HEAT EXCHANGER, HEAT EXCHANGER MANUFACTURING METHOD, AND AIR-CONDITIONER INCLUDING HEAT EXCHANGER

Abstract

Provided is a heat exchanger comprising a flat perforated heat transfer pipe having multiple refrigerant flow paths substantially parallel to each other, a fin provided with an insertion hole into which the flat perforated heat transfer pipe is to be inserted, and headers connected to ones of the refrigerant flow paths at both end portions in a width direction of the flat perforated heat transfer pipe, wherein the refrigerant flow paths are separated by at least four partition walls in the flat perforated heat transfer pipe, and are arranged in the width direction, the flat perforated heat transfer pipe is expanded and joined to the insertion hole, and ones of the refrigerant flow paths arranged at both end portions in the width direction have a greater width than those of other refrigerant flow paths.

Claims

1. A heat exchanger comprising: a flat perforated heat transfer pipe having multiple refrigerant flow paths substantially parallel to each other; a fin provided with an insertion hole into which the flat perforated heat transfer pipe is to be inserted; and headers connected to ones of the refrigerant flow paths at both end portions in a width direction of the flat perforated heat transfer pipe, wherein the refrigerant flow paths are separated by at least four partition walls in the flat perforated heat transfer pipe, and are arranged in the width direction, the flat perforated heat transfer pipe is expanded and joined to the insertion hole, and ones of the refrigerant flow paths arranged at both end portions in the width direction have a greater width than those of other refrigerant flow paths.

2. The heat exchanger according to claim 1, wherein a width L.sub.T of each of the refrigerant flow paths arranged at both end portions in the width direction and a width L.sub.C of one of the refrigerant flow paths arranged at a center portion in the width direction satisfies a relationship of 1.0<(L.sub.T/L.sub.C)<3.5.

3. A heat exchanger comprising: a flat perforated heat transfer pipe having multiple refrigerant flow paths substantially parallel to each other; a fin provided with an insertion hole into which the flat perforated heat transfer pipe is to be inserted; and headers connected to ones of the refrigerant flow paths at both end portions in a width direction of the flat perforated heat transfer pipe, wherein the refrigerant flow paths are separated by at least four partition walls in the flat perforated heat transfer pipe, and are arranged in the width direction, the flat perforated heat transfer pipe is expanded and joined to the insertion hole, and the refrigerant flow paths arranged at both end portions in the width direction have a greater width than an average of widths of other refrigerant flow paths.

4. The heat exchanger according to claim 3, wherein a width L.sub.T of each of the refrigerant flow paths arranged at both end portions in the width direction and a width L.sub.C of one of the refrigerant flow paths arranged at a center portion in the width direction satisfies a relationship of 1.0<(L.sub.T/L.sub.C)<3.5.

5. A heat exchanger comprising: a flat perforated heat transfer pipe having multiple refrigerant flow paths substantially parallel to each other; a fin provided with an insertion hole into which the flat perforated heat transfer pipe is to be inserted; and headers connected to ones of the refrigerant flow paths at both end portions in a width direction of the flat perforated heat transfer pipe, wherein the refrigerant flow paths are separated by at least four partition walls in the flat perforated heat transfer pipe, and are arranged in the width direction, the flat perforated heat transfer pipe is expanded and joined to the insertion hole, and one of the refrigerant flow paths arranged at a center portion in the width direction has a smaller width than an average of widths of other refrigerant flow paths.

6. The heat exchanger according to claim 5, wherein a width L.sub.T of each of the refrigerant flow paths arranged at both end portions in the width direction and a width L.sub.C of the refrigerant flow path arranged at the center portion in the width direction satisfies a relationship of 1.0<(L.sub.T/L.sub.C)<3.5.

7. The heat exchanger according to claim 1, wherein each partition wall has a bent or curved sectional shape, and is arranged symmetrically with respect to a line of an axis perpendicular to the width direction.

8. The heat exchanger according to claim 1, further comprising: a protruding portion extending in a longitudinal direction of the flat perforated heat transfer pipe at an inner surface of each refrigerant flow path.

9. The heat exchanger according to claim 8, wherein the protruding portion is provided at each of other refrigerant flow paths than one of the refrigerant flow paths arranged at a center portion of the flat perforated heat transfer pipe.

10. A heat exchanger comprising: a flat perforated heat transfer pipe having multiple refrigerant flow paths substantially parallel to each other; a fin provided with an insertion hole into which the flat perforated heat transfer pipe is to be inserted; and headers connected to ones of the refrigerant flow paths at both end portions in a width direction of the flat perforated heat transfer pipe, wherein the refrigerant flow paths are separated by six partition walls in the flat perforated heat transfer pipe, and are arranged in the width direction, the flat perforated heat transfer pipe is expanded and joined to the insertion hole, and a width L.sub.T of each of the refrigerant flow paths arranged at both end portions in the width direction and a width L.sub.C of one of the refrigerant flow paths arranged at a center portion in the width direction satisfies a relationship of 1.0<(L.sub.T/L.sub.C)<3.5.

11. The heat exchanger according to claim 1, wherein the insertion hole has a constant hole width.

12. The heat exchanger according to claim 1, wherein the fin made of aluminum or aluminum alloy has a surface subjected to hydrophilic coating treatment, and the flat perforated heat transfer pipe is made of aluminum or aluminum alloy.

13. An air-conditioner comprising: the heat exchanger according to claim 1.

14. A method for manufacturing the heat exchanger according to claim 1, comprising: molding a plate-shaped fin from an aluminum plate member having a surface subjected to hydrophilic coating treatment; inserting multiple flat perforated heat transfer pipes into insertion holes of the plate-shaped fin; joining headers to both ends of each flat perforated heat transfer pipe to connect the flow paths of each flat perforated heat transfer pipe and the headers to each other; and expanding the flat perforated heat transfer pipes by compressed fluid supplied to the headers to join the plate-shaped fin and the flat perforated heat transfer pipes to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 illustrates a main portion of a heat exchanger of the present embodiment;

[0013] FIG. 2 illustrates a section of a flat perforated heat transfer pipe in a longitudinal direction;

[0014] FIG. 3 illustrates an outer appearance of a plate-shaped fin;

[0015] FIG. 4 illustrates the flow of manufacturing the heat exchanger of the present embodiment;

[0016] FIG. 5 illustrates the section of the flat perforated heat transfer pipe;

[0017] FIG. 6 illustrates flatness and joining properties of flat perforated heat transfer pipes having different distances between partition walls;

[0018] FIG. 7 is a sectional view of a flat perforated heat transfer pipe of a first comparative example;

[0019] FIG. 8 is a sectional view of a flat perforated heat transfer pipe of a second comparative example;

[0020] FIG. 9 is a sectional view of a flat perforated heat transfer pipe of a fourth embodiment;

[0021] FIG. 10 is a sectional view of a flat perforated heat transfer pipe having radiation fins formed at refrigerant flow paths; and

[0022] FIG. 11 is a sectional view of a flat perforated heat transfer pipe having radiation fins formed at other refrigerant flow paths than a refrigerant flow path at a center portion.

DETAILED DESCRIPTION

[0023] Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a view of a main portion of a heat exchanger of the present embodiment. The heat exchanger of the present embodiment functions as a condenser or an evaporator of an air-conditioner. Moreover, this heat exchanger is used as any of an indoor heat exchanger or an outdoor heat exchanger.

[0024] The heat exchanger includes flat perforated heat transfer pipes 1 in which refrigerant flows, plate-shaped fins 10 having multiple insertion holes 11 to which the flat perforated heat transfer pipes 1 are expanded and joined, and headers (not shown) connected to the flat perforated heat transfer pipes 1 at both end portions of each flat perforated heat transfer pipe 1.

[0025] Refrigerant having flowed into one header is distributed to the multiple flat perforated heat transfer pipes 1. Then, the refrigerant flows in the flat perforated heat transfer pipes 1. At this point, latent heat and sensible heat are transferred to the plate-shaped fins 10 joined to the flat perforated heat transfer pipes 1. As will be described in detail later, contact thermal resistance between the flat perforated heat transfer pipe 1 and the plate-shaped fin 10 influences heat exchange performance of the heat exchanger. Thus, in the heat exchanger of the embodiment, contact surface pressure of a joint portion between the flat perforated heat transfer pipe 1 and the plate-shaped fin 10 is optimized. The contact thermal resistance is reduced as described above, and therefore, the heat exchange performance of the heat exchanger is improved.

[0026] The flat perforated heat transfer pipe 1 will be described in detail with reference to FIG. 2. FIG. 2 illustrates a section of the flat perforated heat transfer pipe 1 in a longitudinal direction. The flat perforated heat transfer pipe 1 is made of aluminum or aluminum alloy. In the flat perforated heat transfer pipe 1, multiple refrigerant flow paths 2 separated by multiple partition walls 3 and arranged in a long-axis direction of the pipe section (a width direction of the pipe) are provided. As will be described later, upon manufacturing, high-pressure compressed fluid is supplied to each refrigerant flow path 2 surrounded by the partition walls 3 in a bent or curved shape and pipe walls 4 in the flat perforated heat transfer pipe 1. Then, the partition walls 3 are deformed to stretch. Accordingly, the flat perforated heat transfer pipe 1 is expanded in a short-axis direction of the pipe section (a thickness direction of the pipe).

[0027] Next, the plate-shaped fin 10 will be described in detail with reference to FIG. 3. FIG. 3 is a view of an outer appearance of the plate-shaped fin 10. The plate-shaped fin 10 is made of aluminum or aluminum alloy. Hydrophilic coating treatment is performed for an outer surface of the plate-shaped fin 10.

[0028] At the plate-shaped fin 10, the multiple insertion holes 11 into which the flat perforated heat transfer pipes 1 are inserted are provided at predetermined intervals. A fin collar 12 bent to one surface side of the plate-shaped fin 10 is provided at an outer peripheral portion of each insertion hole 11. The fin collar 12 is joined to the flat perforated heat transfer pipe 1 expanded after insertion. With the fin collar 12, the contact thermal resistance at the joint portion between the plate-shaped fin 10 and the flat perforated heat transfer pipe 1 can be decreased. For inserting the pre-expanded flat perforated heat transfer pipe 1, the insertion hole 11 is formed such that a clearance of about 0 to 150 m is formed.

[0029] The contact surface pressure of the joint portion between the plate-shaped fin 10 and the flat perforated heat transfer pipe 1 is influenced by springback accompanied by deformation of the insertion hole 11. Thus, the amount of expansion of the flat perforated heat transfer pipe 1 is set by the sum of the clearance of the insertion hole 11 for insertion of the flat perforated heat transfer pipe 1 and the amount of deformation of the insertion hole 11 for generating the contact surface pressure.

[0030] On this point, for equalizing the contact surface pressure of the joint portion acting in the width direction of the flat perforated heat transfer pipe 1 (the long-axis direction of the section), the amount of expansion of the flat perforated heat transfer pipe 1 in the width direction is preferably constant. However, it is difficult to expand both end portions of the flat perforated heat transfer pipe 1. For this reason, in a case where the flat perforated heat transfer pipe 1 is equally pressurized, the amount of expansion of each end portion of the flat perforated heat transfer pipe 1 is smaller than an expansion amount at a center portion.

[0031] Thus, it is assumed that the hole width of an end portion and the hole width of a center portion in the insertion hole 11 are differentiated such that the amount of deformation of the plate-shaped fin 10 is constant. However, in this case, there is a probability that there is a problem on formation of the fin collar 12. Thus, in the heat exchanger of the embodiment, the hole width of the insertion hole 11 is set constant as will be described later. Moreover, arrangement of the partition walls 3 in the flat perforated heat transfer pipe 1 is changed to optimize the amount of expansion of the flat perforated heat transfer pipe 1.

[0032] The method for manufacturing the heat exchanger of the embodiment will be described herein with reference to FIG. 4. FIG. 4 is a chart of a manufacturing flow of the heat exchanger of the embodiment. At a step S41, the hydrophilic coating treatment is performed for an aluminum plate made of an aluminum or aluminum alloy material. At a step S42, this aluminum plate is pressed into a predetermined shape. In this manner, the plate-shaped fin 10 is manufactured.

[0033] At a step S43, an aluminum or aluminum alloy material is, for example, cut into predetermined dimensions corresponding to the size of the heat exchanger of the present embodiment by extrusion or drawing. In this manner, the flat perforated heat transfer pipe 1 is manufactured. Then, at a step S44, the multiple flat perforated heat transfer pipes 1 are lined up at predetermined intervals.

[0034] At a step S45, the multiple flat perforated heat transfer pipes 1 lined up at the step S44 are each inserted into the insertion holes 11 of the plate-shaped fins 10. At this point, no clearance or a slight clearance (0 to 150 m) is formed between the outer periphery of the flat perforated heat transfer pipe 1 and the fin collar 12.

[0035] Next, at a step S46, both end portions of each flat perforated heat transfer pipe 1 inserted into the insertion hole 11 of the plate-shaped fin 10 are each inserted into joint holes provided at the headers. Then, both end portions of each flat perforated heat transfer pipe 1 and the headers are joined to each other by brazing or other proper methods. At a step S47, compressed fluid is supplied to the flat perforated heat transfer pipes 1 through the headers. By the internal pressure of the refrigerant flow paths 2 increased accordingly, the flat perforated heat transfer pipes 1 are pressurized. Then, the flat perforated heat transfer pipes 1 are expanded. In the above-described manner, the plate-shaped fins 10 and the flat perforated heat transfer pipes 1 are joined to each other. By the above-described method for manufacturing the heat exchanger of the present embodiment, the flat perforated heat transfer pipe 1 formed with small contact thermal resistance as will be described later is expanded and mechanically joined to the plate-shaped fins 10. Thus, the hydrophilic coating treatment can be performed for the plate-shaped fins 10 in advance. As a result, manufacturing of the heat exchanger is facilitated.

[0036] Hereinafter, an arrangement state of the partition walls 3 of the flat perforated heat transfer pipes 1 in the heat exchanger of the present embodiment will be described in detail. FIG. 5 is a view of a section of the flat perforated heat transfer pipe 1.

[0037] The flat perforated heat transfer pipe 1 is a flat pipe molded such that the upper and lower pipe walls 4 are substantially parallel to each other. The flat perforated heat transfer pipe 1 includes the multiple partition walls 3. Each partition wall 3 is connected to the upper and lower pipe walls 4. The face shape of the partition wall 3 is bent in a mountain shape (in the shape of ku (doglegged shape) in a Japanese syllabary character or the shape of a mirror character of ku) in the long-axis direction of the section of the flat perforated heat transfer pipe 1. The inside of the flat perforated heat transfer pipe 1 is divided by these partition walls 3. Thus, the multiple refrigerant flow paths 2 are provided in parallel.

[0038] Solid lines of FIG. 5 indicate the section of the flat perforated heat transfer pipe 1 before expansion. Dashed lines indicate the section of the flat perforated heat transfer pipe 1 after expansion. Note that the section (the dashed lines) after expansion in FIG. 5 exaggeratingly shows the degree of expansion. In the flat perforated heat transfer pipe 1 after expansion, the partition walls 3 bent in the mountain shape are stretched in a planar shape. Thus, the dimension of the section in the short-axis direction (the thickness direction of the pipe) is expanded. A dimension increment in the short-axis direction of this section (the thickness direction of the pipe) is the expansion amount.

[0039] The expansion amount is determined by the shape of the partition wall 3, but one of side portions of the refrigerant flow path 2 at each end portion of the flat perforated heat transfer pipe 1 is not the partition wall 3. Thus, the expansion amount in such a refrigerant flow path 2 is different from those in other refrigerant flow paths 2. Moreover, the refrigerant flow path 2 adjacent to the refrigerant flow path 2 at each end portion of the flat perforated heat transfer pipe 1 is influenced by expansion of the end portion. Thus, in a case where the partition walls 3 are arranged at equal intervals, the expansion amount has distribution in the long-axis direction of the section. Specifically, the expansion amount decreases toward the end portion of the flat perforated heat transfer pipe 1.

[0040] Tension applied to the partition wall 3 upon expansion is caused by the pressure of compressed fluid sandwiched by the partition walls 3 on the inside of the pipe walls 4. Thus, the tension applied to the partition wall 3 is proportional to the interval between the partition walls 3. In the flat perforated heat transfer pipe 1 of the embodiment, the interval between the partition walls 3 is changed accordingly, and therefore, the expansion amount is adjusted. As described above, the flat perforated heat transfer pipe 1 is less expandable at the end portion than at the center portion of the flat perforated heat transfer pipe 1. Thus, the interval between the partition walls 3 at the end portion is preferably wider. Note that the end portions in a length direction of the insertion hole 11 have high stiffness. Thus, the expansion amount for obtaining uniform contact surface pressure has an upper limit. That is, the length of the interval between the partition walls 3 at the end portion of the flat perforated heat transfer pipe 1 has an upper limit. Note that the partition wall 3 is deformed such that the shape of ku is stretched. Thus, the interval between the partition walls 3 does not change before and after expansion.

[0041] Next, a relationship between a difference between the interval between the partition walls 3 of the flat perforated heat transfer pipe 1 and the expansion amount in the long-axis direction of the section and joining properties in the insertion hole 11 will be described with reference to FIGS. 5 to 9. In examples of the flat perforated heat transfer pipe 1 illustrated in FIGS. 5 and 6, the interval (L.sub.C, L.sub.1, L.sub.2, L.sub.T) between the partition walls 3 provided in such a pipe varies. These examples show a ratio (L.sub.T/L.sub.C) between the interval (L.sub.T) between the partition walls 3 at the end portion and the interval (L.sub.C) between the partition walls 3 at the center portion, flatness (YmaxYmin), and joining properties of the flat perforated heat transfer pipe 1 in the insertion hole 11.

[0042] The interval (L.sub.C, L.sub.1, L.sub.2, L.sub.T) between the partition walls 3 corresponds to a distance between the partition walls 3 illustrated in FIG. 5. The interval L.sub.C shows a distance (a length in the pipe walls 4) between the partition walls in the flow path closest to the center of the flat perforated heat transfer pipe 1. The interval L.sub.T shows a distance between linear portions between the partition wall and a pipe end portion in the flow path at the end portion of the flat perforated heat transfer pipe 1. The intervals L.sub.1, L.sub.2 show a distance between the partition walls in the flow path adjacent to the flow path at the center of the flat perforated heat transfer pipe 1 and a distance between the partition walls in the flow path adjacent to such a flow path on an end portion side. In the present specification, the interval (L.sub.C, L.sub.1, L.sub.2, L.sub.T) between the partition walls 3 will be referred to as a flow path width, as necessary. Ymax and ymin show maximum and minimum values of an expansion width of the flat perforated heat transfer pipe 1 on one side. A difference between these values is defined as the flatness. As the flatness decrease, the pipe wall 4 is flatter.

[0043] A flat perforated heat transfer pipe 1 of a first comparison example of FIG. 6 is, as illustrated in FIG. 7, a heat transfer pipe having equal L.sub.C, L.sub.1, L.sub.2, L.sub.T and having equal holes. When the flat perforated heat transfer pipe 1 of the first comparison example is expanded, pipe walls 4 in a center flow path are greatly expanded, and therefore, the flatness increases. The flat perforated heat transfer pipe 1 is expanded to cause an outer surface of the pipe wall 4 and a fin collar 12 to closely contact each other. Thus, high heat exchange performance is obtained. Thus, it is not preferred that the outer surface of the pipe wall 4 changes in a corrugated shape or a recessed-raised shape by expansion. As a result of such an unfavorable change, joining properties between the flat perforated heat transfer pipe 1 and the fin collar 12 are insufficient (a cross mark).

[0044] In a flat perforated heat transfer pipe 1 of a second comparison example of FIG. 6, L.sub.T is smaller than L.sub.C, L.sub.1, L.sub.2 as illustrated in FIG. 8. In this case, pipe walls 4 in a center flow path after expansion are greatly expanded, and therefore, the flatness increases. As a result, the joining properties between the flat perforated heat transfer pipe 1 and a fin collar 12 are insufficient (a cross mark).

[0045] In a flat perforated heat transfer pipe 1 of a first embodiment of FIG. 6, L.sub.T is greater than L.sub.C, L.sub.1, L.sub.2. In this case, pipe walls 4 in refrigerant flow paths 2 are substantially equally expanded after expansion. As a result, the flatness is small. Thus, the joining properties between the flat perforated heat transfer pipe 1 and a fin collar 12 are excellent (a double circle mark). Moreover, a heat exchanger having high heat exchange properties is obtained.

[0046] In a flat perforated heat transfer pipe 1 of a second embodiment of FIG. 6, L.sub.T is greater than the average of L.sub.C, L.sub.1, L.sub.2 other than L.sub.T. In this case, pipe walls 4 in refrigerant flow paths 2 are also substantially equally expanded after expansion. As a result, the flatness is small. Thus, the joining properties between the flat perforated heat transfer pipe 1 and a fin collar 12 are excellent (a double circle mark). Moreover, a heat exchanger having high heat exchange properties is obtained.

[0047] In a flat perforated heat transfer pipe 1 of a third embodiment of FIG. 6, L.sub.C is smaller than the average of L.sub.1, L.sub.2, L.sub.T. In this case, pipe walls 4 in refrigerant flow paths 2 are also substantially equally expanded after expansion. As a result, the flatness is small. Thus, the joining properties between the flat perforated heat transfer pipe 1 and a fin collar 12 are excellent (a double circle mark). Moreover, a heat exchanger having high heat exchange properties is obtained.

[0048] In a flat perforated heat transfer pipe 1 of a fourth embodiment of FIG. 6, L.sub.C is smaller than any of L.sub.1, L.sub.2, L.sub.T as illustrated in FIG. 9. In this case, pipe walls 4 in an end flow path after expansion is expanded, and on the other hand, the pipe walls 4 in a center flow path is not expanded. As a result, the flatness is small. Moreover, the joining properties between the flat perforated heat transfer pipe 1 and a fin collar 12 are favorable (a circle mark).

[0049] As illustrated in FIG. 6, the joining properties between the flat perforated heat transfer pipe 1 and the fin collar 12 in each of the flat perforated heat transfer pipes 1 of the first to fourth embodiments are favorable or excellent. As a result, a heat exchanger having high heat exchange performance can be obtained. On the other hand, the joining properties between the flat perforated heat transfer pipe 1 and the fin collar 12 in each of the flat perforated heat transfer pipes 1 of the first to second comparison examples are insufficient. Thus, a preferable condition for excellent joining properties is specifically a condition where the partition walls 3 are arranged such that the flow path width L.sub.T of each end portion and the flow path width L.sub.C of the center portion in the width direction of the flat perforated heat transfer pipe 1 satisfy a relationship of 1.0<(L.sub.T/L.sub.C)<3.5.

[0050] As described above, according to the flat perforated heat transfer pipe 1 of the embodiment, the asperity of the pipe outer surface upon expansion is decreased, and accordingly, the contact thermal resistance is also decreased. As a result, a heat exchanger having high heat exchange performance can be provided.

[0051] FIGS. 10 and 11 are views of a section of a flat perforated heat transfer pipe 1 having higher heat exchange performance than those of the flat perforated heat transfer pipes 1 of the first to fourth embodiments of FIG. 6. Specifically, protruding portions 13 extending in the longitudinal direction of the flat perforated heat transfer pipe 1 and serving as radiation fins are formed at flat portions of a pipe inner surface in each refrigerant flow path 2. With the protruding portions 13, the coefficient of heat transfer to refrigerant is improved. Moreover, the heat exchange performance of the flat perforated heat transfer pipe 1 is enhanced.

[0052] As illustrated in FIG. 11, the protruding portions 13 are not necessarily formed in the center refrigerant flow path. Thus, a decrease in a flow path sectional area is suppressed. Consequently, a decrease in a refrigerant flow rate (an increase in a pressure loss) can be suppressed. Note that the sectional shape of the protruding portion 13 is not limited to a triangular shape. Needless to say, the sectional shape may be an arc shape or a rectangular shape.

[0053] As described above, the thickness of the pipe wall 4 of the flat perforated heat transfer pipe 1 is designed such that the heat transfer pipe withstands the pressure of fluid in the pipe when the heat exchanger is used. Thus, in the section of the flat perforated heat transfer pipe 1 in the longitudinal direction thereof, the thickness of the pipe wall at each end portion in the long-axis direction of the pipe section is greater than the thickness of the pipe wall connected to the bent or curved partition wall arranged in the pipe. Thus, upon expansion of the flat perforated heat transfer pipe 1, each end portion in the long-axis direction of the pipe section is less stretched in the short-axis direction of the pipe section as compared to stretching of the partition wall 3. As a result, the pipe walls 4 of the flat perforated heat transfer pipe 1 are non-uniformly expanded.

[0054] Upon expansion of the flat perforated heat transfer pipe 1 by the fluid pressure, the force of expanding the pipe section of the heat transfer pipe in the short-axis direction is proportional to the length of the flat portion of the perforated pipe inner surface in each flow path corresponding to a portion between the partition walls. In the flat perforated heat transfer pipe 1 of the present embodiment, the length of the flat portion in each end flow path in the long-axis direction of the pipe section is set longer than the length (the distance between the partition walls) of the flat portion in other flow paths. Thus, a load on the flat portion in the flow path at each end portion increases. As a result, the heat transfer pipe is expanded. Thus, the pipe walls of the flat perforated heat transfer pipe 1 are uniformly expanded. Consequently, the joining properties between the fin and the heat transfer pipe are improved.

[0055] In the above-described embodiment, the flat perforated heat transfer pipe 1 having seven refrigerant flow paths 2 separated by six partition walls 3 has been described. Note that the number of partition walls 3 (refrigerant flow paths 2) is not limited to six. The flat perforated heat transfer pipe 1 may have at least five refrigerant flow paths 2.

[0056] According to the heat exchange and the air-conditioner using the flat perforated heat transfer pipes 1 of the present embodiment, the heat exchange performance of the heat exchanger can be improved. Further, a heat exchanger having high hydrophilic properties, corrosion resistance, deodorization properties, antibiotic properties, and mildew proofing properties can be easily realized. The foregoing detailed description has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is not intended to be exhaustive or to limit the subject matter described herein to the precise form disclosed. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims appended hereto.