Two-stage compression heat pump device and defrosting operation method therefor

Abstract

The present invention relates to a two-stage compression heat pump device and a defrosting operation method therefor. Provided are the two-stage compression heat pump device and the defrosting operation method therefor, the device having a secondary refrigerant, generated from an indoor compressor of an indoor cycle, that absorbs heat through heat exchange with indoor air by means of an auxiliary heat exchanger such that the lowering of low pressure is prevented, and being usable as a heat source in a defrosting operation mode of an outdoor cycle.

Description

Two-stage compression heat pump device and its defrosting operation method

[0001] The present invention relates to a two-stage compression heat pump device and a defrosting operation method thereof, and more particularly, to a two-stage compression heat pump device and a defrosting operation method thereof capable of performing defrosting-related corresponding operation of an outdoor cycle by receiving evaporation heat from an indoor cycle during a defrosting operation mode for an outdoor cycle of the two-stage compression heat pump device.

[0002]

[0003] In general, a heat pump device is a device that incorporates a cooling cycle and a heating cycle into the same unit, so that cooling and heating are performed simultaneously. In the summer, one unit performs cooling through the cooling cycle, and in the winter, it switches to the reverse cycle to perform heating and hot water supply.

[0004] As an example of a heat pump device, a two-stage compression heat pump device uses a high-temperature (50℃) primary refrigerant provided through heat exchange between outdoor air and refrigerant in the outdoor cycle of an outdoor unit to evaporate the secondary refrigerant of the indoor cycle when supplying it to the indoor cycle of an indoor unit. The condensed primary refrigerant is then reintroduced into the outdoor cycle and circulated. The high-temperature, high-pressure secondary refrigerant compressed in the indoor cycle provides high-temperature (80℃) hot water to the user through heat exchange with circulating water, and the secondary refrigerant condensed through heat exchange evaporates after exchanging heat with the primary refrigerant and circulates through the indoor cycle.

[0005] However, when the outdoor temperature is low, moisture in the air passing through the outdoor heat exchanger used as an evaporator during heating operation may condense and freeze, causing frost to form on the outdoor heat exchanger, thereby reducing the heat exchange performance of the outdoor heat exchanger. Ultimately, this causes a problem that significantly reduces the heating efficiency of the heat pump device.

[0006] To solve these problems, a two-stage compression heat pump device can perform defrosting operation by supplying evaporation heat to the outdoor cycle using a hot gas bypass device located in the indoor cycle.

[0007] The defrost operation mode of a two-stage compression heat pump device does not supply the high-temperature, high-pressure secondary refrigerant discharged from the indoor compressor to the first indoor heat exchanger that functions as a condenser, but bypasses the indoor compressor using a hot gas bypass device or a switching valve and circulates the secondary refrigerant directly to the second indoor heat exchanger that functions as an evaporator.

[0008] The secondary refrigerant exchanges heat with the primary refrigerant of the outdoor cycle in the second indoor heat exchanger, and the primary refrigerant circulating to the outdoor heat exchanger of the outdoor unit absorbs the heat of evaporation and circulates through the outdoor cycle, thereby removing the frost formed on the surface of the outdoor heat exchanger.

[0009] A related prior art document is Republic of Korea Patent Publication No. 1203580.

[0010] However, the heat pump device disclosed in the prior art document had a disadvantage in that it could not provide sufficient heat from the indoor unit to the outdoor unit, and thus defrosting operation was not performed properly.

[0011] That is, according to prior art literature, when a conventional heat pump device operates in defrost mode, the high-temperature, high-pressure refrigerant discharged from the indoor compressor is bypassed and supplied to the outdoor cycle, and the second indoor heat exchanger, which was functioning as an evaporator, functions as a condenser. The condensed, subcooled liquid refrigerant is re-introduced into the indoor compressor through the accumulator without evaporation in the second indoor heat exchanger. This causes a shortage of evaporation heat at the suction end of the indoor compressor, resulting in a rapid decrease in low pressure.

[0012] This not only creates low efficiency due to the high compression ratio, but also causes the indoor compressor to go out of its reliability range, causing the indoor compressor to stop working.

[0013] In addition, there was a problem in that the indoor cycle of the conventional heat pump device could not sufficiently respond to the defrosting operation of the outdoor cycle, and thus the heat pump device could not exhibit the best defrosting efficiency.

[0014] In addition, in the case of reverse cycle defrosting operation of a heat pump device, there was a problem of increasing the complexity of the cycle and the complexity of the installation structure as an additional switching valve had to be installed within the indoor cycle of the indoor unit, and increasing the power consumption of the indoor compressor used during defrosting operation.

[0015]

[0016] The purpose of the present invention is to provide a two-stage compression heat pump device and a defrosting operation method thereof, which can prevent a drop in low pressure by absorbing heat from a secondary refrigerant generated from an indoor compressor of an indoor cycle through heat exchange with indoor air by an auxiliary heat exchanger, and can be used as a heat source in the defrosting operation mode of an outdoor cycle.

[0017] The purpose of the present invention is not limited to the aforementioned purposes, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0018]

[0019] In order to achieve the above purpose, the present invention is an invention that can normally and continuously perform defrosting-related response operation by receiving evaporation heat from an indoor cycle during the defrosting operation mode of an outdoor cycle of a two-stage compression heat pump device.

[0020] A two-stage compression heat pump device according to an embodiment of the present invention may include an outdoor cycle including an outdoor compressor that compresses a primary refrigerant to high temperature and high pressure, a switching valve that switches the direction of the primary refrigerant compressed by the outdoor compressor, an outdoor heat exchanger that evaporates the primary refrigerant supplied through the switching valve, and an outdoor expansion valve that decompresses the primary refrigerant supplied to the outdoor heat exchanger; and an indoor cycle including an indoor compressor that compresses a secondary refrigerant to high temperature and high pressure, a first indoor heat exchanger that condenses the secondary refrigerant compressed through the indoor compressor, a first indoor expansion valve that decompresses the secondary refrigerant condensed through the first indoor heat exchanger, and a second indoor heat exchanger that evaporates the secondary refrigerant expanded by the first indoor expansion valve.

[0021] A hot gas bypass device for bypassing the secondary refrigerant discharged from the indoor compressor and supplying it to the second indoor heat exchanger; and a branch passage for supplying the condensed refrigerant of the first indoor heat exchanger or the evaporated refrigerant of the second indoor heat exchanger to the indoor compressor.

[0022] According to an embodiment of the present invention, the branch flow path may include a second indoor expansion valve for reducing the pressure of the secondary refrigerant that has passed through the first indoor heat exchanger; and an auxiliary heat exchanger for evaporating the secondary refrigerant expanded in the second indoor expansion valve through heat exchange with indoor air.

[0023] According to the first embodiment of the present invention, the branch flow path may include a refrigerant flow path connected between a discharge end of the first indoor heat exchanger and a suction end of the first indoor expansion valve, and a first branch flow path provided between a refrigerant flow path connected to a suction end of the indoor compressor.

[0024] According to a second embodiment of the present invention, the branch flow path may include a second branch flow path provided between a refrigerant flow path connected to a discharge end of the second indoor heat exchanger and a refrigerant flow path connected to a suction end of the indoor compressor.

[0025] According to an embodiment of the present invention, a ventilation fan may be further included, which is installed at the discharge end of the auxiliary heat exchanger and improves heat exchange efficiency with the secondary refrigerant through the flow of indoor air to the auxiliary heat exchanger.

[0026] According to an embodiment of the present invention, the auxiliary heat exchanger can exchange heat with indoor air, absorb heat of the indoor air, evaporate the secondary refrigerant, and supply the secondary refrigerant to the indoor compressor.

[0027] According to an embodiment of the present invention, the auxiliary heat exchanger may include a plurality of tubes and a plurality of fins connected to the plurality of tubes.

[0028] According to an embodiment of the present invention, the first indoor expansion valve is opened, and the secondary refrigerant can flow through the first indoor heat exchanger.

[0029] According to an embodiment of the present invention, the first indoor expansion valve may be blocked, and the secondary refrigerant may not flow through the first indoor heat exchanger.

[0030] According to an embodiment of the present invention, the outdoor cycle may further include a switching valve for switching the direction of the primary refrigerant compressed by the outdoor compressor, and an outdoor expansion valve for reducing the pressure of the primary refrigerant condensed through the second indoor heat exchanger.

[0031] According to an embodiment of the present invention, the indoor cycle may further include an indoor accumulator installed at a suction end of the indoor compressor and supplying low-temperature, low-pressure gaseous refrigerant to the indoor compressor, and an oil separator installed at a discharge end of the indoor compressor and recovering a portion of the gaseous secondary refrigerant discharged from the indoor compressor to the indoor compressor.

[0032] According to an embodiment of the present invention, there is provided a defrosting operation method of a two-stage compression heat pump device, comprising a hot gas bypass device for performing a defrosting operation of an outdoor cycle through a high-temperature refrigerant discharged through an indoor compressor of an indoor cycle, and an auxiliary heat exchanger for evaporating condensed secondary refrigerant through heat exchange with indoor air and supplying the evaporated secondary refrigerant to the indoor compressor, the method comprising: when a defrosting operation signal for removing frost in the outdoor cycle is received, performing a defrosting operation of the heat pump device; when the defrosting operation signal is received, driving the hot gas bypass device and driving the auxiliary heat exchanger; measuring a temperature of indoor air and an evaporation temperature of the auxiliary heat exchanger; when the temperature of the indoor air is higher than the evaporation temperature of the auxiliary heat exchanger, increasing an opening amount of a second indoor expansion valve to increase an evaporation heat amount of the auxiliary heat exchanger; when the defrosting of the outdoor cycle is normally performed and frost is removed, determining whether a defrosting operation mode is terminated; And it may include a step of stopping the operation of the hot gas bypass device and the auxiliary heat exchanger to terminate the defrosting operation mode.

[0033] According to an embodiment of the present invention, by measuring the temperature of the indoor air and the evaporation temperature of the auxiliary heat exchanger, if the temperature of the indoor air is lower than the evaporation temperature of the auxiliary heat exchanger, the opening amount of the second indoor expansion valve can be reduced to reduce the evaporation heat of the auxiliary heat exchanger and lower the evaporation temperature of the auxiliary heat exchanger.

[0034]

[0035] According to the two-stage compression heat pump device and its defrosting operation method according to the present invention having the configuration described above, in the defrosting operation mode, the auxiliary heat exchanger and high-temperature indoor air exchange heat to supply evaporation heat to the indoor cycle, thereby increasing the circulation amount of secondary refrigerant circulated to the indoor compressor, thereby having the effect of improving the defrosting efficiency of the outdoor cycle.

[0036] In addition, in the defrosting operation mode, the auxiliary heat exchanger that receives evaporation heat from the indoor air supplies the evaporated secondary refrigerant to the indoor compressor, which has the effect of ensuring normal operation of the indoor compressor.

[0037] When the indoor cycle is in operation, the defrosting efficiency can be maximized by providing evaporation heat to the outdoor cycle while minimizing the temperature decrease of the circulating water.

[0038] By using a hot gas bypass device, the secondary refrigerant at a high temperature can be heat-exchanged with the primary refrigerant of the outdoor cycle, enabling normal defrosting operation.

[0039] In the defrost operation mode, there is an effect that defrost operation is possible without operating the refrigerant circulation cycle in reverse.

[0040] By using the existing ventilation fan in the defrosting operation mode, the heat exchange between the indoor air and the secondary refrigerant is further activated, thereby improving the defrosting efficiency.

[0041]

[0042] FIG. 1 is a schematic diagram showing a two-stage compression heat pump device according to a first embodiment of the present invention.

[0043] FIG. 2 is a cycle diagram showing the flow of refrigerant when a two-stage compression heat pump device according to the first embodiment of the present invention is in a defrosting operation mode.

[0044] Figure 3 is a schematic diagram showing a two-stage compression heat pump device according to a second embodiment of the present invention.

[0045] FIG. 4 is a cycle diagram showing the flow of refrigerant when the heat pump device according to the second embodiment of the present invention is in the defrosting operation mode.

[0046] Fig. 5 is a drawing showing the position of a ventilation fan of a heat pump device according to an embodiment of the present invention.

[0047] FIG. 6 is a flowchart showing the operation logic of an auxiliary heat exchanger and a ventilation fan in a defrosting operation mode of a heat pump device according to an embodiment of the present invention.

[0048]

[0049] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention will be able to easily propose other embodiments within the scope of the same spirit by adding, deleting, modifying, or adding components, etc., but these will also be considered to be within the scope of the present invention.

[0050] When assigning reference numerals to components in each drawing, it should be noted that identical components are assigned the same numerals whenever possible, even if they appear on different drawings. Furthermore, when describing embodiments of the present invention, if a detailed description of a related known configuration or function is deemed to hinder understanding of the embodiments of the present invention, the detailed description will be omitted.

[0051] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of embodiments of the present invention. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by the terms. When it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but another component may also be "connected," "coupled," or "connected" between each component.

[0052] FIG. 1 is a schematic diagram showing a two-stage compression heat pump device according to a first embodiment of the present invention, FIG. 2 is a cycle diagram showing the flow of refrigerant when the two-stage compression heat pump device according to the first embodiment of the present invention performs a defrost operation mode, FIG. 3 is a schematic diagram showing a two-stage compression heat pump device according to a second embodiment of the present invention, and FIG. 4 is a cycle diagram showing the flow of refrigerant when the heat pump device according to the second embodiment of the present invention performs a defrost operation mode.

[0053] As illustrated in FIGS. 1 to 4, a two-stage compression heat pump device according to an embodiment of the present invention includes an outdoor cycle (1) installed in an outdoor unit (10) and through which a primary refrigerant flows, and an indoor cycle (2) installed in an indoor unit (20) and through which hot water is produced through heat exchange with a flowing secondary refrigerant.

[0054] A working fluid may be fluidly connected to the outdoor unit (10) and indoor unit (20) of a two-stage compression heat pump device according to an embodiment of the present invention. For example, the working fluid may include outdoor air, refrigerant, and circulating water. Here, the refrigerant may flow to circulate through the refrigerant path (100) of the outdoor cycle (1) and the indoor cycle (2).

[0055] For example, the refrigerant flowing in the outdoor cycle (1) can be classified as a primary refrigerant, and the refrigerant flowing in the indoor cycle (2) can be classified as a secondary refrigerant.

[0056] Primary and secondary refrigerants can be understood as refrigerants with different condensing and evaporating temperatures. Specifically, the primary refrigerant can be composed of a refrigerant such as R410A, which has lower condensing and evaporating temperatures and is relatively efficient in low-temperature regions. The secondary refrigerant can be composed of R134a, which has higher condensing and evaporating temperatures than the primary refrigerant and is relatively efficient in high-temperature regions. However, this is not necessarily limited to this, and other types of refrigerants can be adopted and used.

[0057] A two-stage compression heat pump device according to an embodiment of the present invention includes an outdoor unit (10) disposed in an outdoor space and exchanging heat with outdoor air, and an indoor unit (20) disposed in an indoor space and having an indoor cycle (2) that produces hot water through heat exchange with a refrigerant.

[0058] Specifically, a two-stage compression heat pump device may include an outdoor cycle (1) in which a primary refrigerant exchanges heat with air and can evaporate a secondary refrigerant, and an indoor cycle (2) in which the secondary refrigerant evaporated by the outdoor cycle (1) exchanges heat with water through a refrigerant circulation path (21a) to heat water. As an example, a two-stage compression heat pump device may utilize air and water as heat sources.

[0059] In a two-stage compression heat pump device, the primary refrigerant can exchange heat with outdoor air in the outdoor heat exchanger (15) of the outdoor unit (10), and the secondary refrigerant can exchange heat with circulating water supplied from the outside in the first indoor heat exchanger (21) of the indoor unit (20).

[0060] As described above, the refrigerant circulated in the outdoor cycle (1) of the outdoor unit (10) will be referred to as the primary refrigerant, and the refrigerant circulated in the indoor cycle (2) of the indoor unit (20) will be referred to as the secondary refrigerant.

[0061]

[0062] [Outdoor unit configuration]

[0063] The outdoor unit (10) includes an outdoor accumulator (11), an outdoor compressor (12) that compresses refrigerant, a switching valve (13) that switches the refrigerant path (100), an outdoor expansion valve (14) that expands and decompresses the primary refrigerant, and an outdoor heat exchanger (15) in which the primary refrigerant and outside air exchange heat.

[0064] Additionally, the outdoor unit (10) includes a refrigerant passage (100) through which a primary refrigerant flows and which is connected to each main component. The primary refrigerant circulating in the outdoor unit (10) flows through the refrigerant passage (100) and can exchange heat with the secondary refrigerant circulating in the indoor unit (20).

[0065] The refrigerant passage (100) includes a first refrigerant passage (110) connecting the outlet of the outdoor compressor (12) and the switching valve (13), a second refrigerant passage (120) connecting the switching valve (13) and the first connecting pipe (210) of the indoor unit (20), a third refrigerant passage (130) connecting the suction end of the outdoor compressor (12) and the discharge end of the outdoor accumulator (11), a fourth refrigerant passage (140) connecting the switching valve (13) and the outdoor heat exchanger (15), and a fifth refrigerant passage (150) connecting the outdoor heat exchanger (15) and the second connecting pipe (220) of the indoor unit (20).

[0066] Specifically, the outdoor accumulator (11) can supply low-temperature, low-pressure gaseous refrigerant to the outdoor compressor (12).

[0067] The outdoor compressor (12) is a device that compresses low-temperature, low-pressure gaseous refrigerant introduced from the outdoor accumulator (11) into high-temperature, high-pressure refrigerant. For example, the outdoor compressor (12) may be equipped with a constant-speed compressor that rotates at a constant speed and compresses to a constant capacity, or an inverter compressor that can adjust the compression capacity by varying the rotation speed according to the load.

[0068] In this way, the primary refrigerant compressed by the outdoor compressor (12) can be introduced into the second indoor heat exchanger (22) and the outdoor heat exchanger (15) through the switching valve (13) depending on the cooling and heating operation mode of the heat pump device.

[0069] The switching valve (13) may be placed at the discharge end of the outdoor compressor (12). The switching valve (13) is connected to the first refrigerant passage (110), the second refrigerant passage (120), and the fourth refrigerant passage (140), respectively. Therefore, the switching valve (13) can switch the refrigerant passage (200) depending on the operating mode. The switching valve (13) may be referred to as a four-way valve.

[0070] The outdoor expansion valve (14) is an expansion valve that expands and depressurizes the condensed primary refrigerant. The outdoor expansion valve (14) is installed on the fifth refrigerant passage (150) and may be installed adjacent to the outdoor heat exchanger (15).

[0071] The outdoor expansion valve (14) decompresses the primary refrigerant flowing through the second indoor heat exchanger (22) of the indoor cycle (2) to the outdoor heat exchanger (15) according to the cooling and heating operation mode of the heat pump device. The primary refrigerant expanded and decompressed by the outdoor expansion valve (14) exchanges heat with air in the outdoor heat exchanger (15).

[0072] The outdoor expansion valve (14) may be an electronic expansion valve such as an EEV whose opening degree can be adjusted.

[0073] The outdoor heat exchanger (15) can function as an evaporator to evaporate the primary refrigerant expanded and depressurized in the outdoor expansion valve (14).

[0074] The outdoor heat exchanger (15) can be connected between the fourth refrigerant passage (140) and the fifth refrigerant passage (150). That is, the outdoor heat exchanger (15) can be connected to the suction end of the fourth refrigerant passage (140) and to the discharge end of the fifth refrigerant passage (150).

[0075] In addition, the outdoor heat exchanger (15) is installed between the outdoor expansion valve (14) and the outdoor compressor (12), and during cooling operation, the primary refrigerant supplied from the outdoor compressor (12) can be condensed through heat exchange with outdoor air. In addition, during heating operation, the outdoor heat exchanger (15) can evaporate the primary refrigerant that has exchanged heat with the secondary refrigerant supplied from the indoor cycle (2). In this way, the outdoor heat exchanger (15) can function as a condenser or an evaporator.

[0076] Additionally, an outdoor fan (16) that forms air flow is installed on one side of the outdoor heat exchanger (15).

[0077] An outdoor fan (16) is installed to circulate outdoor air to the outdoor heat exchanger (15).

[0078] In particular, the outdoor fan (16) rotates when the outdoor compressor (12) is driven to form a flow of outdoor air toward the outdoor heat exchanger (15) to enable fast and efficient heat exchange. By driving the outdoor fan (16), heat exchange can be smoothly performed between the outdoor air flowing into the outdoor heat exchanger (15) and the primary refrigerant.

[0079] In addition, it includes a control valve (17) that controls the flow of refrigerant between the outdoor unit (10) and the indoor unit (20). The control valve (17) includes a first control valve (17b) arranged in the second refrigerant passage (120) and a second control valve (17a) arranged in the fifth refrigerant passage (150).

[0080] The first connecting pipe (210) may include an inlet pipe that guides the primary refrigerant that has passed through the outdoor compressor (12) to the second connecting pipe (220). The second connecting pipe (220) includes a discharge pipe that guides the primary refrigerant that has passed through the first connecting pipe (210) to the outdoor heat exchanger (15).

[0081] Strainers (211, 221) are installed in the first connecting pipe (210) and the second connecting pipe (220). The strainers (211, 221) may be provided to filter out waste or foreign substances in the primary refrigerant flowing in the outdoor cycle. As an example, the strainers (211, 221) may be formed of a metal mesh. The strainers (211, 221) may include a first strainer (211) installed in the first connecting pipe (210) and a second strainer (221) installed in the second connecting pipe (220).

[0082] The first refrigerant can be phase-changed while continuously circulating through the outdoor accumulator (11) of the outdoor cycle (1) -> outdoor compressor (12) -> changeover valve (13) -> second indoor heat exchanger (22) -> outdoor expansion valve (14) -> outdoor heat exchanger (15) -> outdoor accumulator (11).

[0083]

[0084] [Indoor unit configuration]

[0085] The indoor unit (20) can be connected to the outdoor unit (10). The indoor unit (20) exchanges heat between the secondary refrigerant and the circulating water supplied from the outside, and can cool or heat the indoor space or supply hot water to the indoor space.

[0086] The indoor unit (20) includes a first indoor heat exchanger (21), a second indoor heat exchanger (22), an indoor accumulator (23), an indoor compressor (24), an oil separator (25), a hot gas bypass device (30), a first indoor expansion valve (26), an auxiliary heat exchanger (40), a ventilation fan (42), and a second indoor expansion valve (27).

[0087] The indoor accumulator (23) can be placed at the suction end of the indoor compressor (24) as a gas-liquid separator. The indoor accumulator (23) can separate gaseous refrigerant and liquid refrigerant from the refrigerant supplied to the indoor compressor (24) and supply the separated gaseous refrigerant to the indoor compressor (24). Therefore, the indoor accumulator (23) can prevent a decrease in efficiency due to liquid infiltration of the indoor compressor (24).

[0088] The indoor compressor (24), like the outdoor compressor (12), can compress and discharge high-temperature, high-pressure gaseous refrigerant introduced from the indoor accumulator (23).

[0089] A temperature sensor (not shown) that measures the air temperature of the indoor space of the indoor unit (20) may be attached to the indoor compressor (24).

[0090] Meanwhile, the refrigerant passage (100) may include a sixth refrigerant passage (160) connecting the indoor accumulator (23) and the indoor compressor (24). In addition, the refrigerant passage (100) may include a seventh refrigerant passage (170) connecting the indoor compressor (24) and the oil separator (25) so that the refrigerant discharged from the indoor compressor (24) is supplied to the oil separator (25).

[0091] The indoor compressor (24) is installed between the sixth refrigerant passage (160) and the seventh refrigerant passage (170). The indoor compressor (24) can be understood to have the same configuration and function as the outdoor compressor (12), except that the installation location is different.

[0092] The oil separator (25) can recover some of the high-temperature, high-pressure gaseous refrigerant discharged from the indoor compressor (24) to the indoor compressor (24). The oil separator (25) can be installed between the discharge end of the indoor compressor (24) and the suction end of the first indoor heat exchanger (21).

[0093] The oil separator (25) supplies some of the secondary refrigerant discharged from the indoor compressor (24) to the hot gas bypass device (30) and the first indoor heat exchanger (21), and recovers the remaining refrigerant to the indoor compressor (24).

[0094] The oil separator (25) may further include an oil return pipe (25a) for returning oil to the indoor compressor (24), and a check valve (not shown) disposed in the oil return pipe (25a) to ensure that the refrigerant is supplied to the indoor compressor (24) without backflow.

[0095] Additionally, the refrigerant passage (100) may include an eighth refrigerant passage (180) connecting the oil separator (25) and the first indoor heat exchanger (21).

[0096] An oil separator (25) is installed between the seventh refrigerant passage (170) and the eighth refrigerant passage (180).

[0097] The hot gas bypass device (30) can be connected to the eighth refrigerant path (180) connected between the oil separator (25) and the first indoor heat exchanger (21).

[0098] When the hot gas bypass device (30) supplies the high-temperature secondary refrigerant discharged from the oil separator (25) to the second indoor heat exchanger (22) during the defrosting operation, the primary refrigerant that has exchanged heat with the secondary refrigerant circulates through the outdoor cycle (1) and provides evaporation heat to the outdoor heat exchanger (15). As a result, it is possible to remove frost that forms on the outdoor heat exchanger (15).

[0099] The hot gas bypass device (30) is equipped with a hot gas pipe (31) that induces a bypass of the secondary refrigerant and a hot gas valve (32) that opens and closes the hot gas pipe (31).

[0100] The hot gas pipe (31) of the hot gas bypass device (30) is installed in a branched manner so that the secondary refrigerant in a hot gas state can bypass the discharge end (8th refrigerant path) of the oil separator (25) to minimize the loss of hot gas.

[0101] Meanwhile, the refrigerant passage (100) may include a ninth refrigerant passage (190) installed to be connected between the first indoor heat exchanger (21) and the second indoor heat exchanger (22). In addition, the refrigerant passage (100) may include a tenth refrigerant passage (200) connected between the second indoor heat exchanger (22) and the indoor accumulator (23).

[0102] The hot gas pipe (31) of the hot gas bypass device (30) can be connected to the ninth refrigerant passage (190) located at the discharge end of the first indoor expansion valve (26) so that the high-temperature secondary refrigerant discharged from the indoor compressor (24) flows to the evaporation passage (22b) of the second indoor heat exchanger (22).

[0103] Accordingly, the secondary refrigerant flowing through the hot gas pipe (31) exchanges heat with the primary refrigerant in the second indoor heat exchanger (22) and transfers the evaporation heat to the outdoor cycle (1), thereby removing the frost formed on the outdoor heat exchanger (15) in the outdoor cycle (1).

[0104] The hot gas bypass device (30) according to the embodiment of the present invention can be operated by selecting it by a switch or the like only in the defrosting operation mode of the outdoor cycle (1) when the heat exchange performance of the outdoor heat exchanger (15) is deteriorated due to frost formation on the outdoor heat exchanger (15) due to low outdoor temperature.

[0105] The first indoor heat exchanger (21) can exchange heat between the circulating water supplied from the water supply unit (not shown) that supplies water and the secondary refrigerant circulating in the indoor unit (20).

[0106] The first indoor heat exchanger (21) is provided with a refrigerant circulation path (21a) through which high-temperature, high-pressure secondary refrigerant discharged from the indoor compressor (24) passes and is condensed, and a circulating water path (21b) through which circulating water supplied from the water supply unit passes and is heated. In other words, the first indoor heat exchanger (21) can function as a condenser that condenses high-temperature, high-pressure secondary refrigerant discharged from the indoor compressor (24).

[0107] The secondary refrigerant passing through the refrigerant circulation path (21a) and the circulating water passing through the circulating water path (21b) can be heat-exchanged by a heat transfer means (not shown) located between the refrigerant circulation path (21a) and the circulating water path (21b).

[0108] Accordingly, the secondary refrigerant discharged from the indoor compressor (24) can heat the circulating water supplied from the water supply unit to the first indoor heat exchanger (21) to heat the circulating water and supply it to a hot water demand source. In this case, the first indoor heat exchanger (21) may be a water-refrigerant heat exchanger. When the first indoor heat exchanger (21) is a water-refrigerant heat exchanger, a water pipe may be further included in the first indoor heat exchanger (21). The heat pump device can function as a water heater that supplies hot water to a hot water demand source connected to the water pipe. The water pipe may be referred to as a circulating water path (21b).

[0109] The refrigerant circulation path (21a) through which the secondary refrigerant of the first indoor heat exchanger (21) flows is connected to the ninth refrigerant path (190), and the first indoor expansion valve (26) is installed on the ninth refrigerant path (190).

[0110] An inlet pipe (21c) that guides circulating water from a hot water demand source to the circulating water path (21b) of the first indoor heat exchanger (21) can be connected to the circulating water path (21b).

[0111] A pump (not shown) may be installed in the water inlet pipe (21c) to pump the circulating water through the circulating water path (21b) so that it circulates to the hot water demand source. In addition, a relief valve (21d) may be connected to the water inlet pipe (21c) to release the pressure to lower the water pressure when the water pressure in the water inlet pipe (21c) is high.

[0112] In addition, a water outlet pipe (21e) that guides heated circulating water passing through the circulating water path (21b) to a hot water demand source can be connected to the circulating water path (21b) of the first indoor heat exchanger (21).

[0113] The first indoor expansion valve (26) is an expansion valve that expands and reduces the pressure of the secondary refrigerant that passes through the first indoor heat exchanger (21) and flows toward the second indoor heat exchanger (22). The first indoor expansion valve (26) can be installed between the first indoor heat exchanger (21) and the second indoor heat exchanger (22) via the ninth refrigerant passage (190). That is, the first indoor expansion valve (26) can be connected on one side to the refrigerant circulation passage (21a) of the first indoor heat exchanger (21) via the ninth refrigerant passage (190), and on the other side to the evaporation passage (22b) of the second indoor heat exchanger (22).

[0114] The first indoor expansion valve (26) may be an electronic expansion valve such as EEV whose opening degree can be adjusted.

[0115] The two-stage compression heat pump device according to the embodiment of the present invention can circulate along a normal route in which the secondary refrigerant is compressed in the indoor compressor (24), condensed in the first indoor heat exchanger (21), expanded and decompressed in the first indoor expansion valve (26), evaporated in the evaporation path (22b) of the second indoor heat exchanger (22), and then returned to the indoor compressor (24) via the indoor accumulator (23).

[0116] The second indoor heat exchanger (22) can be connected to the refrigerant circulation path (21a) of the first indoor heat exchanger (21) via the ninth refrigerant path (190). In the second indoor heat exchanger (22), the primary refrigerant circulating in the outdoor cycle (1) of the outdoor unit (10) and the secondary refrigerant circulating in the indoor cycle (2) of the indoor unit (20) can undergo heat exchange.

[0117] The second indoor heat exchanger (22) includes a condensation path (22a) through which the primary refrigerant of the outdoor cycle (1) passes and condenses, and an evaporation path (22b) through which the secondary refrigerant of the indoor cycle (2) passes and evaporates.

[0118]

[0119] [Example 1]

[0120] According to the defrosting operation mode of the two-stage compression heat pump device according to the first embodiment of the present invention, the secondary refrigerant can be phase-changed while continuously circulating through the indoor accumulator (23) of the indoor cycle (2) -> indoor compressor (24) -> oil separator (25) -> first indoor heat exchanger (21) -> second indoor expansion valve (27) -> auxiliary heat exchanger (40) -> indoor compressor (24).

[0121] And the hot gas bypass device (30) supplies the evaporation heat of the second indoor heat exchanger (22) to the outdoor heat exchanger (15) of the outdoor cycle (1) to remove the condensation.

[0122] As shown in FIGS. 1 and 2, according to an embodiment of the present invention, the ninth refrigerant passage (190) between the first indoor heat exchanger (21) and the first indoor expansion valve (26) includes a first branch passage (51) connected to the sixth refrigerant passage (160).

[0123] The first branch channel (51) is equipped with an auxiliary heat exchanger (40) and a second indoor expansion valve (27).

[0124] The auxiliary heat exchanger (40) may be configured as a fin-tube type heat exchanger. The auxiliary heat exchanger (40) may include a plurality of tubes and a plurality of fins connected to the plurality of tubes.

[0125] The second indoor expansion valve (27) can expand and depressurize the secondary refrigerant flowing through the first indoor heat exchanger (21) toward the indoor compressor (24) through the sixth refrigerant passage (160).

[0126] The second indoor expansion valve (27) can be connected to the first branch passage (51) together with the auxiliary heat exchanger (40). That is, the secondary refrigerant that has passed through the first indoor heat exchanger (21) can bypass the second indoor expansion valve (27) and flow along the first branch passage (51) and be supplied to the auxiliary heat exchanger (40).

[0127] The auxiliary heat exchanger (40) is a heat exchanger that functions as an evaporator in the defrost operation mode, and is used to properly evaporate the secondary refrigerant discharged from the hot gas bypass device (30) when the second indoor heat exchanger (22) cannot properly perform its function as an evaporator.

[0128] Accordingly, the auxiliary heat exchanger (40) condenses in the first indoor heat exchanger (21) and expands by the second indoor expansion valve (27), causing the depressurized secondary refrigerant to absorb heat from the indoor air and evaporate. The secondary refrigerant in the vapor state thus evaporated can be supplied to the indoor compressor (24) at a sufficient flow rate.

[0129] The auxiliary heat exchanger (40) according to the embodiment of the present invention supplies the low pressure within the indoor cycle (2) to the indoor compressor (24) at a normal flow rate, so that the indoor compressor (24) can maintain normal operation, thereby improving the reliability of the two-stage compression heat pump device.

[0130]

[0131] [Example 2]

[0132] Hereinafter, in describing a second embodiment of a two-stage compression heat pump device according to the present invention, the same component symbols are used for components having the same configuration and function as those of the first embodiment of the present invention, and detailed descriptions of these components are omitted to avoid repetitive configurations.

[0133] According to the defrosting operation mode of the two-stage compression heat pump device according to the first embodiment of the present invention, the secondary refrigerant can be phase-changed while continuously circulating through the indoor accumulator (23) of the indoor cycle (2) -> indoor compressor (24) -> oil separator (25) -> hot gas bypass device (30) -> second indoor heat exchanger (22) -> indoor accumulator (23) -> indoor compressor (24).

[0134] And the hot gas bypass device (30) supplies the evaporation heat of the second indoor heat exchanger (22) to the outdoor heat exchanger (15) of the outdoor cycle (1) to remove the frost.

[0135] At this time, the first indoor expansion valve (26) can be blocked.

[0136] As shown in FIGS. 3 and 4, the tenth refrigerant passage (200) between the second indoor heat exchanger (22) and the indoor accumulator (23) includes a second branch passage (52) connecting the sixth refrigerant passage (160).

[0137] As an example, the second branch flow path (52) can connect the sixth refrigerant flow path (160) connected between the discharge end of the indoor accumulator (23) and the suction end of the indoor compressor (24), and the tenth refrigerant flow path (200) connected between the discharge end of the second indoor heat exchanger (22) and the suction end of the indoor accumulator (23).

[0138] As described above, the second branch channel (52) is equipped with an auxiliary heat exchanger (40) and a second indoor expansion valve (27).

[0139] The second branch flow path (52) is supplied through the hot gas bypass device (30) during the defrosting operation and bypasses the secondary refrigerant that evaporates while passing through the evaporation flow path (22b) of the second indoor heat exchanger (22).

[0140] The secondary refrigerant introduced through the second branch passage (52) into the second indoor heat exchanger (22) can be expanded and decompressed by the second indoor expansion valve (27). The second indoor expansion valve (27) can be connected to the second branch passage (52) together with the auxiliary heat exchanger (40). That is, the secondary refrigerant that has passed through the hot gas bypass device (30) from the indoor compressor (24) can bypass the second indoor expansion valve (27) and flow along the second branch passage (52), and be supplied to the auxiliary heat exchanger (40).

[0141] In the auxiliary heat exchanger (40), the high-temperature secondary refrigerant discharged from the indoor compressor (24) is supplied in an evaporated state from the second indoor heat exchanger (22) via the hot gas pipe (31), and rapidly lowers the surrounding temperature by absorbing heat through heat exchange with the indoor air. The low-temperature, low-pressure gaseous secondary refrigerant that has gone through this process can be supplied to the indoor compressor (24) at a sufficient flow rate.

[0142] As described above, the auxiliary heat exchanger (40) according to the second embodiment of the present invention is a heat exchanger that functions as an evaporator during a defrost operation, and can be used as an evaporator that evaporates secondary refrigerant through heat exchange with indoor air when the second indoor heat exchanger (22) cannot properly function as an evaporator due to the hot gas bypass device (30).

[0143] FIG. 5 is a drawing showing the position of a ventilation fan (42) of a heat pump device according to an embodiment of the present invention. As shown in FIG. 5, referring to the drawing, the ventilation fan (42) is installed at the discharge end of the auxiliary heat exchanger (40) and is located at the bottom of the heat pump device, so that the refrigerant can be ventilated to the outside when the refrigerant leaks.

[0144] In addition, the ventilation fan (42) allows the secondary refrigerant and the indoor air to exchange heat smoothly through the flow of indoor air at a higher temperature than the outdoor air through the auxiliary heat exchanger (40) when the ventilation fan (42) is in operation, thereby increasing the circulation amount of the low-temperature, low-pressure secondary refrigerant circulating to the indoor compressor (24), thereby improving the defrosting efficiency of the outdoor cycle (1).

[0145] Fig. 6 is a flowchart showing the operation logic of the auxiliary heat exchanger (40) and the ventilation fan (42) during the defrosting operation of the heat pump device according to an embodiment of the present invention.

[0146] When the heat pump device of Fig. 6 is operated, the operating logic of the auxiliary heat exchanger (40) and the ventilation fan (42) can be explained with reference to the system diagram of Fig. 2.

[0147]

[0148] <Defrost operation method of a two-stage compression heat pump device>

[0149] In relation to a heat pump device having a first branch flow path (51) installed, when the primary refrigerant passes through the outdoor heat exchanger (15) of the heat pump device, moisture in the outdoor air condenses and freezes during the evaporation process, so that frost may form on the outdoor heat exchanger (15). In addition, in order to remove the frost formed on the outdoor heat exchanger (15) in this way, a defrosting operation may be performed.

[0150] When a defrosting operation signal for removing frost is received in the outdoor cycle (1) of the heat pump device, the controller, which is a control means of the heat pump device, can perform the defrosting operation of the heat pump device (S 10).

[0151] For example, the frost operation signal may be a signal arbitrarily input by the user, or may be a signal provided to the controller by a sensor mounted on the outdoor heat exchanger (15) when the frost accumulation amount detected by the sensor exceeds a certain level. In this case, the sensor may be an infrared sensor, a differential pressure sensor, or a temperature sensor.

[0152] When a defrost operation signal of the heat pump device is provided to the controller, the controller drives the hot gas bypass device (30) and opens the hot gas valve (32) of the hot gas bypass device (30). Then, the first indoor expansion valve (26) is opened.

[0153] When the hot gas bypass device (30) is operated, the hot gas valve (32) is opened to open the flow path of the hot gas pipe (32), and the high-temperature secondary refrigerant discharged from the indoor compressor (24) passes through the hot gas pipe (32) to the evaporation flow path (22b) of the second indoor heat exchanger (22).

[0154] In addition, when the first indoor expansion valve (26) located in the 9th refrigerant passage (190) is opened, the high-temperature secondary refrigerant discharged from the indoor compressor (24) flows along the refrigerant circulation passage (21a) in the first indoor heat exchanger (21). In addition, the circulating water flowing in the circulating water passage (21b) can be heated by absorbing the heat of the secondary refrigerant passing through the refrigerant circulation passage (21a). The heated hot water in this way can be supplied to a hot water use location.

[0155] The secondary refrigerant condensed along the refrigerant circulation path (21a) in the first indoor heat exchanger (21) is branched through the first branch path (51) and supplied to the auxiliary heat exchanger (40) in a depressurized state in the second indoor expansion valve (27).

[0156] The secondary refrigerant, which has been depressurized by the second indoor expansion valve (27), flows into the auxiliary heat exchanger (40) and evaporates while absorbing heat through heat exchange with the high indoor temperature.

[0157] At this time, a ventilation fan (42) that improves heat exchange efficiency can be operated so that heat can be smoothly exchanged with high-temperature indoor air through an auxiliary heat exchanger (40) (S 20).

[0158] The evaporated secondary refrigerant passes through the sixth refrigerant passage (160) and is reintroduced into the indoor compressor (24).

[0159] At this time, when the secondary refrigerant in a high temperature state passes through the evaporation path (22b) of the second indoor heat exchanger (22) by the hot gas bypass device (30), the primary refrigerant circulating in the outdoor cycle (1) of the outdoor unit (10) exchanges heat with the secondary refrigerant while passing through the condensation path (22a).

[0160] The secondary refrigerant in a high temperature state passing through the evaporation path (22b) and the primary refrigerant that has undergone heat exchange in the condensation path (22a) receive evaporation heat and increase in temperature, and can circulate through the outdoor cycle (1) in a high temperature state to remove frost formed on the outdoor heat exchanger (15).

[0161] When the secondary refrigerant flows into the auxiliary heat exchanger (40) and the auxiliary heat exchanger (40) functions as an evaporator, the temperature of the indoor air and the evaporation temperature of the auxiliary heat exchanger (40) can be measured (S 30).

[0162] When the temperature of the indoor air is higher than the evaporation temperature of the auxiliary heat exchanger (40), the heat of the indoor air is absorbed by the secondary refrigerant flowing into the auxiliary heat exchanger (40), thereby increasing the amount of refrigerant circulating to the indoor compressor (24), thereby allowing the normal operation of the indoor compressor (24) to be maintained in the defrosting operation mode.

[0163] In addition, since the indoor cycle (2) of the two-stage compression heat pump device sufficiently responds to the defrosting operation of the outdoor cycle (1), the heat pump device can exhibit the best defrosting efficiency.

[0164] To increase the evaporation heat of the auxiliary heat exchanger (40), the opening degree of the second indoor expansion valve (27) can be increased (S 40). As described above, the circulating amount of secondary refrigerant circulating to the indoor compressor (24) can be increased to improve the defrosting efficiency of the outdoor cycle (1).

[0165] When the outdoor cycle (1) is normally performed and the frost is removed, the controller determines whether to end the defrosting operation mode (S 60).

[0166] The defrost operation mode of the outdoor cycle (1) ends by turning off the operation of the hot gas bypass device (30) and the ventilation fan (42), and by blocking the second indoor expansion valve (27) to stop the operation of the auxiliary heat exchanger (40) (S 70).

[0167] If the temperature of the indoor air and the evaporation temperature of the auxiliary heat exchanger (40) are measured and the evaporation temperature of the auxiliary heat exchanger (40) is higher than the temperature of the indoor air, the heat of the indoor air cannot be absorbed by the secondary refrigerant of the auxiliary heat exchanger (40), so it is necessary to increase the temperature of the indoor air so that the heat of the indoor air can be absorbed by the auxiliary heat exchanger (40). That is, it is necessary to reduce the opening degree of the second indoor expansion valve (27) to temporarily reduce the evaporation heat of the auxiliary heat exchanger (40) for a predetermined period of time, thereby lowering the evaporation temperature of the auxiliary heat exchanger (40) (S 50).

[0168] This acts as a factor in which the secondary refrigerant flowing through the auxiliary heat exchanger (40) absorbs the heat of the indoor air, thereby increasing the amount of secondary refrigerant circulated to the indoor compressor (24), thereby maintaining normal operation of the indoor compressor (24).

[0169] In addition, since the indoor cycle (2) of the two-stage compression heat pump device sufficiently responds to the defrosting operation of the outdoor cycle (1), the heat pump device can exhibit the best defrosting efficiency.

[0170] Therefore, according to the two-stage compression heat pump device of the present invention, by providing the evaporation heat circulating in the indoor cycle (2) of the indoor unit (20) to the outdoor heat exchanger (15) of the outdoor cycle (1), it is possible to easily remove frost formed on the outdoor heat exchanger (15).

[0171]

[0172] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the following claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims

1. An outdoor cycle including an outdoor compressor that compresses a primary refrigerant at high temperature and high pressure, and an outdoor heat exchanger that evaporates the primary refrigerant by exchanging heat between the primary refrigerant and outdoor air; and An indoor cycle comprising an indoor compressor for compressing a secondary refrigerant, a first indoor heat exchanger for condensing the secondary refrigerant through the indoor compressor, a first indoor expansion valve for depressurizing the condensed secondary refrigerant, and a second indoor heat exchanger for evaporating the expanded secondary refrigerant; A hot gas bypass device that performs defrosting operation of the outdoor cycle by bypassing the high-temperature secondary refrigerant circulating in the indoor cycle and exchanging heat with the primary refrigerant of the outdoor cycle; and A two-stage compression heat pump device, comprising a branch passage for bypassing the secondary refrigerant condensed while circulating the indoor cycle or the secondary refrigerant evaporated while circulating the indoor cycle and supplying it to the indoor compressor. In the above branch flow, A second indoor expansion valve for reducing the pressure of the secondary refrigerant; and A two-stage compression heat pump device having an auxiliary heat exchanger installed that evaporates the secondary refrigerant expanded in the second indoor expansion valve through heat exchange with indoor air.

2. In paragraph 1, The above branch flow is: A second indoor expansion valve for reducing the pressure of the secondary refrigerant; and A two-stage compression heat pump device including an auxiliary heat exchanger that evaporates the secondary refrigerant expanded in the second indoor expansion valve through heat exchange with indoor air.

3. In paragraph 1, The above branch flow is: A two-stage compression heat pump device including a refrigerant passage connected between a discharge end of the first indoor heat exchanger and a suction end of the first indoor expansion valve, and a first branch passage provided between a refrigerant passage connected to a suction end of the indoor compressor.

4. In paragraph 1, The above branch flow is: A two-stage compression heat pump device including a second branch passage provided between a refrigerant passage connected to a discharge end of the second indoor heat exchanger and a refrigerant passage connected to a suction end of the indoor compressor.

5. In paragraph 1, A two-stage compression heat pump device further comprising a ventilation fan installed at the discharge end of the auxiliary heat exchanger to improve heat exchange efficiency with the secondary refrigerant through the flow of indoor air to the auxiliary heat exchanger.

6. In paragraph 1, The above auxiliary heat exchanger is a two-stage compression heat pump device that exchanges heat with indoor air, absorbs heat of the indoor air, evaporates the secondary refrigerant, and supplies the secondary refrigerant to the indoor compressor.

7. In paragraph 6, The above auxiliary heat exchanger is a two-stage compression heat pump device comprising a fin tube type heat exchanger including a plurality of tubes and a plurality of fins connected to the plurality of tubes.

8. In paragraph 3, A two-stage compression heat pump device in which the first indoor expansion valve is opened and the secondary refrigerant flows through the first indoor heat exchanger.

9. In paragraph 4, A two-stage compression heat pump device in which the first indoor expansion valve is blocked and the second refrigerant does not flow in the first indoor heat exchanger.

10. In paragraph 1, A two-stage compression heat pump device, wherein the outdoor cycle further includes a switching valve for switching the direction of the primary refrigerant compressed by the outdoor compressor, and an outdoor expansion valve for reducing the pressure of the primary refrigerant condensed through the second indoor heat exchanger.

11. In paragraph 1, A two-stage compression heat pump device, wherein the indoor cycle further includes an indoor accumulator installed at the suction end of the indoor compressor and supplying low-temperature, low-pressure gaseous refrigerant to the indoor compressor, and an oil separator installed at the discharge end of the indoor compressor and recovering a portion of the secondary refrigerant in the gaseous state discharged from the indoor compressor to the indoor compressor.

12. A method for operating a two-stage compression heat pump device, comprising a hot gas bypass device for performing defrosting operation of an outdoor cycle through high-temperature refrigerant discharged through an indoor compressor of an indoor cycle, and an auxiliary heat exchanger for evaporating the condensed secondary refrigerant through heat exchange with indoor air and supplying the evaporated secondary refrigerant to the indoor compressor. When a defrost operation signal for removing heat from the outdoor cycle is received, a step of performing defrost operation of the heat pump device; A step of driving the hot gas bypass device and driving the auxiliary heat exchanger upon receiving the above-mentioned defrosting operation signal; A step of measuring the temperature of indoor air and the evaporation temperature of the auxiliary heat exchanger; A step of increasing the opening amount of the second indoor expansion valve to increase the evaporation heat amount of the auxiliary heat exchanger when the temperature of the indoor air is higher than the evaporation temperature of the auxiliary heat exchanger; When the defrosting of the above outdoor cycle is performed normally and the frost is removed, a step of determining whether the defrosting operation mode is terminated; and A defrosting operation method of a two-stage compression heat pump device, comprising a step of stopping the operation of the hot gas bypass device and the auxiliary heat exchanger to terminate the defrosting operation mode.

13. In paragraph 12, By measuring the temperature of the indoor air and the evaporation temperature of the auxiliary heat exchanger, if the temperature of the indoor air is lower than the evaporation temperature of the auxiliary heat exchanger, A defrosting operation method of a two-stage compression heat pump device, which reduces the opening amount of the second indoor expansion valve to lower the evaporation temperature of the auxiliary heat exchanger by reducing the evaporation heat amount of the auxiliary heat exchanger.

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