JP4334588B2 - Heat exchanger - Google Patents

Abstract

In a parallel-flow-type heat exchanger, the shape of corrugated fins is improved such that heat exchange performance is enhanced and that it is possible to perform smooth draining of defrost water and condensed water. The heat exchanger (1) includes a plurality of horizontal header pipes (2) and (3) arranged parallel at an interval from one another in the vertical direction, a plurality of vertical flat tubes (4) arranged at an interval from one another in the horizontal direction between the header pipes (2) and (3), with refrigerant passage (5) inside the flat tubes (4) communicate with the insides of the header pipes (2) and (3) respectively, and corrugated fins (6) arranges between the flat tubes (4). The corrugated fins (6) include upwind-side corrugated fins (6U) whose fin surface has a downward slope toward the downwind side and downwind-side corrugated fins (6D) whose fin surface has an upward slope toward the downwind side, the former and the latter being arranged with a gap (9) secured therebetween. The gap (9) is so sized as to enable water droplets sticking to the downwind-side ends of the upwind-side corrugated fins (6U) and water droplets sticking to the upwind-side ends the downwind-side corrugated fins (6D) to coalesce.

Description

  The present invention relates to a parallel flow type heat exchanger.

  A parallel flow type heat exchanger in which a plurality of flat tubes are arranged between two header pipes so that a refrigerant passage inside the flat tubes communicates with the inside of the header pipe and corrugated fins are arranged between the flat tubes is a car. Widely used for air conditioners. An example of this can be seen in US Pat.

The heat exchanger described in Patent Document 1 has a header pipe arranged horizontally and a flat tube arranged vertically, and the corrugated fin has a valley shape with the center in the depth direction of the heat exchanger as the bottom. . A through hole is provided in a portion where the corrugated fin is joined to the flat tube, and when the defrosting operation is performed to melt the frost adhering to the heat exchanger, the melted water is drained from the through hole.
JP 2005-24187 A

  In the parallel flow type heat exchanger, the corrugated fins are not linear, but have a shape that forms a valley bottom, that is, a V shape having a downward slope and an upward slope, which increases the heat radiation area and increases the heat exchange efficiency. It is effective on the above. However, there remains a problem of how to treat the dew condensation water or frost generated when this heat exchanger is used as an evaporator.

  If frost adheres between the flat tubes and the corrugated fins, the air flow is hindered and the heat exchange efficiency decreases. For this reason, it is sometimes necessary to perform a defrosting operation that reverses the roles of the evaporator and the condenser to melt the frost. However, even if a through hole as described in Patent Document 1 is provided to drain defrosted water in which frost has melted, a bridging phenomenon (the water film stretches) occurs due to the surface tension of water, It does not easily flow down from the hole. The bridging phenomenon also occurs between the corrugated fins, and even when water drips to the end of the corrugated fins, it often happens that the film is only stretched there and not dripped. The same can be said not only for defrosted water but also for condensed water before it turns into frost.

  In order to overcome the above situation, for example, if the diameter of the through hole is increased, the contact area between the flat tube and the corrugated fin is reduced, and the heat exchange performance is lowered. If the pitch between the corrugated fins is increased, the heat radiation area of the corrugated fins is reduced, and this leads to a decrease in heat exchange performance.

  The present invention has been made in view of the above points, and in a parallel flow type heat exchanger, by improving the shape of the corrugated fins, the heat exchange performance can be improved and defrosted water and condensed water can be smoothed. The purpose is to be able to drain.

In order to achieve the above object, the present invention provides a horizontal header pipe arranged in parallel in the vertical direction and a plurality of horizontal header pipes arranged in the horizontal direction between the header pipes, each having an internal refrigerant. In the heat exchanger comprising a vertical flat tube having a passage communicating with the inside of the header pipe, and a corrugated fin disposed between the flat tubes, the corrugated fin has a fin surface with a downward slope toward the leeward side. A leeward corrugated fin, and a leeward corrugated fin whose fin surface is inclined upward toward the leeward side, the leeward end of the leeward corrugated fin and the leeward end of the leeward corrugated fin DOO are arranged at a gap, said gap, before the water droplets bridging between leeward end adjacent the top and bottom of the windward corrugated fin Is characterized in that between the upwind-side end adjacent to and below the downwind-side corrugated fins in contact with water droplets bridge is set to a size to coalesce flows down each other to break the surface tension with each other.

According to this configuration, since the fin surfaces of the windward corrugated fin and the leeward corrugated fin are respectively inclined, the corrugated fin as a whole extends in the direction of air flow, and the heat radiation area increases. , Heat exchange performance is improved. On the other hand, the leeward corrugated fin and the leeward corrugated fin are not in close contact, and the leeward end of the leeward corrugated fin and the windward end of the leeward corrugated fin are adjacent to the upper and lower sides of the windward corrugated fin. the size of the gap to be in contact with the water droplet to bridge between the upwind-side end adjacent to and below the water droplets and the downwind-side corrugated fins to bridge between the downwind-side ends united by each other to break the surface tension with each other under a stream Since the defrost water is generated in the defrosting operation, the water drops on the windward corrugated fin and the water drops on the leeward corrugated fin meet each other at the gap and destroy the surface tension with each other. It flows out of the gap without causing a bridging phenomenon. For this reason, when returning from the defrosting operation to the normal operation, water droplets remaining without being drained are not frozen and the heat exchange performance is not impaired. Since the condensed water before turning into frost flows out in the same manner, the cross-sectional area of the air flow passage is narrowed by the water, and the heat exchange performance is not deteriorated.

In the heat exchanger configured as described above, by causing the leeward side end portion of the leeward side corrugated fin and the leeward side end portion of the leeward side corrugated fin to partially contact each other, the gap is generated at a place other than the contact portion. Also good. According to this configuration, if the leeward side end of the leeward corrugated fin and the leeward side end of the leeward corrugated fin are brought into contact with each other to cause a partial contact, a gap is generated in a place other than the contact part. Can be assembled easily and with high productivity.

In the heat exchanger configured as described above, the leeward side end portion of the leeward corrugated fin and the leeward side end portion of the leeward corrugated fin may be displaced from each other in the vertical direction.

  According to the present invention, in a parallel flow type heat exchanger, defrost water and dew condensation water can be reliably drained while improving heat exchange performance.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 is a schematic vertical sectional view showing a schematic structure of a heat exchanger, FIG. 2 is a sectional view taken along line AA in FIG. 1, FIG. 3 is an enlarged partial horizontal sectional view, and FIG. FIG. 5 is a perspective view of a set of flat tubes and corrugated fins, and FIG. 6 is a side view of the set of flat tubes and corrugated fins.

  The heat exchanger 1 has two horizontal header pipes 2 and 3 arranged in parallel with a space in the vertical direction, and a vertical flat tube 4 between the header pipes 2 and 3 in the horizontal direction. A plurality of refrigerant passages 5 are arranged at a predetermined pitch, and the refrigerant passages 5 in the flat tubes 4 are communicated with the header pipes 2 and 3. The header pipes 2 and 3 and the flat tube 4 are fixed by welding. Corrugated fins 6 are disposed between the flat tubes 4. The flat tube 4 and the corrugated fin 6 are also fixed by welding. The header pipes 2 and 3, the flat tubes 4, and the corrugated fins 6 are all made of a metal (for example, aluminum) having good heat conduction. In FIG. 1, the upper side of the drawing is the upper side in the vertical direction, the lower side of the drawing is the lower side in the vertical direction, and a plurality of flat tubes 4 are arranged between the upper header pipe 2 and the lower header pipe 3 in the longitudinal direction. The configuration is arranged at a predetermined pitch.

  Since many flat tubes 4 are provided between the header pipes 2 and 3 and corrugated fins 6 are provided between the flat tubes 4, the heat exchanger 1 has a large heat radiation (heat absorption) area, and efficiently exchanges heat. It can be performed. A refrigerant inlet 7 is provided at one end of the lower header pipe 3, and a refrigerant outlet 8 is provided at one end of the upper header pipe 2 at a position diagonal to the refrigerant inlet 7.

  Subsequently, the structure of the corrugated fin 6 will be described with reference to FIGS. 2, 3, 5, and 6. 2, 3, and 6, the left side of the drawing is the windward side, the right side of the drawing is the leeward side, and in FIG. 5, the left front side of the drawing is the upwind side, and the far right side of the drawing is the leeward side.

  As shown in FIGS. 2 and 3, the corrugated fin 6 is divided into an upwind corrugated fin 6 </ b> U and a downwind corrugated fin 6 </ b> D, and each is welded to the flat tube 4. The windward corrugated fin 6U has a downward slope toward the leeward side of the fin surface. The leeward side corrugated fin 6 </ b> D has a fin surface with an upward slope toward the leeward side. The descending slope of the leeward corrugated fin 6U and the ascending slope of the leeward corrugated fin 6D have the same angle. The horizontal lengths of the windward corrugated fin 6U and the leeward corrugated fin 6D in the air flow direction are equal to each other.

  When the windward corrugated fin 6U and the leeward corrugated fin 6D are viewed from a direction perpendicular to the air flow, a large number of V-shaped shapes appear to be lined up and down. However, the bottom of the V shape is not closed but open. That is, the leeward corrugated fin 6U and the leeward corrugated fin 6D are not in close contact with each other but are disposed with a gap 9 therebetween. The gap 9 is set to such a size that the water droplets attached to the leeward end of the leeward corrugated fin 6U and the water droplets attached to the leeward end of the leeward corrugated fin 6D can be combined.

  When the refrigerant flows through the heat exchanger 1 while blowing air with a fan (not shown), in the operation mode in which the heat exchanger 1 is used as an evaporator (for example, outdoor of a separate air conditioner composed of an indoor unit and an outdoor unit) When the heat exchanger 1 is used to perform a heating operation, the heat exchanger 1 acts as an evaporator.) The heat exchanger 1 takes heat from the air and conversely releases cold energy into the air. Since the fin surfaces of the windward corrugated fin 6U and the leeward corrugated fin 6D are respectively inclined, the corrugated fin 6 as a whole is longer in the air flow direction than the case where the corrugated fin is horizontal without being inclined. It exists in the extended form, and high heat exchange performance can be obtained.

  When the operation of taking the heat from the air is continued, moisture in the air is condensed on the surface of the windward corrugated fin 6U, the surface of the leeward corrugated fin 6D, and the surface of the flat tube 4. When water droplets that were initially finely gathered into large water droplets, they flow down along the slope surface of the windward corrugated fin 6U or the leeward corrugated fin 6D and reach the gap 9. If the gap 9 is wide, the water droplets will only cause a bridging phenomenon at the leeward end of the leeward corrugated fin 6U or the leeward end of the leeward corrugated fin 6D. However, the gap 9 is set to such a size that the water droplets attached to the leeward end of the leeward corrugated fin 6U and the water droplets attached to the leeward end of the leeward corrugated fin 6D can be combined. When the water droplets on the fins 6U and the water droplets on the leeward side corrugated fin 6D meet at the gap 9, they break up and merge with each other, and flow out of the gap 9 without causing a bridging phenomenon.

  In the operation mode in which the heat exchanger 1 is used as an evaporator (the operation mode in which the heat exchanger 1 takes heat from the outdoor air), the surface of the flat tube 4 and the corrugated fin 6 depending on the ambient air temperature condition and the operation condition. In some cases, moisture in the air adheres as frost. As time goes on, frost increases in thickness and reduces heat exchange performance, so it must sometimes be defrosted to melt the frost. When defrosted water in which frost has melted also meets in the gap 9, the surface tensions of the defrosted water break apart and coalesce and flow out of the gap 9 without causing a bridging phenomenon. For this reason, when returning from the defrosting operation to the normal operation, water droplets remaining without being drained are not frozen and the heat exchange performance is not impaired.

  The descending slope of the windward corrugated fin 6U and the ascending slope of the leeward corrugated fin 6D can be selected in the range of 5 ° to 40 °. When the gradient becomes stiff, the heat exchange area increases and drainage becomes easier, while resistance to air flow is good. In addition, the distance between the flat tubes 4 is 5.5 mm, the thickness of the flat tubes 4 is 1.3 mm, the horizontal length of the windward corrugated fin 6U and the leeward corrugated fin 6D in the air flow direction is 18 mm, respectively, and the windward side. Examples are numerical values such that the peak-to-valley pitches of the corrugated fins 6U and the leeward corrugated fins 6D are 2 mm to 3 mm, and the size of the gap 9 is 0.5 mm at the maximum. Needless to say, these numerical values are merely examples and do not limit the content of the invention.

  Next, other embodiments of the present invention will be described.

  A second embodiment of the present invention is shown in FIGS. FIG. 7 is a perspective view of a flat tube and corrugated fins. FIG. 8 is a side view of the flat tube and corrugated fins. In FIG. 7, the left front side of the paper is the windward side, the back right side of the paper is the leeward side, and the left side of the paper is the windward side and the right side of the paper is the leeward side in FIG.

  The second embodiment differs from the first embodiment in the angle of the gradient of the windward corrugated fin 6U and the leeward corrugated fin 6D. That is, the descending slope of the windward corrugated fin 6U is gentler than that of the first embodiment, and conversely, the ascending slope of the leeward corrugated fin 6D is steeper than that of the first embodiment.

  A third embodiment of the present invention is shown in FIGS. FIG. 9 is a perspective view of a set of flat tubes and corrugated fins, and FIG. 10 is a side view of the set of flat tubes and corrugated fins. In FIG. 9, the left front side of the paper is the windward side, the back right side of the paper is the leeward side, and the left side of the paper is the windward side and the right side of the paper is the leeward side in FIG.

  The third embodiment is different from the first embodiment in that the gap 9 between the windward corrugated fin 6U and the leeward corrugated fin 6D is shifted from the center of the width of the flat tube 4 in the air flow direction to the windward side. It is a point arranged in. That is, when the windward corrugated fin 6U and the leeward corrugated fin 6D have the same horizontal length in the air flow direction and longer than the first embodiment, the windward end portion of the windward corrugated fin 6U is flat. The leeward end of the leeward corrugated fin 6 </ b> D is disposed so as to be flush with the leeward end of the flat tube 4, while protruding from the leeward end of the tube 4.

  In other words, the sum of the horizontal lengths of the windward corrugated fins 6U and the leeward corrugated fins 6D in the air flow direction and the horizontal width of the gap 9 (hereinafter also referred to as the corrugated fin horizontal length). The flat tube 4 is arranged so as to be larger than the width of the flat tube 4 in the air flow direction so that the leeward side end of the leeward side corrugated fin 6D is flush with the leeward side end of the flat tube 4. For example, if the horizontal length of the windward corrugated fin 6U and the leeward corrugated fin 6D in the air flow direction is 18 mm and the horizontal width of the gap 9 is 0.5 mm, the horizontal length of the corrugated fin 36 is 36 mm. .5mm. If the width of the flat tube 4 in the air flow direction is 30 mm, the gap 9 is disposed at a position shifted from the center of the flat tube 4 by 3 mm to 3.5 mm toward the windward side. The 6U windward end protrudes 6.5 mm beyond the windward end of the flat tube 4.

  The horizontal lengths of the windward corrugated fins 6U and the leeward corrugated fins in the air flow direction are not necessarily the same. They may be different from each other.

  A fourth embodiment of the present invention is shown in FIGS. FIG. 11 is a perspective view of a set of flat tubes and corrugated fins, and FIG. 12 is a side view of the set of flat tubes and corrugated fins. In FIG. 11, the left front side of the page is the windward side, the back right side of the page is the leeward side, and the left side of the page is the windward side and the right side of the page is the leeward side in FIG.

  The fourth embodiment differs from the first embodiment in the lengths of the windward corrugated fin 6U and the leeward corrugated fin 6D. That is, the horizontal length in the air flow direction of the windward corrugated fin 6U and the windward corrugated fin 6D is longer than that of the first embodiment, and the windward end of the windward corrugated fin 6U is the windward end of the flat tube 4. The leeward end of the leeward corrugated fin 6D protrudes from the leeward end of the flat tube 4.

  A fifth embodiment of the present invention is shown in FIGS. FIG. 13 is a perspective view of a set of flat tubes and corrugated fins, and FIG. 14 is a side view of the set of flat tubes and corrugated fins. In FIG. 13, the left front side of the drawing is the windward side, the right back side of the drawing is the leeward side, and the left side of the drawing is the upwind side and the right side of the drawing is the leeward side in FIG.

  The fifth embodiment differs from the first embodiment in the ratio of the lengths of the windward corrugated fin 6U and the leeward corrugated fin 6D. That is, in the first embodiment, the horizontal lengths of the leeward corrugated fin 6U and the leeward corrugated fin 6D in the air flow direction are equal to each other, but in the fifth embodiment, the leeward corrugated fin 6D is closer to the leeward corrugated fin. It is longer than 6U.

  As in the examples from the first embodiment to the fifth embodiment, by changing the ratio of the corrugated fin horizontal length and the width of the flat tube 4 and the relative position of the corrugated fin 6 and the flat tube 4, various forms of The heat exchanger 1 can be realized.

  A sixth embodiment of the present invention is shown in FIG. FIG. 15 is a cross-sectional view similar to FIG. In FIG. 15, the left side of the drawing is the windward side, and the right side of the drawing is the leeward side.

  The sixth embodiment differs from the first embodiment in the configuration of the flat tube 4. That is, in the first embodiment, the windward corrugated fin 6U and the leeward corrugated fin 6D are welded to the single flat tube 4, but in the sixth embodiment, the flat tubes are the windward flat tube 4U and the leeward flat tube 4D. The windward corrugated fin 6U is welded to the windward flat tube 4U, and the leeward corrugated fin 6D is welded to the leeward flat tube 4D.

  A seventh embodiment of the present invention is shown in FIG. FIG. 16 is a cross-sectional view similar to FIG. In FIG. 16, the left side of the paper is the windward side, and the right side of the paper is the leeward side.

  The seventh embodiment is a step further than the sixth embodiment. That is, in the seventh embodiment, not only the flat tube but also the header pipe is separated into the windward header pipes 2U and 3U and the leeward header pipes 2D and 3D.

  Each of the above embodiments can be implemented by combining a plurality of the embodiments as long as there is no contradiction in the configuration.

  Since the gap 9 is the distance between the leeward end of the leeward corrugated fin 6U and the leeward end of the leeward corrugated fin 6D, not only the horizontal distance but also the vertical distance is an element of the gap 9. For example, in the configuration of FIG. 2, the height of the leeward side end of the leeward corrugated fin 6U and the height of the leeward side corrugated fin 6D are the same, so only the horizontal distance between both ends determines the size of the gap 9. Will be determined. Here, considering the configuration in which the heights of the leeward side corrugated fins 6U and the leeward side corrugated fins 6D are different in height, the vertical distance is added to the horizontal distance between both ends. It will determine the size of the gap 9.

  The gap 9 is formed by determining the relative positions of the windward corrugated fin 6U and the leeward corrugated fin 6D using a jig (not shown), and welding to the flat tube 4 in this state. It can also be adopted. The technique is to create a gap 9 at a location other than the contact portion by partially contacting the leeward side end of the leeward corrugated fin 6U and the leeward side corrugated fin 6D. is there.

  For example, the following may be performed. That is, a corrugate is formed so that it crosses the longitudinal direction of the material obliquely with respect to an elongated aluminum material (for example, a thin rectangular plate-shaped elongated aluminum material) like the windward corrugated fin 6U and the leeward corrugated fin 6D shown in FIG. A ridge shape is formed. Since the end portion of the corrugated fin formed in this way does not become straight, when the two pieces are brought into contact with each other, a contact portion (contact portion) and a non-contact portion (non-contact portion) are generated. The non-contact portion can be the gap 9. The ratio between the contact part and the non-contact part is determined so that the presence of the contact part does not extremely hinder the outflow of water.

  According to the above method, when the heat exchanger 1 is produced, the upwind corrugated fin 6U and the downwind corrugated fin 6D may be butted against the flat tube 4 and there is no need to accurately measure the interval. Productivity is improved.

The experimental results of examining the influence of the size of the gap 9 on the drainage are shown in the table of FIG. 17 and the graph of FIG. In the experiment, the heat exchanger 1 immersed in water was pulled up from the water and the mass was measured, and the difference between the measured value and the dry weight of the heat exchanger 1 was defined as the water retention amount. The measurement was performed every 2 seconds from the moment of pulling up (zero elapsed time). The unit of the water retention amount in the table is the mass of water retained therein when the surface area of the heat exchanger is 1 m ² (the actual surface area of the heat exchanger is converted in this way).

The dimensional specifications of the heat exchanger used in the above experiment are as follows. That is, the thickness of the flat tube is 1.3 mm, the size of the gap between the flat tubes is 3.5 mm, the horizontal width of the flat tube in the air flow direction is 23 mm, the horizontal width of the upwind corrugated fin in the air flow direction and the downwind The horizontal width of the air flow direction of the side corrugated fins is 18 mm, the vertical length of the windward corrugated fin and the leeward corrugated fin is both 160 mm, and the peak-valley pitch of the windward corrugated fin and the leeward corrugated fin Are both 1.7 mm, the thickness of the windward corrugated fin and the leeward corrugated fin is both 0.1 mm, and the gradient of the windward corrugated fin and the leeward corrugated fin is both 32 °.

In the table of FIG. 17 and the graph of FIG. 18, the state where the leeward corrugated fin and the leeward corrugated fin are abutted is defined as “a gap size of 0 mm”, and the leeward corrugated fin and the leeward corrugated fin are separated from each other by 1 mm. Repeated measurements. “The size of the gap is 0 mm” is only a story at the contact portion, and the gap is widened at other locations. In other words, “a gap size of 0 mm” does not mean that there is no drainage channel between the windward corrugated fin and the leeward corrugated fin.

According to the above experiment, it can be seen that the amount of water retained after 20 seconds has surely decreased in the experimental sample with a gap of less than 3 mm compared to the experimental sample with a gap of 3 mm or more. From this point, it can be said that it is desirable that the gap is less than 3 mm. Considering the amount of drainage, the gap should be 2 mm or less. Considering the speed of drainage, the gap should be around 1 mm.

  As mentioned above, although each embodiment of the present invention was described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

    The present invention is widely applicable to parallel flow heat exchangers.

Model vertical cross section showing the schematic structure of the heat exchanger Sectional drawing cut | disconnected along the AA line of FIG. Expanded horizontal sectional view of heat exchanger Sectional drawing cut | disconnected along the BB line of FIG. Perspective view of a set of flat tubes and corrugated fins Side view of a set of flat tubes and corrugated fins A perspective view of a flat tube and corrugated fins according to the second embodiment Side view of a set of flat tubes and corrugated fins according to the second embodiment A perspective view of a set of flat tubes and corrugated fins according to the third embodiment Side view of a set of flat tubes and corrugated fins according to the third embodiment A perspective view of a flat tube and corrugated fins according to a fourth embodiment Side view of a set of flat tubes and corrugated fins according to the fourth embodiment A perspective view of a set of flat tubes and corrugated fins according to a fifth embodiment Side view of a set of flat tubes and corrugated fins according to the fifth embodiment Sectional view similar to FIG. 2 according to the sixth embodiment Sectional view similar to FIG. 2 according to the seventh embodiment Table of experimental results investigating the effect of gap size on drainage Graph of the above experimental results

Explanation of symbols

1 Heat exchanger 2, 3 Header pipe 2U, 3U Windward header pipe 2D, 3D Windward header pipe 4 Flat tube 4U Windward flat tube 4D Windward flat tube 5 Refrigerant passage 6 Corrugated fin 6U Windward corrugated fin 6D Windward Corrugated fin 9 gap

Claims (3)

A plurality of horizontal header pipes arranged in parallel at intervals in the vertical direction, and a plurality of horizontal header pipes arranged at intervals in the horizontal direction between the header pipes, each having an internal refrigerant passage communicating with the inside of the header pipe. In a heat exchanger comprising a vertical flat tube and a corrugated fin disposed between the flat tubes,
The corrugated fin comprises a windward corrugated fin whose fin surface is inclined downward toward the leeward side, and a leeward corrugated fin whose fin surface is inclined upward toward the leeward side,
The leeward side end of the leeward corrugated fin and the leeward side end of the leeward corrugated fin are arranged with a gap therebetween,
The gap is formed by contacting water droplets bridging between the leeward end portions adjacent to the upper and lower sides of the windward corrugated fin and water droplets bridging between the windward end portions adjacent to the upper and lower sides of the leeward corrugated fin. A heat exchanger characterized in that it is set to a size that allows tension to break apart and merge and flow down .   2. The gap is generated in a portion other than the contact portion by partially contacting the leeward side end portion of the leeward corrugated fin and the leeward side end portion of the leeward corrugated fin. The described heat exchanger.   The heat exchanger according to claim 1 or 2, wherein a leeward side end portion of the leeward side corrugated fin and a leeward side end portion of the leeward side corrugated fin are shifted from each other in a vertical direction.

Images