MESH-FIN HEAT EXCHANGER AND METHOD FOR MANUFACTURING THE SAME

Abstract: A heat exchanger having a plurality of heat transfer tubes (1, 1 ...) that are disposed in parallel to each other and a number of net-like fins (2, 2 ...) disposed in parallel to the tube axes and joined to said tubes. The heat transfer tubes (1) are each constituted by a pair of tube constituent members (4, 4) each of which is semi-cylindrical and has joining flanges (4a, 4b) extending along the center of the axis at the open ends thereof. The confronting joining flanges (4a, 4b) of these tube constituent members (4, 4) are pressure welded from the outside of the fins (2, 2) so as to be joined to each other. This improves efficiency in fabricating the heat transfer tubes and net-like fins together.

Description: FIELD OF THE INVENTION The present invention relates to a mesh fin type heat exchanger including a multiplicity of heat transfer tubes arranged in parallel and a multiplicity of mesh-form fins arranged parallel to the axes of the heat transfer tubes and joined to the heat transfer tubes, and to a method of making the same. BACKGROUND ART Heat exchangers of a cross fin coil type have hitherto been widely used which has a multiplicity of heat transfer tubes arranged in parallel and a multiplicity of lamellar fins arranged orthogonally to the heat transfer tubes. In order to improve the heat transfer performance of heat exchangers of this type, it has been conventional to work the fins in various ways (as, for example, by providing notched and bent pieces of various configurations on the surfaces of the fins). However, such fin working have a limitation on the effectiveness for the improvement of the heat transfer performance. Therefore, attempts have recently been made to develop heat exchangers having a new constructional arrangement which are known as mesh fin type heat exchangers (see, for example, Japanese Utility Model Application Laid-Open No. 61-192185 in which mesh-form fins are held against heat transfer tubes by shaping the mesh at predetermined locations to conform to the outer surfaces of said tubes and then joining the tubes and mesh together by soldering or brazing). A heat exchanger of the mesh fin type, as illustrated in Figs. 10 and 11, comprises a multiplicity of heat transfer tubes 1, 1 ... arranged in parallel, a multiplicity of mesh-form fins 2, 2 ... arranged parallel to the axes of the heat transfer tubes 1, 1 ... and joined to the outer peripheries of the heat transfer tubes 1, and tube plates 3 supporting the heat transfer tubes 1, 1 ... at the ends thereof. The heat transfer tubes 1 and the mesh-form fins 2 are joined together usually by soldering or brazing after the mesh-form fins 2, 2 ... are tightly held against the heat transfer tubes 1 from opposite sides thereof. For the purpose of holding the mesh-form fins 2, 2 ... against the heat transfer tubes 1, 1 ... from opposite sides thereof as aforesaid, however, one problem is that the mesh-form fins 2, 2 be preformed at predetermined locations with grooves conforming to the outer peripheral surface of the heat transfer tubes 1. Another problem is that the process of placing mesh-form fins 2, 2 in superposed relation and fixing them together requires a high level of technical skill. A prior art heat exchanger that is of interest is CH-A-398 657, one embodiment of which is a flat plate having tube halves welded to its opposite surfaces, thus giving the impression that the plate is passing diametrically through a number of parallel tubes. DISCLOSURE OF THE INVENTION The present invention has been made in view of the above noted problems and it is an object of the invention to provide for improvement in the process of assembling heat transfer tubes and mesh-form fins together. The invention is as defined in the accompanying claims, Claim 1 of which has been divided into a two part form based on the assumption that the aforesaid Japanese document 61 19 218 is the nearest state of the art. The mesh fin type heat exchanger according to the present invention comprises a plurality of heat transfer tubes arranged in parallel and a plurality of mesh-form fins arranged parallel to axes of the heat transfer tubes and joined to the heat transfer tubes, and wherein each of the heat transfer tubes consists of a pair of tube component members having a half cylindrical configuration, the tube component members having, at their respective circumferential ends, joint portions extending along the axis of the heat transfer tube, the opposed joint portions of the tube component members being joined together externally of the fins in such a way as to sandwich the fins between them, there being inner fins formed by parts of said plurality of mesh-form fins being within each transfer tube, said inner fins serving to improve the heat transfer performance. The mesh fin type heater may be such that said inner fins extend through a said heat transfer tube. The mesh fin type heater may be such that said inner fins project a predetermined length into a said heat transfer tube in a flared fashion, there being no fin present in the middle of the heat transfer tube. The mesh fin type heat exchanger may be such that two outermost ones of the fins sandwiched between the joint portions extend through the heat transfer tube, and in that fin portions present within the heat transfer tube of fins other than the two outermost fins comprise portions joined to the joint portion by being sandwiched between the joint portions, and portions projecting a predetermined length from the joined portions into the heat transfer tube in a flared fashion, there being no fin present between the outermost fins in the middle of the heat transfer tube. The mesh fin type heat exchanger may be such that a fin located central of the fins sandwiched between the joint portions extends through the heat transfer tube, and in that portions present within the heat transfer tube of fins located at both sides of the central fin comprise portions joined to the joint portion by being sandwiched between the joint portions, and portions projecting a predetermined length from the joined portions into the heat transfer tube in a flared fashion, there being no fin present at both sides of the central fin in the middle of the heat transfer tube. A method of making a mesh-fin type heat exchanger comprises the steps of stacking a plurality of mesh-form fins and pressing against the fins, at a predetermined location, a pair of tube component members of a half cylindrical configuration having axially extending joint portions at their prespective circumferential ends, against the outer side of said stacked fins in such a way that the joint portions are opposed to each other; and joining the opposed joint portions together to form a heat transfer tube having inner fins formed by parts of said mesh-form fins being within the heat transfer tube, said inner fins serving to improve the heat transfer performance. The aforesaid joint portions may be joining flanges. The heat exchangers of the present invention and the method of making such heat exchangers have the following functions. Since according to the present invention the heat exchanger includes a plurality of heat transfer tubes arranged in parallel, and a plurality of mesh-form fins arranged parallel to the axes of the tubes and joined to the tubes, each of the heat transfer tubes consisting of a pair of tube component members having a half cylindrical configuration, the component members having, at their respective circumferential ends, joint portions extending along an axis of the tube, and the opposed joint portions of the tube component members are joined together externally of the fins in such a manner as to sandwich them between the joint portions, this permits the heat transfer tubes and the mesh-form fins to be assembled in a combination that results in remarkable improvement in working efficiency during the process of heat exchanger making; and in improving the heat transfer performance. Parts of the mesh-form fins, namely the aforesaid inner fins, remain present within each heat transfer tube, and this allows direct contact between a fluid (e. g., refrigerant) flowing in the heat transfer tube and a part of the fins, resulting in improved heat transfer performance. According to the heat exchanger of Claim 2, said mesh-form fins extend through a heat transfer tube, and this permits direct contact between the fins and the fluid flowing in the heat transfer tube, resulting in an improvement in heat exchange performance. According to the heat exchanger of Claim 4, direct heat exchange is effected between the fluid in each heat transfer tube and the fins by virtue of the flaredly projecting fin portions in the heat transfer tube. The flaredly projecting fin portions serve to prevent the mesh-form fin from slipping out of the joint portions. Further, in the heat exchanger of Claim 5, since no fin is present in the middle of the heat transfer tube, the resistance to fluid flow in the heat transfer tube is reduced. According to the heat exchanger of claim 6, only two outermost fins in each heat transfer tube extend through the heat transfer tube. This realizes smaller flow resistance than that in a heat exchanger in which all the fins extend through each heat transfer tube. The flaredly projecting fin portion within the heat transfer tube goes into direct contact with the fluid in the heat transfer tube for heat exchange, which results in increased heat exchange efficiency. Also, it prevents fins from slipping out of the joint portions. According to the heat exchanger of claim 7, only the centrally located fin in each heat transfer tube extends through the tube. This realizes smaller flow resistance than that in a heat exchanger in which all the fins extend through each heat transfer tube. The flaredly projecting fin portion within the heat transfer tube goes into direct contact with the fluid in the heat transfer tube for heat exchange, which results in increased heat exchange efficiency. Also, it prevents fins from slipping out of the joint portions. According to the method of making a heat exchanger of claim 8, after stacking a plurality of mesh-form fins, a pair of tube component members of a half cylindrical configuration having axially extending joint portions at their respective circumferential ends is pressed against the fins at a predetermined location, from outer side of the fins in such a way that the joint portions are opposed to each other, and then the opposed joint portions are joined together to form a heat transfer tube having inner fins formed by parts of said plurality of mesh-form fins being within the heat transfer tube, said inner fins serving to improve the heat transfer performance. Thus, heat transfer tubes and mesh-form fins can be assembled together by such a very simple process, which results in remarkable improvement in the working efficiency during the process of heat exchanger making. Further, according to this method, mesh-form fins remain present within the heat transfer tube, and this allows direct contact between a fluid (e. g., refrigerant) flowing in the heat transfer tube and a part of the fins, resulting in improved heat transfer performance. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing principal portions of a heat exchanger representing Embodiment 1 of the present invention; Fig. 2 is a sectional view showing principal portions of the heat exchanger of Embodiment 1 of the invention; Fig. 3 is a sectional view showing the procedure of making the heat exchanger of Embodiment 1 of the invention; Fig. 4 is a sectional view showing principal portions of a heat exchanger of Embodiment 2 of the invention; Fig. 5 is a sectional view showing the procedure of making the heat exchanger of Embodiment 2 of the invention; Fig. 6 is a sectional view showing principal portions of a heat exchanger of Embodiment 3 of the invention; Fig. 7 is a sectional view showing the procedure of making the heat exchanger of Embodiment 3 of the invention; Fig. 8 is a sectional view showing principal portions of a heat exchanger of Embodiment 4 of the invention; Fig. 9 is a sectional view showing the procedure of making the heat exchanger of Embodiment 4 of the invention; Fig. 10 is a front view showing a mesh-fin type heat exchanger known in the art; and Fig. 11 is a sectional view of principal portions of the known mesh-fin type heat exchanger. BEST MODE FOR CARRYING OUT THE INVENTION Some preferred embodiments of the present invention will now be described with reference of Figs. 1 through 9 of the accompanying drawings. Each of the heat exchangers of the following embodiments includes a multiplicity of heat transfer tubes 1, 1 ... arranged in parallel, and a multiplicity of mesh-form fins 2, 2 ... arranged parallel to the axes of the heat transfer tubes 1, 1 ... and joined to the heat transfer tubes, as does the mesh-fin type heat exchanger noted in the description of the prior art (see Figs. 10 and 11). It is noted in this connection that in the present invention, heat transfer tubes 1, 1 may be parallel to each other in any way; for example, they may be arranged in a staggered fashion and parallel to each other on both sides of one plane. In that case, mesh-form fins will be curved in a wave-like pattern. (Embodiment 1) In Figs. 1 to 3, there are illustrated principal portions of a heat exchanger of Embodiment 1 of the present invention. This embodiment corresponds to the aspects of the invention according to claims 1, 2, 3 and 8. In the heat exchanger of the present embodiment, as Figs. 1 and 2 illustrate, each heat transfer tube 1 consists of a pair of tube component members 4, 4 having a half cylindrical configuration, and having at their respective circumferential ends, joining flanges 4a, 4b extending along the axis of the heat transfer tube which act as joint portions. The opposed joining flanges 4a, 4a and 4b, 4b of the tube component members 4, 4 are joined together to sandwich the mesh-form fins 2, 2 ... by being pressed against the fins externally thereof. Reference numeral 5 designates inner fins formed by parts of the mesh-form fins 2, 2 ... being within the heat transfer tube 1. A heat exchanger of such construction is manufactured in the following manner. As Fig. 3 illustrates, a multiplicity of mesh-form fins 2, 2 ... are stacked together, and a pair of tube component members 4, 4 are pressed against the mesh-form fins 2, 2 ... at a predetermined location externally of the fins as arrows P indicate. Thereafter, the opposed joining flanges 4a, 4a, and 4b, 4b are joined together to form a heat transfer tube 1. For the purpose of such joining operation, for example, laser welding or ultrasonic welding is advantageously employed. In the case of pressing the tube component members 4, 4 against the mesh-form fins 2, 2 ..., where it is required that the mesh-form fins 2, 2 ... be spaced apart from one another, spacing means (e. g., spacer) for keeping the mesh-form fins 2, 2 ... spaced apart may be used. The spacing means is removed after the heat exchanger has been manufactured. Reference numeral 6 in Fig. 1 designates laser weld or ultrasonic weld spots. In the present embodiment, as above described, assembling together of heat transfer tubes 1, 1 ... and mesh-form fins 2, 2 ... can be accomplished by a very simple process such that the opposed joining flanges 4a, 4a and 4b, 4b of a pair of tube component members 4, 4 are pressed against a multiplicity of mesh-form fins stacked together externally thereof, being thereby joined together. This provides for remarkable improvement in working efficiency during the process of making a heat exchanger. Further, the fact that parts of the mesh-form fins 2, 2 ... are retained within the heat transfer tubes 1, 1 ... to form inner fins 5, 5 ... permits direct contact between the fluid (e. g., refrigerant) flowing in the heat transfer tubes 1, 1 ... and parts of the mesh-form fins 2, 2 ... (i. e., inner fins 5, 5 ...), resulting in improvement in the heat transfer performance. (Embodiment 2) In Figs. 4 and 5, there are illustrated principal portions of a heat exchanger of Embodiment 2 of the present invention. This embodiment corresponds to the aspects of the invention as defined in claims 1, 4, 5 and 8. In the present embodiment, portions of the mesh-form fins 2, 2 ... to be located within each heat transfer tube 1 are cut off except portions against which opposed joining flanges 4a, 4a and 4b, 4b of tube component members 4, 4 are pressed, and portions 5 projecting therefrom slightly into the heat transfer tube 1 in a flared fashion. In this case, inner fins consist of short portions 5 projecting flaredly from the joint portions into the heat transfer tube 1. Therefore, the flow resistance of the fluid (e. g., refrigerant) flowing in the heat transfer tube 1 can be greatly reduced, and mesh-form fins 2, 2 can be prevented from slipping out of the joint portions. Other structural and functional features and effects of the embodiment are same as those of Embodiment 1. (Embodiment 3) In Figs. 6 and 7, there are illustrated principal portions of a heat exchanger of Embodiment 3 of the present invention. This embodiment corresponds to the aspects of the invention as defined in claims 1, 6 and 8. In the present embodiment, portions of mesh-form fins 2, 2 ... to be located within the heat transfer tube 1 are cut off except outermost mesh-form fins 2, 2. That is, the outermost mesh-form fins 2, 2 remain as they are, and the other mesh-form fins 2, 2 ... within the heat transfer tube 1 are cut off except portions against which opposed joining flanges 4a, 4a and 4b, 4b of tube component members 4, 4 are pressed, and portions 5 projecting flaredly therefrom. In the case of this embodiment as well, the flow resistance of the fluid (e. g., refrigerant) flowing in the heat transfer tube 1 can be greatly reduced. Other structural and functional features and effects of the embodiment are same as those of Embodiments 1 and 2. (Embodiment 4) In Figs. 8 and 9, there are illustrated principal portions of a heat exchanger of Embodiment 4 of the present invention. This embodiment corresponds to the aspects of the invention as defined in claims 1, 7 and 8. In the present embodiment, portions of mesh-form fins 2, 2 ... to be located within the heat transfer tube 1 are cut off except portions against which opposed joining flanges 4a, 4a and 4b, 4b of tube component members 4, 4 are pressed, portions 5 projecting a short distance therefrom in a flared fashion and a mesh-form fin 5 positioned in the middle of the heat transfer tube 1. In the case of this embodiment as well, the flow resistance of the fluid (e. g., refrigerant) flowing in the heat transfer tube 1 can be greatly reduced. Other structural and functional features and effects of the embodiment are same as those of Embodiments 1 and 2. In the foregoing embodiments, joining flanges are used as joint portions; alternatively, faucet joints or the like may be used. INDUSTRIAL APPLICABILITY The mesh-fin type heat exchangers of the present invention are applicable for use in air conditioners, refrigerators, and the like.

Claims: A mesh fin type heat exchanger comprising a plurality of heat transfer tubes (1,1) arranged in parallel and a plurality of mesh-form fins (2,2) arranged parallel to axes of the heat transfer tubes and joined to the heat transfer tubes (1,1) characterized in that each of the heat transfer tubes (1) consists of a pair of tube component members (4,4) having a half cylindrical configuration, the tube component members having, at their respective circumferential ends, joint portions (4a, 4b) extending along the axis of the heat transfer tube, the opposed joint portions (4a, 4b) of the tube component members (4, 4) being joined together externally of the fins (2, 2) in such a way as to sandwich the fins (2, 2) between them, there being inner fins (5) formed by parts of said plurality of mesh-form fins (2,2) being within each heat transfer tube (1), said inner fins (5) serving to improve the heat transfer performance. The mesh fin type heat exchanger of Claim 1 wherein said plurality of inner fins (5) extend through a said heat transfer tube (1). The mesh fin type heat exchanger of Claim 2 wherein said inner fins (5) are in a spaced apart array. The mesh fin type heat exchanger of Claim 1 wherein said inner fins (5) comprise short portions projecting in a flared apart manner within a said heat transfer tube (1). The mesh fin type heat exchanger of Claim 4 in which there is no fin present in the middle of said heat transfer tube (1). The mesh fin type heat exchanger of Claim 4 wherein said short inner fin portions are between two spaced apart inner fins (5) that extend through a said heat transfer tube. The mesh fin type heat exchanger of Claim 4 wherein said short inner fin portions (5) project in a flared apart manner relative to a central inner fin (5) that extends through said heat transfer tube (1). A method of making a mesh-fin type heat exchanger which comprises the steps of: stacking a plurality of mesh-form fins (2,2) and pressing against the fins (2,2), at a predetermined location, a pair of tube component members (4,4) of a half cylindrical configuration having axially extending joint portions (4a, 4b) at their respective circumferential ends, against the outer sides of said stacked fins in such a way that the joint portions (4a, 4b) are opposed to each other; and joining the opposed joint portions (4a, 4b) together to form a heat transfer tube (1) having inner fins (5) formed by parts of said plurality of mesh-form fins (2) being within the heat transfer tube (1), said inner fins (5) serving to improve the heat transfer performance. The heat exchanger according to any one of Claims 1 to 7, wherein the joint portions (4a, 4b) are joining flanges.

Inventors: KAWABATA KATSUHIRO, SUEHIRO KENICHI, YAMASHITA HIROYUKI, YASUO KOUICHI, KAWABATA, KATSUHIRO, SUEHIRO, KENICHI, YAMASHITA, HIROYUKI, YASUO, KOUICHI, KANAOKA-KOJO, KAWABATA, KATSUHIRO, KANAOKA-KOJO, SUEHIRO, KENICHI, KANAOKA-KOJO, YAMASHITA, HIROYUKI, KANAOKA-KOJO
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1993
Main classification: F28F1
IPC codes: F28F3, F28F1