WO2008007694A1

WO2008007694A1 - Fin-and-tube type heat exchanger, and its return bend pipe

Info

Publication number: WO2008007694A1
Application number: PCT/JP2007/063807
Authority: WO
Inventors: Hiroyuki Takahashi; Tsuneo Haba; Akihiko Ishibashi
Original assignee: Kobelco & Materials Copper Tube, Ltd.
Priority date: 2006-07-14
Filing date: 2007-07-11
Publication date: 2008-01-17
Also published as: EP2042825A1; CN101466992B; CN101466992A; EP2042825A4; JP4728897B2; EP2042825B1; KR20080108620A; MY144548A; JP2008020150A

Abstract

Provided is a fin-and-tube type heat exchanger using a return bend pipe capable of improving the evaporation performance of the heat exchanger still better. This heat exchanger comprises a hair pin unit having a multiplicity of hair pin pipes arranged in parallel, a return bend unit having a multiplicity of such return bend pipes arranged in parallel as are jointed to the individual hair pin pipe end portions of the hair pin portions, and a fin portion having a multiplicity of fins arranged in parallel at a constant spacing on the outer surfaces of the hair pin pipes. The pipe insides are fed with a coolant. The heat exchanger has first grooves formed in the inner faces of the return bend pipes. The groove pitch ratio (P1/P2) between a first groove pitch (P1), as taken in the section normal to the pipe axis, of the first grooves, and a second groove pitch (P2), as taken in the section normal to the pipe axis, of second grooves of a helical shape formed in the pipe inner faces of the hair pin pipes satisfies 0.65 to 2.2. At the same time, the groove sectional area ratio (S1/S2) between a first groove sectional area (S1) per groove, as taken in the section normal to the pipe axis, of the first grooves and a second groove sectional area (S2) per groove, as taken in the section normal to the pipe axis, of the second grooves satisfies 0.3 to 3.6.

Description

Specification

Fin-and-tube heat exchanger and its return bend pipe

Technical field

[0001] The present invention is a heat exchanger such as an air conditioner, and in particular, a refrigerant such as a chlorofluorocarbon refrigerant or a natural refrigerant is allowed to flow inside the pipe, and a large number of fins formed of aluminum or the like are installed in parallel on the outer surface of the pipe. The fin-and-tube heat exchanger and the return bend pipe connected to the hairpin pipe.

Background art

[0002] Conventionally, Patent Document 1 or Patent Document 2 proposes a fin-and-tube heat exchanger using a smooth tube having a smooth inner surface as a return bend tube and an inner grooved tube as a hairpin tube. In Patent Document 1, the return bend pipe is described as a U-bend pipe, and the hairpin pipe is described as an electric sewing pipe. In Patent Document 2, the return bend pipe is described as a U-bend pipe, and the hairpin pipe is described as a heat transfer pipe.

[0003] Further, Patent Document 3 proposes a fin-and-tube heat exchanger for an evaporator (evaporator) using an internally grooved tube as a return bend tube and a smooth tube as a hairpin tube. In Patent Document 3, a return bend pipe is described as a U-bend pipe, and a hairpin pipe is described as a tube. Furthermore, Patent Document 4 discloses a fin-and-tube heat exchanger using inner grooved tubes for both the return bend tube and the hairpin tube.

[0004] On the other hand, hide-mouthed fluorocarbon refrigerants such as R22 (chlorofluoromethane), which has been used as a refrigerant for fin-and-tube heat exchangers, protect the global environment by destroying the ozone layer. In view of this point, it is no longer possible to use it, and a high-mouth fluorocarbon refrigerant such as R410A in which all of the contained chlorine is replaced with hydrogen has begun to be used in earnest as a cooling medium for air conditioning equipment.

Patent Document 1: Japanese Utility Model Publication No. 63-154986 (Example, FIGS. 1 to 4)

Patent Document 2: JP-A-11-190597 (paragraphs 0022 to 0026, FIG. 1)

Patent Document 3: Japanese Utility Model Publication No. 4-122986 (paragraphs 0007 to 0008, FIG. 1)

Patent Document 4: Japanese Unexamined Patent Publication No. 2006-98033 (Claim 1, FIG. 4) Disclosure of the invention

Problems to be solved by the invention

[0005] However, in the heat exchangers of Patent Documents 1 and 2, the refrigerant flowing in the hairpin tube becomes a swirl flow along the groove formed on the inner surface of the tube, flows into the return bend tube, and the swirl flow for a while. Maintained. However, since the inner surface of the return bend pipe is smooth, the swirling flow is maintained at the outlet side of the return bend pipe, and at the bent portion of the return bend pipe, a droplet (refrigerant liquid film) is maintained. The liquid film flow becomes unstable. Therefore, after the next hairpin tube flow, it is spent for a while to re-apply the swirl flow to the refrigerant. In this section, the flow of the refrigerant is unstable, and a thick part of the refrigerant liquid film is formed. As a result, the heat transfer coefficient in the pipe decreased and sufficient evaporation performance could not be obtained immediately.

[0006] Further, in the heat exchanger of Patent Document 3, since a groove is formed in the return bend pipe and no groove is formed in the hairpin pipe, the shapes of both pipes are greatly different. For this reason, the heat exchanger has a problem in that the pressure loss of the refrigerant circulating inside increases, thereby reducing the flow rate of the refrigerant, so that the heat transfer performance of the heat exchanger, in particular, the evaporation performance decreases. It was.

[0007] Then, as described in Patent Document 3, if the thickness of the pipe is increased in consideration of the strength reduction due to the formation of the groove in the return bend pipe, the flow of the refrigerant to the inner surface of the joint between the return bend pipe and the hairpin pipe is increased. A step that becomes a common obstacle occurs, and the pressure loss of the refrigerant is likely to increase! /.

[0008] In addition, in the heat exchanger of Patent Document 4, the force, groove pitch, and groove breakage in which the groove lead angle formed by the groove formed on the return bend tube and the hairpin tube and the tube shaft is limited to a predetermined one. Because the area has not been studied, the refrigerant liquid film in the pipe is disturbed, the liquid film in the straight portion of the hairpin tube becomes non-uniform, and the refrigerant liquid film is thick. There was a thing. As a result, there is a problem that sufficient evaporation performance cannot be obtained.

More specifically, the non-uniform refrigerant liquid film means that the liquid film thickness becomes non-uniform, and if the liquid film thickness is non-uniform, the thick part of the liquid film A state difference (a function of the surface tension of the refrigerant liquid film and the curvature of the liquid film) occurs in the thin part. When this state difference occurs, in principle, a liquid film with a thin refrigerant liquid film is pulled in a direction where the refrigerant liquid film is thicker. The thin part of the liquid film becomes thinner, and evaporation is promoted in this part, while the thick part of the refrigerant liquid film remains. The remaining refrigerant liquid film results in a dry-out state except for the remaining portion, which reduces the effective heat transfer area and lowers the evaporation performance.

Yes

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a fin-and-tube heat exchanger that can further improve the evaporation performance of the heat exchanger and its return bend pipe. Say it.

Means for solving the problem

[0011] A first aspect of the present invention provides a hairpin portion in which a large number of hairpin tubes are arranged in parallel, and a retarder in which a large number of return bend tubes joined to the hairpin tube ends of the hairbin portions are arranged in parallel. A fin-and-tube heat exchanger having a bent portion and a fin portion composed of a large number of fins arranged in parallel at regular intervals on the outer surface of the hairpin tube, wherein a refrigerant is supplied into the tube,

A first groove formed on the inner surface of the return bend pipe;

The first groove pitch (P1) in the cross section perpendicular to the tube axis of the first groove and the second groove pitch (P2) in the cross section perpendicular to the tube axis of the spiral second groove formed on the tube inner surface of the hairpin tube. Groove pitch ratio (P1 / P2) satisfies 0.665-2.

The first groove cross-sectional area (S1) per groove in the cross section perpendicular to the tube axis of the first groove and the second cross-sectional area (S2) per groove in the cross section perpendicular to the tube axis of the second groove Groove cross-sectional area ratio (S1

/ S2) is configured as a fin-and-tube heat exchanger satisfying 0.3 to 3.6.

[0012] According to the above configuration, the predetermined first groove is formed on the inner surface of the return bend pipe of the fin-and-tube heat exchanger, so that the refrigerant liquid film is flattened on the return bend pipe inlet side. Furthermore, an “annular flow” can be formed in the refrigerant liquid film inside the pipe, and the disturbance of the refrigerant liquid film in the return bend pipe can be reduced. When the liquid refrigerant flows into the next hairpin tube from the return bend tube outlet side, a uniform “annular flow” is formed inside the tube, and the liquid film in the straight portion of the hairpin tube becomes uniform. In addition, heat exchange with the outside of the tube is stabilized and evaporation performance is improved. [0013] It is preferable that a second groove lead angle (θ2) formed by the second groove of the hairpin tube and the tube axis is 15 ° or more.

[0014] According to the above configuration, when the liquid refrigerant flows into the next hairpin tube from the return bend tube outlet, a uniform "annular flow" is formed inside the tube, and the refrigerant is generated in the straight tube portion of the hairpin tube. The liquid film becomes uniform, heat exchange with the outside of the tube is stabilized, and evaporation performance is further improved.

[0015] Further, it is preferable that at least a part of the refrigerant flow path constituted by the hairpin tube and the return bend pipe is branched to form a plurality of refrigerant flow paths.

[0016] According to the above configuration, the refrigerant flow rate of the fin-and-tube heat exchanger is branched, so that the refrigerant mass velocity per branch is lowered, and in particular, the refrigerant velocity at the return bend pipe inlet side is lowered. In addition, the “annular flow” of the refrigerant liquid film formed inside the pipe is further stabilized. When the liquid refrigerant flows into the next hairpin tube from the return bend tube outlet side, a uniform “annular flow” is formed inside the tube, and the liquid film of the refrigerant becomes uniform in the straight portion of the hairpin tube. The heat exchange with the outside of the tube is stabilized and the evaporation performance is further improved.

[0017] Further, it is preferable that the refrigerant is a hydrated fluorocarbon non-azeotropic refrigerant mixture.

According to the above configuration, the evaporation performance of the heat exchanger is further improved, and the pressure loss of the refrigerant is reduced.

[0018] A second aspect of the present invention is a fin-and-tube heat exchange which is joined to a tube end of a hepin tube provided with a large number of fins arranged in parallel at regular intervals on an outer surface, and a refrigerant is supplied into the tube. In return bend pipes used in

A first groove formed on the inner surface of the return bend pipe;

The first groove pitch (P1) in the tube axis orthogonal cross section of the first groove and the second groove pitch (Ρ2) in the tube axis orthogonal cross section of the spiral second groove formed on the tube inner surface of the hairpin tube. Groove pitch ratio (P1 / P2) satisfies 0.665-2.

The first groove cross-sectional area (S1) per groove in the cross section perpendicular to the tube axis of the first groove and the second cross-sectional area (S2) per groove in the cross section perpendicular to the tube axis of the second groove It is constructed as a return bend pipe that satisfies the groove cross-sectional area ratio (S1 / S2) of 0.3 to 3.6.

[0019] According to the above configuration, the groove pitch ratio (P1 / P2) and the groove cross-sectional area ratio (S1 / S2) are predetermined. By setting the range, the “swirl flow” of the liquid refrigerant formed in the hairpin tube is maintained even in the return bend tube. At the same time, when the liquid coolant flows from the hairpin tube into the return bend tube, the coolant liquid film can be flattened on the return bend tube inlet side, and the coolant liquid film inside the tube becomes uniform. Flow "can be formed. As a result, the disturbance of the refrigerant liquid film inside the return bend pipe is reduced. When liquid refrigerant flows into the next hairpin tube from the return bend tube outlet side, a uniform "annular flow" is formed inside the tube, and the liquid film in the straight tube portion of the hairpin tube becomes uniform. , Heat exchange with the outside of the tube (air) is stabilized, and evaporation performance is improved.

[0020] An angle difference (Θ;) between a first groove lead angle (θ1) formed by the first groove and the tube axis and a second groove lead angle (Θ2) formed by the second groove and the tube shaft. -Θ 2) satisfies -15 to + 15 °, and the first groove depth (hi) in the cross section perpendicular to the tube axis of the first groove and the second groove in the cross section perpendicular to the tube axis of the second groove It is preferable that the groove depth ratio (hl / h2) to the depth (h2) satisfies 0.47 to 1.5.

[0021] According to the above configuration, when the liquid refrigerant flows from the hairpin tube into the return bend tube by setting the angle difference (θ 1-Θ 2) of the groove lead angle to a predetermined range, Suppresses the splashing of the film. When the liquid refrigerant flows into the next hairpin tube from the return bend tube outlet side, a uniform “annular flow” is formed inside the tube, and the coolant liquid film is evenly distributed in the straight portion of the hairpin tube. Thus, heat exchange with the outside of the tube is stabilized, and the evaporation performance is further improved. Further, by setting the groove depth ratio (hl / h2) within a predetermined range, it is difficult for the refrigerant liquid film to be disturbed, which makes it difficult for the refrigerant to detach inside the pipe. When liquid refrigerant flows from the return bend pipe outlet side into the next-stage hepin pipe, a uniform “annular flow” is formed inside the pipe, and the liquid film of the refrigerant in the straight pipe portion of the hairpin pipe is uniform. Therefore, heat exchange with the outside of the tube is stabilized, and the evaporation performance is further improved.

[0022] Further, the foot length of the return bend pipe (U is preferably 1.0 to 1.5 times the pitch (P)).

[0023] According to the above configuration, when the straight pipe portion of the hairpin tube and the return bend tube are joined and used, the leg length of the return bend tube (U is set to a predetermined multiple of the bending pitch (P). As a result, the “circular flow” is sufficiently formed in the refrigerant liquid film in the straight pipe part up to the bent part, and the refrigerant liquid film in the bent part of the return bend pipe is disturbed ( Peeling flow) Does not occur. Then, when the liquid refrigerant flows into the hairpin tube in the next stage, the “annular flow” flows in, forming a uniform liquid film in the straight portion of the hairpin tube, and heat exchange with the outside of the tube. The conversion is stabilized and the evaporation performance is further improved.

[0024] The material of the return bend tube is preferably made of a material having a lower thermal conductivity than the material of the hairpin tube.

[0025] According to the above configuration, the heat conductivity of the tube main body (return bend tube) is lower than that of the hairpin tube, thereby suppressing heat loss in the return bend tube. Reducing the heat loss in the return bend pipe causes the refrigerant liquid film to splash due to the evaporation of the refrigerant inside the return bend pipe or the collapse of the “annular flow” of the refrigerant liquid film. Disturbance (separated flow) does not occur. As a result, when the liquid refrigerant flows into the hairpin tube in the next stage, the “annular flow” flows in, forming a uniform liquid film in the straight tube portion of the hairpin tube, and heat from the outside of the tube. Exchange is stabilized and evaporation performance is further improved.

[0026] The material of the return bend tube is preferably made of a copper alloy that is more heat resistant than the material of the hairpin tube.

[0027] According to the above configuration, when the return bend pipe is made of a heat resistant copper alloy, when the return bend pipe and the hairpin pipe are joined (brazed), the strength of the return bend pipe after brazing is increased. Since the decrease is small, the pressure inside the pipe during use of the heat exchanger does not cause pipe breakage at the junction of the return bend pipe, for example, the temperature-affected zone of brazing.

Further, it is not necessary to increase the wall thickness of the return bend pipe.

[0028] Further, the first maximum inner diameter (ID1) of the return bend tube is preferably (ID1) ≥ (ID2) in relation to the second maximum inner diameter (ID2) of the hairpin tube.

[0029] According to the above configuration, when the liquid refrigerant flows from the return bend pipe into the hairpin pipe, the formation state of the "annular flow" is maintained more uniformly, and further, the refrigerant liquid near the hairpin pipe inlet side is maintained. The film spreads in the circumferential direction, and the refrigerant liquid film can be thinned. As a result, the evaporation performance in the straight tube portion of the hairpin is further improved.

The invention's effect

[0030] According to the fin-and-tube heat exchanger of the first aspect of the present invention, it is possible to improve the evaporation performance of the heat exchanger by using the return bend pipe. The Further, by using a hairpin tube having a groove lead angle within a predetermined range, a branched refrigerant flow path, and a predetermined refrigerant, it is possible to further improve the evaporation performance of the heat exchanger.

[0031] According to the return bend pipe of the second aspect of the present invention, by setting the groove pitch and the groove cross-sectional area of the first groove of the return bend pipe within a predetermined range, the ring is formed on the refrigerant liquid film inside the pipe. As a result, the refrigerant liquid film in the straight portion of the hairpin tube becomes uniform, and the evaporation performance of the heat exchanger can be improved. In addition, by setting the groove lead angle, groove depth, foot length, thermal conductivity, and maximum inner diameter of the first groove of the return bend pipe within predetermined ranges, the evaporation performance of the heat exchanger can be further improved. It becomes possible. By configuring the return bend tube from a heat-resistant copper alloy, it is possible to increase the reliability of the joint with the hairpin tube and achieve a weight reduction.

Brief Description of Drawings

FIG. 1 is a perspective view showing a configuration of a return bend pipe according to the present invention.

FIG. 2 is a partially broken front view showing an example of a fin-and-tube heat exchanger incorporating a return bend pipe according to the present invention.

[FIG. 3] (a) is a perspective view of the heat exchanger of FIG. 2 as viewed from the return bend tube side, (b) is a perspective view of the heat exchanger as viewed from the hairpin tube side, and (c) is the inside of the heat exchanger. FIG. 6 is a schematic diagram schematically showing the flow of the refrigerant.

FIG. 4 is an enlarged end view when cut in the tube axis direction showing an example of a joint portion between a hairpin tube and a return bend tube.

[Fig. 5] (a) is an end view perpendicular to the axis of the return bend pipe, and (b) is a partially enlarged end view of (a).

Yes

[Fig. 6] (a) is an end view of the hairpin tube perpendicular to the tube axis, and (b) is a partially enlarged end view of (a).

[FIG. 7] (a) and (b) are schematic views schematically showing the flow of refrigerant in a heat exchanger according to another embodiment of the present invention.

[Fig. 8] (a) is a schematic diagram of a suction type wind tunnel used for measuring the evaporation performance of a heat exchanger, and (b) is a schematic diagram of a refrigerant supply device for supplying refrigerant to the suction type wind tunnel of (a). It is.

Explanation of symbols [0033] 1 return bend pipe

la tube body

2 1st groove

3 First fin

1 1 hairpin tube

12 Second groove

13 2nd fin

20, 20A, 20B heat exchanger

21 fin ¾

21 a fin

22 Return bend section

23 hairpin part

P1 1st groove pitch

P2 2nd groove pitch

S 1 Groove cross section

S2 Second groove cross-sectional area

Θ 1 1st groove lead angle

Θ2 2nd groove lead angle

hi 1st groove depth

h2 2nd groove depth

L foot length

P pitch

ID1 1st maximum inner diameter

ID2 2nd maximum inner diameter

OD1 1st pipe outer diameter

OD2 second pipe outer diameter

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be specifically described with reference to the drawings. Figure 1 shows the return bend pipe Fig. 2 is a partially broken front view showing an example of a fin-and-tube heat exchanger incorporating a return bend tube. Fig. 3 (a) shows the heat exchanger of Fig. 2 on the return bend tube side. (B) is a perspective view of the heat exchanger as viewed from the hairpin tube side, (c) is a schematic diagram schematically showing the flow of refrigerant in the heat exchanger, and FIG. Fig. 5 (a) is an enlarged end view when cut in the tube axis direction showing an example of a joint with the return bend pipe, Fig. 5 (a) is a pipe bend orthogonal end view of the return bend pipe, and (b) is a part of (a). Fig. 6 (a) is an end view orthogonal to the axis of the hairpin tube, (b) is a partially enlarged end view of (a), and Figs. 7 (a) and (b) are heat exchanges of other embodiments. Fig. 8 (a) is a schematic diagram of the refrigerant flow in the exchanger. Fig. 8 (a) is a schematic diagram of a suction wind tunnel used to measure the evaporation performance of the heat exchanger. (B) is a schematic diagram of (a). Supply refrigerant to suction type wind tunnel It is a schematic diagram of a medium supply device.

[0035] (1) Return bend pipe

First, the return bend pipe of the present invention will be described. As shown in FIGS. 1 to 3, the return bend pipe 1 of the present invention is used in a fin-and-tube heat exchanger (hereinafter referred to as a heat exchanger) 20 and a hairpin for supplying refrigerant to the inside of the pipe. It is joined to the pipe end of the pipe 11. This return bend pipe 1 is formed on a pipe body la formed in a U-shape, a pipe end lb connected to the hairpin pipe 11 at the pipe end of the pipe body la, and an inner surface of the pipe body la. A number of first grooves 2 are provided (see FIG. 4; the description of the first groove is omitted in FIG. 1). Since the return bend tube 1 is interposed between the two hairpin tubes 11 and 11 and connects the hairpin tubes 11 to each other, as shown in FIG. 2, a plurality of hairpin tubes 11 and 11 are connected in series. By connecting to, a long-distance refrigerant flow path is formed.

[0036] As shown in Figs. 5 and 6, the return bend pipe 1 incorporates the return bend pipe 1 by restricting the inner groove shape of the first groove 2 formed on the inner surface of the pipe as follows. The evaporation performance of the heat exchanger 20 (see Fig. 2 and Fig. 3) can be improved. In addition, since the return bend pipe 1 uses 3 to 10 mm as the outer diameter of the hairpin pipe 11 to be joined (second outer diameter OD2), the outer diameter of the pipe (first outer diameter OD1) is It is preferable to use a 3 to 1 Omm tube that is the same as a hairpin tube!

[0037] <Inner groove shape>

The first groove 2 of the return bend pipe 1 has the first groove pitch (P1) in the cross section perpendicular to the pipe axis, The groove pitch ratio (P1 / P2) to the second groove pitch (P2) in the cross section perpendicular to the tube axis of the spiral second groove 12 formed on the inner surface of the hairpin tube 11 satisfies 0.665-2. In addition, the first groove cross-sectional area (S1) per groove in the cross section perpendicular to the pipe axis of the first groove 2 and the second cross-sectional area per groove in the cross section perpendicular to the pipe axis of the second groove 12 ( The groove cross-sectional area ratio (S1 / S2) with S2) must satisfy 0.3 to 3.6. The groove cross-sectional area ratio (S1 / S2) is more preferably 0.54-2.7. The reason for limiting the numerical values of the groove pitch ratio (P1 / P2) and the groove cross-sectional area ratio (S1 / S2) will be described below.

[0038] (Groove pitch ratio (P1 / P2): 0.65-2. 2)

When the groove pitch ratio (P1 / P2) is less than 0.65, the number of grooves in the return bend pipe 1 that occupy one groove in the hairpin pipe 11 increases, so that the liquid refrigerant flows from the hairpin pipe 11 to the return bend pipe 1. Flows into the refrigerant liquid film inside the pipe (first groove 2) on the return bend pipe inlet side, and the refrigerant liquid film is disturbed. Then, when the liquid refrigerant flows into the hairpin tube 11 at the next stage, the refrigerant liquid film flows in a turbulent state, and a thick portion is formed in the refrigerant liquid film at the straight tube portion of the hairpin tube, and heat exchange with the outside of the tube is performed. It becomes unstable and the evaporation performance decreases.

[0039] When the groove pitch ratio (P1 / P2) exceeds 2.2, when the liquid refrigerant flows into the return bend pipe 1 from the hairpin pipe 11, the return bend pipe 1 occupying one groove in the hairpin pipe 11 By reducing the number of grooves, the retention of the refrigerant liquid film in the first groove 2 of the return bend pipe 1 is greatly reduced, the formation of the “annular flow” is disrupted, and the refrigerant liquid film is disturbed. Then, when the liquid refrigerant flows into the hairpin tube 11 in the next stage, the refrigerant liquid film flows in a turbulent state, and a thick portion is formed in the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and heat from the outside of the tube is generated. Exchange becomes unstable and evaporation performance decreases.

[0040] (Groove cross-sectional area ratio (S 1 / S2): 0.3-3 · 6)

When the groove cross-sectional area ratio (S1 / S2) is less than 0.3, when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1, the cross-sectional area of the first groove 2 is greatly reduced, so that the return bend The refrigerant liquid film contracts on the pipe inlet side, and the refrigerant liquid film is disturbed. Then, when the liquid refrigerant flows into the next-stage air pipe 11, the refrigerant liquid film flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and the outside of the tube. Heat exchange becomes unstable and evaporation performance decreases. [0041] When the groove sectional area ratio (S1 / S2) exceeds 3.6, when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1, the resistance decreases due to the increase in the sectional area of the first groove 2. Conversely, the retention of the refrigerant liquid film in the first groove 2 decreases, so that the “annular flow” is lost and the refrigerant liquid film is disturbed. Then, when the liquid refrigerant flows into the hairpin tube 11 in the next stage, the refrigerant liquid film flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and heat exchange with the outside of the tube Becomes unstable and the evaporation performance decreases.

Further, as shown in FIGS. 4 to 6, the first groove 2 of the return bend tube 1 has a first groove lead angle (θ 1) formed by the first groove 2 and the tube axis, and a hairpin tube 11 The angle difference (θ: ΐ_θ 2) between the second groove 12 formed on the inner surface of the tube and the second groove lead angle (Θ 2) formed by the tube axis satisfies −15 to + 15 °, and Groove depth ratio (hl / h2) between the first groove depth (hi) in the cross section perpendicular to the pipe axis of the first groove 2 and the second groove depth (h2) in the cross section perpendicular to the pipe axis of the second groove 12 ) Is preferably between 0.47 and 1.5; Further, the first groove 2 includes the case where the first groove lead angle (θ1) is 0 °, that is, the first groove 2 is parallel to the tube axis. The reason for limiting the numerical values of the angle difference (θ 1-Θ 2) and the groove depth ratio (hl / h2) will be described below.

[0043] (Angle difference (θ 1- Θ 2): -15 to + 15 °)

If the angle difference (θ 1- Θ 2) is less than -15 °, that is, the first groove lead angle (θ 1) is smaller than (second groove lead angle (Θ 2) -15 °), the return bend pipe inlet side Thus, the coolant liquid film splashes from the peak of the first fin 3 formed between the first grooves 2, and turbulence (separation flow) occurs in the coolant liquid film. Then, when the liquid refrigerant flows into the hairpin tube 11 in the next stage, the refrigerant liquid film flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and heat exchange with the outside of the tube Becomes unstable and the evaporation performance tends to decrease.

[0044] When the angle difference (Θ 卜 Θ 2) exceeds + 15 °, ie, the first groove lead angle (θ 1) is larger than (second groove lead angle (Θ 2) + 15 °), When liquid refrigerant flows into the return bend pipe 1 from the hairpin pipe 11, the pressure loss on the return bend pipe side increases, causing a contraction of the refrigerant liquid film on the return bend pipe inlet side, thereby disturbing the refrigerant liquid film. . Then, when the liquid refrigerant flows into the next-stage air pipe 11, the refrigerant liquid film flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight pipe portion of the hairpin tube 11, and Heat exchange becomes unstable and evaporation performance tends to decrease. Note that the direction of the first groove lead angle (θ 1) formed by the first groove 2 and the tube axis is the second groove formed by the second groove 12 formed on the tube inner surface of the hairpin tube 11 and the tube axis. It is preferably formed in the same direction as the direction of the groove lead angle (Θ 2). If the direction of the first groove lead angle (θ 1) and the direction of the second groove lead angle (Θ 2) are different, the pressure loss of the refrigerant in the return bend pipe 1 becomes large, and the evaporation performance tends to deteriorate.

[0046] (Groove depth ratio (hl / h2): 0.47-1.5)

When the groove depth ratio (hl / h2) is smaller than 0.47, the refrigerant liquid film in the first groove 2 is released immediately on the return bend pipe inlet side, and the liquid droplet of the refrigerant liquid film is formed immediately. Disturbance (separated flow) occurs. Then, when the liquid refrigerant flows into the hairpin tube 11 in the next stage, the refrigerant liquid film flows in a turbulent state, and a thick portion is formed in the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and heat exchange with the outside of the tube Becomes unstable and the evaporation performance tends to decrease.

[0047] When the groove depth ratio (hl / h2) is greater than 1.5, when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1, the first fin 3 of the return bend tube 1 becomes a resistance, The refrigerant liquid film contracts at the return bend pipe inlet side, and the refrigerant liquid film is disturbed. Then, when the liquid refrigerant flows into the next-stage heat sink pipe, the refrigerant liquid film flows in a turbulent state, and a thick portion of the refrigerant liquid film is generated in the straight pipe portion of the hairpin tube 11, which Heat exchange becomes unstable and evaporation performance decreases.

[0048] In addition, the first groove 2 of the return bend pipe 1 includes the first fin peak angle (δ 1) and the first fin root radius (rl) force of the first fin 3 formed between the first grooves 2. S, more preferably formed so as to be the same as the second fin peak angle (δ 2) and the second fin root radius (r2) of the second fin 13 formed between the second grooves 12 of the hairpin tube 11. preferable. More preferably, the first fin peak angle (δ 1) is 4.5 to 45 °, and the first fin root radius (rl) is 1/12 to 1/2 of the first groove depth (hi). Furthermore, the first fin peak angle (δ ΐ) is 4.5 to 28.5 °, and the first fin root radius (rl) is 1/12 to the first groove depth (hi); 1/4 is optimal. It is. This further maintains the formation of the “annular flow” of the refrigerant liquid film in the return bend pipe 1.

As a result, the evaporation performance of the heat exchanger 20 (see FIGS. 2 and 3) is further improved. The reason for limiting the numerical values of the first fin peak angle (δ 1) and the first fin root radius (rl) is explained below. [0049] (1st fin peak angle (δ 1): 4 · 5 ~ 45 °)

When the first fin peak angle (δ 1) is less than 4.5 °, the resistance decreases due to the increase in the cross-sectional area of the first groove 2 when the liquid refrigerant flows into the return bend pipe 1 from the hairpin pipe 11. However, conversely, when the groove bottom width of the first groove 2 is widened, the retention of the refrigerant liquid film is deteriorated, and the formation of the “annular flow” is easily broken, and the refrigerant liquid film is disturbed. Then, when the liquid cooling medium flows into the hairpin tube 11 in the next stage, the refrigerant liquid film flows in a turbulent state, and a thick portion is generated in the cooling liquid film in the straight tube portion of the hairpin tube 11, and the outside of the tube is disconnected. Heat exchange becomes unstable and evaporation performance tends to decrease.

[0050] When the first fin peak angle (δ 1) exceeds 45 °, the cross-sectional area of the first groove 2 decreases when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1. As a result, the refrigerant liquid film contracts immediately on the return bend pipe inlet side, and the refrigerant liquid film is disturbed immediately. Then, when the liquid refrigerant flows into the hairpin tube 11 at the next stage, the refrigerant liquid film is likely to flow in a turbulent state, and a thick portion is formed in the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and the outside of the tube is Heat exchange becomes unstable, and evaporation performance tends to decrease.

[0051] (First fin root radius (rl): 1/12 to 1st groove depth (hi); 1/2)

When the first fin root radius (rl) is less than 1/12 of the first groove depth (hi), the cross-sectional area of the first groove 2 increases when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1. Although the resistance is reduced by the above, conversely, because the groove bottom width of the first groove 2 widens, the retention of the refrigerant liquid film decreases, and the formation of the "annular flow" tends to collapse, and the refrigerant liquid film is disturbed. . Then, when the liquid refrigerant flows into the next-stage air pipe 11, the refrigerant liquid film flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube 11, and the outside of the tube. Heat exchange becomes unstable and evaporation performance tends to decrease.

[0052] When the first fin root radius (rl) exceeds 1/2 of the first groove depth (hi), when the liquid refrigerant flows from the hairpin tube 11 into the return bend tube 1, the first groove As the cross-sectional area of 2 decreases, the refrigerant liquid film contracts immediately on the return bend pipe inlet side, and the refrigerant liquid film is immediately disturbed. Then, when the liquid refrigerant flows into the hairpin tube 11 in the next stage, the refrigerant liquid film tends to flow in a turbulent state, resulting in a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube 11 and the outside of the tube. Heat exchange becomes unstable, and evaporation performance tends to decrease. Further, as shown in FIG. 1, the evaporation performance as a heat exchanger in which the return bend pipe 1 is incorporated is also improved by restricting the pipe body la of the return bend pipe 1 as follows. Use force S.

[0054] <Tube body part>

(Foot length (L): 1 · 0 ~ of pitch (P);! · 5 times)

The return bend pipe 1 (pipe body la) preferably has a foot length (U is 1 · 0 to; 5 times the pitch (P). Note that the foot length (U is U-shaped) In the pipe-shaped main part la, the distance between the pipe end 1 b and the outer surface of the bent tip part, and the pitch (P) is the distance between the center of both pipe ends in the U-shaped pipe main part 1 a. Distance.

[0055] When the foot length (U is smaller than 1 · 0 times the bending pitch (P), the length from the inlet side of the return bend pipe to the bending start portion is short, so that an “annular flow” is formed. If the refrigerant liquid film splashes on the inner side of the bending, the refrigerant liquid film is disturbed (separated flow), and when the liquid refrigerant flows into the next hairpin tube, the refrigerant liquid film The liquid flows in a turbulent state, and a thick layer of liquid is formed in the refrigerant liquid film in the straight part of the hepin tube, making the heat exchange with the outside of the tube unstable, and the evaporation performance tends to deteriorate.

[0056] If the foot length (U is larger than 1 · 5 times the bending pitch (P), the length from the return bend pipe inlet side to the bending start part becomes longer, and the formation of “annular flow” is easy. On the other hand, the evaporation loss tends to decrease due to the increased pressure loss in the return bend pipe 1.

[0057] (Material)

The material of the return bend tube 1 (tube body portion la) is preferably made of a material having a lower thermal conductivity than the material of the hairpin tube. When the return bend pipe 1 is used in the heat exchanger 20 (see Figs. 2 and 3), especially in the air heat exchanger, the return bend pipe 1 is used outside the heat exchange section. Therefore, when the material of the return bend pipe 1 has higher thermal conductivity than the material of the hairpin pipe, heat loss occurs in the return bend pipe 1 portion. When heat loss occurs in the return bend pipe 1, the refrigerant evaporates in the return bend pipe 1, and the formation of the "annular flow" of the refrigerant liquid film breaks down. Disturbance (separated flow) of the refrigerant liquid film due to the occurrence occurs. When the liquid refrigerant flows into the hairpin tube in the next stage, the refrigerant liquid film flows in a turbulent state, and a thick portion of the refrigerant liquid film in the straight tube portion of the hairpin tube is generated, and the outside of the tube The heat exchange becomes unstable and the evaporation performance tends to decrease.

[0058] Conventionally, phosphorous deoxidized copper is often used as the material for the hairpin tube and the return bend tube 1 (tube body la). Then, when splicing, the ends of both pipes are heated to about 800-900 ° C with a gas burner or the like. At this time, if phosphorus deoxidized copper is used for the return bend pipe 1 (pipe main body la), the strength of the return bend pipe 1 (heat affected zone) is reduced by this heating, and the pressure inside the pipe during use is reduced. This makes it easier to break the tube. In order to avoid this point, it is necessary to increase the first pipe wall thickness (T1) (see Fig. 4) of the return bend pipe 1 (the pipe body la). However, by using a heat-resistant copper alloy that is more heat resistant than the hairpin tube as the material of the return bend tube 1 (tube main body la), strength reduction due to heating can be avoided, pressure resistance strength can be further improved, and meat Thickening of the thickness can be suppressed. As a result, the return bend pipe 1 (pipe main body la) can be reduced in weight. As the heat-resistant copper alloy, for example, Cu-Sn-P and Cu-Sn-Zn-P based copper alloys having a pressure strength of 10 MPa or more at room temperature even after heating at 850 ° C are preferable. As the hairpin tube, a heat-resistant copper alloy tube made of the same material as the return bend tube 1 may be used.

[0059] (First maximum inner diameter (ID1)

As shown in FIGS. 5 and 6, the first maximum inner diameter (ID1) of the return bend tube 1 (tube main body la) is (ID1) ≥ () in relation to the second maximum inner diameter (ID2) of the hairpin tube 11. ID2) is preferred. If (ID1) <(ID2), the force of the "annular flow" of the refrigerant liquid film formed in the pipe of the return bend pipe 1 is expanded when the liquid refrigerant flows into the hairpin pipe 11, and the lower part in the pipe As a result, the refrigerant liquid film accumulates, and the thickness of the refrigerant liquid film becomes non-uniform, thereby disturbing the refrigerant liquid film. Then, the refrigerant liquid film near the inlet of the next-stage hairpin tube flows in a turbulent state, resulting in a thick portion of the refrigerant liquid film, which makes the heat exchange with the outside of the tube unstable and reduces the evaporation performance. Wow.

[0060] (2) Hairpin tube

Next, as shown in FIGS. 2 and 3, a hairpin tube 11 constituting a heat exchanger 20 together with the return bend tube 1 of the present invention will be described. As shown in FIG. 6, the hairpin tube 11 has a plurality of spiral second grooves 12 formed on the inner surface of the tube, and the inner surface groove shape of the second groove 12 is regulated as follows. Power to control S is preferable. In addition, since the hairpin tube 11 is mainly a 3 to 10 mm tube as a heat transfer tube for air conditioning equipment, the outer diameter of the tube (second tube outer diameter OD2) is the same as that of the hairpin tube 3 to; It is preferable to use a 10 mm tube. Further, as the material of the hairpin tube 11, a heat-resistant copper alloy having higher heat resistance than phosphorus-deoxidized copper, which is preferably phosphorous-deoxidized copper having excellent forming processability, may be used.

[0061] (Second groove pitch (P2), second groove cross-sectional area (S2))

2nd pitch (P2) (p 0.37-0.42mm, second cross section (S2) (p 0.04—0.06mm ² ). Second groove pitch (P2) Is less than 0.37 mm and the second groove cross-sectional area (S2) is less than 0.04 mm ² when forming the second groove 12 on the inner surface of the pipe (eg, grooved plug) As the fluidity of the material into the groove of the tube decreases, the pushing force from the outside of the tube increases, and as a result, the groove forming tool breaks and immediately forms the second groove 12 on the tube inner surface stably. In addition, if the second groove pitch (P2) exceeds 0.42 mm and the second groove cross-sectional area (S2) exceeds 0.06 mm ² , the refrigerant liquid is inserted between the second grooves 12 inside the pipe. Since the film is hard to be formed thinly, the refrigerant liquid film inside the pipe becomes a thermal resistance, and the evaporation performance is likely to deteriorate.

[0062] (Second groove lead angle (Θ 2): See Fig. 4)

The second groove lead angle (Θ 2) is preferably 15 ° or more. When the second groove lead angle (Θ2) is less than 15 °, the formation of the “swirl flow” of the refrigerant liquid film in the pipe is insufficient, and the evaporation performance tends to be lowered. When liquid refrigerant flows from the return bend pipe outlet side into the hairpin pipe 11 of the next stage, the formation of a uniform “annular flow” of the refrigerant liquid film in the second groove 12 decreases, and the straight pipe portion of the hairpin pipe 11 As a result, the liquid film of the refrigerant becomes uneven, heat exchange with the outside of the tube becomes unstable, and evaporation performance tends to deteriorate. Also, if the second groove lead angle (Θ 2) force exceeds 5 °, the speed when forming the second groove 12 on the inner surface of the tube by rolling will become extremely slow and will soon stabilize and become long. Since the hairpin tube 11 is difficult to manufacture, the second groove lead angle (Θ 2) is more preferably 45 ° or less.

[0063] (2nd groove depth (h2))

The second groove depth (h2) is preferably 0.10-0.28 mm. If the second groove depth (h2) is less than 0.10 mm, the second fin 13 formed between the second grooves 12 on the inner surface of the pipe It becomes lower than the liquid level of the refrigerant and is buried in the refrigerant liquid film. For this reason, the effective heat transfer area inside the pipe is remarkably reduced, and the evaporation performance tends to be lowered. Also, if the second groove depth (h2) exceeds 0.28 mm, the groove forming tool (for example, grooved plug) will be damaged immediately when forming the second groove 12 on the pipe inner surface. It is difficult to form the second groove 12 stably on the inner surface of the tube.

[0064] (2nd fin peak angle (δ 2))

The second fin peak angle (δ 2) is preferably 5 to 45 °! /. If the peak angle (δ 2) of the second fin is less than 5 °, the second fin 13 may fall over when the hairpin tube 11 is expanded (not shown) when the hairpin tube 11 is installed in the heat exchanger 20 for an air conditioner. Crushing tends to occur. Further, when forming the second groove 12 on the inner surface of the tube for forming the second fin 13, the groove forming tool is easily damaged, and it is difficult to stably form the second groove 12 on the inner surface of the tube. In addition, when the peak angle (δ 2) of the second fin exceeds 45 °, the cross-sectional area of the second groove 12 is remarkably reduced, and the heat transfer performance is likely to deteriorate. In addition, the cross-sectional area of the second fin 13 (the second tube thickness (Τ2) of the hairpin tube 11) is increased, the mass of the hairpin tube 11 is increased, and the weight reduction of the heat exchanger 20 is difficult.

[0065] (2nd fin root radius (r2))

The second fin root radius (r2) is preferably 1/10 to 1/3 of the second groove depth (h2). When the second fin root radius (r2) is less than 1/10 of the groove depth (h2), the formability of the second fin 13 (second groove 12) is increased when the second fin 13 becomes higher. It becomes difficult to obtain the second fin 13 having a predetermined shape, and the groove forming tool that comes into contact with the root of the second groove 12 on the inner surface of the pipe is easily damaged. If the ratio exceeds 1/3, the cross-sectional area of the second fin 13 increases, the second tube thickness (T2) of the hairpin tube 11 increases, and the mass of the hairpin tube 11 increases.

Yes

[0066] (2nd maximum inner diameter (ID2))

It is preferable that the second maximum inner diameter (ID2) of the hairpin tube 11 is 0.80 to 0.96 of the outer diameter (OD2) of the hairpin tube 11. If the second maximum inner diameter (ID2) is less than 0.80 of the outer diameter (OD2) of the hairpin tube 11, the thickness of the second tube (T2) is increased, the mass of the hairpin tube 11 is increased, and heat exchange is performed. It becomes difficult to reduce the weight of the vessel 20 (see Fig. 2 and Fig. 3). In addition, when the second maximum inner diameter (ID2) exceeds 0.96 of the outer diameter (OD2) of the hairpin tube 11, the second tube wall thickness (T2) is reduced and the tube strength of the hairpin tube 11 is reduced. Tube breakage is likely to occur during use of the low heat exchanger 20. [0067] (3) Manufacturing method of return bend tube and hairpin tube

Next, a method for manufacturing a return bend tube and a hairpin tube will be described. Both the return bend tube and the hairpin tube are manufactured, for example, by the following known manufacturing method. Usually, a soft material is used for the raw tube to which the following first step is applied. Further, the first to third steps described below are continuously performed using a rolling device provided with a diameter reducing device at the former stage and the latter stage. After the third diameter reduction in the third step, the inner grooved tube is usually rolled up on a level wound coil and annealed in an annealing furnace to form a soft material, and the fourth step is applied. To produce return bend tubes and hairpin tubes.

[0068] (First step)

The raw pipe made of a material such as phosphorous deoxidized copper or heat-resistant copper alloy is pulled out so as to pass between the reduced diameter die and the reduced diameter plug, so that the first reduced diameter processing is performed on the raw pipe. .

(Second process)

Inserting a grooved plug into the element pipe reduced in diameter in the first step and pressing the grooved plug inserted into the element pipe with a plurality of rolling balls or rolling rolls. The second diameter reduction process is applied to the base tube. At the same time, the groove shape of the grooved plug is transferred to the inner surface of the reduced diameter pipe, and the first groove 2 or the second groove 12 (see FIG. 4) is formed. Here, the grooved plug has a groove shape corresponding to the above-described inner surface groove shape (see FIGS. 5 and 6).

(Third process)

By pulling out the raw tube in which the first groove 2 or the second groove 12 is formed on the inner surface of the tube in the second step with a shaping die, the third diameter reduction processing is performed, and the first tube outer diameter (OD1) Alternatively, a heat transfer tube with an inner groove with the second tube outer diameter (OD 2) is manufactured.

(4th process)

The inner grooved tube manufactured in the third step is bent with a predetermined jig to manufacture a return bend tube 1 and a hairpin tube 11 (see FIGS. 1 and 2) having a predetermined shape.

[0069] (4) Fin and tube heat exchanger

Next, the heat exchanger of the present invention will be described. As shown in FIGS. 2 and 3 (a), (b), and (c), the heat exchanger 20 is supplied with a refrigerant inside the tube, and a large number of hairpin tubes 11, 11,... The hairpin portions 23 arranged in parallel, and the hairpin tubes 11 of each of the hairpin portions 23, 11 '''' Tube end 1, lb (see Fig. 1) joined to many return bend pipes 1, 1 ... And a fin portion 21 composed of a large number of fins 21a, 21a '... Arranged in parallel at a constant interval (fin pitch Pb). With such a configuration, a large number of hairpin tubes 11, 11 '''are connected in series in a plurality of stages through the return bend tubes 1, 1, ..., and the heat exchanger 20 is long! / It has a heat pipe length (refrigerant flow path). Further, as shown in FIG. 3 (b), the hairpin tubes 11 may be arranged in a plurality of rows at a predetermined row direction pitch Pc. Further, as shown in FIG. 3 (c), the refrigerant supplied into the pipe of the heat exchanger 20 is in the same direction when the refrigerant is condensed with respect to the air flow blown to the heat exchanger 20, and when the refrigerant is evaporated. Flowed in the opposite direction.

[0070] At least a partial force of the return bend portion 22 is constituted by a return bend pipe 1 in which a large number of first grooves 2 (see Fig. 5) are formed on the inner surface of the pipe. With this configuration, it is possible to reduce a decrease in evaporation performance in the heat exchanger 20. Also, the inner surface groove shape of the return bend pipe 1, for example, groove pitch ratio (Pl / P2), groove cross-sectional area ratio (S1 / S 2), groove depth ratio (hl / h2) (see Fig. 5 and Fig. 6) In consideration of the refrigerant flow (upstream or downstream) of the heat exchanger 20, the difference in groove lead angle (Θ1-Θ2) (see Fig. 4), etc., or the first maximum inner diameter (ID1) It may be changed depending on the location of the return bend section 22. Furthermore, in consideration of the pressure loss of the refrigerant, a return bend section 22 may be used as a return bend section 22 made of a smooth pipe.

[0071] In addition, the heat exchanger of the present invention may be one in which at least a part of the refrigerant flow path constituted by the hairpin tube and the return bend pipe is branched to form a plurality of refrigerant flow paths. For example, as shown in FIGS. 7 (a) and 7 (b), a two-pass heat exchanger 20A in which the entire refrigerant flow path is branched, and a partial two-pass heat exchanger 20B in which a part of the refrigerant flow path is branched. Is mentioned. Here, in FIGS. 7 (a) and 7 (b), the refrigerant flow path is branched into two flow paths (refrigerant flow path A and refrigerant flow path B). It may be branched more than the road. Further, the branched refrigerant flow paths (refrigerant flow path A and refrigerant flow path B) may be further branched into a plurality of refrigerant flow paths. Further, in the partial two-pass heat exchanger 20B in FIG. 7 (b), the number of branches is one, but it may be two or more, that is, the refrigerant flow path shown in FIG. 3 (c). Is not branched 1-pass heat exchanger 20 is connected to multiple 2-pass heat exchangers 20A It may be a combination.

[0072] In the heat exchangers 20A (two-pass heat exchanger) and 20B (partial two-pass heat exchanger) as shown in FIG. 7, the one-pass heat exchanger 20 (see FIG. 3 (c)) is used. As with), the evaporation performance is improved by maintaining the swirling flow of the refrigerant. Further, in the heat exchangers 20A and 20B in which the refrigerant flow path is branched, the refrigerant mass velocity per branch is lowered, particularly the refrigerant velocity at the return bend pipe inlet side is lowered, and the refrigerant liquid film formed inside the pipe is reduced. The “annular flow” becomes more stable. When the liquid refrigerant flows into the next hairpin tube from the outlet side of the return bend tube, a uniform “annular flow” is formed inside the tube, and the liquid film in the straight tube portion of the hairpin tube becomes uniform. , Heat exchange with the outside of the tube (air side) is stabilized, and the evaporation performance is further improved. Further, by forming a plurality of refrigerant channels (refrigerant channel A and refrigerant channel B), the parallel hairpin tubes and return bends that form the refrigerant channel (refrigerant channel A or refrigerant channel B) are formed. The number of tube stages is reduced compared to the one-pass heat exchanger 20 (Fig. 3 (c), it is reduced from 11 to 6 in Fig. 7).

Thereby, the pressure loss of the refrigerant is reduced, and the evaporation performance is further improved.

[0073] The refrigerant used in the heat exchanger 20 of the present invention is a hydrated fluorocarbon (HFC) -based refrigerant, which is a non-azeotropic refrigerant mixture, for example, difluoromethane (R410) which is preferred. R410A in which 50% of R32) and pentafluoroethane (R125) are mixed is more preferable. By using an HFC non-azeotropic refrigerant mixture, the evaporation performance of the heat exchanger 20 is improved, and the pressure loss of the refrigerant is also reduced. In addition, the R410 system has excellent heat transfer performance, but the compressor tends to be large due to the high operating pressure. Therefore, the R407 system in which the evaporation performance is slightly lower than the R410 system and the operating pressure force is lower than the 410 system may be used as the refrigerant of the present invention.

Example

[0074] <Examples !! to 20 (except Example 9)>

Examples of the present invention will be specifically described below.

First, Examples;! To 6, Examples 8 to 20 are phosphorus deoxidized copper of alloy number C1220 or oxygen-free copper of alloy number C1020 specified in JISH3300, Example 7 is Cu-Sn-P (0.65 (Mass%, 0.03 mass%, Cu balance heat-resistant copper alloy) is melted, forged, hot extruded, cold pressure It was extended and cold drawn to give a blank tube. Next, after annealing the element pipe, the first diameter reduction processing is performed, and the inner diameter groove-shaped spiral grooves or parallel grooves shown in Tables 1 and 2 are formed on the diameter-reduced element pipe. The test tube (for return bend pipe) with a first pipe outer diameter (OD 1) of 7 mm was prepared by subjecting the grooved tube to the third diameter reduction and annealing. In addition, a test tube (for hairpin tube) with a second tube outer diameter (OD2) of 7 mm was prepared in the same manner using phosphorous deoxidized copper with alloy number C 1220 specified in JISH3300.

Next, a fin-and-tube heat exchanger (one-pass heat exchanger) 20 shown in FIG. 2, FIG. 3 (a), (b) was produced using each of the test tubes. First, a plurality of hairpin tubes 11 were prepared by bending a test tube (for hairpin tubes) into a hairpin shape at a predetermined bending pitch (Pa) at the center thereof. Next, a plurality of hairpin tubes 11 were passed through a plurality of fins 21a arranged in parallel with each other at a predetermined interval (fin pitch (Pb)). Then, a bullet having a tube expansion rate of 105.5% based on the outer diameter standard of the copper tube (hairpin tube 11) is inserted into the heavy tube 11 and a contraction type tube expander (tube expander), and fin 2 la and hepin tube 1 1 were joined. Next, a plurality of return bend pipes 1 were produced by bending a test pipe (for return bend pipes) with a predetermined foot length and pitch (P) (see Fig. 1). Then, as shown in Fig. 4, the tube end of the adjacent hairpin tube 11 is further expanded, and a return bend tube 1 with a ring of phosphor copper brazing (B CuP-2) is attached, Heat exchanger 20 was produced by flowing both tubes with a burner while heating them with nitrogen gas to prevent oxidation (850 ° C, 1 minute). The specifications of the heat exchanger 20 are as follows. (Heat exchanger 20)

The opening $ is 500mm long x 250mm high x 25.4mm wide.

(Hairpin tube 1 1)

They were arranged in two rows and 12 steps (bending pitch (Pa) 21 mm, row direction pitch (Pc) 13.4 mm) (foot length (La) before tube expansion was about 535 mm).

(Return bend pipe 1)

Foot length (U = 20. Omm, 21.2 mm, 22.5 mm, 31.4 mm,

3. Omm

Pitch (Ρ) = 21 · Omm (see Fig. 1). (Fin 21a)

This is a plate material made of aluminum with alloy number 1N30 specified in JISH4000, and the surface of the plate material is coated with resin. The thickness of the fin 21a was l lO ^ m. Then, 4 10 fins 21a were arranged in parallel with a fin pitch (Pb) of 1.25 mm.

[0076] In Example 9, the same test tube (hairpin tube, return bend tube) as in Example 1 was used, and in the same manner as in Example 1, the fin-and-tube type thermal tube shown in Fig. 7 (a) was used. Exchanger (2-pass heat exchanger) 20A was produced. The number of stages of the hairpin tubes 11 in the refrigerant flow paths A and B is 6 in 2 rows.

[0077] <Comparative Example;! ~ 5>

As shown in Table 3, Comparative Example 1 was the same as Example 1 except that a smooth tube with no grooves formed on the inner surface was used as the test tube (return bend tube). In Comparative Examples 2 to 5, except that at least one of the groove pitch ratio (P1 / P2) and the groove cross-sectional area ratio (S 1 / S2) uses an internally grooved tube that is outside the scope of the claims of the present invention, Same as Example 1. Then, a heat exchanger (one-pass heat exchanger) 20 was produced in the same manner as in Example 1.

[0078] Using the heat exchangers of Examples 1 to 20 and Comparative Examples 1 to 5, the evaporation performance was measured based on JIS C 9612. The results are shown in Table 1, Table 2, and Table 3. The evaporation performance was described as a ratio when the heat transfer amount of each heat exchanger was measured and Comparative Example 1 was set to 1.

[0079] Fig. 8 (a) shows a schematic diagram of a measuring apparatus for measuring the evaporation performance. As shown in FIG. 8 (a), the measuring device includes a suction type wind tunnel 100 having a constant temperature and humidity function, a refrigerant supply device 110 (see FIG. 8 (b)), and an air conditioner (not shown). In the suction type wind tunnel 100, the heat exchanger 20 (20A) is arranged in the flow path of the air flowing in from the air inlet 108 and discharged from the air outlet 109, and upstream of the heat exchanger 20 (20A). Air samplers 101 and 102 are arranged on the side and downstream, respectively. The air samplers 101 and 102 are connected to temperature and humidity measuring boxes 103 and 104, respectively. The temperature and humidity measuring boxes 103 and 104 measure the temperature and humidity of the air by measuring the dry bulb temperature and wet bulb temperature of the air sampled by the air samplers 101 and 102, respectively. An induction fan 105 is provided downstream of the air sampler 102 and discharges air to the air discharge port 109. Also, between the heat exchanger 20 (20A) and the air sampler 102, and the air Rectifiers 106 and 106 for rectifying the air that has passed through the heat exchanger 20 (20A) are provided between the sambra 102 and the induction fan 105.

FIG. 8 (b) shows a schematic diagram of the refrigerant supply device 110. In Fig. 8 (b), 107 is a refrigerant pipe, 111 is a sight glass, 112 is a liquid (refrigerant) heating and cooling heat exchanger, 113 is a dryer, 114 is a liquid receiver (refrigerant), and 115 is a solution. Plug, 116 is a condenser, 117 is an oil separator, 118 is a compressor, 119 is an accumulator, 120 is an evaporator, 121 is an expansion valve, and 122 is a flow meter. Then, the refrigerant whose pressure and temperature are adjusted is supplied through the refrigerant pipe 107 into the hairpin pipe 11 (see FIG. 2) of the heat exchanger 20 (20A) provided in the suction type wind tunnel 100. In addition, pressure gauges 123 (the temperature is a saturation temperature corresponding to the measurement pressure) for measuring the temperature and pressure of the refrigerant are provided at the inlet and outlet of the heat exchanger 20 (20A). Further, the air conditioner (not shown) supplies air having a controlled temperature and humidity to the air inlet 108 of the suction type wind tunnel 100.

[0081] The measurement conditions were as follows.

<Refrigerant> R22, R410A

<Air side> Dry bulb temperature 27.0 ° C, wet bulb temperature 19.0 ° C

Front wind speed of heat exchanger 0.8m / s

<Refrigerant side> Evaporation temperature (outlet reference) 7.5 ° C, inlet dryness 0.2 ° C, outlet superheat 5.0 ° C [0082] [Table 1]

^ 00832

[0085] From the results of Table 1, Table 2, and Table 3, the heat exchangers of Examples;! -20 were compared to the heat exchanger of Comparative Example 1 using a smooth tube as the return bend tube, and the evaporation performance. Was confirmed to be excellent.

The heat exchanger of Comparative Example 2 has a groove cross-sectional area ratio (S 1 / S2) that is less than the lower limit, and the heat exchanger of Comparative Example 3 has a groove pitch ratio (P1 / P2) and a groove cross-sectional area ratio (S1 / S2). ) Exceeds the upper limit, the groove pitch ratio (P1 / P2) of the heat exchanger of Comparative Example 4 exceeds the upper limit, and the groove pitch ratio (P1 / P2) of the heat exchanger of Comparative Example 5 is less than the lower limit. Therefore, it was confirmed that the evaporation performance was inferior to that of the heat exchanger of Example 120.

As shown in Table 4, Example 21 uses the material Cu-S as the test tube (return bend tube). Example 1 except that a pipe with a first tube thickness (T1) 0.20mm made of nP (0.65% by mass, 0.03% by mass ?, the balance being Cu heat-resistant copper alloy) is used. And the same.

Example 22 was the same as Example 1 except that an inner grooved tube having a first tube thickness (T1) of 0.34 mm was used as the test tube (return bend tube). Then, a heat exchanger (1-pass heat exchanger) was produced in the same manner as in Example 1. Next, using the heat exchangers of Example 1, Example 21, and Example 22, a pressure resistance test by water pressure was performed. The pressure when breakage occurred in the return bend section (return bend pipe) of the heat exchanger was measured with a Bourdon tube pressure gauge to determine the pressure resistance. The results are shown in Table 4.

[Table 4]

From the results in Table 4, the heat exchanger of Example 21 has a small decrease in strength due to brazing even if the first pipe wall thickness (T1) of the return bend pipe is thinner than Example 1. It was confirmed that the pressure strength was higher than Further, in the heat exchanger of Example 22 in which the material of the return bend pipe is the same as that of Example 1, the pressure strength is the same as that of Example 21. The first pipe thickness (T1) of the return bend pipe is It was 1.7 times that of Example 1 and it was confirmed that the amount of material used increased.

Claims

The scope of the claims

[1] A hairpin portion in which a large number of hairpin tubes are arranged in parallel, a return bend portion in which a large number of return bend tubes joined to the hairpin tube ends of the hairpin portions are arranged in parallel, and an outer surface of the hairpin tube And a fin-and-tube heat exchanger in which a refrigerant is supplied to the inside of the pipe.

A first groove formed on the inner surface of the return bend pipe;

/ S2) satisfies 0.3 to 3.6, and is a fin-and-tube heat exchanger.

[2] The fin-and-tube heat exchanger according to claim 1, wherein the second groove lead angle (Θ2) formed by the second groove of the hairpin tube and the tube axis is 15 ° or more.

[3] The fin according to claim 1, wherein at least a part of the refrigerant flow path constituted by the hairpin tube and the return bend pipe is branched to form a plurality of refrigerant flow paths. And tube type heat exchanger.

4. The fin-and-tube heat exchanger according to claim 1, wherein the refrigerant is a hydrated fluorocarbon non-azeotropic refrigerant mixture.

[5] Return bend pipes used in fin-and-tube heat exchangers that are joined to the ends of hairpin pipes with a large number of fins arranged in parallel at regular intervals on the outer surface, and in which refrigerant is supplied into the pipes In

A first groove formed on the inner surface of the return bend pipe;

The first groove cross-sectional area (S1) per groove in the cross section perpendicular to the tube axis of the first groove and the second cross-sectional area (S2) per groove in the cross section perpendicular to the tube axis of the second groove Groove cross-sectional area ratio (S1 A return bend pipe characterized by / S2) satisfying 0 · 3 to 3 · 6.

[6] The angle difference (θ 1) between the first groove lead angle (θ 1) formed by the first groove and the tube axis and the second groove lead angle (Θ 2) formed by the second groove and the tube axis. -Θ 2) satisfies -15 to + 15 °, and

Groove depth ratio (hl / h2) between the first groove depth (hi) in the cross section perpendicular to the tube axis of the first groove and the second groove depth (h2) in the cross section perpendicular to the tube axis of the second groove The return bend pipe according to claim 5, characterized in that: 0.47 to 1.5 is satisfied.

7. The return bend pipe according to claim 5, wherein a foot length of the return bend pipe (U is 1.0 to 1.5 times a pitch (P); 1.5 times).

8. The return bend pipe according to claim 5, wherein the return bend pipe is made of a material having a lower thermal conductivity than the hairpin pipe.

9. The return bend pipe according to claim 5, wherein the material of the return bend pipe is made of a copper alloy that is more heat resistant than the material of the hairpin pipe.

[10] The first maximum inner diameter (ID1) of the return bend tube is the second maximum inner diameter (I

The return bend pipe according to claim 5, wherein (IDl) ≥ (ID2) in relation to D2).