Heat exchange system

Abstract

The present invention relates to a heat exchange system. According to the present invention, oil in a compressor is prevented from flowing inside a heat exchange system together with a working fluid. According to the present invention, a lower part of a header of a heat exchanger and a low-pressure side of a compressor are connected by an oil return pipe to enable oil collected in the lower part of the header of the heat exchanger to be transferred to the low-pressure side of the compressor.

Description

heat exchange system

[0001] The present invention relates to a heat exchange system, and to recovering oil used in a compressor of a heat exchange system to the compressor.

[0002] Heat pumps and vapor-compression refrigeration and air-conditioning units use compressors to convert the cycle's working fluid into a high-temperature, high-pressure gas. These compressors use oil to ensure smooth operation of the internal components. This oil readily dissolves in the working fluid, allowing it to flow through the cycle along with the compressed working fluid.

[0003] If the compressor oil flows within the cycle along with the working fluid, the amount of oil required to be sealed within the compressor increases. Furthermore, if the oil dissolves within the working fluid and flows within the cycle along with it, the heat exchange performance of the heat exchangers that make up the cycle deteriorates.

[0004] To address this issue, a separate oil separator is used in the heat exchange cycle to separate the oil from the compressor's working fluid and return it to the compressor. However, using an oil separator increases the number of components in the heat exchange system and requires additional space for its installation.

[0005] Prior literature related to this includes EP registered patent 3690361 and Japanese published patent 2014-145497.

[0006]

[0007] The purpose of the present invention is to solve the problems of the prior art as described above, and to separate oil discharged together with the working fluid from the compressor of a heat exchange system from the working fluid without a separate device and to return it to the compressor.

[0008] An object of the present invention is to prevent oil from a compressor in a heat exchange system from passing through a heat exchanger within the heat exchange system.

[0009]

[0010] In order to achieve the above-described purpose, the heat exchange system according to the present invention connects the header of the heat exchanger and the low pressure side of the compressor with an oil return pipe so that the oil collected in the header is returned to the compressor.

[0011] In the present invention, the oil recovery pipe has a capillary or exchange mechanism so that only oil flows.

[0012] A heat exchange system according to a feature of the present invention may include a compressor that compresses a working fluid, a first heat exchanger that performs heat exchange between the working fluid coming from the compressor and the outside, a first header that branches the flow path of the working fluid into a plurality of paths at the inlet side of the first heat exchanger, an expander that expands the working fluid that has passed through the first heat exchanger, a second heat exchanger that performs heat exchange between the working fluid coming from the expander and the outside, and an oil return pipe that connects the inlet header and the low-pressure side of the compressor and transfers oil collected in the inlet header to the low-pressure side of the compressor.

[0013] The above oil recovery pipe may use a capillary tube.

[0014] A throttling mechanism may be provided inside the above oil recovery pipe.

[0015] The above oil recovery pipe is connected to the lower part of the inlet header in the direction of gravity to recover oil collected in the inlet header.

[0016] An accumulator may be further provided between the compressor and the second heat exchanger to allow a gaseous working fluid to flow into the compressor.

[0017] A four-way valve may be further provided between the connecting pipe on the outlet side of the compressor and the connecting pipe on the inlet side of the accumulator to selectively send the working fluid from the compressor to the first heat exchanger or the second heat exchanger.

[0018] A second oil return pipe connecting the gravity-directed lower portion of the outlet header of the second heat exchanger and the low-pressure side of the compressor may be further provided.

[0019] The heat exchange system according to the present invention comprises: a compressor for compressing a working fluid; a four-way valve for controlling the flow of the working fluid from the compressor; a first heat exchanger that performs heat exchange between the working fluid delivered in one direction through the four-way valve and the outside while selectively playing the roles of a condenser and an evaporator; a second heat exchanger that performs heat exchange between the working fluid delivered in another direction through the four-way valve and the outside while selectively playing the roles of an evaporator and a condenser; an expander that expands the working fluid that has passed through the first heat exchanger or the second heat exchanger and transfers it to the second heat exchanger or the first heat exchanger; a first header provided on the side of the first heat exchanger connected to the outlet side of the compressor and causing the working fluid to flow through a plurality of paths into the interior of the first heat exchanger; a second header provided on the side of the second heat exchanger connected to the outlet side of the compressor and causing the working fluid to flow through a plurality of paths into the interior of the second heat exchanger; and a compressor that connects the first header and the low-pressure side of the compressor and discharges oil collected in the first header. It may include a first oil recovery pipe that delivers oil to the low pressure side of the compressor, and a second oil recovery pipe that connects the second header and the low pressure side of the compressor and delivers oil collected in the second header to the low pressure side of the compressor.

[0020] The first oil recovery pipe and the second oil recovery pipe may use capillary tubes.

[0021] A throttling mechanism may be provided inside the first oil recovery pipe and the second oil recovery pipe.

[0022] The first oil recovery pipe may be connected to the lower part of the first header in the direction of gravity, and the second oil recovery pipe may be connected to the lower part of the second header in the direction of gravity.

[0023] An accumulator is connected to the low pressure side of the compressor, and the accumulator can allow only the gaseous working fluid from the working fluid that has passed through the second heat exchanger or the first heat exchanger to flow into the compressor.

[0024] The heat exchange system according to the present invention may have at least one of the following effects.

[0025] In the present invention, the working fluid from the discharge side of the compressor is transferred to the header of the heat exchanger. The header of the heat exchanger distributes the working fluid so that it flows through various paths of the heat exchanger. Therefore, as the flow speed of the working fluid in the header slows down, the mixed oil collects relatively lower in the header due to gravity. In the present invention, the oil collected at the lower part of the header is transferred to the compressor through an oil return pipe. That is, the header at the inlet side of the heat exchanger and the low-pressure side of the compressor are connected by an oil return pipe, so that the oil collected in the header is guided to the compressor. By recovering the oil in this way, the working fluid entering the inside of the heat exchanger is almost oil-free. Therefore, heat exchange between the working fluid in the heat exchanger and the outside can be performed more smoothly.

[0026] Furthermore, the present invention utilizes an oil return pipe to deliver the separated oil to the compressor. This allows the oil from the compressor to be more easily returned to the compressor without the need for a separate oil separator. Therefore, oil can be recovered from the compressor with a relatively simple configuration, reducing the space required for the heat exchange cycle.

[0027] In particular, the present invention installs a header or distribution manifold at the inlet where the working fluid enters the heat exchanger. Therefore, compared to using a distributor that uniformly distributes and collects the working fluid, a heat exchange system can be constructed at a relatively low cost.

[0028] Figure 1 is a system configuration diagram showing a preferred embodiment to which a heat exchange system according to the present invention is applied.

[0029] Figure 2 is a system configuration diagram showing another embodiment to which a heat exchange system according to the present invention is applied.

[0030] Figure 3 is a system configuration diagram showing another embodiment to which a heat exchange system according to the present invention is applied.

[0031] Fig. 4 is an operational state diagram showing the embodiment illustrated in Fig. 1 in operation.

[0032] Fig. 5 is an operational state diagram showing the embodiment illustrated in Fig. 2 in operation.

[0033] Figure 6 is an operational state diagram showing the heating operation of the embodiment illustrated in Figure 3.

[0034] Figure 7 is an operational state diagram showing the embodiment illustrated in Figure 3 in cooling operation.

[0035] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. When designating components in each drawing, it should be noted that, where possible, identical components will be given the same reference numerals, even if they appear in different drawings. Furthermore, when describing embodiments of the present invention, if a detailed description of a related known structure or function is deemed to hinder understanding of the embodiments of the present invention, such detailed description will be omitted.

[0036] 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.

[0037] The heat exchange system according to the present invention is applied to, for example, a vapor compression refrigeration cycle, a heat pump cycle, etc., so that oil coming out of a compressor constituting the heat exchange system can be simply recovered and transferred to the compressor.

[0038] Fig. 1 illustrates a preferred embodiment of a heat exchange system according to the present invention. A compressor (10), a first heat exchanger (20), an expander (30), and a second heat exchanger (40) are connected to each other by connecting pipes (10', 20', 30', 40'), and a working fluid sequentially passes through the compressor (10), the first heat exchanger (20), the expander (30), and the second heat exchanger (40) and undergoes a phase change, thereby exchanging heat with the outside.

[0039] The compressor (10) compresses the gaseous working fluid to create a relatively high temperature and high pressure. The first heat exchanger (20) can be viewed as a condenser. The working fluid transmitted from the compressor (10) through the connecting pipe (10') exchanges heat with the outside. Through this heat exchange, the working fluid becomes a relatively low temperature and high pressure liquid.

[0040] The above expander (30) receives the working fluid that has passed through the first heat exchanger (20) through the connecting pipe (20'). The expander (30) expands the working fluid so that it becomes a liquid state with a relatively low temperature and low pressure. The working fluid that has passed through the expander (30) enters the second heat exchanger (40) and performs heat exchange, so that it becomes a gas state with a relatively high temperature and low pressure. The working fluid in this state is transmitted to the compressor (10) through the connecting pipe (40') and compressed. This operation occurs repeatedly.

[0041] Meanwhile, there is an inlet header (22) at the inlet of the first heat exchanger (20). The inlet header (22) allows the working fluid to flow simultaneously through multiple paths when it flows within the first heat exchanger (20). Therefore, the flow speed of the working fluid in the inlet header (22) is slower than that of the working fluid in the connecting pipe (10'). There may be an outlet header (24) at the outlet of the first heat exchanger (20). The outlet header (24) serves to collect the working fluid that has passed through multiple paths within the first heat exchanger (20) into one and deliver it to the connecting pipe (20').

[0042] An inlet distributor (42) may be provided at the inlet of the second heat exchanger (40). An outlet header (44) may be provided at the outlet of the second heat exchanger (40). The inlet distributor (42) uniformly distributes the working fluid transmitted in gaseous and liquid phases by passing the same through capillaries of different lengths and delivers the same to the flow path within the second heat exchanger (40). The inlet distributor (42) is relatively expensive compared to the inlet header (22) and is used to ensure uniform flow of the working fluid.

[0043] Meanwhile, there is an oil return pipe (60) to connect the low pressure side of the compressor (10) and the inlet header (22) of the first heat exchanger (20). A capillary tube may be used as the oil return pipe (60). Alternatively, the oil return pipe (60) may be provided with a throttling mechanism. The oil return pipe (60) is connected to the lower portion of the first header (22), that is, the lower portion in the direction of gravity. This is because, as the flow speed of the working fluid within the inlet header (22) slows down, oil that is relatively heavier than the working fluid may accumulate in the lower portion in the direction of gravity of the inlet header (22).

[0044] Next, an embodiment illustrated in Fig. 2 will be described. In the embodiment illustrated in Fig. 2, a compressor (110), a first heat exchanger (120), an expander (130), and a second heat exchanger (140) are connected to each other by connecting pipes (110', 120', 130', 140'), and a working fluid sequentially passes through the compressor (110), the first heat exchanger (120), the expander (130), and the second heat exchanger (140) while undergoing a phase change and exchanging heat with the outside. In addition, when necessary, the working fluid can be caused to flow from the compressor (110) to the second heat exchanger (140) by controlling the four-way valve (112) for defrosting operation.

[0045] The compressor (110) compresses the gaseous working fluid to create a relatively high-temperature, high-pressure gaseous working fluid. The first heat exchanger (120) allows the working fluid transmitted from the compressor (110) through the connecting pipe (110') to exchange heat with the outside. Through this heat exchange, the working fluid undergoes a phase change and becomes a relatively low-temperature, high-pressure liquid.

[0046] The above expander (130) receives the working fluid that has passed through the first heat exchanger (120) through the connecting pipe (120'). The expander (130) expands the working fluid so that it becomes a liquid state with a relatively low temperature and low pressure. The working fluid that has passed through the expander (130) enters the second heat exchanger (140) and performs heat exchange, thereby becoming a gas state with a relatively high temperature and low pressure. The working fluid in this state is transmitted to the compressor (110) through the connecting pipe (140') and compressed. This operation occurs repeatedly.

[0047] The working fluid coming out of the compressor (110) through the connecting pipe (110') can be transmitted through the four-way valve (112). The four-way valve (112) changes the flow path of the working fluid when the system of the present embodiment operates in the reverse direction. That is, the working fluid coming out of the compressor (110) is transmitted to the second heat exchanger (140) through the four-way valve (112) to perform defrosting operation, etc.

[0048] Meanwhile, a first header (122) is provided at the inlet of the first heat exchanger (120). The first header (122) has a plurality of branched paths so that the working fluid flowing through the connecting pipe (110') is divided into a plurality of paths and flows simultaneously when flowing inside the first heat exchanger (120). Therefore, the flow speed in the first header (122) is slower than the flow of the working fluid inside the connecting pipe (110'). A first distributor (124) may be provided at the outlet of the first heat exchanger (120). Instead of using the first distributor (124), an outlet header may be used. That is, an outlet header having the same configuration as the first header (122) but having the opposite function (function of collecting working fluid transmitted through a plurality of paths) may be used as the first distributor (124).

[0049] In addition, a second distributor (142) may be provided at the inlet of the second heat exchanger (140). A second header (144) may be provided at the outlet of the second heat exchanger (140). The second distributor (142) allows the working fluid, which is a mixture of liquid and gas phases, to flow uniformly through a plurality of passages within the second heat exchanger (140).

[0050] An accumulator (150) is provided to ensure that only the gaseous working fluid from the working fluid flowing out of the connecting pipe (140') of the second heat exchanger (140) enters the compressor (110). The gaseous working fluid flowing out of the accumulator (150) enters the low pressure side of the compressor (110) through the connecting pipe (150'). For reference, in actual cycles, the phases of the working fluid are mostly mixed, which is different from the theory. Therefore, the phases of the working fluid flowing into each component are adjusted by using an accumulator (150) or a gas-liquid separator.

[0051] Meanwhile, there is an oil return pipe (160) to connect the low pressure side of the compressor (110) and the first header (122) of the first heat exchanger (120). The oil return pipe (160) may use a capillary tube. Alternatively, the oil return pipe (160) may be provided with a throttling mechanism. The oil return pipe (160) may be connected to the lower portion of the first header (122), that is, the lower portion in the direction of gravity. This is because, as the flow speed of the working fluid within the first header (122) slows down, relatively heavy oil may accumulate in the lower portion in the direction of gravity of the first header (122).

[0052] Next, FIG. 3 illustrates another embodiment of the present invention. In the embodiment illustrated in FIG. 3, a compressor (210), a first heat exchanger (220), an expander (230), and a second heat exchanger (240) are connected to each other by connecting pipes (210', 220', 230', 240'), so that the working fluid changes phases and exchanges heat with the outside while passing through the compressor (210), the first heat exchanger (220), the expander (230), and the second heat exchanger (240) in a forward and reverse direction. In addition, the present embodiment includes a four-way valve (212), an accumulator (250), and first and second oil recovery pipes (260, 260').

[0053] The embodiment illustrated in Fig. 3 is a system in which the system of the present invention is applied to a heater pump cycle. That is, it is a system that can selectively perform cooling and heating operations.

[0054] In this embodiment, the compressor (210) compresses the gaseous working fluid to create a relatively high-temperature, high-pressure gaseous state. For example, during heating operation, the first heat exchanger (220) allows the working fluid transmitted from the compressor (210) through the connecting pipe (210') to exchange heat with the outside. Through this heat exchange, the working fluid becomes a relatively low-temperature, high-pressure liquid state.

[0055] The above expander (230) receives the working fluid that has passed through the first heat exchanger (220) through the connecting pipe (220'). The expander (230) expands the delivered working fluid so that it becomes a liquid state with a relatively low temperature and low pressure. The working fluid that has passed through the expander (230) enters the second heat exchanger (240) and performs heat exchange, thereby becoming a gas state with a relatively high temperature and low pressure. The working fluid in this state is transmitted to the compressor (210) through the connecting pipe (240') and compressed. This operation occurs repeatedly.

[0056] And, in the case where cooling operation occurs in this embodiment, the working fluid made into a relatively high temperature and high pressure in the compressor (210) can be transferred to the second heat exchanger (240) through the connecting pipe (240'). The working fluid that has undergone heat exchange in the second heat exchanger (240) becomes a relatively low temperature and high pressure liquid state and goes to the expander (230). In the expander (230), the working fluid expands and becomes a relatively low temperature and low pressure liquid state. The working fluid exiting the expander (230) enters the second heat exchanger (240) and performs heat exchange, thereby taking away heat from the outside and becoming a relatively high temperature and low pressure gas state. The working fluid in this state is transferred to the compressor (210) through the connecting pipe (210') and compressed. This operation occurs repeatedly.

[0057] The working fluid coming out of the above compressor (210) through the connecting pipe (210') can be transmitted through the four-way valve (212). The four-way valve (212) determines the flow direction of the working fluid during cooling and heating operations.

[0058] Meanwhile, a first header (222) is provided at the inlet of the first heat exchanger (220). The first header (222) has a plurality of branched paths so that the working fluid flowing through the connecting pipe (210') flows simultaneously through a plurality of paths when flowing within the first heat exchanger (220). Therefore, the flow speed in the first header (222) is slower than that of the working fluid within the connecting pipe (210'). A first distributor (224) may be provided at the outlet of the first heat exchanger (220). The first distributor (224) serves to collect the working fluid flowing through a plurality of paths and send it to the connecting pipe (220'), and when the cycle is operated in reverse, it distributes the working fluid passing through the expander (230) so that the working fluid flows uniformly through a plurality of paths within the first heat exchanger (220).

[0059] And, in the second heat exchanger (240), there is a second header (244) on the side connected to the compressor (210). The second header (244) collects the working fluid that has flowed through a plurality of paths and sends it to the connecting pipe (240'), or divides the working fluid that has flowed through the connecting pipe (240') into a plurality of paths and allows it to flow within the second heat exchanger (240). A second distributor (242) may be provided on the part of the second heat exchanger (240) that is connected to the expander (230). The second distributor (242) allows the working fluid from the expander (230) to be evenly divided into a plurality of paths within the second heat exchanger (240) and to flow, or it also serves to collect the working fluid that has passed through a plurality of paths of the second heat exchanger (240) and send it to the expander (230).

[0060] An accumulator (250) is provided to ensure that only the gaseous working fluid from the working fluid flowing out of the connecting pipe (240') of the second heat exchanger (240) enters the compressor (210). The gaseous working fluid flowing out of the accumulator (250) enters the low-pressure side of the compressor (210) through the connecting pipe (250').

[0061] Meanwhile, there is a first oil return pipe (260) to connect the low pressure side of the compressor (210) and the first header (222) of the first heat exchanger (220). And, there is a second oil return pipe (260') to connect the low pressure side of the compressor (210) and the second header (244) of the second heat exchanger (240). These first and second oil return pipes (260, 260') can be used selectively. The oil return pipes (260, 260') can use capillary tubes. Alternatively, the oil return pipes (260, 260') may be provided with a throttling mechanism. The oil return pipes (260, 260') can be connected to the lower portion of the first header (222) or the second header (244), that is, to the lower portion in the direction of gravity. This is because, in the direction of gravity of the first header (222) or the second header (244), relatively heavy oil may accumulate as the flow speed of the working fluid within the first header (222) or the second header (244) slows down.

[0062] The operation of the heat exchange systems according to the present invention having the configuration described above will be described in detail below.

[0063] First, the embodiment illustrated in FIG. 1 in operation is illustrated in FIG. 4. As illustrated in FIG. 4, the working fluid compressed in the compressor (10) becomes a relatively high-temperature, high-pressure gaseous state and flows in the direction indicated by the arrow in the connecting pipe (10') and enters the condenser, which is the first heat exchanger (20). The working fluid, which has exchanged heat with the outside in the first heat exchanger (20), becomes a relatively low-temperature, high-pressure liquid state and flows in the direction indicated by the arrow in the connecting pipe (20') and enters the expander (30). In the expander (30), the working fluid expands and becomes a relatively low-temperature, low-pressure liquid state. The working fluid exiting the expander (30) flows in the direction indicated by the arrow through the connecting pipe (30') and enters the second heat exchanger (40), and exchanges heat with the outside in the second heat exchanger (40) and becomes a relatively high-temperature, low-pressure gaseous state. The working fluid coming out of the second heat exchanger (40) enters the compressor (10). And, this operation is repeated.

[0064] Meanwhile, the working fluid coming out of the compressor (10) is mixed with the oil of the compressor (10). This oil flows together with the working fluid flowing through the connecting pipe (10'). However, when the flow cross-sectional area at the inlet header (22) suddenly increases and the flow velocity of the working fluid decreases, the relatively heavy oil gathers at the bottom of the inlet header (22).

[0065] In this way, the oil collected in the lower part of the inlet header (22) in the direction of gravity flows through the oil return pipe (60) and enters the low pressure side of the compressor (10). Since the oil return pipe (60) is a capillary or has a throttling mechanism, only the oil in the lower part of the inlet header (22) can flow, and the working fluid does not flow through the oil return pipe (60). By doing so, the oil mixed in the working fluid can be separated and re-entered into the compressor (10), so that the amount of oil injected into the compressor (10) can be reduced. In addition, since the oil flowing in the first heat exchanger (20) or the second heat exchanger (40) can be made almost non-existent or in small amount, the heat exchange efficiency in the heat exchangers (20, 40) can be relatively increased.

[0066] Next, the operation of the embodiment illustrated in FIG. 2 will be described with reference to FIG. 5. The working fluid compressed in the compressor (110) becomes a relatively high-temperature, high-pressure gaseous state and flows in the direction indicated by the arrow in the connecting pipe (110') and enters the first heat exchanger (120). The working fluid that has exchanged heat with the outside in the first heat exchanger (120) becomes a relatively low-temperature, high-pressure liquid state and flows in the direction indicated by the arrow in the connecting pipe (120') and enters the expander (130).

[0067] In the expander (130), the working fluid expands and becomes a relatively low-temperature, low-pressure liquid. The working fluid exiting the expander (130) flows in the direction of the arrow through the connecting pipe (130') and enters the second heat exchanger (140), where it exchanges heat with the outside in the second heat exchanger (140) and becomes a relatively high-temperature, low-pressure gaseous state. The working fluid exiting the second heat exchanger (140) enters the compressor (110). And, this operation is repeated.

[0068] Meanwhile, the working fluid coming out of the compressor (110) is mixed with the oil of the compressor (110). This oil flows together with the working fluid flowing through the connecting pipe (110'). However, when the flow cross-sectional area in the first header (122) suddenly increases and the flow speed of the working fluid decreases, the relatively heavy oil gathers at the bottom of the first header (122).

[0069] In this way, the oil collected in the lower part of the first header (122) in the direction of gravity flows through the oil return pipe (160) and enters the low pressure side of the compressor (110). Since the oil return pipe (160) is a capillary or has a throttling mechanism, only the oil in the lower part of the first header (122) can flow, and the working fluid does not flow through the oil return pipe (160). By doing so, the oil mixed in the working fluid can be separated and re-entered into the compressor (110), so that the amount of oil injected into the compressor (110) can be reduced. In addition, since the oil flowing in the first heat exchanger (120) or the second heat exchanger (140) can be made almost non-existent or in small amount, the heat exchange efficiency in the heat exchangers (120, 140) can be relatively increased. For reference, in FIG. 5, the working fluid from the compressor (110) can be sent to the second heat exchanger (140) by controlling the four-way valve (112) to perform defrosting.

[0070] Next, FIG. 6 illustrates the embodiment illustrated in FIG. 3 performing heating operation. The working fluid compressed in the compressor (210) becomes a relatively high-temperature, high-pressure gaseous state and flows in the direction indicated by the arrow in the connecting pipe (210') and enters the first heat exchanger (220). The working fluid, which performs heating by discharging heat to the outside in the first heat exchanger (220), becomes a relatively low-temperature, high-pressure liquid state and flows in the direction indicated by the arrow in the connecting pipe (220') and enters the expander (230). In the expander (230), the working fluid expands and becomes a relatively low-temperature, low-pressure liquid state. The working fluid discharged from the expander (230) flows in the direction indicated by the arrow through the connecting pipe (230') and enters the second heat exchanger (240). In the second heat exchanger (240), the working fluid receives heat from the outside and becomes a gas in a relatively high-temperature, low-pressure state. The working fluid exiting the second heat exchanger (240) enters the compressor (210). This operation is repeated.

[0071] Meanwhile, the working fluid coming out of the compressor (210) is mixed with the oil of the compressor (210). This oil flows together with the working fluid flowing through the connecting pipe (210'), and when the flow cross-sectional area suddenly increases in the first header (222) and the flow speed of the working fluid decreases, the relatively heavy oil gathers at the bottom of the first header (222).

[0072] In this way, the oil collected in the lower part of the first header (222) in the direction of gravity flows through the first oil recovery pipe (260) and enters the low pressure side of the compressor (210). Since the first oil recovery pipe (260) is a capillary or has a throttling mechanism, only the oil in the lower part of the first header (222) can flow, and the working fluid does not flow through the first oil recovery pipe (260). By doing so, the oil mixed in the working fluid can be separated and re-entered into the compressor (210), so that the amount of oil injected into the compressor (210) can be reduced. In addition, since the oil flowing in the first heat exchanger (220) or the second heat exchanger (240) can be made to be almost non-existent or a small amount, the heat exchange efficiency in the heat exchangers (220, 240) can be relatively increased.

[0073] For reference, in Fig. 6, the working fluid from the compressor (210) can be sent to the second heat exchanger (240) by controlling the four-way valve (212) to perform defrosting. The defrosting operation is similar to the cooling operation described below.

[0074] Meanwhile, Fig. 7 illustrates the embodiment of Fig. 3 operating in cooling mode. In this case, the medium that has exchanged heat with the working fluid in the first heat exchanger (220) can be transferred to the outside and used for cooling.

[0075] In the cooling operation of Fig. 7, the working fluid compressed in the compressor (210) and converted into a relatively high-temperature, high-pressure gas flows into the connecting pipe (240') under the control of the four-way valve (212). This working fluid enters the second heat exchanger (240) through the second header (244), and exchanges heat while flowing through the multiple paths of the second heat exchanger (240) by the second header (244). The working fluid heat-exchanged in the second heat exchanger (240) is collected through the second distributor (242) and enters the expander (230). In the expander (230), the working fluid becomes a relatively low-temperature, low-pressure liquid. The working fluid exiting the expander (230) enters the first heat exchanger (220) through the connecting pipe (220'). At this time, it is distributed through the first distributor (224) and flows evenly into a plurality of paths. The working fluid that receives heat from the outside in the first heat exchanger (220) and undergoes heat exchange becomes a relatively high temperature, low pressure gas, is collected by the first header (222), and is transmitted to the compressor (210) and compressed. The working fluid that passes through the compressor (210) becomes a relatively high temperature, high pressure gas, and flows to the second heat exchanger (240) to repeat the process described above.

[0076] Meanwhile, the working fluid coming out of the compressor (210) is mixed with the oil of the compressor (210). This oil flows together with the working fluid flowing through the connecting pipe (240'), and when the flow cross-sectional area suddenly increases in the second header (244) and the flow speed of the working fluid decreases, the relatively heavy oil gathers at the bottom of the second header (242).

[0077] In this way, the oil collected in the lower part of the gravity direction of the second header (242) flows through the second oil return pipe (260') and enters the low pressure side of the compressor (210). Since the second oil return pipe (260') is a capillary or has a throttling mechanism, only the oil in the lower part of the second header (244) can flow, and the working fluid does not flow through the second oil return pipe (260'). By doing so, the oil mixed in the working fluid can be separated and re-entered into the compressor (210), so that the amount of oil injected into the compressor (210) can be reduced. In addition, since the oil flowing in the first heat exchanger (220) or the second heat exchanger (240) can be made almost non-existent or in small amount, the heat exchange efficiency in the heat exchangers (220, 240) can be relatively increased.

[0078] Even though all components constituting the embodiments according to the present invention have been described as being combined or operating in combination, the present invention is not necessarily limited to such embodiments. That is, within the scope of the purpose of the present invention, all components may be selectively combined and operated one or more times. In addition, terms such as "include," "comprise," or "have" described above, unless specifically stated to the contrary, mean that the corresponding component may be inherent, and therefore should be interpreted as including other components rather than excluding other components. All terms, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the art to which the present invention pertains, unless otherwise defined. Commonly used terms, such as terms defined in a dictionary, should be interpreted as being consistent with the contextual meaning of the related technology, and shall not be interpreted in an ideal or overly formal sense, unless explicitly defined in the present invention.

[0079] The above description is merely an illustrative illustration of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims

1. A compressor that compresses the working fluid, A first heat exchanger that performs heat exchange between the working fluid from the compressor and the outside, A first header that branches the flow path of the working fluid into multiple paths at the inlet side of the first heat exchanger, An expander that expands the working fluid that has passed through the first heat exchanger, A second heat exchanger that performs heat exchange between the working fluid from the above expander and the outside, A heat exchange system including an oil return pipe connecting the inlet header and the low pressure side of the compressor and transferring oil collected in the inlet header to the low pressure side of the compressor.

2. A heat exchange system according to claim 1, characterized in that a capillary tube is used as the oil recovery tube.

3. A heat exchange system characterized in that, in the first paragraph, a throttling mechanism is provided inside the oil recovery pipe.

4. A heat exchange system according to any one of paragraphs 1 to 3, wherein the oil recovery pipe is connected to the lower part of the inlet header in the direction of gravity to recover oil collected in the inlet header.

5. In the fourth paragraph, a heat exchange system further comprising an accumulator between the compressor and the second heat exchanger to allow a gaseous working fluid to flow into the compressor.

6. In the fifth paragraph, a heat exchange system further includes a four-way valve for selectively sending the working fluid from the compressor to the first heat exchanger or the second heat exchanger between the connecting pipe on the outlet side of the compressor and the connecting pipe on the inlet side of the accumulator.

7. A heat exchange system in accordance with claim 6, further comprising a second oil recovery pipe connecting the gravity-direction lower portion of the outlet header of the second heat exchanger and the low-pressure side of the compressor.

8. A compressor that compresses the working fluid, A four-way valve that controls the flow of working fluid from the compressor, A first heat exchanger that selectively functions as a condenser and an evaporator while performing heat exchange with the outside and the working fluid transmitted one-way through the above four-way valve, A second heat exchanger that selectively functions as an evaporator and a condenser while performing heat exchange with the outside and the working fluid transmitted in different directions through the above four-way valve; An expander that expands the working fluid that has passed through the first or second heat exchanger and transfers it to the second heat exchanger or the first heat exchanger, A first header provided on the side of the first heat exchanger connected to the outlet side of the compressor and configured to cause the working fluid to flow through a plurality of paths into the interior of the first heat exchanger; A second header provided on the second heat exchanger side connected to the outlet side of the compressor and allowing the working fluid to flow through multiple paths into the interior of the second heat exchanger; A first oil return pipe connecting the first header and the low pressure side of the compressor and delivering the oil collected in the first header to the low pressure side of the compressor; A heat exchange system including a second oil recovery pipe connecting the second header and the low pressure side of the compressor and transferring oil collected in the second header to the low pressure side of the compressor.

9. A heat exchange system according to claim 8, characterized in that the first oil recovery pipe and the second oil recovery pipe use capillaries.

10. A heat exchange system characterized in that, in paragraph 8, a throttling mechanism is provided inside the first oil recovery pipe and the second oil recovery pipe.

11. A heat exchange system according to any one of paragraphs 8 to 10, wherein the first oil recovery pipe is connected to the lower part of the first header in the direction of gravity, and the second oil recovery pipe is connected to the lower part of the second header in the direction of gravity.

12. In the 11th paragraph, an accumulator is connected to the low pressure side of the compressor, and the accumulator is a heat exchange system that allows only the gaseous working fluid from the working fluid that has passed through the second heat exchanger or the first heat exchanger to flow into the compressor.

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