Heat exchanger, outdoor unit for refrigeration cycle device, and refrigeration cycle device

Abstract

This heat exchanger is provided with: a plurality of flat tube groups each composed of a plurality of flat tubes that are disposed upright in the vertical direction and are provided in parallel at intervals in a direction orthogonal to an air flow direction, the flat tube groups being disposed at intervals in the air flow direction; corrugated fins that are disposed between the plurality of flat tubes of each of the plurality of flat tube groups; and a pair of headers that are disposed above and below each of the plurality of flat tube groups. A refrigerant inlet is formed in one of the pair of headers on the most windward side when the heat exchanger is functioning as an evaporator, and a temperature difference forming structure is provided between the most windward flat tube group and the second most windward flat tube group.

Description

Heat exchanger, outdoor unit of refrigeration cycle device, and refrigeration cycle device

[0001] The present disclosure relates to a heat exchanger having corrugated fins, an outdoor unit of a refrigeration cycle device, and a refrigeration cycle device.

[0002] For example, corrugated fin tube-type heat exchangers, which are constructed by alternately stacking flat tubes and corrugated fins, are widely used. When such heat exchangers function as evaporators, the surface temperature of the corrugated fins may drop below freezing, causing condensation on the surfaces of the corrugated fins to freeze and form frost. Frost on the surfaces of the corrugated fins creates resistance to air passing through the heat exchanger, which reduces the heat transfer performance of the corrugated fins. Therefore, there are conventional heat exchangers with improved frost resistance (see, for example, Patent Document 1).

[0003] The heat exchanger of Patent Document 1 is designed so that the leading edges of the corrugated fins protrude beyond the tips of the flat tubes. When the heat exchanger functions as an evaporator, the temperature of the leading edges of the corrugated fins becomes higher than the flat tube temperature (refrigerant temperature), and the temperature difference between the air and the refrigerant on the upwind side of the corrugated fins becomes smaller. This prevents sudden blockage of frost at the leading edges (upwind side) of the heat exchanger, improving frost resistance.

[0004] International Publication No. 2013 / 035436

[0005] However, in Patent Document 1, depending on the protruding length of the leading edge of the corrugated fin, residual frost may form on the leading edge of the corrugated fin during defrosting operation, and there was also the problem that the effect of suppressing sudden blockage of frost was not significant to begin with.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a heat exchanger, an outdoor unit of a refrigeration cycle device, and a refrigeration cycle device that can sufficiently suppress sudden frost blockage.

[0007] The heat exchanger of the present disclosure comprises a plurality of flat tubes arranged vertically and side by side at intervals in a direction perpendicular to the air flow direction, a plurality of flat tube groups arranged at intervals in the air flow direction, corrugated fins arranged between the flat tubes in each of the plurality of flat tube groups, and a pair of headers arranged above and below each of the plurality of flat tube groups, one of the pair of headers on the windward side has a refrigerant inlet formed therein when it functions as an evaporator, and a temperature difference forming structure is provided between the windward side flat tube group and the second-windward side flat tube group.

[0008] An outdoor unit of a refrigeration cycle apparatus according to the present disclosure includes the above-described heat exchanger.

[0009] In addition, the refrigeration cycle device according to the present disclosure includes a compressor, an outdoor unit of the above-mentioned refrigeration cycle device, a throttling device, and an indoor unit of the refrigeration cycle device, which are connected by refrigerant piping to form a refrigerant circuit through which the refrigerant circulates.

[0010] According to the present disclosure, in a heat exchanger, one of a pair of headers on the windward side is formed with a refrigerant inlet when functioning as an evaporator, and a temperature difference generating structure is provided between the windward side flat tube bank and the second windward side flat tube bank. This makes it possible to increase the refrigerant temperature (saturation temperature) in the windward side flat tube bank, thereby suppressing the temperature difference between the air and the refrigerant in the windward side flat tube bank and sufficiently suppressing sudden frost blockage.

[0011] 1 is a refrigerant circuit diagram showing a refrigeration cycle apparatus including a heat exchanger according to a first embodiment. FIG. 2 is a front view schematically showing the heat exchanger according to the first embodiment. FIG. 3 is a perspective view schematically showing a refrigerant flow when the heat exchanger according to the first embodiment functions as an evaporator. FIG. 4 is a diagram showing temperatures versus positions in the refrigerant paths of the heat exchanger according to the first embodiment and a conventional heat exchanger. FIG. 5 is a front view schematically showing a heat exchanger according to a second embodiment. FIG. 6 is a perspective view schematically showing a refrigerant flow when the heat exchanger according to the second embodiment functions as an evaporator. FIG. 7 is a cross-sectional perspective view, with an upper part enlarged, schematically showing the refrigerant flow when the heat exchanger according to the second embodiment functions as an evaporator. FIG. 8 is a diagram showing pressure loss in the row-to-row header versus the distance between the upper ends of the flat tubes of the heat exchanger according to the second embodiment and the inner wall of the row-to-row header. FIG. 9 is a cross-sectional side view, with an upper part enlarged, schematically showing the heat exchanger according to a third embodiment. FIG. 10 is a front view schematically showing a heat exchanger according to a fourth embodiment. FIG. 11 is a perspective view schematically showing a refrigerant flow when the heat exchanger according to the fourth embodiment functions as an evaporator. FIG. 12 is a cross-sectional perspective view, with an upper part enlarged, schematically showing the refrigerant flow when the heat exchanger according to the fourth embodiment functions as an evaporator. 10 is a perspective view showing a refrigerant flow when the heat exchanger according to the fifth embodiment functions as an evaporator. FIG. 11 is a plan view of a flat tube of the heat exchanger according to the fifth embodiment.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, the size relationships between components in the drawings may differ from those in reality. Furthermore, in the following description, terms indicating directions, such as "upper," "lower," "right," "left," "front," and "rear," are used as appropriate to facilitate understanding, but these terms are for explanatory purposes and do not limit the embodiments. Furthermore, in the embodiments, "upper," "lower," "right," "left," "front," and "rear" are used when viewing the heat exchanger from the front.

[0013] Embodiment 1. <Configuration of refrigeration cycle apparatus 100> Fig. 1 is a refrigerant circuit diagram showing a refrigeration cycle apparatus 100 including a heat exchanger 30 according to embodiment 1. Note that solid arrows in Fig. 1 indicate the refrigerant flow during cooling operation, and dashed arrows in Fig. 1 indicate the refrigerant flow during heating operation.

[0014] First, a refrigeration cycle apparatus 100 including a heat exchanger 30 will be described with reference to Figure 1. In the first embodiment, an air conditioner is illustrated as the refrigeration cycle apparatus 100, but the refrigeration cycle apparatus 100 is used for refrigeration or air conditioning purposes, such as refrigerators, freezers, vending machines, air conditioners, refrigeration systems, and water heaters. Note that the refrigerant circuit 101 shown in the figure is merely an example, and the configuration of the circuit elements and the like are not limited to those described in the embodiment, and can be modified as appropriate within the scope of the technology related to the embodiment.

[0015] As shown in Fig. 1 , the refrigeration cycle apparatus 100 according to the first embodiment includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 includes a compressor 11, a flow path switching device 12, a fan 13, and a heat exchanger 30. The indoor unit 20 includes an expansion device 21, an indoor heat exchanger 22, and an indoor fan 23.

[0016] The refrigeration cycle apparatus 100 is also configured with an outdoor unit 10 and an indoor unit 20, and includes a refrigerant circuit 101 through which a refrigerant circulates. Specifically, the refrigerant circuit 101 is configured by connecting a compressor 11, a flow path switching device 12, a heat exchanger 30, a throttling device 21, and an indoor heat exchanger 22 with refrigerant piping. The refrigeration cycle apparatus 100 can perform both cooling and heating operations by switching the flow path switching device 12.

[0017] The refrigerant circulating through the refrigerant circuit 101 is any one of R1234yf, R1234ze, and R290, a mixture of two or more of these, a mixture of any one of these with other refrigerants, a mixed refrigerant including R1132(E), or a mixed refrigerant including R1123. Using these refrigerants can significantly improve the refrigerant distribution performance because low-boiling-point refrigerants have low vapor density and high flow velocity, which increases the influence of inertia. Furthermore, because poor distribution of mixed refrigerants can cause concentration variations, the improved refrigerant distribution performance can significantly improve performance.

[0018] The compressor 11 draws in a low-temperature, low-pressure refrigerant, compresses the drawn refrigerant, and discharges a high-temperature, high-pressure refrigerant. The compressor 11 is, for example, an inverter compressor whose capacity, which is the amount of refrigeration per unit time, is controlled by changing the operating frequency.

[0019] The flow path switching device 12 is, for example, a four-way valve, and switches between cooling operation and heating operation by switching the direction of refrigerant flow. During cooling operation, the flow path switching device 12 switches to the state shown by the solid line in Fig. 1, connecting the discharge side of the compressor 11 to the heat exchanger 30. During heating operation, the flow path switching device 12 switches to the state shown by the dashed line in Fig. 1, connecting the discharge side of the compressor 11 to the indoor heat exchanger 22.

[0020] The heat exchanger 30 exchanges heat between the outdoor air and the refrigerant. During cooling operation, the heat exchanger 30 functions as a condenser that radiates heat from the refrigerant to the outdoor air to condense the refrigerant. During heating operation, the heat exchanger 30 evaporates the refrigerant and cools the outdoor air with the heat of vaporization.

[0021] The fan 13 supplies outdoor air to the heat exchanger 30, and the amount of air blown to the heat exchanger 30 is adjusted by controlling the rotation speed.

[0022] The expansion device 21 is, for example, an electronic expansion valve that can adjust the opening of the expansion valve, and by adjusting the opening, the pressure of the refrigerant flowing into the heat exchanger 30 or the indoor heat exchanger 22. In the embodiment, the expansion device 21 is provided in the indoor unit 20, but it may also be provided in the outdoor unit 10, and the installation location is not limited.

[0023] The indoor heat exchanger 22 exchanges heat between the indoor air and the refrigerant. During cooling operation, the indoor heat exchanger 22 functions as an evaporator that evaporates the refrigerant and cools the outdoor air with the heat of vaporization. During heating operation, the indoor heat exchanger 22 functions as a condenser that radiates heat from the refrigerant to the outdoor air to condense the refrigerant.

[0024] The indoor fan 23 supplies indoor air to the indoor heat exchanger 22, and the amount of air blown to the indoor heat exchanger 22 is adjusted by controlling the rotation speed.

[0025] Fig. 2 is a front view schematically illustrating the heat exchanger 30 according to the first embodiment. Fig. 3 is a perspective view schematically illustrating the refrigerant flow when the heat exchanger 30 according to the first embodiment functions as an evaporator. In Fig. 3, dashed arrows indicate the refrigerant flow, and hollow arrows indicate the air flow direction. In Fig. 3, the components on the windward side of the heat exchanger 30 are labeled "A," and the components on the leeward side are labeled "B."

[0026] 2 and 3, the heat exchanger 30 according to the first embodiment is composed of a plurality of flat tubes 38 (38A, 38B) arranged vertically and spaced apart in a direction perpendicular to the air flow direction, a plurality of flat tube groups 31 (31A, 31B) (two in the first embodiment) arranged at intervals in the air flow direction, corrugated fins 39 (39A, 39B) arranged between the plurality of flat tubes 38 (38A, 38B) of each of the plurality of flat tube groups 31 (31A, 31B), and a pair of headers arranged above and below each of the plurality of flat tube groups 31 (31A, 31B). The pair of headers is composed of a lower header 34 (34A, 34B) and an upper header 35 (35A, 35B). The upper end of the windward flat tube group 31A is inserted into the windward upper header 35A, and the lower end of the windward flat tube group 31A is inserted into the windward lower header 34A. The upper end of the downwind flat tube group 31B is inserted into the downwind upper header 35B, and the lower end of the downwind flat tube group 31B is inserted into the downwind lower header 34B. A lower refrigerant inlet / outlet 34Aa is formed at one end of the windward lower header 34A, and an upper refrigerant inlet / outlet 35Aa is formed at one end of the windward upper header 35A. An upper refrigerant inlet / outlet 35Ba is formed at one end of the downwind upper header 35B, and a lower refrigerant inlet / outlet 34Ba is formed at one end of the downwind lower header 34B. The upper refrigerant inlet / outlet 35Aa of the windward upper header 35A and the upper refrigerant inlet / outlet 35Ba of the leeward upper header 35B are connected by a connecting pipe 41, and a flow resistor 42 is provided on the connecting pipe 41. The flow resistor 42 is, for example, a capillary tube or a flow control valve. Hereinafter, the connecting pipe 41 and the flow resistor 42 are also referred to as a temperature difference generating structure.

[0027] When the heat exchanger 30 functions as an evaporator, gas-liquid two-phase refrigerant flows in through the lower refrigerant inlet / outlet 34Aa (hereinafter also referred to as the refrigerant inlet) of the upwind lower header 34A, flows through the upwind lower header 34A, the upwind flat tube group 31A, the upwind upper header 35A, the temperature difference forming structure, the downwind upper header 35B, the downwind flat tube group 31B, and the downwind lower header 34B in that order, and the gas refrigerant flows out through the lower refrigerant inlet / outlet 34Ba of the downwind lower header 34B.

[0028] In the first embodiment, the upper refrigerant inlet / outlet 35Aa of the windward-side upper header 35A and the upper refrigerant inlet / outlet 35Ba of the leeward-side upper header 35B are connected by the connection pipe 41, but this is not limiting. It is sufficient that one of the lower refrigerant inlet / outlet 34Aa and the upper refrigerant inlet / outlet 35Aa of the pair of windward-side headers is connected by the connection pipe 41 to one of the lower refrigerant inlet / outlet 34Ba and the upper refrigerant inlet / outlet 35Ba of the pair of leeward-side headers. However, by connecting the upper refrigerant inlet / outlet 35Aa of the upwind side upper header 35A to the upper refrigerant inlet / outlet 35Ba of the downwind side upper header 35B with the connecting pipe 41, or by connecting the lower refrigerant inlet / outlet 34Aa of the upwind side lower header 34A to the lower refrigerant inlet / outlet 34Ba of the downwind side lower header 34B with the connecting pipe 41, the length of the connecting pipe 41 can be shortened compared to a configuration in which the upper refrigerant inlet / outlet 35Aa of the upwind side upper header 35A to the lower refrigerant inlet / outlet 34Ba of the downwind side lower header 34B is connected with the connecting pipe 41, or the lower refrigerant inlet / outlet 34Aa of the upwind side lower header 34A to the upper refrigerant inlet / outlet 35Ba of the downwind side upper header 35B is connected with the connecting pipe 41, thereby enabling space savings.

[0029] Furthermore, in the first embodiment, the heat exchanger 30 has two flat tube groups 31 arranged at a distance in the air flow direction, but this is not limited to this and may have three or more. In this case, one of the lower refrigerant inlet / outlet and the upper refrigerant inlet / outlet of the windward-most pair of headers is connected to one of the lower refrigerant inlet / outlet and the upper refrigerant inlet / outlet of the second-windward pair of headers by a connecting pipe 41, and a flow resistor 42 is provided on the connecting pipe 41. In other words, a temperature difference generating structure is provided between the windward-most flat tube group 31 and the second-windward flat tube group 31.

[0030] FIG. 4 shows the temperature versus position in the refrigerant path of the heat exchanger 30 according to the first embodiment and a conventional heat exchanger. Here, the position of the refrigerant path refers to the position of the refrigerant path within the heat exchanger when the heat exchanger functions as an evaporator. That is, the left side of FIGS. 4(a) and 4(b) shows the inlet side when the heat exchanger functions as an evaporator, and the right side of FIGS. 4(a) and 4(b) shows the outlet side when the heat exchanger functions as an evaporator. Note that FIG. 4(a) shows the conventional heat exchanger, i.e., a heat exchanger without a temperature difference-generating structure between a pair of upwind headers and a pair of downwind headers. FIG. 4(b) shows the heat exchanger 30 according to the first embodiment, i.e., a heat exchanger with a temperature difference-generating structure, i.e., a connecting pipe 41 and a flow resistor 42, between a pair of upwind headers and a pair of downwind headers.

[0031] In the heat exchanger 30 according to the first embodiment, by providing a temperature difference generating structure, namely, connecting pipes 41 and flow resistors 42, between a pair of headers on the windward side and a pair of headers on the leeward side, as shown in FIG. 4( b), the refrigerant temperature (saturation temperature) in the flat tube bank 31 on the windward side can be increased compared to the conventional structure shown in FIG. 4( a). Furthermore, by increasing the refrigerant temperature (saturation temperature) in the flat tube bank 31 on the windward side, the temperature difference between the air and the refrigerant in the flat tube bank 31 on the windward side can be reduced, thereby sufficiently reducing sudden frost blockage. In other words, the temperature difference generating structure reduces the temperature difference between the air and the refrigerant in each flat tube bank 31 by generating a temperature difference between the flat tube banks 31.

[0032] Furthermore, by configuring the flow resistor 42 as a flow control valve whose opening can be adjusted, the flow resistor 42 can provide flow resistance appropriate for the operating conditions, thereby improving frost resistance.

[0033] As described above, the heat exchanger 30 of embodiment 1 consists of a plurality of flat tubes 38 arranged vertically and side by side at intervals in a direction perpendicular to the air flow direction, and is equipped with a plurality of flat tube groups 31 arranged at intervals in the air flow direction, corrugated fins 39 arranged between the plurality of flat tubes 38 in each of the plurality of flat tube groups 31, and a pair of headers arranged above and below each of the plurality of flat tube groups 31, one of the pair of headers on the windward side has a refrigerant inlet formed therein when it functions as an evaporator, and is equipped with a temperature difference forming structure between the windward side flat tube group 31 and the second-windward side flat tube group 31.

[0034] According to the heat exchanger 30 of the first embodiment, one of the pair of windward-most headers is formed with a refrigerant inlet when functioning as an evaporator, and is provided with a temperature difference generating structure between the windward-most flat tube bank 31 and the second-windward flat tube bank 31. This makes it possible to increase the refrigerant temperature (saturation temperature) in the windward-side flat tube bank 31, thereby suppressing the temperature difference between the air and the refrigerant in the windward-side flat tube bank 31 and sufficiently suppressing sudden blockages due to frost.

[0035] In addition, in the heat exchanger 30 according to embodiment 1, the connecting pipe 41 connects the upper side of the windward-most pair of headers to the upper side of the second-windward pair of headers, or connects the lower side of the windward-most pair of headers to the lower side of the second-windward pair of headers.

[0036] According to the heat exchanger 30 of the first embodiment, the length of the connection pipe 41 can be shortened, thereby achieving space saving.

[0037] In the heat exchanger 30 according to the first embodiment, the flow resistor 42 is a flow rate adjusting valve.

[0038] According to the heat exchanger 30 of embodiment 1, by configuring the flow resistor 42 as a flow control valve whose opening can be adjusted, the flow resistor 42 can provide flow resistance appropriate for the operating conditions, thereby improving frost resistance.

[0039] In addition, in the refrigeration cycle apparatus 100 according to the first embodiment, the refrigerant is a mixed refrigerant of two or more of R1234yf, R1234ze, and R290, or a mixed refrigerant of any of these with another refrigerant, a mixed refrigerant containing R1132(E), or a mixed refrigerant containing R1123.

[0040] In the refrigeration cycle apparatus 100 according to the first embodiment, the use of the above-described refrigerant can enhance the effect of improving the refrigerant distribution performance, since the low-boiling-point refrigerant has a low vapor density and a high flow velocity, which increases the effect of inertia. Furthermore, since the mixed refrigerant causes concentration variations due to poor distribution, the improved refrigerant distribution performance can enhance the effect of improving performance.

[0041] Second Embodiment A second embodiment will be described below, but explanations of parts that overlap with those of the first embodiment will be omitted, and parts that are the same as or equivalent to those of the first embodiment will be given the same reference numerals.

[0042] Fig. 5 is a front view schematically illustrating the heat exchanger 30 according to the second embodiment. Fig. 6 is a perspective view schematically illustrating the refrigerant flow when the heat exchanger 30 according to the second embodiment functions as an evaporator. In Fig. 6, dashed arrows indicate the refrigerant flow, and hollow arrows indicate the air flow direction. In Fig. 6, the components on the windward side of the heat exchanger 30 are labeled "A," and the components on the leeward side are labeled "B."

[0043] As shown in Figures 5 and 6, the heat exchanger 30 according to the second embodiment includes a plurality of flat tubes 38 (38A, 38B) arranged vertically and spaced apart in a direction perpendicular to the airflow direction. The heat exchanger 30 includes a plurality of flat tube groups 31 (31A, 31B) (two in the second embodiment) spaced apart in the airflow direction, corrugated fins 39 (39A, 39B) arranged between the flat tubes 38 (38A, 38B) of each of the flat tube groups 31 (31A, 31B), and a pair of headers arranged above and below each of the flat tube groups 31 (31A, 31B). The pair of headers includes lower headers 34 (34A, 34B) and a row-transfer header 36. The upper ends of the upwind-side flat tube group 31A and the downwind-side flat tube group 31B are inserted into the row-transfer header 36. The lower end of the windward flat tube group 31A is inserted into the windward lower header 34A, and the lower end of the leeward flat tube group 31B is inserted into the leeward lower header 34B. A lower refrigerant inlet / outlet 34Aa is formed at one end of the windward lower header 34A. A lower refrigerant inlet / outlet 34Ba is formed at one end of the leeward lower header 34B.

[0044] When the heat exchanger 30 functions as an evaporator, gas-liquid two-phase refrigerant flows in from the lower refrigerant inlet / outlet 34Aa (hereinafter also referred to as the refrigerant inlet) of the upwind lower header 34A, flows through the upwind lower header 34A, the upwind flat tube group 31A, the row header 36, the downwind flat tube group 31B, and the downwind lower header 34B in that order, and the gas refrigerant flows out from the lower refrigerant inlet / outlet 34Ba of the downwind lower header 34B.

[0045] Fig. 7 is an enlarged cross-sectional perspective view of the upper portion of the heat exchanger 30 according to the second embodiment, schematically illustrating the refrigerant flow when the heat exchanger 30 functions as an evaporator. Fig. 8 is a diagram illustrating the pressure loss in the row header 36 relative to the distance between the upper end 38a of the flat tube 38 of the heat exchanger 30 according to the second embodiment and the inner wall 36a of the row header 36. The white arrows in Fig. 7 indicate the refrigerant flow.

[0046] As shown in FIG. 7 , the heat exchanger 30 according to the second embodiment is configured so that the distance δ between the upper end 38 a of each flat tube 38 and the inner wall 36 a of the row header 36 is 2 mm or less. As shown in FIG. 8 , the pressure loss in the row header 36 increases or decreases depending on the distance δ. Therefore, by adjusting the distance δ between the upper end 38 a of each flat tube 38 and the inner wall 36 a of the row header 36, flow resistance can be provided without additional components. Furthermore, as shown in FIG. 8 , if the distance δ is greater than 2 mm, the pressure loss in the row header 36 increases rapidly. Therefore, by setting the distance δ to 2 mm or less, the pressure loss in the row header 36 can be suppressed. The heat exchanger 30 according to the second embodiment is configured so that the distance δ between the upper end 38 a of each flat tube 38 and the inner wall 36 a of the row header 36 is 2 mm or less, but is not limited thereto. The row transfer header 36 may be provided at the lower end of the upwind side flat tube group 31A and the lower end of the downwind side flat tube group 31B, and configured so that the distance δ between the lower end of each flat tube 38 and the inner wall 36a of the row transfer header 36 is 2 mm or less.

[0047] As described above, the temperature difference generating structure according to the second embodiment is configured such that the distance between the end of the windward-most flat tube bank 31 and the end of the second-windward flat tube bank 31 and the inner wall 36a of the row-to-row header 36 facing them is 2 mm or less. By configuring the temperature difference generating structure in this way, flow resistance can be provided without any additional parts, so the number of parts can be reduced while suppressing the temperature difference between the air and the refrigerant in the windward-side flat tube bank 31 and sufficiently suppressing sudden blockages due to frost.

[0048] As described above, the heat exchanger 30 of embodiment 2 is configured such that the upper sides of the windwardest pair of headers and the upper sides of the second-windmost pair of headers, or the lower sides of the windwardest pair of headers and the lower sides of the second-windmost pair of headers, are configured with a common row header 36, and the temperature difference forming structure is configured such that the distance between the end of the windwardest flat tube group 31 and the end of the second-windmost flat tube group 31 and the inner wall 36a of the row header 36 facing them is 2 mm or less.

[0049] According to the heat exchanger 30 of embodiment 2, the number of parts can be reduced while suppressing the temperature difference between the air and the refrigerant in the upwind flat tube group 31, and sudden blockage of frost can be sufficiently suppressed.

[0050] Third Embodiment Hereinafter, a third embodiment will be described, but explanations of parts that overlap with those of the first and second embodiments will be omitted, and parts that are the same as or equivalent to those of the first and second embodiments will be denoted by the same reference numerals.

[0051] 9 is a cross-sectional side view showing an enlarged upper portion of a heat exchanger 30 according to embodiment 3. As shown in FIG. 9, a plurality of protrusions 36b protruding downward are provided on an inner wall 36a of the row-transfer header 36. The plurality of protrusions 36b position each flat tube 38 relative to the row-transfer header 36, so that the distance δ between the upper end 38a of each flat tube 38 and the inner wall 36a of the row-transfer header 36 can be easily set to a predetermined value.

[0052] As described above, in the heat exchanger 30 according to embodiment 3, the row-transfer header 36 has a plurality of protrusions 36b that determine the distance between the end of the most windward flat tube group 31 and the end of the second most windward flat tube group 31 and the inner wall 36a of the row-transfer header 36 that face them.

[0053] According to the heat exchanger 30 of embodiment 3, each flat tube 38 is positioned relative to the row-transfer header 36, so that the distance δ between the end of each flat tube 38 and the inner wall 36a of the row-transfer header 36 can be easily set to a predetermined value.

[0054] Fourth Embodiment A fourth embodiment will be described below, but explanations of parts that overlap with those of the first to third embodiments will be omitted, and parts that are the same as or equivalent to those of the first to third embodiments will be given the same reference numerals.

[0055] Fig. 10 is a front view schematically illustrating a heat exchanger 30 according to the fourth embodiment. Fig. 11 is a perspective view schematically illustrating a refrigerant flow when the heat exchanger 30 according to the fourth embodiment functions as an evaporator. In Fig. 11, dashed arrows indicate the refrigerant flow, and hollow arrows indicate the air flow direction. In Fig. 11, the components on the windward side of the heat exchanger 30 are labeled "A," and the components on the leeward side are labeled "B."

[0056] As shown in Figures 10 and 11, the heat exchanger 30 according to the fourth embodiment includes a plurality of flat tubes 38 (38A, 38B) arranged vertically and spaced apart in a direction perpendicular to the airflow direction. The heat exchanger 30 includes a plurality of flat tube groups 31 (31A, 31B) (two in the second embodiment) spaced apart in the airflow direction, corrugated fins 39 (39A, 39B) arranged between the flat tubes 38 (38A, 38B) of each of the flat tube groups 31 (31A, 31B), and a pair of headers arranged above and below each of the flat tube groups 31 (31A, 31B). The pair of headers includes lower headers 34 (34A, 34B) and a row-transfer header 36. The upper ends of the upwind-side flat tube group 31A and the downwind-side flat tube group 31B are inserted into the row-transfer header 36. The lower end of the windward flat tube group 31A is inserted into the windward lower header 34A, and the lower end of the leeward flat tube group 31B is inserted into the leeward lower header 34B. A lower refrigerant inlet / outlet 34Aa is formed at one end of the windward lower header 34A. A lower refrigerant inlet / outlet 34Ba is formed at one end of the leeward lower header 34B.

[0057] When the heat exchanger 30 functions as an evaporator, gas-liquid two-phase refrigerant flows in from the lower refrigerant inlet / outlet 34Aa (hereinafter also referred to as the refrigerant inlet) of the upwind lower header 34A, flows through the upwind lower header 34A, the upwind flat tube group 31A, the row header 36, the downwind flat tube group 31B, and the downwind lower header 34B in that order, and the gas refrigerant flows out from the lower refrigerant inlet / outlet 34Ba of the downwind lower header 34B.

[0058] 12 is an enlarged cross-sectional perspective view of an upper portion of the heat exchanger 30 according to the fourth embodiment, schematically illustrating the flow of refrigerant when the heat exchanger 30 functions as an evaporator. The white arrows in FIG. 12 indicate the flow of refrigerant.

[0059] As shown in Fig. 12, the heat exchanger 30 according to the fourth embodiment has a plate member 37 provided inside the row header 36, the plate member 37 extending in the juxtaposition direction of the flat tubes 38 (38A, 38B). The plate member 37 is provided between the flat tubes 38A on the windward side and the flat tubes 38B on the leeward side. The plate member 37 also has a plurality of small holes 37a formed at intervals in the juxtaposition direction of the flat tubes 38 (38A, 38B). The small holes 37a are formed to provide flow resistance.

[0060] As described above, the temperature difference forming structure according to the fourth embodiment is a plate material 37 that is provided within the row header 36 between the end of the windward-most flat tube bank 31 and the end of the second-windward flat tube bank 31, and has a plurality of small holes 37a formed in the juxtaposition direction of the flat tubes 38. By configuring the temperature difference forming structure in this way, the temperature difference between the air and the refrigerant in the windward-side flat tube bank 31 can be suppressed with a simple structure, and sudden blockage of frost can be sufficiently suppressed.

[0061] As described above, in the heat exchanger 30 according to embodiment 4, the upper side of the windwardest pair of headers and the upper side of the second-windmost pair of headers, or the lower side of the windwardest pair of headers and the lower side of the second-windmost pair of headers, are configured with a common row-transfer header 36, and the temperature difference forming structure is a plate material 37 that is provided within the row-transfer header 36 between the end of the windwardest flat tube group 31 and the end of the second-windmost flat tube group 31, and has a plurality of small holes 37a formed in the direction in which the plurality of flat tubes 38 are arranged side by side.

[0062] The heat exchanger 30 according to the fourth embodiment has a simple structure and can suppress the temperature difference between the air and the refrigerant in the windward flat tube bank 31, thereby sufficiently suppressing sudden blockage due to frost.

[0063] Fifth Embodiment A fifth embodiment will be described below, but explanations of parts that overlap with those of the first to fourth embodiments will be omitted, and parts that are the same as or equivalent to those of the first to fourth embodiments will be given the same reference numerals.

[0064] FIG. 13 is a perspective view schematically illustrating the refrigerant flow when the heat exchanger 30 according to the fifth embodiment functions as an evaporator. FIG. 14 is a plan view schematic diagram of the flat tubes 38 of the heat exchanger 30 according to the fifth embodiment. Note that the dashed arrows in FIG. 13 indicate the refrigerant flow, and the outline arrows indicate the airflow direction. In FIG. 13, the components on the windward side of the heat exchanger 30 are labeled "A" and the components on the leeward side are labeled "B." FIG. 14(a) is a diagram of the windward-side flat tube 38A, FIG. 14(b) is a diagram of a modified version of the windward-side flat tube 38A, and FIG. 14(c) is a diagram of the leeward-side flat tube 38B.

[0065] 13 and 14 , the heat exchanger 30 according to the fifth embodiment is configured so that the sum of the flow path cross-sectional areas S of the upwind-side flat tube group 31A, i.e., the sum of the flow path cross-sectional areas S of the flat tubes 38A, is smaller than the sum of the flow path cross-sectional areas S of the downwind-side flat tube group 31B, i.e., the sum of the flow path cross-sectional areas S of the flat tubes 38B. In this way, by making the sum of the flow path cross-sectional areas S of the upwind-side flat tube group 31A smaller than the sum of the flow path cross-sectional areas S of the downwind-side flat tube group 31B, the temperature difference between the air and the refrigerant in the upwind-side flat tube group 31 can be reduced with a simple structure, and sudden blockage of frost can be sufficiently reduced.

[0066] In the fifth embodiment, the heat exchanger 30 has two flat tube groups 31 spaced apart in the air flow direction, but the number is not limited to two and may be three or more. In this case, the total flow path cross-sectional area S of the windward-most flat tube group 31 is configured to be smaller than the total flow path cross-sectional area S of the second-windward flat tube group 31.

[0067] As described above, in the heat exchanger 30 according to embodiment 5, the sum of the flow path cross-sectional areas S of the flat tube bank 31 on the windward side is smaller than the sum of the flow path cross-sectional areas S of the flat tube bank 31 on the second windward side.

[0068] The heat exchanger 30 according to the fifth embodiment has a simple structure and can suppress the temperature difference between the air and the refrigerant in the windward flat tube bank 31, thereby sufficiently suppressing sudden blockage due to frost.

[0069] REFERENCE SIGNS LIST 10 Outdoor unit, 11 Compressor, 12 Flow path switching device, 13 Fan, 20 Indoor unit, 21 Throttle device, 22 Indoor heat exchanger, 23 Indoor fan, 30 Heat exchanger, 31 Flat tube group, 31A Flat tube group, 31B Flat tube group, 34 Lower header, 34A Lower header, 34Aa Lower refrigerant inlet / outlet, 34B Lower header, 34Ba Lower refrigerant inlet / outlet, 35 Upper header, 35A Upper header, 35Aa Upper refrigerant inlet / outlet, 35B Upper header, 35Ba Upper refrigerant inlet / outlet, 36 Row header, 36a Inner wall, 36b Protrusion, 37 Plate material, 37a Small hole, 38 Flat tube, 38A Flat tube, 38B Flat tube, 38a Upper end, 39 Corrugated fin, 41 Connecting piping, 42 Flow resistor, 100 refrigeration cycle device, 101 refrigerant circuit.

Claims

1. A heat exchanger comprising: a plurality of flat tube groups arranged vertically and spaced apart in the direction perpendicular to the air flow direction, the plurality of flat tube groups arranged at intervals in the air flow direction; corrugated fins arranged between the flat tubes in each of the plurality of flat tube groups; and a pair of headers arranged above and below each of the plurality of flat tube groups, wherein one of the pair of headers on the windward side has a refrigerant inlet formed therein when functioning as an evaporator, and wherein a temperature difference creating structure is provided between the windward side flat tube group and the second windward side flat tube group.

2. A heat exchanger as described in claim 1, wherein the temperature difference forming structure comprises a connecting pipe connecting one of the pair of headers that is most windward with one of the pair of headers that is second most windward, and a flow resistor provided on the connecting pipe.

3. A heat exchanger as described in claim 2, wherein the connecting pipe connects the upper side of the windward-most pair of headers to the upper side of the second-windward pair of headers, or connects the lower side of the windward-most pair of headers to the lower side of the second-windward pair of headers.

4. A heat exchanger according to claim 2 or 3, wherein the flow resistor is a flow control valve.

5. A heat exchanger as claimed in any one of claims 1 to 4, wherein the upper side of the windward-most pair of headers and the upper side of the second-windward pair of headers, or the lower side of the windward-most pair of headers and the lower side of the second-windward pair of headers, are constituted by a common row header, and the temperature difference forming structure is constituted so that the distance between the end of the windward-most flat tube group and the end of the second-windward flat tube group and the inner wall of the row header facing them is 2 mm or less.

6. A heat exchanger as claimed in any one of claims 1 to 4, wherein the upper side of the windward-most pair of headers and the upper side of the second-windward pair of headers, or the lower side of the windward-most pair of headers and the lower side of the second-windward pair of headers, are constituted by a common row header, and the temperature difference forming structure is a plate material provided within the row header between the end of the windward-most flat tube group and the end of the second-windward flat tube group, and having a plurality of small holes formed in the direction in which the flat tubes are arranged side by side.

7. A heat exchanger as described in claim 5 or 6, wherein the row header has a plurality of protrusions that define the distance between the end of the windward-most flat tube group and the end of the second-windward flat tube group and the inner wall of the row header facing them.

8. A heat exchanger according to any one of claims 1 to 7, wherein the sum of the flow path cross-sectional areas of the flat tube bank on the windward side is smaller than the sum of the flow path cross-sectional areas of the flat tube bank on the second windward side.

9. An outdoor unit of a refrigeration cycle device equipped with a heat exchanger according to any one of claims 1 to 8.

10. A refrigeration cycle device comprising a compressor, an outdoor unit of the refrigeration cycle device according to claim 9, a throttle device, and an indoor unit of the refrigeration cycle device, connected by refrigerant piping to a refrigerant circuit through which the refrigerant circulates.

11. The refrigeration cycle device according to claim 10, wherein the refrigerant is any one of R1234yf, R1234ze, and R290, or a mixed refrigerant of two or more of these, or a mixed refrigerant of any one of these with another refrigerant, or a mixed refrigerant including R1132(E), or a mixed refrigerant including R1123.

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