant from a liquid flow path (33) flows and a second flow path (16b) through which a refrigerant diverted from the liquid flow path (33) flows, a subcooling heat exchanger (16) that exchanges heat between the refrigerant from the first flow path (16a) and the refrigerant from the second flow path (16b), an injection flow path (40) branching from the liquid flow path (33) and connected to a compression chamber of the compressor (11) via the second flow path (16b), and an injection valve (43) that adjusts the flow rate of the refrigerant in the injection flow path (40). The injection flow path (40) includes an upstream injection flow path (41) upstream of the second flow path (16b) and a downstream injection flow path (42) downstream of the second flow path (16b). The liquid drainage flow path (50) includes an upstream liquid drainage flow path (51) that is connected to the liquid flow path (33) and is shared with the upstream injection flow path (41), and a downstream liquid drainage flow path (52) that branches off from the upstream injection flow path (41) and connects to the suction side of the compressor (11).

[0011] In the third aspect, the refrigerant in the first flow path (16a) can be cooled by the subcooling heat exchanger (16), and intermediate-pressure gas refrigerant can be introduced into the compression chamber of the compressor (11) through the injection flow path (40), thereby improving the COP of the refrigeration cycle.

[0012] The upstream liquid-draining flow path (51) of the liquid-draining flow path (50) is shared with a part of the injection flow path (40), specifically with the upstream injection flow path (41), thereby making it possible to shorten the refrigerant piping or reduce the number of refrigerant piping.

[0013] In a fourth aspect, the opening / closing elements (43, 53) include an injection valve (43) arranged in the upstream injection flow path (41) and a drain valve (53) arranged in the downstream drain flow path (52) and opening and closing the downstream drain flow path (52). When a first condition is met, the controller (100) opens the injection valve (43) and the drain valve (53).

[0014] In the fourth aspect, the injection valve (43) for performing the injection operation also serves as a valve for performing the liquid draining operation of the water heat exchanger (14).

[0015] In a fifth aspect, in the fourth aspect, when a first condition is met, the controller (100) adjusts the opening degree of the injection valve (43) based on the degree of subcooling of the refrigerant flowing out of the water heat exchanger (14).

[0016] In the fifth aspect, when the liquid refrigerant is removed from the water heat exchanger (14), it is possible to prevent a large amount of liquid refrigerant from being sent to the suction side of the compressor (11).

[0017] In a sixth aspect, in any one of the first to fifth aspects, the refrigerant circuit (10) has an accumulator (17) upstream of the compressor (11). An outlet end of the liquid drainage channel (50) is connected to the refrigerant circuit (10) between the accumulator (17) and the compressor (11).

[0018] In the sixth aspect, the liquid refrigerant from the water heat exchanger (14) is sent to the compressor (11) without passing through the accumulator (17), thereby cooling the compressor (11) with the liquid refrigerant. As a result, the degree of superheat of the refrigerant discharged from the compressor (11) can be prevented from becoming excessively high.

[0019] In a seventh aspect, in any one of the first to sixth aspects, the internal volume of the water heat exchanger (14) is smaller than the internal volume of the air heat exchanger (12).

[0020] In the seventh aspect, the internal volume of the water heat exchanger (14) is reduced, which makes it easier for liquid refrigerant to accumulate inside the water heat exchanger (14). This problem can be solved by draining the liquid refrigerant from the water heat exchanger (14) through the liquid drain passage (50).

[0021] An eighth aspect is any one of the first to seventh aspects, wherein the distance from the compressor (11) to the water heat exchanger (14) is 5 m or less.

[0022] In the eighth aspect, the distance between the compressor (11) and the water heat exchanger (14) is relatively short, and therefore the length of the pipe connecting them is also short, which makes it easier for the high-pressure to increase. This problem can be solved by draining the liquid refrigerant from the water heat exchanger (14) through the liquid drain passage (50). [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a piping diagram of a refrigeration cycle device according to an embodiment. [Figure 2] FIG. 2 is a block diagram of the controller and the main devices. [Figure 3] FIG. 3 is a flowchart of the liquid removal operation. [Figure 4] FIG. 4 is a view corresponding to FIG. 1 for explaining the liquid draining operation. [Figure 5] FIG. 5 is a view corresponding to FIG. 1 of a first example of another embodiment. [Figure 6] FIG. 6 is a view corresponding to FIG. 1 of a second example of another embodiment. [Figure 7] FIG. 7 is a view corresponding to FIG. 1 of a third example of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present disclosure. Since the drawings are intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary to facilitate understanding.

[0025] (1) Configuration of the refrigeration cycle device The refrigeration cycle apparatus (1) of the present disclosure constitutes a heat source unit of an air conditioner. The air conditioner provides air conditioning for offices, shopping malls, factories, etc. The refrigeration cycle apparatus (1) of this embodiment is a heat pump type chilling unit that performs cooling operation and heating operation.

[0026] As shown in FIG. 1, the refrigeration cycle apparatus (1) has a refrigerant circuit (10) and a water circuit (5). The refrigeration cycle apparatus (1) of this example has one refrigerant circuit (10). The refrigeration cycle apparatus (1) may have two or more refrigerant circuits (10). The refrigerant circuit (10) performs a vapor compression refrigeration cycle by circulating a refrigerant filled therein. The water circuit (5) is connected to the refrigerant circuit (10) via a water heat exchanger (14). The water circuit (5) is connected to a utilization unit (not shown) of an air conditioner.

[0027] (1-1) Basic configuration of the refrigerant circuit 1, the refrigerant circuit (10) includes, as its main components, a compressor (11), an air heat exchanger (12), an expansion element (13), and a water heat exchanger (14). The expansion element (13) of this embodiment includes a heat source side expansion valve (13a) and a user side expansion valve (13b). The refrigerant circuit (10) of this embodiment includes, as its secondary components, a four-way switching valve (15), a subcooling heat exchanger (16), and an accumulator (17).

[0028] The compressor (11) compresses the sucked low-pressure refrigerant. The compressor (11) discharges the compressed high-pressure refrigerant. The compressor (11) has a motor and a compression mechanism driven by the motor to compress the refrigerant. A discharge pipe (31) is connected to the discharge side of the compressor (11), and a suction pipe (32) is connected to the suction side of the compressor (11).

[0029] The air heat exchanger (12) is a heat source side heat exchanger that exchanges heat between the refrigerant and outdoor air. The air heat exchanger (12) is a fin-and-tube type heat exchanger. One end of a liquid flow path (33) is connected to a liquid side end of the air heat exchanger (12). The refrigeration cycle apparatus (1) has a fan (18) that transports air passing through the air heat exchanger (12). The fan (18) is a propeller fan. The refrigerant circuit (10) may have a plurality of air heat exchangers (12) connected in parallel to each other.

[0030] The water heat exchanger (14) is a plate-type heat exchanger. The water heat exchanger (14) has a refrigerant flow path (14a) and a water flow path (14b). The refrigerant flow path (14a) is connected to the refrigerant circuit (10), and the water flow path (14b) is connected to the water circuit (5). The water heat exchanger (14) exchanges heat between the refrigerant in the refrigerant flow path (14a) and the water in the water flow path (14b). The other end of the liquid flow path (33) is connected to the liquid side end of the refrigerant flow path (14a) of the water heat exchanger (14).

[0031] The internal volume V1 of the water heat exchanger (14) is smaller than the internal volume V2 of the air heat exchanger (12). Here, the internal volume means the total internal volume of the refrigerant pipes that constitute the heat exchanger. In other words, the internal volume is the total amount of refrigerant that can be held inside the heat exchanger.

[0032] The distance between the compressor (11) and the water heat exchanger (14) is 5 m or less, so the length of the pipe connecting the compressor (11) and the water heat exchanger (14) is relatively short.

[0033] The subcooling heat exchanger (16) has a first flow path (16a) and a second flow path (16b). The first flow path (16a) is connected to a middle portion of the liquid flow path (33). In other words, the liquid flow path (33) includes a first liquid pipe (33a) between the first flow path (16a) and the air heat exchanger (12) and a second liquid pipe (33b) between the first flow path (16a) and the water heat exchanger (14). The refrigerant of the liquid flow path (33) flows through the first flow path (16a). The refrigerant diverted from the liquid flow path (33) flows through the second flow path (16b). The subcooling heat exchanger (16) exchanges heat between the refrigerant of the first flow path (16a) and the refrigerant of the second flow path (16b).

[0034] The heat source side expansion valve (13a) is provided in the first liquid pipe (33a). The utilization side expansion valve (13b) is provided in the second liquid pipe (33b). The heat source side expansion valve (13a) and the utilization side expansion valve (13b) are electronic expansion valves whose opening degrees are variable.

[0035] The four-way selector valve (15) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port (P1) is connected to the discharge side of the compressor (11) via a discharge pipe (31). The second port (P2) is connected to the suction side of the compressor (11) via a suction pipe (32). The third port (P3) is connected to the gas side end of the air heat exchanger (12) via a refrigerant pipe. The fourth port (P4) is connected to the gas side end of the refrigerant channel (14a) of the water heat exchanger (14) via a refrigerant pipe.

[0036] The four-way switching valve (15) switches between a first state (a state shown by a solid line in FIG. 1) in which the first port (P1) and the third port (P3) communicate with each other and simultaneously the second port (P2) and the fourth port (P4) communicate with each other, and a second state (a state shown by a dashed line in FIG. 1) in which the first port (P1) and the fourth port (P4) communicate with each other and simultaneously the second port (P2) and the third port (P3) communicate with each other.

[0037] In a cooling operation of the refrigeration cycle device (1), the four-way selector valve (15) is in the first state, and the air heat exchanger (12) functions as a radiator and the water heat exchanger (14) functions as an evaporator, thereby performing a refrigeration cycle (first refrigeration cycle).In a heating operation of the refrigeration cycle device (1), the four-way selector valve (15) is in the second state, and the water heat exchanger (14) functions as a radiator and the air heat exchanger (12) functions as an evaporator, thereby performing a refrigeration cycle (second refrigeration cycle).

[0038] The accumulator (17) is connected to a suction pipe (32). The accumulator (17) is a sealed container that stores liquid refrigerant contained in a low-pressure refrigerant. The suction pipe (32) includes an upstream suction passage (32a) located upstream of the accumulator (17) and a downstream suction passage (32b) located downstream of the accumulator (17).

[0039] The refrigerant circuit (10) of this embodiment does not have a receiver for storing excess refrigerant, which allows the refrigeration cycle apparatus (1) to be made compact.

[0040] (1-2) Water circuit configuration The water circuit (5) is a flow path through which water circulates. The water circuit (5) includes an upstream water passage (5a) located upstream of the water flow path (14b) of the water heat exchanger (14) and a downstream water passage (5b) located downstream of the water flow path (14b) of the water heat exchanger (14). In this embodiment, a pump (6) is provided in the upstream water passage (5a). The pump (6) transports water from the water flow path (14b) and circulates the water circuit (5).

[0041] (1-3) Injection channel and drainage channel The refrigerant circuit (10) has an injection flow path (40) and a liquid drain flow path (50). The injection flow path (40) is a flow path for introducing intermediate-pressure refrigerant into the compression chamber of the compressor (11). The liquid drain flow path (50) is a flow path for draining liquid refrigerant accumulated in the water heat exchanger (14). The injection flow path (40) and the liquid drain flow path (50) share a portion with each other.

[0042] One end of the injection flow path (40) is connected to the liquid flow path (33) (more precisely, the second liquid pipe (33b)). The other end of the injection flow path (40) is connected to a compression chamber in the compression mechanism of the compressor (11). In other words, the injection flow path (40) is connected to the middle of the compression of the compressor (11).

[0043] The injection flow path (40) includes an upstream injection flow path (41) and a downstream injection flow path (42). One end of the upstream injection flow path (41) is connected to the liquid flow path (33), and the other end of the upstream injection flow path (41) is connected to the inlet end of the second flow path (16b). One end of the downstream injection flow path (42) is connected to the outlet end of the second flow path (16b), and the other end of the downstream injection flow path (42) is connected to a compression chamber of the compressor (11).

[0044] An injection valve (43) is provided in the upstream injection flow path (41). The injection valve (43) adjusts the flow rate of the refrigerant flowing through the injection flow path (40). The injection valve (43) is an electronic expansion valve with a variable opening. The injection flow path (40) constitutes an opening / closing element that opens and closes the liquid-draining flow path (50).

[0045] One end of the liquid-draining flow path (50) is connected to the liquid flow path (33) (more precisely, the second liquid pipe (33b)). The other end of the liquid-draining flow path (50) is connected to the suction pipe (32). More precisely, the other end of the liquid-draining flow path (50) is connected to the downstream suction path (32b), which is the flow path in the suction pipe (32) between the accumulator (17) and the compressor (11).

[0046] The liquid discharge flow path (50) includes an upstream liquid discharge flow path (51) and a downstream liquid discharge flow path (52). One end of the upstream liquid discharge flow path (51) is connected to the liquid flow path (33). The upstream liquid discharge flow path (51) is shared by the upstream injection flow path (41). In other words, the upstream portion of the upstream injection flow path (41) and the upstream liquid discharge flow path (51) are configured by the same piping. The downstream liquid discharge flow path (52) branches off from a midway point of the upstream injection flow path (41). One end of the downstream liquid discharge flow path (52) is connected to a midway point of the upstream injection flow path (41). The other end of the downstream liquid discharge flow path (52) is connected to the downstream suction path (32b).

[0047] The downstream liquid-draining flow path (52) is provided with a liquid-draining valve (53). The liquid-draining valve (53) constitutes an opening / closing element that opens and closes the liquid-draining flow path (50). The liquid-draining valve (53) is constituted by an electromagnetic opening / closing valve. The liquid-draining valve (53) may be a flow rate control valve whose opening degree is variable.

[0048] (2) Sensor The refrigeration cycle device (1) has a plurality of sensors, including a high-pressure sensor (61), a low-pressure sensor (62), a discharge temperature sensor (63), a suction temperature sensor (64), a first refrigerant temperature sensor (65), a second refrigerant temperature sensor (66), a third refrigerant temperature sensor (67), a high-pressure switch (68), and a water temperature sensor (7).

[0049] The high-pressure sensor (61) is provided in the discharge pipe (31). The high-pressure sensor (61) detects a high-pressure pressure (HP) of the refrigerant circuit (10), in other words, a discharge pressure of the compressor (11). The low-pressure sensor (62) is provided in the suction pipe (32). The low-pressure sensor (62) detects a low-pressure pressure (LP) of the refrigerant circuit (10), in other words, a suction pressure of the compressor (11).

[0050] The discharge temperature sensor (63) is provided in the discharge pipe (31). The discharge temperature sensor (63) detects a discharge temperature (Td), which is the temperature of the refrigerant on the discharge side of the compressor (11). The suction temperature sensor (64) is provided in the suction pipe (32). The suction temperature sensor (64) detects a suction temperature (Ts), which is the temperature of the refrigerant on the suction side of the compressor (11).

[0051] The first refrigerant temperature sensor (65) is provided in the second liquid pipe (33b). The second liquid pipe (33b) is used to determine the degree of subcooling (Sc) of the water heat exchanger (14) functioning as a radiator during the heating operation. The first refrigerant temperature sensor (65) detects the temperature of the refrigerant that has flowed out of the water heat exchanger (14) functioning as a radiator. The first refrigerant temperature sensor (65) is provided at the outlet of the water heat exchanger (14) functioning as a radiator.

[0052] The second refrigerant temperature sensor (66) is provided in the upstream injection flow path (41). The second refrigerant temperature sensor (66) detects the temperature of the refrigerant after passing through the injection valve (43) and before flowing into the second flow path (16b). The third refrigerant temperature sensor (67) is provided in the downstream injection flow path (42). The third refrigerant temperature sensor (67) detects the temperature of the refrigerant after flowing out of the second flow path (16b). The second refrigerant temperature sensor (66) and the third refrigerant temperature sensor (67) are used to determine the intermediate degree of superheat (M-SH), which is the degree of superheat of the gas refrigerant after passing through the second flow path (16b).

[0053] The high-pressure switch (68) is provided on the discharge pipe (31). When the high-pressure in the refrigerant circuit (10) reaches or exceeds a predetermined value, the high-pressure switch (68) is activated to forcibly terminate the operation of the refrigeration cycle apparatus (1).

[0054] The refrigeration cycle apparatus (1) includes a water temperature sensor (7). The water temperature sensor (7) is provided in the downstream water passage (5b) of the water circuit (5). The water temperature sensor (7) detects the temperature of the water flowing out of the water passage (14b) of the water heat exchanger (14).

[0055] (3) Controller As shown in Fig. 2, the refrigeration cycle apparatus (1) has a controller (100). The controller (100) includes an MCU (Micro Control Unit), an electric circuit, and an electronic circuit. The MCU includes a CPU (Central Processing Unit), a memory, and a communication interface. The memory stores various programs to be executed by the CPU.

[0056] The controller (100) controls the refrigeration cycle apparatus (1). Specifically, the controller (100) controls ON / OFF switching of the compressor (11), the rotation speed of the compressor (11), ON / OFF switching of the fan (18), the rotation speed of the fan (18), ON / OFF switching of the pump (6), the rotation speed of the pump (6), the aperture of the heat source side expansion valve (13a), the aperture of the utilization side expansion valve (13b), the aperture of the injection valve (43), and opening / closing of the liquid drain valve (53).

[0057] The controller (100) receives the detected values ​​of the above-mentioned sensors. The controller (100) calculates a predetermined index based on the received detected values ​​and controls the devices based on the detected values. The controller (100) controls the rotation speed of the compressor (11) so that the water temperature detected by the water temperature sensor (7) approaches a target temperature.

[0058] (4) Driving behavior The operation of the refrigeration cycle apparatus (1) will be described. The refrigeration cycle apparatus (1) performs a cooling operation and a heating operation as normal operations. In Fig. 1, the flow of refrigerant in the cooling operation is indicated by solid arrows, and the flow of refrigerant in the heating operation is indicated by dashed arrows.

[0059] (4-1) Cooling operation In the cooling operation, the controller (100) operates the compressor (11), the fan (18), and the pump (6), sets the four-way switching valve (15) to the first state, and appropriately adjusts the apertures of the heat-source-side expansion valve (13a) and the utilization-side expansion valve (13b). The controller (100) appropriately adjusts the aperture of the injection valve (43) and closes the liquid-drain valve (53).

[0060] The refrigerant compressed by the compressor (11) flows through the air heat exchanger (12). In the air heat exchanger (12), the refrigerant dissipates heat to the outdoor air and is condensed. The condensed high-pressure liquid refrigerant flows through the liquid flow path (33).

[0061] In the cooling operation, an injection operation is performed as needed. In the injection operation, the opening of the injection valve (43) is adjusted so that the intermediate degree of superheat (M-SH) approaches a target value. A part of the liquid refrigerant in the first liquid pipe (33a) of the liquid flow path (33) flows through the first flow path (16a) of the subcooling heat exchanger (16), and the rest flows through the upstream injection flow path (41). The liquid refrigerant in the upstream injection flow path (41) is reduced in pressure to an intermediate pressure when passing through the injection valve (43).

[0062] In the subcooling heat exchanger (16), high-pressure liquid refrigerant flowing through the first flow path (16a) exchanges heat with intermediate-pressure liquid refrigerant flowing through the second flow path (16b). As a result, the refrigerant in the second flow path (16b) evaporates, and the refrigerant in the first flow path (16a) is cooled.

[0063] The refrigerant cooled in the first flow path (16a) is decompressed to a low pressure when passing through the heat source side expansion valve (13a). The decompressed refrigerant flows through the refrigerant flow path (14a) of the water heat exchanger (14). In the water heat exchanger (14), the refrigerant in the refrigerant flow path (14a) evaporates, and the water in the water flow path (14b) is cooled. The water cooled in the water flow path (14b) is supplied to the utilization unit. The refrigerant evaporated in the water heat exchanger (14) passes through the accumulator (17), and is then drawn into the compressor (11) and compressed again.

[0064] The refrigerant evaporated in the second flow path (16b) of the subcooling heat exchanger (16) flows through the downstream injection flow path (42) and is introduced into the compression chamber of the compressor (11).

[0065] (4-2) Heating operation In the heating operation, the controller (100) operates the compressor (11), the fan (18), and the pump (6), sets the four-way switching valve (15) to the second state, and appropriately adjusts the apertures of the heat-source-side expansion valve (13a) and the utilization-side expansion valve (13b). The controller (100) appropriately adjusts the aperture of the injection valve (43). In the heating operation, the controller (100) generally closes the liquid-drain valve (53).

[0066] The refrigerant compressed by the compressor (11) flows through the refrigerant flow path (14a) of the water heat exchanger (14). In the water heat exchanger (14), the refrigerant dissipates heat to the water in the water flow path (14b) and is condensed, and the water in the water flow path (14b) is heated. The heated water is supplied to the utilization unit. The condensed high-pressure liquid refrigerant flows through the liquid flow path (33).

[0067] In the heating operation, an injection operation is performed as needed. In the injection operation, the opening of the injection valve (43) is adjusted so that the intermediate degree of superheat (M-SH) approaches a target value. The liquid refrigerant in the second liquid pipe (33b) of the liquid flow path (33) passes through the first flow path (16a) of the subcooling heat exchanger (16) and flows through the first liquid pipe (33a). A portion of the refrigerant in the first liquid pipe (33a) is sent to the air heat exchanger (12), and the remainder flows through the upstream injection flow path (41). The liquid refrigerant in the upstream injection flow path (41) is reduced in pressure to an intermediate pressure when passing through the injection valve (43).

[0068] In the subcooling heat exchanger (16), high-pressure liquid refrigerant flowing through the first flow path (16a) exchanges heat with intermediate-pressure liquid refrigerant flowing through the second flow path (16b). As a result, the refrigerant in the second flow path (16b) evaporates, and the refrigerant in the first flow path (16a) is cooled.

[0069] The refrigerant cooled in the first flow path (16a) is decompressed to a low pressure when passing through the user-side expansion valve (13b). The decompressed refrigerant flows through the air heat exchanger (12). In the air heat exchanger (12), the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the air heat exchanger (12) passes through the accumulator (17), and is then drawn into the compressor (11) and compressed again.

[0070] In the heating operation, the controller (100) adjusts the opening degree of the heat source side expansion valve (13a) based on the degree of subcooling (Sc) of the refrigerant on the outlet side of the water heat exchanger (14). Specifically, the controller (100) increases the opening degree of the heat source side expansion valve (13a) as the degree of subcooling (Sc) increases, and decreases the opening degree of the heat source side expansion valve (13a) as the degree of subcooling (Sc) decreases.

[0071] (4-3) Problems with liquid accumulation The water heat exchanger (14) is of a plate type. As described above, the internal volume V1 of the water heat exchanger (14) is smaller than the internal volume V2 of the air heat exchanger (12). In the heating operation, the water heat exchanger (14) functions as a radiator (condenser), and therefore liquid refrigerant is likely to accumulate inside the water heat exchanger (14). If liquid refrigerant accumulates inside the water heat exchanger (14) in the heating operation, the high-pressure may rise suddenly. If the high-pressure of the refrigerant circuit (10) becomes excessively high in the heating operation, the system may switch to an operation for protecting the compressor (11) or the high-pressure switch (68) may be activated.

[0072] The refrigeration cycle device (1) is a heat pump type that switches between a cooling operation and a heating operation. During the cooling operation, liquid refrigerant tends to accumulate in the air heat exchanger (12), which functions as a radiator. Therefore, in order to ensure the cooling operation capacity, the amount of liquid refrigerant must be taken into consideration when charging the refrigerant. On the other hand, during the heating operation, liquid refrigerant tends to accumulate in the water heat exchanger (14), which has a relatively small internal volume, as described above. Furthermore, the refrigerant circuit (10) does not have a receiver for storing excess refrigerant. For these reasons, during the heating operation, liquid refrigerant tends to accumulate, particularly in the water heat exchanger (14).

[0073] (4-4) Liquid draining operation The refrigeration cycle apparatus (1) performs a liquid removal operation to prevent a sudden increase in high-pressure due to accumulation of liquid refrigerant in the water heat exchanger (14). The liquid removal operation will be described in detail with reference to FIGS. 3 and 4. In step ST11, the controller (100) executes the heating operation described above. In normal heating operation, the controller (100) closes the liquid drain valve (53) and appropriately adjusts the opening of the injection valve (43). In heating operation, if the first condition is met (YES in step ST12), the controller (100) starts the liquid draining operation of steps ST13 to ST17.

[0074] The first condition is a condition indicating that the high-pressure pressure of the refrigerant circuit (10) is greater than a predetermined value (first pressure) and that liquid refrigerant accumulates in the water heat exchanger (14). Even if liquid refrigerant accumulates in the water heat exchanger (14), no serious problem occurs as long as the high-pressure pressure is low to a certain extent. Furthermore, if liquid refrigerant does not accumulate in the water heat exchanger (14), the liquid removal operation cannot be performed in the first place. Therefore, the controller (100) determines, as the first condition, whether condition A, in which the high-pressure pressure of the refrigerant circuit (10) is greater than a predetermined first pressure, and condition B, in which liquid refrigerant accumulates in the water heat exchanger (14) are satisfied.

[0075] The controller (100) may determine whether or not the condition A is satisfied based not only on the high-pressure (HP) detected by the high-pressure sensor (61) but also on the discharge temperature (Td) detected by, for example, the discharge temperature sensor (63). The first pressure of the condition A is set to a predetermined value that is lower than the threshold value at which protection control of the compressor (11) is initiated and the threshold value at which the high-pressure switch (68) is activated.

[0076] Specifically, the condition B is that the degree of subcooling (Sc) of the refrigerant at the outlet side of the water heat exchanger (14) is greater than the first degree of subcooling (Sc1). This is because, when liquid refrigerant accumulates inside the water heat exchanger (14), the degree of subcooling (Sc) of the refrigerant at the outlet side of the water heat exchanger (14) increases. Here, the degree of subcooling (Sc) is the difference (Tc-T1) between the saturation temperature (condensation temperature (Tc)) corresponding to the high-pressure (HP) detected by the high-pressure pressure sensor (61) and the first temperature (T1) detected by the first refrigerant temperature sensor (65). The controller (100) may determine whether the condition B is satisfied based on, for example, the refrigerant temperature in the refrigerant passage (14a) of the water heat exchanger (14) or the water temperature in the water passage (14b) of the water heat exchanger (14).

[0077] When the first condition of step ST12 is satisfied, the controller (100) opens the liquid drain valve (53) in step ST14. In step ST15, the controller (100) controls the opening degree of the injection valve (43) so that the degree of supercooling (Sc) approaches the target degree of supercooling (Sc-o). In this way, in the liquid draining operation, the controller (100) opens the liquid drain valve (53) and the injection valve (43), which are opening / closing elements.

[0078] As described above, in the heating operation, the controller (100) controls the opening degree of the heat source side expansion valve (13a) based on the degree of subcooling (Sc). Therefore, when the first condition is met, that is, when the degree of subcooling (Sc) is greater than the first degree of subcooling (Sc1), the opening degree of the heat source side expansion valve (13a) is basically fully opened. In other words, in the heating operation described above, the controller (100) controls the opening degree of the heat source side expansion valve (13a) so that the degree of subcooling (Sc) approaches a predetermined degree of subcooling that is smaller than the first degree of subcooling (Sc1).

[0079] When the injection valve (43) and the liquid drain valve (53) are opened, the liquid refrigerant accumulated in the water heat exchanger (14) flows sequentially through the second liquid pipe (33b), the subcooling heat exchanger (16), and the first liquid pipe (33a). A portion of the refrigerant in the first liquid pipe (33a) flows into the liquid drain passage (50), that is, the injection passage (40). The refrigerant in the upstream liquid drain passage (51) passes through the injection valve (43) and flows into the downstream liquid drain passage (52). This refrigerant passes through the liquid drain valve (53) and flows into the suction pipe (32). Strictly speaking, the refrigerant in the liquid drain passage (50) mixes with the gas refrigerant evaporated in the air heat exchanger (12) in the suction pipe (32) and is sucked into the compressor (11). The liquid discharge passage (50) connects the high-pressure liquid passage (33) and the low-pressure suction pipe (32), thereby ensuring a sufficient pressure difference for discharging the liquid refrigerant.

[0080] The controller (100) adjusts the opening of the injection valve (43) so that the degree of subcooling (Sc) becomes the target degree of subcooling (Sc-o), thereby preventing a large amount of liquid refrigerant from being drawn into the compressor (11). The target degree of subcooling (Sc-o) is a predetermined value that is, for example, smaller than the first degree of subcooling (Sc1).

[0081] By feeding an appropriate amount of liquid refrigerant to the suction side of the compressor (11), it is possible to prevent the degree of superheat (discharge superheat) of the refrigerant discharged from the compressor (11) from becoming excessively high.

[0082] If the second condition is met during the liquid-draining operation (YES in step ST16), the controller (100) closes the liquid-draining valve (53) in step ST17, and restarts the heating operation in step ST18.

[0083] The second condition includes, for example, a condition C in which the degree of supercooling (Sc) is smaller than a predetermined second degree of supercooling (Sc2). Here, the second degree of supercooling (Sc) is a predetermined value smaller than the first degree of supercooling (Sc1) or smaller than the target degree of supercooling (Sc-o). In addition to condition C, the second condition may include a condition D in which the high pressure (HP) is smaller than a predetermined value (second pressure). The second pressure is preferably a predetermined value smaller than the above-mentioned first pressure, but may be the same as the first pressure. By setting the second condition in this manner, the heating operation can be resumed while suppressing accumulation of liquid inside the water heat exchanger (14).

[0084] (5) Effects of the embodiment (5-1) The refrigerant circuit (10) includes a liquid flow path (33) connecting a liquid side end of the water heat exchanger (14) and a liquid side end of the air heat exchanger (12), a liquid drainage flow path (50) connecting the liquid flow path (33) and the suction side of the compressor (11), and opening / closing elements (43, 53) for opening and closing the liquid drainage flow path (50). The controller (100) opens the opening / closing elements (43, 53) when a first condition is met, which indicates that the high-pressure of the refrigerant circuit (10) is greater than a predetermined value and liquid refrigerant is accumulating in the water heat exchanger (14).

[0085] Thus, when the high-pressure in the refrigerant circuit (10) is high and liquid refrigerant accumulates in the water heat exchanger (14), the liquid refrigerant in the water heat exchanger (14) can be sent to the suction side of the compressor (11) through the liquid drain passage (50). As a result, the liquid refrigerant in the water heat exchanger (14) can be drained before the high-pressure in the refrigerant circuit (10) suddenly increases, thereby preventing the protection control of the compressor (11) from being executed and the high-pressure switch (68) from being activated.

[0086] In addition, since a certain amount of liquid refrigerant can be stored in the water heat exchanger (14), there is no need to provide a receiver in the refrigerant circuit (10), which allows the refrigeration cycle apparatus (1) to be made smaller.

[0087] By sending the liquid refrigerant from the water heat exchanger (14) to the suction side of the compressor (11), it is possible to prevent the degree of superheat of the refrigerant discharged from the compressor (11) from increasing.

[0088] (5-2) The first condition is that the high pressure of the refrigerant circuit (10) is greater than a predetermined value and the degree of subcooling (Sc) of the refrigerant flowing out of the water heat exchanger (14) is greater than a predetermined value.

[0089] When liquid refrigerant accumulates in the water heat exchanger (14), the degree of subcooling of the refrigerant flowing out of the water heat exchanger (14) increases. Therefore, by using this condition, accumulation of liquid refrigerant in the water heat exchanger (14) can be easily determined.

[0090] (5-3) The refrigerant circuit (10) includes a subcooling heat exchanger (16), an injection flow path (40), and an injection valve (43). Therefore, by performing the above-described injection operation, the COP of the refrigeration cycle can be improved.

[0091] The liquid discharge flow path (50) has an upstream liquid discharge flow path (51) that is connected to the liquid flow path (33) and is also shared with the upstream injection flow path (41). As a result, the liquid discharge flow path (50) and the injection flow path (40) share some of the piping, which allows the number of piping and the length of the piping to be reduced.

[0092] (5-4) The opening / closing elements (43, 53) include an injection valve (43) and a liquid drain valve (53). Therefore, the injection valve (43) can be used not only for the injection operation but also for the liquid drain operation.

[0093] In particular, when the first condition of step ST12 is satisfied, the controller (100) adjusts the opening of the injection valve (43) based on the degree of subcooling (Sc) of the refrigerant flowing out of the water heat exchanger (14). This makes it possible to prevent a large amount of liquid refrigerant from being sent to the suction side of the compressor (11), thereby avoiding so-called liquid compression.

[0094] (5-5) The outlet end of the liquid drain passage (50) is connected to the downstream suction passage (32b) between the accumulator (17) and the compressor (11) in the refrigerant circuit (10). This allows an appropriate amount of liquid refrigerant to be sent to the suction side of the compressor (11), thereby preventing the refrigerant discharged from the compressor (11) from being overheated excessively.

[0095] (6) Other embodiments The refrigeration cycle apparatus (1) may be of a type that performs only a heating operation in which the water heat exchanger (14) functions as a radiator and the air heat exchanger (12) functions as an evaporator. The refrigeration cycle apparatus (1) may be a hot water supply apparatus that produces hot water.

[0096] One end of the injection channel (40) may be connected to the first liquid pipe (33a) instead of the second liquid pipe (33b).

[0097] As shown in Fig. 5, the outlet end of the liquid-draining channel (50) may be connected to the accumulator (17). As shown in Fig. 6, the outlet end of the liquid-draining channel (50) may be connected to the upstream suction channel (32a) upstream of the accumulator (17). These configurations make it easier to avoid liquid compression in the compressor (11).

[0098] As shown in FIG. 7, the refrigeration cycle apparatus (1) does not necessarily have to include the subcooling heat exchanger (16). In this case, the liquid-draining passage (50) is connected between the liquid passage (33) and the suction side of the compressor (11). The liquid-draining passage (50) is provided with a liquid-draining valve (53) as an opening / closing element. In this case, the liquid-draining valve (53) is preferably a flow control valve whose opening degree is variable. In the liquid-draining operation, the controller (100) preferably adjusts the opening degree of the liquid-draining valve (53) so that the degree of subcooling (Sc) becomes a predetermined value.

[0099] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0100] The terms "first," "second," "third," etc. mentioned above are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0101] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for refrigeration cycle devices. [Explanation of symbols]

[0102] 1 Refrigeration cycle device 10 Refrigerant circuit 11 Compressor 12 Air heat exchanger 13 Expansion Factor 14 Water heat exchanger 16 Subcooling heat exchanger 16a First flow path 16b Second flow path 17 Accumulator 33 Liquid flow path 40 Injection channel 41 Upstream injection channel 42 downstream injection channel 43 Injection valve (opening / closing element) 50 Liquid drainage channel 51 Upstream liquid discharge flow path 52 Downstream liquid discharge channel 53 Liquid drain valve (opening / closing element) 100 Controllers HP High Pressure Sc Supercooling degree

Claims

1. a refrigerant circuit (10) having a compressor (11), a plate-type water heat exchanger (14), an expansion element (13), and an air heat exchanger (12), in which the water heat exchanger (14) functions as a radiator and the air heat exchanger (12) functions as an evaporator, and which performs a refrigeration cycle; a controller (100) that controls the refrigerant circuit (10), The refrigerant circuit (10) a liquid flow path (33) connecting a liquid side end of the water heat exchanger (14) and a liquid side end of the air heat exchanger (12); a liquid discharge flow path (50) connecting the liquid flow path (33) and a suction side of the compressor (11); an opening / closing element (43, 53) for opening and closing the liquid discharge channel (50); The controller (100) opens the opening / closing elements (43, 53) when a first condition is met, which indicates that the high pressure of the refrigerant circuit (10) is greater than a predetermined value and liquid refrigerant is accumulating in the water heat exchanger (14). Refrigeration cycle equipment.

2. The first condition is that the high pressure of the refrigerant circuit (10) is greater than a predetermined value, and the degree of subcooling of the refrigerant flowing out of the water heat exchanger (14) is greater than a predetermined value. The refrigeration cycle device according to claim 1.

3. The refrigerant circuit (10) a subcooling heat exchanger (16) having a first flow path (16a) through which a refrigerant from the liquid flow path (33) flows and a second flow path (16b) through which a refrigerant diverted from the liquid flow path (33) flows, and exchanging heat between the refrigerant in the first flow path (16a) and the refrigerant in the second flow path (16b); an injection flow path (40) branching from the liquid flow path (33) and connected to a compression chamber of the compressor (11) via the second flow path (16b); an injection valve (43) that adjusts the flow rate of the refrigerant in the injection flow path (40); The injection channel (40) an upstream injection flow path (41) located upstream of the second flow path (16b); a downstream injection flow path (42) downstream of the second flow path (16b), The liquid discharge channel (50) an upstream liquid discharge flow path (51) connected to the liquid flow path (33) and shared with the upstream injection flow path (41); a downstream liquid discharge flow path (52) branching from the upstream injection flow path (41) and connecting to the suction side of the compressor (11); The refrigeration cycle device according to claim 1.

4. The opening and closing elements (43, 53) the injection valve (43) disposed in the upstream injection flow path (41); a liquid discharge valve (53) that is disposed in the downstream liquid discharge flow path (52) and opens and closes the downstream liquid discharge flow path (52); When the first condition is satisfied, the controller (100) opens the injection valve (43) and the liquid drain valve (53). The refrigeration cycle device according to claim 3.

5. The controller (100) If the first condition is satisfied, the opening degree of the injection valve (43) is adjusted based on the degree of subcooling of the refrigerant flowing out of the water heat exchanger (14). The refrigeration cycle device according to claim 4.

6. The refrigerant circuit (10) has an accumulator (17) upstream of the compressor (11), The outlet end of the liquid drainage channel (50) is connected to the refrigerant circuit (10) between the accumulator (17) and the compressor (11). The refrigeration cycle device according to any one of claims 1 to 5.

7. The internal volume of the water heat exchanger (14) is smaller than the internal volume of the air heat exchanger (12). The refrigeration cycle device according to any one of claims 1 to 5.

8. The distance from the compressor (11) to the water heat exchanger (14) is 5 m or less. The refrigeration cycle device according to any one of claims 1 to 5.

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