JP2008111618A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the degradation of heat exchanging performance of a heat exchanger caused by heat conduction by preventing heat conduction between heat transfer tubes 4, in the cross fin type heat exchanger of a refrigerant circuit in which a refrigerant, changing its temperature in a heat radiation stroke, flows. <P>SOLUTION: Cut portions 10 are formed on heat transfer fins 5 respectively between the heat transfer tube 4a at an inlet side and the heat transfer tube 4d at an outlet side adjacent to each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat exchanger provided in a refrigerant circuit, and more particularly, to a shape of a heat transfer fin of a cross fin type heat exchanger provided in a refrigerant circuit in which a refrigerant that changes in temperature in a heat dissipation process flows.

  2. Description of the Related Art Conventionally, heat exchangers that perform heat exchange between refrigerant and air by flowing refrigerant and air so as to be orthogonal to each other, so-called cross fin type heat exchangers are known (see, for example, Patent Document 1). . This heat exchanger is connected to, for example, a refrigerant circuit that performs a vapor compression refrigeration cycle, and is used to perform a heat radiation process and a heat absorption process of the refrigerant circulating in the refrigerant circuit.

  FIG. 8 is a perspective view showing the external shape of a conventional cross fin type heat exchanger. As shown in FIG. 8, the heat exchanger (61) includes a heat transfer fin group (69) having a plurality of heat transfer fins (65), a plurality of heat transfer tubes (64), and a plurality of U-shaped tubes (62 ) Having a heat transfer tube group (68).

  Here, out of the plurality of heat transfer tubes (64), excluding the heat transfer tube (64a) in which the inlet end (66) is formed and the heat transfer tube (64d) in which the outlet end (67) is formed. By connecting the ends of the heat pipe (64) with the U-shaped pipe (62), at least one refrigerant flow path is formed in the heat transfer pipe group (68). And a refrigerant | coolant flows through the said refrigerant | coolant flow path, and air flows between the heat-transfer fins (65) in the said heat-transfer fin group (69) so that it may orthogonally cross with the flow of this refrigerant | coolant.

By the way, in a refrigerant circuit that performs a vapor compression refrigeration cycle, when carbon dioxide is used as a refrigerant, generally, as shown by a thick line in FIG. 7, a supercritical heat release process (between bc), A refrigeration cycle (abcd) having an endothermic process (between da) below the critical temperature is configured. As can be seen from FIG. 7, in the case of the endothermic process, carbon dioxide absorbs heat while undergoing a phase change, so the refrigerant temperature during the endotherm is constant. On the other hand, in the case of the heat dissipation process, since carbon dioxide includes a portion exceeding the critical temperature (e), the carbon dioxide dissipates heat without causing a phase change. Therefore, the refrigerant temperature during heat dissipation changes greatly (in the example of FIG. 7, the temperature difference ΔT≈50 ° C.). And in order to perform this heat radiation process, it is possible to use the cross fin type heat exchanger mentioned above.
Japanese Patent Laid-Open No. 11-248385

  However, when the cross fin type heat exchanger is used to perform the heat radiation process, there is a problem that the heat exchange capability of the heat exchanger is lowered.

  That is, the temperature of the refrigerant flowing through the heat transfer tube group in the heat exchanger decreases as the refrigerant dissipates. For this reason, a temperature difference is generated between the inlet side and the outlet side of the refrigerant flow path formed in the heat transfer tube group, and due to this temperature difference, the heat transfer tube group located on the inlet side of the heat transfer tube group is generated. The heat tube becomes the high temperature part, and the heat transfer tube on the outlet side becomes the low temperature part. And heat transfer by heat conduction occurs from the heat transfer tube (high temperature part) on the inlet side to the heat transfer tube (low temperature part) on the outlet side through the heat transfer fins. As a result, the heat transfer tube on the outlet side is heated, and the temperature of carbon dioxide flowing through the heat transfer tube on the outlet side is difficult to decrease. That is, the heat exchange capability of the heat exchanger is reduced.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a heat exchanger provided in a refrigerant circuit in which a refrigerant that changes in temperature in a heat release stroke flows, and between an inlet side and an outlet side of a heat transfer tube group. The purpose is to suppress the heat conduction that occurs between them and to suppress the decrease in the heat exchange capability of the heat exchanger due to the heat conduction.

  The first invention includes a plurality of heat transfer fins (5) arranged in parallel to each other, and a plurality of heat transfer tubes (4 that pass through the heat transfer fins (5) and are fixed to the heat transfer fins (5). ) And U-shaped tubes (2) that connect the ends of each heat transfer tube (4) except for the inlet end (6) and outlet end (7) of the heat transfer tube (4) The heat exchanger (4) is premised on a heat exchanger in which a refrigerant whose temperature changes from the inlet side to the outlet side flows inside the pipe and dissipates heat to the air.

  The heat transfer fin (5) of the heat exchanger is provided with a notch (10) for preventing heat conduction from the inlet heat transfer tube (4) to the outlet heat transfer tube (4). It is characterized by that.

  Here, supercritical carbon dioxide and the like can be cited as the refrigerant whose temperature changes. Further, by using such a fluid as a refrigerant, a temperature difference is generated between the heat transfer tube (4) on the inlet side and the heat transfer tube (4) on the outlet side, and the heat transfer tube (4) on the inlet side The heat transfer tube (4) on the outlet side becomes a low temperature part in the high temperature part. The cut portion (10) here may be either wide or narrow.

  In the first invention, in the heat transfer fin (5) through which the heat transfer tube (4) on the inlet side and the heat transfer tube (4) on the outlet side pass, the heat transfer tube (4) on the inlet side and the outlet side By providing a notch (10) between the heat transfer tube (4) and the heat transfer tube (4) (high temperature part) on the inlet side of the heat exchanger (1), the heat transfer tube (4) ( Heat conduction to the low temperature part) can be prevented. Accordingly, the heat transfer tube (4) on the outlet side can be prevented from being heated by the heat transfer tube (4) on the inlet side.

  Here, the inlet-side heat transfer tube (4) is not necessarily the heat transfer tube (4) into which the refrigerant flows first. Further, the heat transfer tube (4) on the outlet side is not necessarily the heat transfer tube (4) into which the refrigerant flows most recently. For example, in any two heat transfer tubes (4b, 4c) in the heat exchanger (1), the heat transfer tube on the upstream side with respect to the refrigerant flow is the heat transfer tube (4b) on the inlet side, and downstream The heat transfer tube on the side is the heat transfer tube (4c) on the outlet side.

  The second invention is characterized in that, in the first invention, the heat transfer fin (5) is provided with notches (10) between all the adjacent heat transfer tubes (4).

  In 2nd invention, the heat which generate | occur | produces between all the adjacent heat exchanger tubes (4) by providing a notch part (10) in the heat transfer fin (5) between all the adjacent heat exchanger tubes (4). Can prevent conduction.

  According to a third invention, in the first or second invention, the cut portion (10) is formed by a cut line (20) formed in the heat transfer fin (5) between all the heat transfer fins (5). It is characterized by being composed. Here, the cut line (20) has a small cut width, and may be a slit, for example.

  In 3rd invention, while the said notch | incision part (10) is comprised by the notch line (20), while preventing the heat conduction produced between adjacent heat exchanger tubes (4), in the said heat-transfer fin (5) The cut width to be formed can be made minute compared to the cut portion (10). Here, the effect of preventing heat conduction is not related to the width of the cut. This is because heat conduction is the movement of heat in the same substance. If there is a gap in the heat transfer fin (5), heat conduction will not occur in that part even if the gap is very small. is there.

  In a fourth aspect based on the third aspect, the cut line (20) is provided such that the heat transfer fin pieces (5a) separated from each other are formed around all the heat transfer fins (5). It is characterized by being.

  In 4th invention, the said heat-transfer fin (5) can be divided | segmented into a some heat-transfer fin piece (5a) by providing the said score line (20). Here, the adjacent heat transfer fin pieces (5a) are configured not to contact each other.

  A fifth invention is characterized in that, in the third or fourth invention, the cut line (20) is constituted by an inclined line inclined with respect to a side of the heat transfer fin (5).

  In the fifth aspect of the present invention, when the heat exchanger (1) is used as an evaporator, the condensed water generated on the heat transfer fin (5) is smoothly cut along the cut line (20). The line (20) can be sent in the direction of inclination.

  According to a sixth invention, in any one of the first to fourth inventions, the heat transfer fin (5) has a cut-and-raised portion (30) obtained by cutting and raising the edge of the cut portion (10). It is characterized by that.

  In 6th invention, the edge part in the notch part (10) of the said heat-transfer fin (5) is cut and raised, and the heat transfer pipe (4) and outlet side by the side of an inlet are formed by forming a cut and raised part (30). Heat conduction between the heat transfer pipe (4) and the air flowing along the heat transfer fin (5) can be promoted at the same time that heat conduction between the heat transfer pipe (4) and the heat transfer fin (5) is prevented. .

  The seventh invention includes a plurality of heat transfer tubes (50a), radial heat transfer fins (50b) formed on the outside of the heat transfer tubes (50a), and an inlet side end (6 of the heat transfer tubes (50)). ) And the U-shaped tube (2) that connects the ends of each heat transfer tube (50) except for the end (7) on the outlet side, and the inside of the heat transfer tube (50) from the inlet side to the outlet side It is premised on a heat exchanger in which a temperature-changing refrigerant flows and radiates heat to the air.

  The adjacent heat transfer tubes (50) in the heat transfer tube group (8) of the heat exchanger are arranged so as to maintain a predetermined gap between the heat transfer fins (50b). Here, the radial heat transfer fin (50b) may be a heat transfer fin (50b) formed for each heat transfer tube (50a), for example, a spine fin or a spiral fin. Good.

  In the seventh invention, in the heat exchanger, adjacent heat transfer tubes (50) in the heat transfer tube group (8) are arranged adjacent to each other so as to maintain a predetermined gap between the heat transfer fins (50b). The heat transfer tubes (50) can be prevented from contacting each other via the heat transfer fins (50b). This prevents heat transfer from the inlet heat transfer tube (50) to the heat transfer tube (50) on the outlet side due to the temperature difference even if there is a temperature difference between adjacent heat transfer tubes (50). Can do.

  According to the present invention, in the heat transfer fin (5) of the heat exchanger (1), the notch (10) is provided between the heat transfer tube (4) on the inlet side and the heat transfer tube (4) on the outlet side. Thus, the heat transfer tube (4) on the outlet side can be prevented from being heated by the heat transfer tube (4) on the inlet side. Thereby, the fall of the heat exchange capability in the said heat exchanger (1) can be suppressed. Here, in the refrigerant flow path formed in the heat transfer tube group (8), the heat transfer tubes having the largest temperature difference are the heat transfer tube (4a) and the outlet side end (7) close to the inlet side end (6). It is a heat transfer tube (4d) close to. That is, providing the cut portion (10) between the two has a greater effect of suppressing the decrease in heat exchange capability than providing the cut portion (10) in the other portion.

  Moreover, according to the said 2nd invention, by providing a notch part (10) in the heat-transfer fin (5) between all the adjacent heat exchanger tubes (4), all the adjacent heat-transfer tubes (4) The heat conduction that occurs during Thereby, the fall of the heat exchange capability of the said heat exchanger (1) can further be suppressed.

  Further, according to the third aspect of the present invention, even if the notch portion (10) is formed between the adjacent heat transfer tubes (4) in the heat transfer fin (5), the notch line (20) is formed adjacent to each other. Since the effect of hindering heat conduction generated between the matching heat transfer tubes (4) does not change, it is possible to suppress a decrease in the heat exchange capacity of the heat exchanger (1). In addition, since the cut line (20) is formed, the cut width is narrower than that of the cut part (10), so that a decrease in strength of the heat exchanger (1) due to the cut can be suppressed.

  According to the fourth aspect of the invention, by providing the cut line (20), the heat transfer fin (5) can be divided into a plurality of heat transfer fin pieces (5a). The heat transfer between the heat transfer tubes (4) can be prevented. Thereby, the fall of the heat exchange capability of the said heat exchanger (1) can be suppressed reliably.

  According to the fifth aspect of the present invention, when the heat exchanger (1) is used as an evaporator, the cut line (20) causes dew condensation water generated on the heat transfer fin (5) to flow. It can flow smoothly in an inclined direction. Thereby, since dew condensation water does not stay on a heat transfer fin (5), the fall of the heat transfer performance by the side of the air by retention of this dew condensation water can be suppressed.

  Moreover, according to the said 6th invention, the edge part of the notch | incision part (10) in the said heat-transfer fin (5) is cut and raised, and the cut-and-raised part (30) is formed. 4) and heat transfer between the heat transfer fins (5) and the air flowing on the heat transfer fins (5), while preventing heat conduction between the heat transfer tubes (4) on the outlet side Can be made. Thereby, while suppressing the fall of the heat exchange capability of the said heat exchanger (1), the heat-transfer performance by the side of the air of this heat exchanger (1) can be improved further.

  According to the seventh aspect, the heat transfer tubes (50) of the heat transfer tube group (8) are arranged so that a predetermined gap is maintained between the heat transfer fins (50b). As a result, the heat transfer fins (50b) of the heat transfer tubes (50) do not come into contact with each other, so even if there is a temperature difference between adjacent heat transfer tubes (50), the heat transfer fins (50b) are generated due to the temperature difference. Heat conduction can be hindered. From this, the fall of the heat exchange capability of this heat exchanger can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The heat exchanger (1) of this embodiment is connected to a refrigerant circuit that performs a vapor compression refrigeration cycle using carbon dioxide as a refrigerant, and carbon dioxide and air compressed to a supercritical pressure in the refrigerant circuit. And the carbon dioxide is cooled.

-Heat exchanger configuration-
FIG. 1 is a perspective view conceptually showing the external shape of the heat exchanger (1). The heat exchanger (1) is a cross fin type heat exchanger as shown in the figure, and includes a heat transfer fin group (9) having a plurality of heat transfer fins (5), a plurality of heat transfer tubes (4), and And a heat transfer tube group (8) having a plurality of U-shaped tubes (2).

<Heat transfer fin group>
As shown in FIG. 1, the heat transfer fins (5) of the rectangular flat plate are arranged in a row so as to be parallel to each other with a predetermined interval therebetween, thereby forming the heat transfer fin group (9). Yes. Here, the reason why the predetermined interval is provided between the heat transfer fins (5) is to form an air passage through which air smoothly flows. A pair of tube plates (3) are arranged on both sides of the heat transfer fin group (9) so as to sandwich the heat transfer fin group (9).

  FIG. 2 is a view showing the heat transfer fin (5) of the heat exchanger (1) shown in FIG. As shown in the figure, the heat transfer fin (5) has through-holes (40) penetrating in the front and back directions at a predetermined interval in the row direction (vertical direction in FIG. 2) and the step direction (horizontal direction in FIG. 2). ). Further, the tube plate (3) on both sides of the heat transfer fin group (9) is also provided with a through hole (40) penetrating in the front and back direction. The heat transfer tube (4) is inserted into the through hole (40).

  Further, the heat transfer fin (5) is provided with notches (10), which is also a feature of the present invention, between all adjacent through holes (40). And by providing the notch | incision part (10) in this way, a heat-transfer fin (5) is divided | segmented into the same number of heat-transfer fin pieces (5a) as a through-hole (40).

<Heat transfer tube group>
The heat transfer tube group (8) includes a plurality of heat transfer tubes (4) and a plurality of U-shaped tubes (2). As shown in FIG. 1, the heat transfer tubes (4) are arranged so as to penetrate the heat transfer fin group (9) and the tube plates (3) on both sides of the heat transfer fin group (9). ing. And each end of each heat transfer tube (4) that has penetrated is fixed by the tube plate (3). Of the plurality of heat transfer tubes (4), the heat transfer tube (4a) in which the refrigerant inlet side end (inlet side end) (6) is formed and the refrigerant outlet side end (outlet side end) (7) By connecting the end portions of the heat transfer tubes (4) excluding the heat transfer tube (4d) formed with the U-shaped tube (2), the heat transfer tube group (8) has the end portion on the inlet side. One refrigerant flow path is formed with (6) as the inlet side and the outlet side end (7) as the outlet side.

-Heat exchanger operation-
The heat exchanger (1) is used in a refrigerant circuit that performs a vapor compression refrigeration cycle using carbon dioxide as a refrigerant, and the refrigerant circulating in the refrigerant circuit is a heat release stroke of the refrigeration cycle (FIG. 7). Between bc) and bc).

  First, the flow of carbon dioxide in the heat exchanger (1) will be described. In addition, the arrow of FIG. 2 has shown the flow of the carbon dioxide. The high-temperature carbon dioxide compressed to supercritical pressure by a compressor (not shown) provided in the refrigerant circuit is the refrigerant inlet side end formed at one end of the second-stage heat transfer tube (4a) from the bottom. It flows into the heat exchanger (1) from the section (6). The inflowed carbon dioxide flows while meandering upward in the column direction along the refrigerant flow path formed in the heat transfer tube group (8). The carbon dioxide flowing into the uppermost heat transfer tube (4b) flows into the second heat transfer tube (4c) from the top in the adjacent row. The carbon dioxide that has flowed into the second-stage heat transfer tube (4c) from above flows while meandering along the refrigerant flow path downward in the column direction. The refrigerant flowing into the lowermost heat transfer tube (4d) flows out from the refrigerant outlet side end (7) formed in the lowermost heat transfer tube (4d) toward the refrigerant circuit.

  Here, at the refrigerant inlet side end portion (6), the carbon dioxide at the temperature of point b in FIG. 7 flows through the heat transfer tube (4) and radiates heat to the air outside the tube, thereby finally At the refrigerant outlet side end (7), the temperature falls to the temperature at point c in FIG. Thus, since the temperature of carbon dioxide itself falls along the flow of carbon dioxide, a temperature difference is generated between the plurality of heat transfer tubes (4) through which the carbon dioxide flows. That is, the temperature of each of the heat transfer tubes (4) is higher as it is closer to the refrigerant inlet side end (6), that is, closer to the inlet side of the refrigerant flow path, and closer to the refrigerant outlet side end (7), that is, The lower the outlet side of the refrigerant flow path, the lower the temperature. In this embodiment, the heat transfer tube (4a) on the inlet side of the heat transfer tube group (8) and the heat transfer tube (4d) on the outlet side are arranged side by side.

  Next, the flow of air in the heat exchanger (1) will be described. Air flows between the fins of the heat transfer fin group (9). When passing between the fins, heat exchange is performed with the carbon dioxide flowing through the heat transfer tube group (8), and the air is heated and flows out of the heat exchanger (1).

-Effect of the embodiment-
In this embodiment, as shown in FIG. 2, in the heat transfer fin (5), the heat exchanger (1) is provided by providing notches (10) between all adjacent heat transfer tubes (4). Because the heat transfer between the heat transfer tube (4a) on the inlet side and the heat transfer tube (4d) on the outlet side is hindered, the heat transfer tube (4) on the outlet side is heated by the heat transfer tube (4) on the inlet side. Can be prevented. Thereby, the fall of the heat exchange capability in the said heat exchanger (1) can be suppressed.

-Modification 1 of embodiment-
In the first modification of the embodiment, the heat transfer fins (5) are not divided entirely, but as shown in FIG. 3, all the heat transfer tubes (4) adjacent to each other in the heat transfer fins (5). A slit (cut line) (20) is provided horizontally along the step direction. This slit portion constitutes a minute gap that makes the heat transfer fins (5) non-contact with each other. In other words, heat conduction from the inlet-side heat transfer tube (4a) to the outlet-side heat transfer tube (4d) can be prevented by the minute gap. In addition, since the communicating portions remain on both sides of the slit (20), the strength of the heat exchanger (1) can be prevented from being reduced compared to the case where the heat transfer fin (5) is divided as a whole. it can.

-Modification 2 of embodiment-
In the second modification of the embodiment, unlike the first modification, the slit (20) is inclined as shown in FIG. Here, when the heat exchanger (1) is used as an evaporator, the dew condensation water generated on the heat transfer fin (5) can flow smoothly in an inclined direction. As a result, heat exchange in the heat exchanger (1) is prevented by the heat conduction prevention effect by the slit (20) while suppressing the deterioration of the heat transfer performance on the air side due to the condensation water remaining on the heat transfer fin (5). A decrease in ability can be suppressed.

—Modification 3 of Embodiment—
In the modification 3 of embodiment, as shown in FIG. 5, the edge part in the notch part (10) of the said heat-transfer fin (5) is cut and raised, and the cut and raised part (30) is formed. In this way, heat conduction generated between the heat transfer tubes (4) is prevented, and at the same time, heat transfer between the heat transfer fins (5) and the air flowing over the heat transfer fins (5) is promoted. Therefore, it is possible to further improve the heat transfer performance on the air side of the heat exchanger (1) while suppressing a decrease in the heat exchange capacity of the heat exchanger (1).

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

  In the said embodiment, although the said heat exchanger (1) was comprised with the cross fin type heat exchanger, it is not a cross fin type heat exchanger but the radial heat transfer fin formed in the tube outer side of each heat exchanger tube You may comprise by arranging two or more heat exchanger tubes (50) in which (50b) was formed. However, when arranging the heat transfer tubes (50), as shown in FIG. 6, a predetermined gap is maintained so that the heat transfer fins (50b) of the adjacent heat transfer tubes (50) do not contact each other. Need to be arranged.

  Moreover, although the heat exchanger (1) of the said embodiment comprised the heat exchanger tube (4) with the heat exchanger of 2 rows, it does not necessarily need to be 2 rows and may be 3 or more rows. Further, the number of stages of the heat transfer tubes (4) may be freely configured.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for the shape of the heat transfer fins of the cross fin type heat exchanger suitable for use in the refrigerant circuit in which the refrigerant that changes in temperature in the heat dissipation process flows.

It is the perspective view which showed the external appearance shape of the cross fin type heat exchanger in embodiment of this invention. It is an enlarged view of the heat-transfer fin in the cross fin type heat exchanger of FIG. It is an enlarged view of the heat-transfer fin in the modification 1 of embodiment of this invention. It is an enlarged view of the heat-transfer fin in the modification 2 of embodiment of this invention. It is an enlarged view of the heat-transfer fin in the modification 3 of embodiment of this invention. It is sectional drawing of the heat exchanger in other embodiment. It is the figure which represented the refrigerating cycle on the TS diagram of a carbon dioxide. It is the perspective view which showed the external appearance shape of the conventional cross fin type heat exchanger.

Explanation of symbols

1 Heat exchanger
2 U-tube
3 Tube sheet
4 Heat transfer tube
5 Heat transfer fin
5a Heat transfer fin
6 Refrigerant inlet side end (inlet side end)
7 Refrigerant outlet end (outlet end)
8 Heat transfer tube group
9 Heat transfer fin group
10 notch
20 Slit (cut line)
30 Cut and raised part
40 Through hole

Claims (7)

A plurality of heat transfer fins (5) arranged in parallel to each other, a plurality of heat transfer tubes (4) passing through the heat transfer fins (5) and fixed to the heat transfer fins (5), 4) U-tube (2) connecting the ends of each heat transfer tube (4) except for the inlet end (6) and outlet end (7), and the heat transfer tube (4) A heat exchanger in which a refrigerant whose temperature changes from the inlet side toward the outlet side flows and radiates heat to the air,
The heat transfer fin (5) is provided with a notch (10) for preventing heat conduction from the heat transfer tube (4) on the inlet side to the heat transfer tube (4) on the outlet side. Exchanger. In claim 1,
The heat exchanger fin (5) is provided with notches (10) between all adjacent heat transfer tubes (4). In claim 1 or 2,
The said notch part (10) is comprised by the notch line (20) formed in the said heat-transfer fin (5) between all the heat-transfer fins (5), The heat exchanger characterized by the above-mentioned. In claim 3,
The heat exchanger, wherein the score line (20) is provided so that the heat transfer fin pieces (5a) separated from each other are formed around all the heat transfer fins (5). In claim 3 or 4,
The said score line (20) is comprised by the inclined line inclined with respect to the side of a heat-transfer fin (5), The heat exchanger characterized by the above-mentioned. In any one of Claims 1-4,
The heat transfer fin (5) has a cut-and-raised portion (30) obtained by cutting and raising the edge of the cut portion (10). A plurality of heat transfer tubes (50a), radial heat transfer fins (50b) formed on the outside of the heat transfer tubes (50a), inlet side end portions (6) and outlet side end portions of the heat transfer tubes (50) A refrigerant that includes a U-shaped tube (2) that connects the ends of each heat transfer tube (50) except (7), and changes the temperature of the heat transfer tube (50) from the inlet side to the outlet side. Is a heat exchanger that radiates heat to the air,
The heat exchanger, wherein the adjacent heat transfer tubes (50) in the heat transfer tube group (8) are arranged so as to maintain a predetermined gap between the heat transfer fins (5).

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