JP2010286196A - Heat transfer tube, heat exchanger, and air conditioner having heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger applying a heat transfer tube capable of performing heat exchange of high efficiency by improving adhesiveness with radiation fins by tube expansion and improving draining performance, and to provide an air conditioner having the heat exchanger. <P>SOLUTION: This heat transfer tube is composed of two circular tubes 3a, 3b arranged in parallel with each other in the long axial direction in the cross-sectional shape, and outer wall sections 3c, 3d for joining two circular rubes 3a, 3b to each other in the short axial direction in the cross-sectional shape, a distance B between the outer wall sections 3c, 3d is longer than outer diameters d of the circular tubes 3a, 3b, and a distance C between central axes of two circular tubes 3a, 3b is longer than the outer diameters d of the circular tubes 3a, 3b and is less than two times of the outer diameter d of the circular tubes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat transfer tube, a heat exchanger, and an air conditioner including the heat exchanger.

  For example, many of the heat exchangers used in air conditioners that perform air conditioning in buildings are composed of heat transfer tubes through which refrigerant flows and heat radiating fins joined to the heat transfer tubes. Usually, a heat exchanger tube penetrates the insertion hole formed in a radiation fin, and both are firmly joined by expanding a heat exchanger tube in that state. For this reason, when the refrigerant flows through the heat transfer tubes, heat exchange is efficiently performed through the heat radiation fins.

  Examples of heat transfer tubes that employ such a joining method include the following Patent Documents 1 to 3. For example, the multi-hole tube for a heat exchanger disclosed in Patent Document 1 has an oval cross section, and is expanded by inserting a tube expansion burette into a central flow path.

  Further, the tube described in Patent Document 2 is provided with circular pipe portions at both ends in the minor axis direction of the tube, and a planar passage is formed in a region sandwiched between both the circular pipe portions. The expansion of the circular pipe portion is also performed by inserting a tube expander into the circular pipe portion.

  The heat transfer tube disclosed in Patent Document 3 is provided with a substantially semicircular refrigerant flow path that swells in an arc shape on both sides of a through-hole having a quadrangular cross section provided in the center in the longitudinal direction. It has been. The pipe is expanded by inserting a pipe expansion bullet ball into the semicircular refrigerant flow path.

JP 2005-164221 A JP 2005-249333 A JP 2008-261518 A

  However, in the tubes (heat transfer tubes) disclosed in Patent Documents 1 to 3 described above, the deformation amount is small and the tube expandability is poor in either the short axis direction or the long axis direction during tube expansion, or both. , There is a possibility that inconvenience will occur. If the tube expandability is poor, the adhesion between the heat dissipating fins is insufficient, and the two are not completely joined. In addition, if the expansion ratios in the short axis direction and the long axis direction at the time of tube expansion are different, an irregular tube (heat transfer tube) is formed, which also causes a decrease in adhesion to the radiation fin. If the adhesion is deteriorated, the efficiency of heat exchange is deteriorated.

  Furthermore, in the case of the tube disclosed in Patent Document 2, for example, the flat portion sandwiched between both circular tube portions is a portion that becomes a concave portion when the circular tube portion is expanded. When such a concave portion is generated, drain water or a liquid generated by the dissolution of the attached frost is accumulated in the concave portion, and the drainage performance is deteriorated. The deterioration of drainage also deteriorates the efficiency of heat exchange.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to achieve high-efficiency heat exchange by improving the drainage as well as improving the adhesion with the radiating fins by expanding the tube. It is providing the heat exchanger using a heat exchanger tube, and an air conditioner provided with this heat exchanger.

  The first feature according to the embodiment of the present invention is that, in the heat transfer tube, two circular tubes formed in parallel with the long-axis direction of the cross-sectional shape, and the two circular tubes in the short-axis direction of the cross-sectional shape In which the distance between the outer wall portions is equal to or greater than the outer diameter of the circular tube, the distance between the central axes of the two circular tubes is greater than the outer diameter of the circular tube, and The outer diameter of the tube is less than twice.

  The second feature of the embodiment of the present invention is that, in the heat exchanger, the heat radiation fins having insertion holes formed therein and the insertion holes formed in the plurality of heat radiation fins are inserted at predetermined intervals. And two outer circular tubes formed in parallel with the major axis direction of the cross-sectional shape, and an outer wall portion that joins the two circular tubes to each other in the minor axis direction of the sectional shape. The distance is greater than or equal to the outer diameter of the circular tube, and the distance between the central axes of the two circular tubes is greater than the outer diameter of the circular tube and less than or equal to twice the outer diameter of the circular tube. With heat transfer tubes.

  A third feature according to the embodiment of the present invention is that an air is provided with a compressor, a four-way valve, an outdoor heat exchanger, an expansion device, an indoor heat exchanger, and a refrigeration cycle in which these are connected by a refrigerant pipe. In the conditioner, at least one of the outdoor heat exchanger or the indoor heat exchanger includes two circular pipes formed in parallel to the long axis direction of the cross-sectional shape, and the two circular pipes in the short axis direction of the cross-sectional shape. In which the distance between the outer wall portions is equal to or greater than the outer diameter of the circular tube, the distance between the central axes of the two circular tubes is greater than the outer diameter of the circular tube, and It is comprised by the heat exchanger provided with the heat exchanger tube currently formed so that it may become 2 times or less of the outer diameter of a pipe | tube.

  According to the present invention, a heat exchanger using a heat transfer tube that realizes high-efficiency heat exchange by improving the close contact with the radiating fins by expanding the tube and improving the drainage performance, and an air equipped with the heat exchanger A harmony machine can be provided.

It is a perspective view showing the whole heat exchanger concerning an embodiment of the invention. It is a perspective view which shows the heat exchanger tube which comprises the heat exchanger which concerns on embodiment of this invention. It is sectional drawing which cut | disconnects the heat exchanger tube shown in FIG. 2 by the AA line, and shows the cross section. It is a flowchart which shows the flow which manufactures the heat exchanger which concerns on embodiment of this invention. It is a top view which shows the state which fits the heat exchanger tube which concerns on embodiment of this invention to a radiation fin. It is a figure which expands and shows the area | region of M shown in the top view of FIG. It is a graph showing the result obtained by conducting an experiment by the applicant. It is a graph showing the result obtained by conducting an experiment by the applicant. It is a graph showing the relationship between the ratio (C / d) of the distance C and the outer diameter d, and the pressure-resistant strength ratio of a double circular pipe. It is a figure which expands and shows the area | region of M shown in the top view of FIG. It is a figure explaining the connection structure of the edge part of a heat exchanger tube. It is a circuit diagram of an air conditioner incorporating a heat exchanger according to an embodiment of the present invention.

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

  FIG. 1 is a perspective view showing the entire heat exchanger 1 according to the embodiment of the present invention. The heat exchanger 1 is mainly composed of heat radiating fins 2 and heat transfer tubes 3 through which the refrigerant passes.

  In the heat exchanger 1 shown in FIG. 1, the heat radiating fins 2 are shown only near both ends of the heat transfer tubes 3 in order to show the relationship between the heat radiating fins 2 and the heat transfer tubes 3. Moreover, as will be described later, the ends of the adjacent heat transfer tubes 3 are connected to each other, and one or two refrigerant flow paths are formed in the heat exchanger 1.

  Any method such as a header method or a return bend method (an elliptical return bend, a circular tube return bend, etc.) may be employed for connecting the ends of the heat transfer tubes 3 as described later. However, in FIG. 1, in order to clarify the cross section of the heat transfer tube 3, the ends of the adjacent heat transfer tubes 3 are joined, for example, a circular tube return bend is not drawn.

  A plurality of heat radiation fins 2 are arranged in parallel from the one end to the other end of the heat transfer tube 3 in parallel with the air inflow direction (see the arrow shown in FIG. 1) and at a predetermined interval in the Z direction of FIG. ing. The heat radiating fins 2 are made of, for example, a metal plate such as copper (Au) or aluminum (Al).

  The radiating fin 2 is provided with an insertion hole 2a through which the heat transfer tube 3 described below passes in the long side direction (Y direction shown in FIG. 1). The insertion hole 2a is formed in accordance with the cross-sectional shape of the heat transfer tube 3 that passes therethrough. In the embodiment of the present invention, as will be described later, the case where the cross section of the heat transfer tube 3 is mainly elliptical will be described as an example, so that the insertion hole 2a is also formed in a substantially cross sectional shape. Yes.

  Further, in the heat radiation fin 2 in the heat exchanger 1 shown in FIG. 1, four insertion holes 2 a are formed in one heat radiation fin 2. In addition, how many insertion holes 2a are formed in one radiation fin 2 can be arbitrarily set according to the capability of the heat exchanger 1 (the number of heat transfer tubes 3 to be joined).

  The heat transfer tubes 3 are joined to the respective insertion holes 2a. As shown in FIG. 2, the entire heat transfer tube 3 has a substantially elliptical shape. FIG. 3 is a cross-sectional view showing the heat transfer tube 3 shown in FIG. 2 cut along line AA.

  In the heat transfer tube 3, two circular tubes 3a and 3b are formed in parallel in the longitudinal direction (X direction) of the cross section of the heat transfer tube 3 shown in FIG. These two circular tubes 3a and 3b extend in parallel in the heat transfer tube 3 extending in the Z direction shown in FIG. Further, outer wall portions 3c and 3d are formed to join these two circular tubes 3a and 3b to each other in the cross-sectional minor axis direction (Y direction) of the heat transfer tube 3, and the heat transfer tube 3 includes the circular tubes 3a and 3b and the outer wall portion. 3c and 3d. Between the circular pipe 3a and the circular pipe 3b, a region (hereinafter, this region is referred to as a “central region”) 3e through which the refrigerant flows is formed.

  As shown in FIG. 3, the circular tubes 3a and 3b have a circular cross section. As will be described later, the circular tubes 3a and 3b, that is, the entire heat transfer tube 3 are expanded by inserting a tube expander into the two circular tubes 3a and 3b. A refrigerant flows through the circular tubes 3a and 3b, and heat exchange is performed via the radiating fins 2 to be joined.

  The outer wall portions 3c and 3d that connect the circular tubes 3a and 3b in the minor axis direction (Y direction) are drawn in an arc so that the outer wall portion 3c and the outer wall portion 3d are parallel to each other or outward. It is formed to have a shape. Therefore, in the latter case, the heat transfer tube 3 as a whole is formed in an elliptical shape. Accordingly, there is no portion that becomes a concave portion in the heat transfer tube 3, and even if a liquid or the like is generated by the drainage water or adhering frost being dissolved, it flows down from the heat transfer tube 3. Will not accumulate.

  The heat transfer tube 3 is manufactured by extrusion using a material such as a copper alloy material or an aluminum alloy material, for example. Therefore, the circular tubes 3a and 3b, the outer wall portions 3c and 3d, and the central region 3e are formed integrally.

  Next, a manufacturing method of the heat exchanger according to the embodiment of the present invention including the joining of the radiation fins 2 and the heat transfer tubes 3 will be described with reference to the flowchart shown in FIG. 4 and FIGS. 5 to 7.

  First, the heat transfer tube 3 is manufactured. The heat transfer tube 3 is manufactured by performing extrusion processing as described above (ST1) (see FIG. 2). The formed heat transfer tubes 3 are passed through the insertion holes 2a formed in advance in the radiating fins 2, and both are combined (ST2). In this state, since the diameter of the insertion hole 2a is larger than the diameter of the heat transfer tube 3, there is a gap between the heat radiating fins 2 and the heat transfer tubes 3, and they are not joined.

  FIG. 5 is a plan view showing a state in which the heat transfer tube 3 is expanded and fitted to the radiating fins 2. Since the heat radiation fin 2 shown in FIG. 5 has three insertion holes 2a, the heat transfer tubes 3 are also fitted in the three insertion holes 2a. A slit 2b is provided between the insertion holes 2a (heat transfer tubes 3). FIG. 5 is a plan view showing a state in which the heat transfer tube 3 is fitted to the heat radiating fins 2, so that only one heat radiating fin 2 is shown. However, the heat radiating fins 2 are formed as described above. Are combined in almost the entire region from one end to the other end (see FIG. 1).

  6 is an enlarged view of a region M shown in the plan view of FIG. As described above, in a state where the heat transfer tube 3 is passed through the insertion holes 2 a formed in the heat radiating fins 2, the diameter E of the insertion hole 2 a is larger than the diameter of the heat transfer tubes 3 as shown in FIG. 6. . Therefore, a gap is generated between the heat transfer tube 3 and the insertion hole 2a. In addition, the code | symbol F shown in FIG. 6 is the folding | turning (fin color) of the insertion hole 2a which appears on the surface of the radiation fin 2. FIG.

  In this state, the circular tubes 3a and 3b of the heat transfer tube 3 are expanded (ST3). The pipe expansion is performed mechanically using a pipe expander (not shown) such as a mandrel. The expansion tube is inserted from the ends of the circular tubes 3a and 3b and gradually moved in the Z direction. As a result, the circular tubes 3a and 3b are uniformly expanded as a whole. When the circular tubes 3a and 3b are expanded, the heat transfer tube 3 as a whole becomes equally large in the X direction and the Y direction.

  Here, as shown in FIG. 3, the distance between the outer wall portions 3c and 3d is represented by B, and the distance between the central axes of the two circular tubes 3a and 3b is represented by C. The outer diameter of the circular tube is d. When expressed in this way, in the size of the heat transfer tube 3 in the embodiment of the present invention, the distance B has a distance greater than or equal to the outer diameter d of the circular tubes 3a and 3b. Therefore, as described above, the outer wall 3c and the outer wall 3d are parallel to each other, or the heat transfer tube 3 as a whole has an elliptical shape.

  Moreover, when making the whole shape of the heat exchanger tube 3 into an elliptical shape, it is preferable that the length of the distance B shall be 1.5 times or less of the outer diameter d. This is because even when the circular tubes 3a and 3b are expanded, the deformation amount of the entire heat transfer tube 3 in the X direction and the Y direction can be made substantially equal.

  FIG. 7 is a graph showing the results obtained by the applicant conducting experiments. The vertical axis represents the ratio between the elongation of distance B and the elongation of outer diameter d (elongation of B / elongation of d), and the horizontal axis represents the ratio of the elongation ratio in the Y direction and the elongation ratio in the X direction (Y direction). Elongation rate / X direction elongation rate). If the elongation ratio in the Y direction is substantially equal to the elongation ratio in the X direction (if the ratio is close to 1), it can be said that the deformation amount in the X direction and the Y direction are substantially equal. According to FIG. 7, if B / d is 1.5 or less, it can be determined that the ratio of elongation in the Y direction / the ratio of elongation in the X direction is substantially equal.

  FIG. 8 is a graph showing the results obtained by the applicant conducting experiments as in FIG. 7 described above. The vertical axis represents the expansion ratio (%), and the horizontal axis represents the ratio (C / d) between the distance C and the outer diameter d. The broken line drawn in parallel with the horizontal axis in the graph of FIG. 8 indicates the required tube expansion rate. Here, the tube expansion ratio required for the two circular tubes 3 a and 3 b is a ratio required for the heat transfer tube 3 to be reliably joined to the heat radiating fins 2. According to the graph shown in FIG. 8, when C / d exceeds twice, the pipe expansion ratio required for the two circular pipes 3a and 3b cannot be maintained. Although FIG. 8 shows the X direction, similar results were obtained in the Y direction, though not shown.

  Furthermore, since the deformation amounts are substantially equal, the entire heat transfer tube 3 can be prevented from being distorted, and the circular tubes 3a and 3b can also maintain a circular shape, so that the pressure of the refrigerant flowing inside the tubes 3a and 3b Can be received evenly. In addition, even if a pressure other than the specified pressure is applied to the circular tubes 3a and 3b, the deformation of the circular tubes 3a and 3b and consequently the heat exchanger 1 can be minimized.

  FIG. 9 is a graph showing the relationship between the ratio (C / d) between the distance C and the outer diameter d and the pressure resistance ratio of the two circular tubes 3a and 3b. The horizontal axis represents C / d, the vertical axis represents the pressure strength ratio, and the required strength required for the two circular tubes 3a and 3b is represented by broken lines in parallel to the horizontal axis. According to FIG. 9, when C / d exceeds 2, the required pressure resistance strength cannot be obtained. From the above, the ratio between the distance C between the central axes of the two circular tubes 3a and 3b and the outer diameter d of the circular tube is required to be twice or less.

  FIG. 10 shows a state where the expansion of the circular tubes 3a and 3b has been completed. In this state, the diameter E of the insertion hole 2a shown in FIG. 6 is equal to the outer diameter of the heat transfer tube 3, and both are joined. In other words, the outer wall portions 3c and 3d and the circular tubes 3a and 3b constituting both ends in the long axis direction of the heat transfer tube 3 are fixed to the diameter E (radiation fin 2) (ST4).

  After the heat transfer tubes 3 and the radiation fins 2 are joined and fixed to each other, the ends of the heat transfer tubes 3 adjacent to each other in the long side direction (Y direction shown in FIG. 1) of the radiation fins 2 are connected and illustrated. However, a refrigerant flow path constituting the refrigeration cycle is formed (ST5).

  In addition, about the connection structure of the edge part of the heat exchanger tube 3, the connection structure etc. which are mentioned, for example to Fig.11 (a) thru | or (c) are employable. That is, as shown in FIG. 11 (a), the first connection structure is connected by an elliptical return bend 30, and as shown in FIG. 11 (b), adjacent circular tubes 3a and 3a are connected to each other in a circular tubular shape. A second connection structure (in this case, the central region 3e is connected to the refrigerant by connecting the bend 31 and connecting the adjacent circular pipes 3b and 3b with a circular return bend 32). (Not used as a flow path) and a third connection configuration connected by a header 33 as shown in FIG.

  FIG. 12 is a circuit diagram of the air conditioner 10 incorporating the heat exchanger 1 according to the embodiment of the present invention. The air conditioner 10 includes a compressor 11, a four-way valve 12, an indoor heat exchanger 13, an expansion device 14, and an outdoor heat exchanger 15, and these are sequentially connected by piping so that a refrigeration cycle is achieved. It is formed. In the embodiment of the present invention, the heat exchanger 1 is used as the outdoor heat exchanger 15 (referred to as “outdoor heat exchanger 15” in FIG. 12).

  Here, for example, the flow of the refrigerant in the refrigeration cycle when performing heating will be briefly described. First, as shown by the solid line arrow, the gaseous refrigerant is first pressurized in the compressor 11 to generate a high temperature and high pressure. And supplied to the indoor heat exchanger 13 through the four-way valve 12. The refrigerant supplied to the indoor heat exchanger 13 undergoes heat exchange between the refrigerant and the heat transfer medium (air). That is, the heat of the refrigerant heats the heat transfer medium (air) sent to the indoor heat exchanger 13 by an indoor fan (not shown), and the refrigerant is cooled by the heat transfer medium (air) and changes from gas to liquid. The heated heat transfer medium (air) is supplied by the indoor fan to the room where the air conditioner 10 is installed. The refrigerant, which has been deprived of heat by the indoor heat exchanger 13 and turned into a liquid, enters the expansion device 14 and expands to a low pressure. Further, the refrigerant is supplied to the outdoor heat exchanger 15 and is again made into gas by the outdoor outdoor fan 16, and returns to the compressor 11 through the four-way valve 12. Then repeat the previous cycle.

  Further, during the cooling operation, by switching the four-way valve 12, the refrigerant passes through the four-way valve 12 that flows in the order of the compressor 11, the four-way valve 12, the outdoor heat exchanger 15, the expansion device 14, and the indoor heat exchanger 13. Return to. Then repeat the previous cycle.

  In the heat exchanger 1, the circular tubes 3 a and 3 b are formed on the heat transfer tube 3 as described above. Connection of the end portions of the heat transfer tubes 3 employs the above-described second connection configuration to form two refrigerant flow paths, and flow different refrigerants through the circular tubes 3a and 3b, thereby connecting different refrigerant circuits. It can be created. Therefore, in the following, a state where two different refrigerant circuits are created in the outdoor heat exchanger 15 will be described.

  These two systems are divided into a first system R1 and a second system R2, and for convenience, outdoor heat on the side of the circular tube (one of the circular tubes 3a, 3b) of the heat transfer tube 3 connected to the first system R1. The exchanger part (one side in the short side direction of the radiating fin 2) is referred to as a first outdoor heat exchanger 15a, and the circular tubes (the circular tubes 3a and 3b) of the heat transfer tubes 3 connected to the second system R2. The outdoor heat exchanger portion on the other side (the other side in the short side direction of the radiating fin 2) is referred to as a second outdoor heat exchanger 15b. The second outdoor heat exchanger 15b is configured on the leeward side, and the first outdoor heat exchanger 15a is configured on the leeward side. Incidentally, in FIG. 12, the outdoor heat exchanger far from the outdoor fan 16 is the second outdoor heat exchanger 15b on the windward side.

  A first on-off valve 17 is provided on a path that branches before flowing into the expansion device 14 and into which refrigerant flows into the second outdoor heat exchanger 15b, and passes through the expansion device 14 to reduce the pressure. The second on-off valve 18 is provided in the path through which the refrigerant flows into the second outdoor heat exchanger 15b. In addition, a third on-off valve 19 is provided between the time of leaving the second outdoor heat exchanger 15 b and the time of entering the four-way valve 12. The opening / closing of the first opening / closing valve 17 to the third opening / closing valve 19 is controlled by a control device (not shown).

  A resistor 20 is connected so as to bypass the third on-off valve 19. The resistor 20 is, for example, a capillary tube, and the coolant flows through the capillary tube. The resistor 20 has a function of depressurizing (squeezing) the refrigerant flowing through the resistor 20. When the third on-off valve 19 is in an open state, the resistance is large, so that the refrigerant hardly flows in the resistance 20.

  The operation of the air conditioner 10 having such a refrigeration cycle will be described by dividing it into three operation modes of cooling, heating, and defrosting. First, the operation methods in “cooling” and “heating” are as described above. In other words, the first on-off valve 17 is closed and the second on-off valve 18 and the third on-off valve 19 are both open, so that the first outdoor heat exchanger 15a and the second outdoor valve It works the same as the heat exchanger 15b.

  On the other hand, when frost forms on the outdoor heat exchanger 15 during the heating operation, it is necessary to melt the frost. This is because the heat exchange efficiency of the outdoor heat exchanger 15 is lowered. In this “defrosting” operation mode, the first on-off valve 17 is “opened” while the four-way valve 12 is in the same state as in the heating operation, and the second on-off valve 18 and the third on-off valve 19. Both of them are “closed”. When each on-off valve is operated in this way, a high-pressure refrigerant that does not become low pressure in the expansion device 14 flows into the second system R2.

  In this case, in the indoor heat exchanger 13, the rotation of an indoor fan (not shown) is adjusted to reduce the air volume, and the heat radiation amount of the refrigerant in the second outdoor heat exchanger 15b is increased. As a result, the frost on the outdoor heat exchanger 15 can be melted. In addition, by using the heat transfer tube 3 in the embodiment of the present invention, the second outdoor heat exchanger 15b from the high temperature side circular tube (one of the circular tubes 3a and 3b) of the first outdoor heat exchanger 15a. Heat conduction through the outer wall portions 3c and 3d to the circular tube on the low temperature side (the other of the circular tubes 3a and 3b) can also be expected.

  Therefore, in particular, the defrosting can be performed while performing the heating operation without switching the four-way valve 12 to the same side as the cooling operation and performing the defrosting operation. Therefore, comfortable air conditioning during heating can be performed.

  Note that when the operation is performed in the “defrosting” operation mode, the third on-off valve 19 is closed for the refrigerant supplied to the second outdoor heat exchanger 15 b through the first on-off valve 17. Therefore, it passes through the resistor 20. The refrigerant that has passed through the resistor 20 is decompressed by the expansion device 14 and decompressed so as to be approximately equal to the pressure of the refrigerant that has passed through the first heat exchanger 15a, and is joined to the four-way valve 12. Will return.

  As described above, a heat exchanger using a heat transfer tube that realizes high-efficiency heat exchange by improving the close contact with the heat dissipating fins by expanding the tube and improving the drainage performance, and the air provided with the heat exchanger A harmony machine can be provided.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, the efficiency of heat exchange of the heat transfer tubes can be increased more than ever by forming grooves in and out of the circular tubes formed in the heat transfer tubes described above.

  Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

  DESCRIPTION OF SYMBOLS 1 ... Heat exchanger, 2 ... Radiation fan, 3 ... Heat exchanger tube, 10 ... Air conditioner, 11 ... Compressor, 12 ... Four-way valve, 13 ... Indoor heat exchanger, 14 ... Expansion device, 15 ... Outdoor heat exchanger 15a ... 1st outdoor heat exchanger, 15b ... 2nd outdoor heat exchanger, 17 ... 1st on-off valve, 18 ... 2nd on-off valve, 19 ... 3rd on-off valve, 20 ... Resistance, R1 ... first flow path, R2 ... second system

Claims (7)

Two circular tubes formed in parallel to the major axis direction of the cross-sectional shape;
An outer wall portion that joins the two circular pipes to each other in the minor axis direction of the cross-sectional shape,
The distance between the outer wall portions is equal to or larger than the outer diameter of the circular pipe, the distance between the central axes of the two circular pipes is larger than the outer diameter of the circular pipe, and 2 of the outer diameter of the circular pipe. A heat transfer tube formed so as to be less than double.   2. The heat transfer tube according to claim 1, wherein a distance between the outer wall portions is formed to be not more than 1.5 times an outer diameter of the circular tube. A radiating fin in which an insertion hole is formed;
The heat transfer tube according to claim 1 or 2, wherein the heat transfer tubes are inserted at a predetermined interval perpendicular to the insertion holes respectively formed in the plurality of radiation fins.
A heat exchanger characterized by comprising:   4. The heat exchange according to claim 3, wherein the heat transfer tube is joined to the heat radiation fin by expanding the two circular tubes after being inserted into the insertion hole of the heat radiation fin. vessel.   The heat transfer tubes are respectively joined to the insertion holes formed in the longitudinal direction of the radiation fins, and the circular tubes of the adjacent heat transfer tubes are connected by a return bend to form a flow path. The heat exchanger according to claim 3 or 4. In an air conditioner including a compressor, a four-way valve, an outdoor heat exchanger, an expansion device, an indoor heat exchanger, and a refrigeration cycle in which these are connected by a refrigerant pipe,
An air conditioner comprising at least one of the outdoor heat exchanger or the indoor heat exchanger configured by the heat exchanger according to any one of claims 3 to 5.   The heat exchanger forms two independent flow paths by connecting circular pipes of adjacent heat transfer tubes with a return bend, and causes the high-pressure side refrigerant of the refrigeration cycle to flow in one flow path, and the flow path to the other flow path. The air conditioner according to claim 6, wherein the low-pressure side refrigerant of the refrigeration cycle is flowed.

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