US20250164195A1

US20250164195A1 - Heat exchanger and refrigeration cycle apparatus including the same

Info

Publication number: US20250164195A1
Application number: US18/841,396
Authority: US
Inventors: Yoji ONAKA; Rihito ADACHI; Nanami KISHIDA; Tetsuji Saikusa; Yuki NAKAO; Atsushi KIBE; Hiroyuki Morimoto
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2022-03-09
Filing date: 2022-03-09
Publication date: 2025-05-22
Also published as: DE112022006802T5; CN118829842A; GB2630483A; WO2023170834A1; GB202411387D0; JPWO2023170834A1

Abstract

A heat exchanger includes: a plurality of flat heat transfer tubes each having an elongated cross-sectional shape, each including refrigerant flow passages therein, and arranged apart from and in parallel with each other; and corrugated fins each provided between associated adjacent ones of the flat heat transfer tubes. Each of the corrugated fins has fin portions each having a plate shape, and is bent into a wave shape such that the fin portions are arranged alongside of each other in an axial direction of the flat heat transfer tubes. The fin portions include louvers. The louvers are made as different types of louvers to have different configurations, such that the different types of louvers are provided at respective selected sets of fin portions, to thereby cause different amounts of frost to be formed on the fin portions.

Description

TECHNICAL FIELD

The present disclosure relates to a heat exchanger and a refrigeration cycle apparatus including the heat exchanger.

BACKGROUND ART

As a configuration of an existing heat exchanger, the following configuration is known: a plurality of flat heat transfer tubes are arranged apart from each other and in parallel with each other and each of a plurality of corrugated fins is provided between associated adjacent ones of the flat heat transfer tubes as in a heat exchanger disclosed in Patent Literature 1. In the case where such a heat exchanger is used as an evaporator, when the surface temperature of the corrugated fin decreases, moisture in air close to the surface of the corrugated fin is precipitated to become condensed water, and when the surface temperature further decreases to fall below freezing, the condensed water freezes to change into frost. When frost forms on the surface of the corrugated fin, the frost hinders the flow of air that passes through the heat exchanger and thus reduces the heat transfer performance of the corrugated fin. In view of this point, in the heat exchanger, in order to drain the condensed water, the corrugated fin is formed to have a slit for drainage, and the condensed water is drained through the slit.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-183908

SUMMARY OF INVENTION

Technical Problem

In the heat exchanger disclosed in Patent Literature 1, a plurality of louvers are provided at each of planar portions of each of the corrugated fins. Because of provision of the louvers, the heat transfer coefficient of the corrugated fin is increased, and frost formation is thus promoted in the vicinity of each of the louvers. As a result, the frost may grow and close an air passage.
The present disclosure is applied to solve the above problem, and relates to a heat exchanger that is provided with corrugated fins including louvers and is capable of reducing the likelihood that formed frost will close an air passage and a refrigeration cycle apparatus including the heat exchanger.

Solution to Problem

A heat exchanger according to one embodiment of the present disclosure, includes: a plurality of flat heat transfer tubes each having an elongated cross-sectional shape, each including a plurality of refrigerant flow passages therein, and arranged apart from each other and in parallel with each other; and a plurality of corrugated fins each provided between associated adjacent ones of the flat heat transfer tubes. Each of the plurality of corrugated fins has a plurality of fin portions each having a plate shape, and is bent into a wave shape such that the plurality of fin portions are arranged alongside of each other in an axial direction of the flat heat transfer tubes. The plurality of fin portions include louvers. The louvers are made as different types of louvers to have different configurations, such that the different types of louvers are provided at respective selected sets of fins portions of the plurality of fin portions, to thereby cause different amounts of frost to be formed on the plurality of fin portions.
A refrigeration cycle apparatus according to another embodiment of the present disclosure includes the above heat exchanger.

Advantageous Effects of Invention

According to the embodiments of the present disclosure, the louvers are formed to have different configurations, and the louvers having different configurations are provided at respective selected ones of the fin portions, to cause amounts of frost to be formed on the respective selected fin portions to differ from each other. Thus, since the fin portions include the louvers that reduce the amount of frost to be formed, it is possible to reduce the likelihood that the formed frost will close an air passage and to cause air to flow from the upstream side to the downstream side.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic front view of a heat exchanger according to Embodiment 1.

FIG. 2 is a schematic perspective view of a related part of the heat exchanger according to Embodiment 1.

FIG. 3 is a schematic front view of another related part of the heat exchanger according to Embodiment 1.

FIG. 4 is a schematic front view of still another related part of the heat exchanger, according to Embodiment 1 that is different in configuration from the related part as illustrated in FIG. 3

FIG. 5 is an explanatory view schematically illustrating an example in which a corrugated fin of the heat exchanger according to Embodiment 1 is manufactured by roll forming.

FIG. 6 is a refrigerant circuit diagram of a refrigeration cycle apparatus including the heat exchanger according to Embodiment 1.

FIG. 7 is a schematic plan view of a related part of a heat exchanger according to Embodiment 2.

FIG. 8 is a schematic plan view of another related part of the heat exchanger according to Embodiment 2.

FIG. 9 is a schematic plan view of a related part of a heat exchanger according to Embodiment 3.

FIG. 10 is a schematic plan view of another related part of the heat exchanger according to Embodiment 3.

FIG. 11 is a schematic plan view of a related part of a heat exchanger according to Embodiment 4.

FIG. 12 is a sectional view that is taken along line A-A in FIG. 11 .

FIG. 13 is a sectional view that is taken along line A-A in FIG. 11 and illustrates a configuration different from that in FIG. 12 .

FIG. 14 is a graph indicating a relationship between time that is required to drain condensed water and varies depending on an inclination angle of a plate portion and the amount of remaining water on the surface of the fin portion that varies depending on the inclination angle of the plate portion, in the heat exchanger according to Embodiment 4.

FIG. 15 is a schematic plan view of a related part of a heat exchanger according to Embodiment 5.

FIG. 16 is a schematic plan view of another related part of the heat exchanger according to Embodiment 5.

FIG. 17 is a schematic plan view of a related part of a modification of the heat exchanger according to Embodiment 5.

FIG. 18 is a schematic plan view of another related part of the modification of the heat exchanger according to Embodiment 5.

FIG. 19 is a schematic plan view of a related part of a heat exchanger according to Embodiment 6.

FIG. 20 is a graph indicating a relationship between a dimension of a fin in the flow direction of air and the rate of improvement of a heating performance at low temperature.

DESCRIPTION OF EMBODIMENTS

Embodiments according to the present disclosure will be described with reference to the drawings. It should be noted that in each of figures in the drawings, components that are the same as or equivalent to those in a previous figure or previous figures are denoted by the same reference sigs, and their descriptions will thus be omitted or simplified as appropriate. In addition, for example, the shapes, the sizes, and the arrangement of the components as illustrated in the figures can be changed as appropriate. In addition, throughout the following description, an upper part and a lower part of each of the figures are referred to as the “upper side” and “lower side”, respectively. Furthermore, although the terms representing directions (such as “right” and “left”) are appropriately used in order that the embodiments be easily understood, such terms are not limiting.

Embodiment 1

First of all, a heat exchanger 100 according to Embodiment 1 will be described. FIG. 1 is a schematic front view of the heat exchanger 100 according to Embodiment 1. FIG. 2 is a schematic perspective view of a related portion of the heat exchanger 100 according to Embodiment 1. FIG. 3 is a schematic front view of another related portion of the heat exchanger 100 according to Embodiment 1.
As illustrated in FIG. 1 , the heat exchanger 100 according to Embodiment 1 includes a pair of headers 1 and 2 spaced from each other in an up-down direction, a plurality of flat heat transfer tubes 3 arranged apart from each other and in parallel with each other in a lateral direction, and a plurality of corrugated fins 4 each provided between associated adjacent ones of the flat heat transfer tubes 3.
The pair of headers 1 and 2 are the header 1 on the upper side, that is, the upper header 1 and the header 2 on the lower side, that is, the lower header 2. The upper header 1 and the lower header 2 are pipes that are connected by pipes to other components included in a refrigeration cycle apparatus, into and from which refrigerant serving as a heat exchanging medium flows, and in which the refrigerant is branched into refrigerant streams or refrigerant streams join each other. Gas refrigerant passes through the upper header 1, and liquid refrigerant passes through the lower header 2. The plurality of flat heat transfer tubes 3 are arranged in parallel between the upper header 1 and the lower header 2.
Each of the flat heat transfer tubes 3 is made of, for example, an aluminum alloy and has a section that is elongated as illustrated in FIG. 2 . In the flat heat transfer tube 3, outer surfaces (flat surfaces 31) of the flat heat transfer tube that extend in a longitudinal direction thereof are formed in the shape of a flat plate, and outer surfaces of the flat heat transfer tube that extend in a width direction thereof are curved surfaces. In the flat heat transfer tube 3, a plurality of refrigerant flow passages 30 are provided to extend in the up-down direction. The flat heat transfer tubes 3 are set upright in the up-down direction such that the flat surfaces 31 are substantially parallel to each other and substantially perpendicular to the headers 1 and 2. That is, the flat heat transfer tubes 3 are arranged such that the flat surfaces 31 extend in a flow direction Z of air. Upper end portions of the flat heat transfer tubes 3 are inserted into respective insertion holes (not illustrated) formed in the upper header 1, and are joined to the upper header 1 by brazing. Lower end portions of the flat heat transfer tubes 3 are inserted into respective insertion holes (not illustrated) formed in the lower header 2, and are joined to the lower header 2 by brazing. The refrigerant flow passages 30 in the flat heat transfer tube 3 extend in the up-down direction and communicate with the upper header 1 and the lower header 2. It should be noted that a brazing material containing, for example, aluminum is used in the brazing.
The corrugated fin 4 is made of, for example, an aluminum alloy and is provided to increase the heat transfer area between outside air and refrigerant that flows in the refrigerant flow passages 30 of associated flat heat transfer tubes 3. An airflow passage through which air flows is provided between the corrugated fin 4 and each of the associated flat heat transfer tubes 3. The corrugated fin 4 is shaped as illustrated in FIGS. 1 and 2 , that is, the corrugated fin 4 is formed as follows: a plate-shaped fin material is subjected to corrugating processing, and wound and corrugated such that mountain folds and valley folds alternate, and formed in the shape of a bellows. It should be noted that, for example, a surface of the fin material is clad with a brazing material layer that is made mainly of a brazing material containing aluminum-silicon based aluminum. The thickness of the corrugated fin 4 is, for example, approximately 50 to 200 μm.
The corrugated fin 4 has fin portions 40 each formed in the shape of a flat plate and ridge portions 41 formed on both ends of each of the fin portions 40. The ridge portions 41 are bent portions that correspond to undulations formed by the corrugating processing. The corrugated fin 4 is provided between associated adjacent two of the flat heat transfer tubes 3 such that folded portions of the corrugated fin are continuous with each other in an axial direction Y along the axis of each of the flat heat transfer tubes 3. That is, as illustrated in FIG. 1 , the corrugated fin 4 is provided such that the fin portions 40 are alternately inclined in opposite directions as viewed in the flow direction Z of air. The bent ridge portions 41 of the corrugated fin 4 are in surface contact with the flat surfaces 31 of the associated two flat heat transfer tubes 3 and are joined thereto by brazing.
In addition, as illustrated in FIG. 2 , at each of the fin portions 40 of the corrugated fin 4, a plurality of louvers 5 are provided. The louvers 5 are provided to increase the heat transfer coefficient between outside air and refrigerant that flows in the refrigerant flow passages 30 of the associated flat heat transfer tubes 3. Each of the louvers 5 has a slit 5 a through which air passes and a plate portion 5 b that is inclined in the up-down direction to guide air into the slit 5 a. The slit 5 a is formed in the shape of a rectangle that is long in a parallel arrangement direction X of the flat heat transfer tubes 3 that is a direction where the flat heat transfer tubes 3 are arranged. In general, part of the louver 5 that is pressed down and cut when the slit 5 a is formed is raised to form the plate portion 5 b. Thus, the plate portion 5 b has a rectangular shape according to the shape of the slit 5 a. The louvers 5 are provided at the respective slits 5 a formed along the axial direction Y of the flat heat transfer tubes 3. The louvers 5 are arranged in parallel in a depth direction of the fin portion 40 that corresponds to the flow direction Z of air. That is, the louvers 5 are arranged in parallel along an air flow. It should be noted that the shapes and sizes of the slit 5 a and the plate portion 5 b are not limited to those illustrated in the figures. In addition, of the plurality of fin portions 40, some fins portions 40 may be formed to include louvers 5 or all the fin portions 40 may be formed to include the louvers 5.
The fin portions 40 each have a drain hole 6 that allows condensed water W flowing over the upper surface of the fin portion 40 to drain therefrom. Of the fin portions 40, only some fin portions 40 or all the fin portions 40 may have such drain holes 6 as described above. In addition, for example, the shape of each of the drain holes 6 and the number and arrangement of the drain holes 6 as illustrated in the figures are examples and are not limited to those illustrated in the figures.
When the heat exchanger 100 operates as a condenser, high-temperature and high-pressure refrigerant flows through the refrigerant flow passages 30 of the flat heat transfer tubes 3. By contrast, when the heat exchanger 100 operates as an evaporator, low-temperature and low-pressure refrigerant flows through the refrigerant flow passages 30 of the flat heat transfer tubes 3. When the heat exchanger 100 operates as an evaporator, as indicated by an arrow in FIG. 1 , the refrigerant flows into the lower header 2 through an inlet pipe 10 that is provided for supplying of the refrigerant into the heat exchanger 100 from an external device (not illustrated). The refrigerant that has flowed into the lower header 2 is distributed to the flat heat transfer tubes 3 and passes through the refrigerant flow passages 30 of each of the flat heat transfer tubes 3. At each of the flat heat transfer tubes 3, heat exchange is performed between refrigerant that passes through the refrigerant flow passages 30 and outside air that flows outside the tube. At this time, the refrigerant receives heat from the outside air while passing through the refrigerant flow passages 30. The refrigerant that has passed through the refrigerant flow passages 30 of each of the flat heat transfer tubes 3 and has been subjected to heat exchange flows into the upper header 1 and joins other refrigerant in the upper header 1; that is, those refrigerant is combined into single refrigerant. The single refrigerant obtained through the above joining in the upper header 1 passes through an outlet pipe 11 connected to the upper header 1 and flows back to an external device (not illustrated).
In the case where the heat exchanger 100 operates as an evaporator, when the surface temperature of each of the fin portions 40 decreases, moisture in air close to the surface of the fin portion 40 is precipitated to change into condensed water W, and, when the surface temperature further decreases to fall below freezing, the condensed water W freezes to change into frost. It should be noted that in general, in the heat exchanger 100, the amount of heat exchange is large on the upstream side of an air passage where the difference in temperature between air and the fin portion 40 is great, and the amount of the condensed water W generated on the surface of the fin portion 40 is thus also large on the upstream side of the air passage. In addition, according to the analyses and experiments conducted by the inventors and other participants, it is found as a problem that at part of the fin portion 40 where the louver 5 is formed and the heat transfer coefficient is thus high, the amount of the condensed water W is large, and when being formed, frost tends to close a gap between adjacent louvers 5, as a result of which resistance to frost formation is low. The resistance to frost formation means that the heating performance for the operating time under a low temperature condition is large. That is, in the case where the heat exchanger 100 is configured such that the resistance to frost formation is high, it is possible to reduce deterioration of the performance for the operating time that would be caused by closure of an air passage due to frost formation. It should be noted that at part of the fin portion 40 where no louver 5 is provided, closure of the air passage due to frost formation does not easily occur, and the resistance to frost formation is thus high.
Thus, in the heat exchanger 100 according to Embodiment 1, as illustrated in FIG. 3 , louvers 5A and 5B that have different configurations to vary the amount of frost that is to be formed are provided at respective selected ones of the fin portions 40. The louvers 5A and 5B having different configurations have different widths in the parallel arrangement direction X of the flat heat transfer tubes 3. The louvers 5A and 5B having different configurations are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in the heat exchanger 100 as illustrated in FIG. 3 , fin portions 40A each including a plurality of louvers 5A having a great width in the parallel arrangement direction X of the flat heat transfer tubes 3 and fin portions 40B each including a plurality of louvers 5B having a small width in the parallel arrangement direction X of the flat heat transfer tubes 3 are alternately arranged in the axial direction Y of the flat heat transfer tubes 3. Thus, as illustrated in FIG. 3 , as the heat exchanger 100 is viewed from the upstream side in the flow direction Z of air, low frost formation spaces S are formed on both sides of each of the louvers 5B having a small with.
As illustrated in FIG. 3 , the fin portions 40A and 40B each appear to be linear as the heat exchanger 100 is viewed from the upstream side in the flow direction Z of air. In addition, inclined surfaces of the louvers 5A and 5B appear to protrude upward and downward from such linear portions of the fin portions 40A and 40B. In the heat exchanger 100, air flows in parallel with the surfaces of the fin portions 40A and 40B, and when air comes into contact with the louvers 5A and 5B protruding upward and downward and performs heat exchange, water vapor contained in the air is cooled to change into condensed water W and freezes to change into frost. Thus, the larger the areas of portions of the louvers 5A and 5B that protrude upward and downward from the surfaces of the fin portions 40A and 40B as the louvers 5A and 5B are viewed from the upstream side in the flow direction Z of air, the larger the amount of formed frost. In general, the sum of the areas of the protruding portions of the louvers 5A and 5B at each of the fin portions 40A and the fin portions 40B is calculated, and a fin portion in which the sum of the protruding areas of louvers 5A is large is the fin portion 40A including the louvers 5A, on which a large amount of frost is to be formed; and a fin portion in which the sum of the protruding areas of louvers 5B is small is the fin portion 40B including the louvers 5B, on which a small amount of frost is to be formed.
In the heat exchanger 100 according to Embodiment 1, the fin portions 40A each including the louvers 5A, on which a large amount of frost is to be formed, and the fin portions 40B each including the louvers 5B, on which a small amount of frost is to be formed, are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3. Thus, as illustrated in FIG. 3 , as the heat exchanger 100 is viewed from the upstream side in the flow direction Z of air, the low frost formation spaces S where frost is not easily formed are provided, whereby it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and to cause air to flow from the upstream side to the downstream side, thereby improving the resistance to frost formation.
In addition, in the heat exchanger 100 according to Embodiment 1, the plurality of fin portions 40 may include fin portions 40 including no louver 5. Because frost is not easily formed on the fin portions 40 including no louver 5, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and thus cause air to flow from the upstream side to the downstream side.
It should be noted that FIG. 4 is a front view schematically illustrating still another related part of the heat exchanger 100 according to Embodiment 1 that is different in configuration from the related part as illustrated in FIG. 3 . As illustrated in FIG. 4 , in the heat exchanger 100 according to Embodiment 1, the plurality of fin portions 40 may be paired such that any two fin portions 40 arranged consecutively in the axial direction Y are provided in a pair, and in each of pairs formed in such a manner, the louvers 5A or the louvers 5B may be provided, the louvers 5 and 5B having different widths in the parallel arrangement direction X of the flat heat transfer tubes 3. In addition, although it is not illustrated, in the heat exchanger 100 according to Embodiment 1, the plurality of fin portions 40 may be divided into sets of fin portions 40 such that any three or more fin portions 40 arranged consecutively in the axial direction Y is provided as a set of fin portions 40, or the fin portions 40 may be divided into sets of fin portions 40 in another manner. In addition, three or more types of louvers 5 that have three or more different configurations may be provided at respective sets of fin portions 40. Also, in those cases, different types of louvers 5 that have different configurations are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
In addition, FIG. 5 is an explanatory view schematically illustrating an example in which the corrugated fin 4 of the heat exchanger 100 according to Embodiment 1 is manufactured by roll forming. The corrugated fin 4 is manufactured by causing a fin material 7 to pass between corrugating cutters 80 that are arranged in the up-down direction. Each of the corrugating cutters 80 may have, for example, a blade 80 a and a blade 80 b that differ in specifications. In the corrugated fins 4, it is possible to form the louvers 5A and 5B that differ in width in the parallel arrangement direction X of the flat heat transfer tubes 3, as illustrated in FIGS. 3 and 4 , by adjusting the arrangement patterns of the blades 80 a and 80 b of the corrugating cutters 80. It should be noted that the louvers 5A and 5B having different configurations may be arranged irregularly in the axial direction Y of the flat heat transfer tubes 3, but preferably, should be arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3 as illustrated in FIG. 4 , in view of the point that the corrugated fin 4 is generally manufactured by roll forming.
Next, an example of a refrigeration cycle apparatus 200 including the heat exchanger 100 having the above configuration will be described with reference to FIG. 6 . FIG. 6 is a refrigerant circuit diagram of the refrigeration cycle apparatus 200 including the heat exchanger 100 according to Embodiment 1. Regarding Embodiment 1, an air-conditioning apparatus will be described as an example of the refrigeration cycle apparatus 200.
As illustrated in FIG. 6 , in the refrigeration cycle apparatus 200 according to Embodiment 1, an outdoor unit 201 and an indoor unit 202 are connected by a gas refrigerant pipe 300 and a liquid refrigerant pipe 301, whereby a refrigerant circuit is formed. The outdoor unit 201 includes a compressor 203, a flow switching device 204, an outdoor-side heat exchanger 205, and an outdoor-side fan 206. The indoor unit 202 includes an expansion mechanism 207, an indoor-side heat exchanger 208, and an indoor-side fan 209. The compressor 203, the flow switching device 204, the outdoor-side heat exchanger 205, the expansion mechanism 207, and the indoor-side heat exchanger 208 are sequentially connected by the gas refrigerant pipe 300 and the liquid refrigerant pipe 301, whereby the refrigerant circuit is formed.
The heat exchanger 100 described regarding Embodiment 1 is used mainly as the outdoor-side heat exchanger 205. It should be noted that the heat exchanger 100 described regarding Embodiment 1 may be used as the indoor-side heat exchanger 208 or the heat exchangers 100 may be used as both the outdoor-side heat exchanger 205 and the indoor-side heat exchanger 208. In addition, the following description is made on the assumption that the refrigeration cycle apparatus 200 as illustrated in the figures is configured such that one outdoor unit 201 and one indoor unit 202 are connected to each other by the gas refrigerant pipe 300 and the liquid refrigerant pipe 301. However, the number of outdoor units 201 and the number of indoor units 202 are not limited to one.
The compressor 203 compresses sucked refrigerant to change it to high-temperature and high-pressure refrigerant and discharges the high-temperature and high-pressure. The compressor 203 is, for example, a positive displacement compressor whose operation capacity is variable and that is driven by a motor controlled by an inverter.
The flow switching device 204 is, for example, a four-way valve and has a function of switching a refrigerant flow passage between plural refrigerant flow passages. In a cooling operation, the flow switching device 204 switches the refrigerant flow passage to a refrigerant flow passage in which a refrigerant discharge side of the compressor 203 and a gas side of the outdoor-side heat exchanger 205 are connected and a refrigerant suction side of the compressor 203 and a gas side of the indoor-side heat exchanger 208 are connected. By contrast, in a heating operation, the flow switching device 204 switches the refrigerant flow passage to a refrigerant flow passage in which the refrigerant discharge side of the compressor 203 and the gas side of the indoor-side heat exchanger 208 are connected and the refrigerant suction side of the compressor 203 and the gas side of the outdoor-side heat exchanger 205 are connected. It should be noted that the flow switching device 204 may be a combination of two-way valves or three-way valves.
The outdoor-side heat exchanger 205 operates as an evaporator in the heating operation, and causes heat exchange to be performed between outdoor air and refrigerant that flows out of the expansion mechanism 207 and flows in the outdoor-side heat exchanger 205. In addition, the outdoor-side heat exchanger 205 operates as a condenser in the cooling operation, and causes heat exchange to be performed between outside air and refrigerant that is discharged from the compressor 203 and flows in the outdoor-side heat exchanger 205. The outdoor-side heat exchanger 205 sucks the outside air with the outdoor-side fan 206 and discharges air subjected to heat exchange with the refrigerant to the outside.
The expansion mechanism 207 reduces the pressure of refrigerant that flows out of the condenser to expand the refrigerant, and is, for example, an electronic expansion valve whose opening degree can be adjusted. The expansion mechanism 207 is adjusted in opening degree to control the pressure of refrigerant that flows into the outdoor-side heat exchanger 205 or the indoor-side heat exchanger 208.
The indoor-side heat exchanger 208 operates as a condenser in the heating operation, and causes heat exchange to be performed between indoor air and refrigerant that is discharged from the compressor 203 and flows in the indoor-side heat exchanger 208. In addition, the indoor-side heat exchanger 208 operates as an evaporator in the cooling operation, and causes heat exchange to be performed between the indoor air and refrigerant that flows out of the expansion mechanism 207 and flows in the indoor-side heat exchanger 208. The indoor-side heat exchanger 208 sucks the indoor air with the indoor-side fan 209 and supplies air subjected to heat exchange with the refrigerant into an indoor space.
Next, it will be described how the refrigeration cycle apparatus 200 operates in the heating operation. In the heating operation, the state of the flow switching device 204 is switched to a state indicated by dotted lines in FIG. 6 . The high-temperature and high-pressure gas refrigerant discharged from the compressor 203 after being obtained through compression by the compressor 203 passes through the flow switching device 204 and flows into the indoor-side heat exchanger 208. The gas refrigerant that has flowed into the indoor-side heat exchanger 208 exchanges heat with air in an air-conditioning target space that is sent from the indoor-side fan 209, and thus condenses and liquefies. The refrigerant that has liquefied is reduced in pressure in the expansion mechanism 207 to change into low-temperature and low-pressure two-phase gas-liquid refrigerant, and the low-temperature and low-pressure two-phase gas-liquid refrigerant then flows into the outdoor-side heat exchanger 205. The liquid refrigerant that has flowed into the outdoor-side heat exchanger 205 exchanges heat with outdoor air sent from the outdoor-side fan 206, and thus evaporates and gasifies. The refrigerant that has gasified passes through the flow switching device 204 and is re-sucked into the compressor 203.
Next, it will be described how the refrigeration cycle apparatus 200 operates in the cooling operation. In the cooling operation, the state of the flow switching device 204 is switched to a state indicated by solid lines in FIG. 6 . The high-temperature and high-pressure gas refrigerant discharged from the compressor 203 after being obtained through compression by the compressor 203 passes through the flow switching device 204 and flows into the outdoor-side heat exchanger 205. The gas refrigerant that has flowed into the outdoor-side heat exchanger 205 exchanges heat with outdoor air sent from the outdoor-side fan 206, and thus condenses and liquefies. The refrigerant that has liquefied is reduced in pressure in the expansion mechanism 207 to change into low-temperature and low-pressure two-phase gas-liquid refrigerant, and the low-temperature and low-pressure two-phase gas-liquid refrigerant then flows into the indoor-side heat exchanger 208. The liquid refrigerant that has flowed into the indoor-side heat exchanger 208 exchanges heat with air in the air-conditioning target space that is sent from the indoor-side fan 209, and thus evaporates and gasifies. The refrigerant that has gasified passes through the flow switching device 204 and is re-sucked into the compressor 203.

Embodiment 2

Next, a heat exchanger 101 according to Embodiment 2 will be described with reference to FIGS. 7 and 8 . FIGS. 7 and 8 are schematic plan views of related parts of the heat exchanger 101 according to Embodiment 2. It should be noted that components in Embodiment 2 that are the same as those of the heat exchanger 100 that are described above regarding Embodiment 1 will be denoted by the same reference sigs, and their descriptions will thus be appropriately omitted.
In the heat exchanger 101 according to Embodiment 2, as illustrated in FIGS. 7 and 8 , regarding the plurality of fin portions 40, different types of louver sets that are different in the number of louvers 5 are provided at respective selected sets of fin portions 40. In such a manner, different types of louver sets that are different in the number of louvers 5 are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in the heat exchanger 101 according to Embodiment 2, fin portions 40A including a large number of louvers 5 as illustrated in FIG. 7 and fin portions 40B including a small number of the louvers 5 as illustrated in FIG. 8 are alternately arranged in the axial direction Y of the flat heat transfer tubes 3. In each of the fin portions 40B having a small number of louvers 5, because the coefficient of heat transfer to which the louvers 5 contribute is small, the amount of frost to be formed is reduced, and a low frost formation space can thus be formed. Thus, in the heat exchanger 100 according to Embodiment 2, because of the fin portions 40B each including a small number of louvers 5 are provided, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and to cause air to flow from the upstream side to the downstream side, thereby improving the resistance to frost formation. It should be noted that the number of the louvers 5 is not limited to the numbers of louvers 5 illustrated in the figures and are changed as appropriate depending on the performance of the heat exchanger 101.
It should be noted that the heat exchanger 101 according to Embodiment 2 may be configured such that the plurality of fin portions 40 include fin portions 40 including no louver 5. Because frost is not easily formed on the fin portions 40 including no louver 5, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and cause air to flow from the upstream side to the downstream side. In addition, although it is not illustrated, in the heat exchanger 101 according to Embodiment 2, the plurality of fin portions 40 may be paired such that any two fin portions 40 consecutively arranged in the axial direction Y of the flat heat transfer tubes 3 are provided in a pair, and in pairs formed in such a manner, respective types of louvers 5 having different configurations may be provided. In addition, although it is not illustrated, the plurality of fin portions 40 may be divided into sets of fin portions 40 such that any three or more fin portions 40 consecutively arranged in the axial direction Y of the flat heat transfer tubes 3 are provided as a set of fin portions, or the fins portions 40 may be divided in sets of fin portions 40 in another manner. In addition, three or more types of louver sets that are different in the number of louvers 5 may be provided at respective selected sets of fin portions 40. In the above cases, different types of louver sets that are different in the number of louvers 5 as described above are arranged at respective repetitive patterns intervals in the axial direction Y of the flat heat transfer tubes 3.
In addition, the heat exchanger 101 according to Embodiment 2 may incorporate such features of the heat exchanger 100 as described above regarding Embodiment 1.

Embodiment 3

Next, a heat exchanger 102 according to Embodiment 3 will be described with reference to FIGS. 9 and 10 . FIGS. 9 and 10 are schematic plan views of related parts of the heat exchanger 102 according to Embodiment 3. It should be noted that in Embodiment 3, components that are the same as those of the heat exchangers 100 and 101 described above regarding Embodiments 1 and 2 will be denoted by the same reference sigs, and their descriptions will thus be omitted as appropriate.
In the heat exchanger 102 according to Embodiment 3, as illustrated in FIGS. 9 and 10 , the fin portions 40 are provided such that the positions of louvers 50 and 51 located on the most upstream sides of air passages at selected ones of the fin portions 40 are different from each other. The louvers 50 and 51 that are different in the above manner are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in a fin portion 40A as illustrated in FIG. 9 , a louver 50 located on the most upstream side of the air passage is formed at a position that is separated in a direction toward the downstream side, by a distance L1, from the upstream end portion of the flat heat transfer tube 3. In addition, in a fin portion 40B as illustrated in FIG. 10 , louver 51 located on the most upstream side of the air passage is formed at a position that is separated in the direction toward the downstream side, by a distance L2, from the upstream end portion of the flat heat transfer tube 3. The relationship between the distance L1 and the distance L2 is expressed by L1 >L2. The fin portions 40A including the louvers 50 and the fin portions 40B including the louvers 51 are alternately arranged in the axial direction Y of the flat heat transfer tubes 3.
By forming a louver 50 located on the most upstream side of the air passage, at a position that is located apart from the upstream end portion of the flat heat transfer tube 3 in the direction toward the downstream side, like the fin portion 40A as illustrated in FIG. 9 , air is gently subjected to heat exchange on a surface of part of the fin portion 40A that is located upstream of the louver 50, and frost is thus formed uniformly. In the fin portion 40A, the amount of water that is condensed at a position close to the louver 50 provided on the most upstream side of the air passage is small. Thus, frost formation is reduced, and a low frost formation space can thus be formed. Therefore, in the heat exchanger 100 according to Embodiment 3, with the fin portion 40A in which the louver 50 provided on the most upstream side of the air passage is formed at a position located apart from the upstream end portion of the flat heat transfer tube 3 in the direction toward the downstream side, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and cause air to flow from the upstream side to the downstream side, thereby improving the resistance to frost formation. It should be noted that the number of the louvers 5 is not limited to that of the louvers 5 as illustrated in the figures, and is changed as appropriate depending on the performance of the heat exchanger 102.
It should be noted that in the heat exchanger 102 according to Embodiment 3, the plurality of fin portions 40 may include fin portions 40 including no louver 5. At the fin portions 40 including no louver 5, because front is not easily formed, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and cause air to flow from the upstream side to the downstream side.
Although it is not illustrated, in the heat exchanger 102 according to Embodiment 3, the plurality of fin portions 40 may be paired such that any two fin portions 40 consecutively arranged in the axial direction Y of the flat heat transfer tubes 3 are provided in a pair, and in pairs formed in such a manner, respective types of louvers 5 having different configurations may be provided. In addition, although It is not illustrated, the plurality of fin portions 40 may be divided into sets of fin portions 40 such that any three or more fin portions 40 consecutively arranged in the axial direction Y of the flat heat transfer tubes 3 are provided as a set of fin portions 40, or the fins portions 40 may be divided into sets of fin portions 40 in another manner. In addition, three or more types of louvers 5 having different configurations may be provided at respective selected fin portions 40. In the above cases, different types of louvers 5 having different configurations as described above are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
In addition, the heat exchanger 100 according to Embodiment 3 may incorporate such features of the heat exchangers 100 and 101 as described above regarding Embodiments 1 and 2.

Embodiment 4

Next, a heat exchanger 103 according to Embodiment 4 will be described with reference to FIGS. 11 to 14 . FIG. 11 is a schematic plan view of a related part of the heat exchanger 103 according to Embodiment 4. FIG. 12 is a sectional view that is taken along line A-A in FIG. 11 . FIG. 13 is a sectional view that is taken along line A-A in FIG. 11 and illustrates a configuration different from that in FIG. 12 . It should be noted that regarding Embodiment 4, components that are the same as those of the heat exchangers 100 to 102 as described above regarding Embodiments 1 to 3 will be denoted by the same reference sigs, and their descriptions will thus be omitted.
In the heat exchanger 103 according to Embodiment 4, as illustrated in FIGS. 11 to 13 e, different types of louvers 5 that are different in inclination angle θ of the plate portion 5 b are provided at respective selected fin portions 40. The different types of louvers 5 that have different configurations are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in the heat exchanger 103 according to Embodiment 4, fin portions 40 A including louvers 52 each including a plate portion 5 b whose inclination angle θ1 is small as illustrated in FIG. 12 and fin portions 40 B including louvers 53 each including a plate portion 5 b whose inclination angle θ2 is large as illustrated in FIG. 13 are alternately arranged in the axial direction Y of the flat heat transfer tubes 3. Arrows B as shown in FIGS. 12 and 13 indicate the flows of air that pass through the slits 5 a. It should be noted that the plate portion 5 b formed upstream of the drain hole 6 in the air passage and the plate portion 5 b formed downstream of the drain hole 6 in the air passage are inclined in opposite directions but may be inclined in the same direction.
As compared with the fin portion 40A including the louver 53 including the plate portion 5 b whose inclination angle θ2 is large, the fin portion 40A including the louver 52 including the plate portion 5 b whose inclination angle θ1 is small can reduce frost formation because the heat transfer coefficient at the louver 52 is small. Therefore, a low frost formation space can be formed. Accordingly, in the heat exchanger 100 according to Embodiment 4, because of the presence of the fin portions 40A including the louvers 52 having the plate portions 5 b whose inclination angles θ1 are small, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and to cause air to flow from the upstream side to the downstream side, thereby improving the resistance to frost formation.
FIG. 14 is a graph indicating a relationship between time that is required to drain the condensed water W and varies depending on the inclination angle θ of the plate portion 5 b and the amount of remaining water on the surface of the fin portion 40 that varies depending on the inclination angle θ of the plate portion 5 b, in the heat exchanger 103 according to Embodiment 4. In FIG. 14 , the horizontal axis represents time and the vertical axis represents the amount of remaining water; and the inclination angles θ of the plate portion 5 b are angles of 15 degrees, 20 degrees, 30 degrees, and 40 degrees. The graph of FIG. 14 demonstrates that in a short time period, the smaller the amount of remaining water, the better the drainage. In the heat exchanger 103, when the inclination angle θ of the plate portion 5 b is excessively decreased, the drainage is worsened, and the remaining water may refreeze. As a result, formed frost is increased, and the resistance to frost formation is reduced. According to the experiments and analyses made by the inventors and other participants, it is preferable that the louver 5 be formed such that the inclination angle θ of the plate portion 5 b falls within the range of 20 degrees ≤θ≤40 degrees, in order to improve the resistance to frost formation in consideration of the drainage performance. For example, in the case illustrated in FIGS. 12 and 13 , it is appropriate that the inclination angles θ1 and θ2 of the plate portions 5 b are set to 20 degrees ≤θ1<θ2≤40.
It should be noted that in the heat exchanger 103 according to Embodiment 4, the plurality of fin portions 40 may include fin portions 40 including no louver 5. In this case, because frost is not easily formed on the fin portions 40 including no louver 5, it is possible to reduce the likelihood that the air passage will be closed, for a long time period, and to cause air to flow from the upstream side to the downstream side.
In addition, although it is not illustrated, in the heat exchanger 103 according to Embodiment 4, the plurality of fin portions 40 are paired such that any two fin portions 40 arranged consecutively in the axial direction Y are provided in a pair, and in pairs formed in such a manner, respective different types of louvers 5 having different configurations may be provided. In addition, although it is not illustrated, the plurality of fin portions 40 may be divided into sets of fin portions such that any three or more fin portions 40 arranged consecutively in the axial direction Y are provided as a set of fin portions 40, or the fin portions 40 may be divided into sets of fin portions 40 in another manner. In addition, three or more types of louvers 5 having respective three or more different configurations may be provided at respective selected sets of fin portions 40. Also, in the above cases, different types of louvers 5 having different configurations are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
In addition, the heat exchanger 103 according to Embodiment 4 may incorporate such features of the heat exchangers 100 to 102 as described above regarding Embodiments 1 to 3.

Embodiment 5

Next, a heat exchanger 104 according to Embodiment 5 will be described with reference to FIGS. 15 and 16 . FIGS. 15 and 16 are schematic plan views of related parts of the heat exchanger 104 according to Embodiment 5. It should be noted that regarding Embodiment 5, components that are the same as those of the heat exchangers 100 to 103 as described regarding Embodiments 1 to 4 will be denoted by the same reference signs, and their descriptions will thus be omitted as appropriate.
In the heat exchanger 104 according to Embodiment 5, as illustrated in FIGS. 15 and 16 , different types of rain holes 6 that have different configurations to cause different amounts of frost to be formed are provided in respective selected sets of fin portions 40. The above drain holes 6 having different configurations are drain holes that are made different from each other such that the total opening area of drain holes 6 formed in one fin portion 40 is different from that of drain holes formed in another fin potion 40. The different types of drain holes 6 having different configurations are provided arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in the heat exchanger 104 according to Embodiment 5, fin portions 40A as illustrated in FIG. 15 each of which has a plurality of drain holes 6 whose total opening area is small and fin portions 40B as illustrated in FIG. 16 each of which has a plurality of drain holes 6 whose total opening area is large are alternately arranged in the axial direction Y of the flat heat transfer tubes 3. As illustrated in FIG. 15 , in the fin portion 40A having the drain holes 6 whose total opening area is small, for example, two drain holes 6 having the same shape and size are arranged in the flow direction Z of air.
As illustrated in FIG. 16 , in the fin portion 40B having the drain holes 6 whose total opening area is large, for example, four drain holes 6 having the same shape and size are provided, and two of the four drain holes 6 are arranged in the flow direction Z of air and the other two of the four drain holes 6 are arranged in the parallel arrangement direction X of the flat heat transfer tubes 3.
In the fin portion 40B having the drain holes 6 whose total opening area is large, the drainage rate of the condensed water W is high and the amount of remaining water is thus small, whereby the condensed water W on the surface does not easily freeze even under the low temperature condition. Furthermore, in the heat exchanger 104, because the fin portions 40B have a small heat transfer coefficient because of the presence of the drain holes 6, low frost formation spaces where frost does not easily grow are provided in the vicinities of the drain holes 6, and the resistance to frost formation can thus be improved. In addition, part of the fin portion 40B that is located between adjacent drain holes 6 serves as a water guiding region, and the condensed water W falls down along the water guiding region to enter the drain holes 6, thereby improving the drainage performance.
It should be noted that, for example, the shapes, the number, and the arrangement of the drain holes 6 are not limited to those as illustrated in the figures.
For example, drain holes 6 having different shapes may be formed in the same fin portion 40. In addition, the louvers 5 of the heat exchanger 104 according to Embodiment 5 are formed to have any of the configurations described above regarding Embodiments 1 to 4.
In addition, although it is not illustrated, in the heat exchanger 104 according to Embodiment 5, the plurality of fin portions 40 may be paired such that any two fin portions 40 arranged consecutively in the axial direction Y of the flat heat transfer tubes 3 are provided in a pair, and in pairs formed in such a manner, respective types of drain holes 6 that have different configurations may be provided. In addition, although it is not illustrated, the plurality of fin portions 40 may be divided into sets of fin portions 40 such that any three or more fin portions 40 arranged consecutively in the axial direction Y of the flat heat transfer tubes 3 are provided as a set of fin portions 40, or the fin portions 40 may be divided into sets of fin portions 40 in another manner. In addition, three or more types of drain holes 6 that have different configurations may be formed in respective selected sets of fin portions 40. In the above cases, different types of drain holes 6 that have different configurations are arranged at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
FIGS. 17 and 18 are schematic plan views of related parts of a modification of the heat exchanger 104 according to Embodiment 5. In a heat exchanger 104A as illustrated in FIGS. 17 and 18 , different types of drain holes 6 that have different opening areas are provided in respective selected sets of fin portions 40. In the heat exchanger 104A as illustrated in FIGS. 17 and 18 , each of the fin portions 40 is formed to have a single drain hole 6. The different types of drain holes 6 that have different configurations are formed at respective repetitive patterns in the axial direction Y of the flat heat transfer tubes 3.
Specifically, in the heat exchanger 104A, fin portions 40A as illustrated in FIG. 17 each of which has a drain hole 60 having a small opening area and fin portions 40B as illustrated in FIG. 18 each of which has a drain hole 61 having a large opening area are alternately arranged in the axial direction Y. In the heat exchanger 104A as illustrated in FIGS. 17 and 18 , in the fin portion 40B having the drain hole 61 having a large opening area, the drainage rate of the condensed water W is high and the amount of remaining water is thus small, whereby the condensed water W on the surface does not easily freeze even under the low temperature condition. In addition, in the heat exchanger 104A, because the fin portion 40B has a small heat transfer coefficient because of the presence of the drain hole 61, a low frost formation space where frost does not easily grow in the vicinity of the drain hole 61 is provided, and the resistance to frost formation can be improved. It should be noted that the shapes and the arrangements of the drain holes 60 and 61 are illustrated by way of example and are not limited to those illustrated in the figures.

Embodiment 6

Next, a heat exchanger 105 according to Embodiment 6 will be described with reference to FIGS. 19 and 20 . FIG. 19 is a schematic plan view of a related part of the heat exchanger 105 according to Embodiment 6. It should be noted that regarding Embodiment 6, components that are the same as those of the heat exchangers 100 to 104 described above regarding Embodiments 1 to 5 will be denoted by the same reference signs, and their descriptions will thus be omitted as appropriate.
As illustrated in FIG. 19 , the heat exchanger 105 according to Embodiment 6 includes flat heat transfer tubes 3 arranged in two rows in the flow direction Z of air. The flat heat transfer tubes 3 include flat heat transfer tubes 3A arranged on the upstream side of the air passage and flat heat transfer tubes 3B arranged on the downstream side of the air passage. It should be noted that the arrangement of the flat heat transfer tubes 3 is not limited to the arrangement of two rows as illustrated in the figure and may be the arrangement of three or more rows in the flow direction Z of air. The louvers 5 or the drain holes 6 that have any of the configurations described above regarding Embodiments 1 to 5 are formed in the fin portions 40. In general, in the heat exchanger 105, at part of the fin portion 40 that is surrounded by the flat heat transfer tubes 3B on the downstream side of the air passage, the amount of formed frost is smaller and a lower frost formation space is formed than at part of the fin portion 40 that is surrounded by the flat heat transfer tubes 3A on the upstream side of the air passage. Thus, by applying any of the configurations described above regarding Embodiments 1 to 5 to the part of the fin portion 40 that is surrounded by the flat heat transfer tubes 3A on the upstream side of the air passage, the heat exchanger 105 can reduce the likelihood that the air passage will be closed at parts of the fin portion 40 that are located on the downstream side and upstream side of the air passage, for a long time period, and to cause air to flow from the upstream side to the downstream side, thus improving the resistance to frost formation.
FIG. 20 is a graph indicating a relationship between the dimension of the fin portion 40 in the flow direction Z of air and the rate of improvement of the heating performance at low temperature. In FIG. 20 , the horizontal axis represents the dimension of the fin portion 40 in the flow direction Z of air and the vertical axis represents the rate of improvement of the heating performance at low temperature. In the heat exchanger 105, as indicated by FIG. 20 , the longer the fin portion 40 in the flow direction Z of air, the greater the improvement of the heating performance at low temperature. It should be noted that according to the experiments and analyses made by the inventors and other participants, it is confirmed that as illustrated in FIG. 19 , a remarkable advantage can be obtained, especially when a length L3 of the fin portion 40 in the flow direction Z of air is set to 22 mm or more.
The above description is made by referring to the embodiments of the heat exchanger 100 and the refrigeration cycle apparatus 200, but is not limiting. For example, the configurations of the heat exchangers (100 to 105) and the refrigeration cycle apparatus 200 are not limited to those as illustrated in the figures and may include another component. In short, the heat exchangers (100 to 105) and the refrigeration cycle apparatus 200 encompass design changes and application variations that are ordinarily made by a person with ordinarily skill in the art, without departing from the technical ideas of the heat exchangers (100 to 105) and the refrigeration cycle apparatus 200.

REFERENCE SIGNS LIST

1, 2: header, 3, 3A, 3B: flat heat transfer tube, 4: corrugated fin, 5, 5A, 5B: louver, 5 a: slit, 5 b: plate portion, 6: drain hole, 7: fin material, 10: inlet pipe, 11: outlet pipe, 30: refrigerant flow passage, 31: flat surface, 40, 40A, 40B: fin portion, 41: ridge portion, 50, 51, 52, 53: louver, 60, 61: drain hole, 80: corrugating cutter, 80 a, 80 b: blade, 100, 101, 102, 103, 104, 104A, 105: heat exchanger, 200: refrigeration cycle apparatus, 201: outdoor unit, 202: indoor unit, 203: compressor, 204: flow switching device, 205: outdoor-side heat exchanger, 206: outdoor-side fan, 207: expansion mechanism, 208: indoor-side heat exchanger, 209: indoor-side fan, 300: gas refrigerant pipe, 301: liquid refrigerant pipe, S: low frost formation space, X: parallel arrangement direction, Y: pipe axial direction, Z: flow direction, W: condensed water

Claims

1. A heat exchanger comprising:

a plurality of flat heat transfer tubes each having an elongated cross-sectional shape, each including a plurality of refrigerant flow passages therein, and arranged apart from each other and in parallel with each other; and

a plurality of corrugated fins each provided between associated adjacent ones of the flat heat transfer tubes,

wherein

each of the plurality of corrugated fins has a plurality of fin portions each having a plate shape, and is bent into a wave shape such that the plurality of fin portions are arranged alongside of each other in an axial direction of the flat heat transfer tubes,

the plurality of fin portions include louvers, and

the louvers are made as different types of louvers to have different configurations, such that the different types of louvers are provided at respective selected sets of fins portions of the plurality of fin portions, to thereby cause different amounts of frost to be formed on the plurality of fin portions.

2. The heat exchanger of claim 1, wherein the different types of louvers are arranged at respective repetitive patterns in the axial direction of the flat heat transfer tubes.

3. The heat exchanger of claim 1 , wherein the different types of louvers are different in width in a direction in which the flat heat transfer tubes are arranged.

4. The heat exchanger of claim 1, wherein the different types of louvers are different in number of the louvers provided at one fin portion.

5. The heat exchanger of claim 1, wherein

each of the louvers has a slit through which air passes and a plate portion that is inclined relative to an associated one of the plurality of fin portions and guides air into the slit, and

the different types of louvers are different in inclined angle of the plate portion.

6. The heat exchanger of claim 1, wherein the plurality of fin portions include the fin portions having no louver.

7. The heat exchanger of claim 1, wherein

the plurality of fin portions have drain holes to drain water that flows over upper surfaces of the plurality of fin portions, and

the drain holes are made as different types of drain holes to have different configurations, such that the different types of drain holes are formed in respective selected sets of fin portions of the plurality of fin portions, to thereby cause different amounts of frost to be formed on the fins portions.

8. The heat exchanger of claim 7, wherein the drain types of drain holes are different in total opening area of the drain holes formed in the one fin portion.

9. The heat exchanger of claim 1, wherein a dimension of each of the plurality of fin portions in a flow direction of air is 22 mm or more.

10. A refrigeration cycle apparatus comprising the heat exchanger of claim 1.