CA1316907C

CA1316907C - Heat exchanger and method of manufacturing the same

Info

Publication number: CA1316907C
Application number: CA000597600A
Authority: CA
Inventors: Minoru Ishida; Toshio Isobe
Original assignee: Asahi Kasei Kogyo KK
Current assignee: Asahi Kasei Corp
Priority date: 1988-04-25
Filing date: 1989-04-24
Publication date: 1993-04-27
Anticipated expiration: 2010-04-27
Also published as: EP0339552A1; KR900016723A; US5107575A; EP0339552B1; DE68907636T2; DE68907636D1

Abstract

HEAT EXCHANGER AND METHOD OF
MANUFACTURING THE SAME

ABSTRACT OF THE DISCLOSURE

A pin-fin type heat exchanger comprising a plurality of wire-like heat conductive elements arranged in parallel and spaced from each other, and formed into a corrugated shape, and a method of manufacturing the same by making a corrugated sheet including the wire-like heat conductive elements and a temporary fixing material and removing the temporary fixing material after the heat conductive element is joined to a pipe through which fluid passes.

Description

1~16907 HEAT EXCHANGER AND METHOD OF

BACKGROUND t:)F THE INVENTION
1. Field of the Invention The present invention relates to a heat exchanger and a method of manufacturing the heat exchanger. More particularly, the present invention relates to a pin-fin type heat exchanger having an excellent heat transfer efficiency and a method of manufacturing same.

2. Description of the Related Art It is known to provide a fin around a pipe through which a fluid is passed, to improve a heat transfer efficiency between a fluid passing through the ; pipe and a fluid passing over the pipe in a heat exchanger. Usually, a pl~te-like fin is used and is 15~ formed~on the pipe by~winding the~plate in ~ spiral~or a ring around the pipe. When the heat exchanger equipped with the plate-like fin is used, a~boundary layer of air is generated on a~surface of~the plate-like fin and this boundary layer remains on~the surface of the pIate to 2~ form~a heat insulating barrier and thus it is impossible to obtaln a high heat transfer efficiency with this heat exchanger.
To solve this problem, various improvements such~as providing a louver or the like, made by 5 ~ providlng~a~hold(s) in the plate-like fin to increase !~?~ the~heat transfer e~fficiency;have been proposed, as t~ disclosed~in, for~example, Japanese~Unexamined Patent Publication (Kokai) No. 56-155391. ~ ~
A heat~exchanger 101 having a plurality of ; metal pins 104 fixed between two adjac~ent pipes 103, as shown~in~Fig?ur?3 l(A)~and Fi~ure l(B), an~ a~heat exchanger 102 provided wi~th a plurality of metal pins 104a and 104b having one end Eixed on a pipe 103 . .

' ; ' '~ ``: .' ``

and the other end protruded toward ~n adjacent pipe 103, as shown in Fig. (2), is disclosed in Japanese Unexamined Utility Model Publications 55-145284 and 57-172283. With this method, a heat transfer area of the fins per unit volume of the heat exch~nger can be enlarged by increasing the density of the pins on a surface of the pipe through which the fluid passes, and thus the heat exchanging efficiency is increased.
Nevertheless, this heat exchanger has a disadvantage in that a pressure loss of a fluid passing around the pipes is increased when the density of the pins is increased.
Further, the work necessary to fix the pins on the surfaces of the pipes is cumbersome and requires much time.
SUMMARY OF THE INVENTION
A primary ob~ect of the present invention is to provide a novel pin-fin type heat exchanger capable of reducing a pressure loss of a fluid passing around the pipe and increasing a heat transfer efficiency of the ; 20 heat exchanger.
A second object of the present invention is to provide a method by which the above pin-fin type heat exchanger is efficiently manufactured.
- The first object of the present invention is realized by a pin-fin type heat exchanger comprising a pipe through which a fluid flows and a fin arranged on a circumferential surface thereof, wherein the fin is comprised of a plurality of wire~like heat conductive elements arranged in parallel and spaced from each other, the wire-like heat conductive elements have a corrugated;shape formed by bending the heat conductive elements in a lengthwise direction, and curved tops ~arranged at~at least a side of the corrugated heat conductive elements are fixed to the pipe.
A preferable method of manufacturing the pin-fin type heat exchanger having corruga~ed pin fins is a method which includes the following sequential steps:
:

1 3 1 6~ 07 a step of arranging a plurality of wire-like heat conductive elements in parallel and spaced from each other;
a step of temporarily fixing the plurality of wire-like heat conductive elements in the above arranged state to form a sheet constituted by the wire-like heat conductive elements and a temporary fixing material~
a step of treating the sheet in a corrugated state;
a step of ~oining curved tops of the wire-like heat conductive elements applied on at least a side of the corrugated sheet to the pipe; and a step of removing the temporary fixing material.
BRIEF DESCRIPTION OE' THE DRAWINGS
: Figure l(A) is a schematical front view of anexample of a conventional pin-fin type heat exchanger;
: Fig. l(B) is a sectional view of the heat exchanger illustrated in Fig. 1 (A?, taken along the lines lB
: and lB';
: ~; Fig. 2~is a sectional view of another example of : ~: the conventional pin-fin type heat exchanger;
; : ~ Fig. 3 is a perspective view of an embodiment of a pin-fin type heat exchanger in accordance with the present in~ention;
Fig. 4 ~is a perspective view of another embodiment ~; :of the pin-fin type heat exchanger in accordance with the present lnvention;
~ : Fig.: 5 is a perspective;view of a further embodiment of the pin-fin type heat exchanger in :: : accordance with the present~invention;
Fig. 6(A) is a perspective view of another ~; embodiment of:the pin-fin type heat exchanger having a ~:: 35 constitution similar to that of the heat exchanger :~ : : illustrated in Fig. 5, but equipped with a pair of : headers;
:~ :

' , , I ' ' , ' " ' ' ' ' Fig. 6~B) is a front view of the heat exchanger illustrated in Fig. 5(A);
Fig. 7 is a front view still another embodiment of the pin-fin type heat exchanger in accordance with the present invention;
Fig. 8 is a front view of a moclification of the pin-fin type hea-t exchanger illustrated in Fig. ~;
Fig. 9 is a perspective view of another embodiment of the pin-fin type heat exchanger having a constitution similar to that of the heat exchanger illustrated in Fig. 3, but equipped with a pair of headers;
Fig. lO(A) is an enlarged front view illustrating a heat transfer mechanism between a pipe side fluid and-an lS outside fluid in the pin-fin type heat exchanger in accordance with the present invention;
Fig. lO(B) is an enlarged sectional view corre-sponding to Fig. lO(A);
Fig. ll(A) is an enlaryed front view illustrating a heat transfer mechanism between a pipe-side fluid and an outside fluid in a conventional pin-fin type heat exchanger;
Fig. ll(B) is an enlarged sectional view corre-sponding to Fig. ll(A);
Fig. 12 is a perspective view illustrating a part of an example of a corrugated sheet used to make the pin-fin type heat exchanger in accordance with the present invention;
Flg. 13 is a front view schematically illustrating ~an apparatus for manufacturing a sheet composed of a plurality of wire-like heat conductive;elements and a temporary fixing material;
Fig. 14 is a plan view illustrating a sheet in `: :
which a plurality of wire-like heat conductive elements are fixed by another plurality of wire-like heat conductive elements arranged in a direction perpen-dicular to the former elements;

, .

- 5 - 13~6907 Fig. 15 is a perspective view illustrating an example of the corrugated sheet used to make the pin-fin type heat-exchanger in accordance with the present inventini Fig. 16 is a perspective view illustrating an example of a piece cut from the corrugated sheet illustrating in Fig. 15;
Fig. 17 is a front view illustrating a piece of the corrugated sheet from which the temporary fixing lo material on a curved top of the sheet has been removed;
Fig. 18 is a perspective view explaining an application of a solder on a surface of a pipe;
Fig. 19 is a perspective view illustrating a winding of the corrugated sheet on the surface of the pipe;
Fig. 20 is a perspective view illustrating an example of a fin-pipe assembly;
Fig. 21 is a perspective view explaining a procedure of removing the temporary fixing material from the fin-pipe assembly;
Fig. 22(A) is a longitudinal sectional view of the fin-pipe assembly from which the temporary fixing material has been completely removed;
; Fig. 22(B) is a traverse sectional view of the pipe-~in assembly corresponding to Fig. 22(A);
Fig. 23 is a perspective view illustrating an embodiment of the pin-fin type heat exchanger made of the pipe-fin assembly illustrated in Fig. 22(A);
Fig.;24(A)~ is a front view illustrating a flat pipe used in another embodiment of the pin-fin type heat exchanger~in accordance with the present invention;
Fig. 24~B) is a sectional view taken along the line I and I~j ;
Fig. 25 is a perspective view illustrating an example of a piece of the corrugated sheet used to make another emhodiment of the pin-fin type heat exchanger in accordance with the present invention;

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. ~ :

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- 6 - ~ 3 1 69 07 Fig. 26 is a perspective view ~xplaining an application of a solder on a surface of a flat pipe;
Fig. 27 is a perspective view illustrating a method of making a plurality of pipe-fin assemblies to a piling body;
Fig. 28 is a perspective view illustrating another method of making a plurality of pipe-fin assemblies to another piling body;
Fig. 29 is a perspective view illustrating a relationship between the piling body illustrated in Fig. 27 and a header;
Fig. 30 is a front view illustrating an apparatus for manufacturing a conventional anisotropic heat conductive structure;
Fig. 31 is a perspective view illustrating the conventional anisotropic heat conductive structure made by using the apparatus illustrated in Fig. 30;
Fig. 32 is a perspective view illustratlng a conventional anisotropic heat conductive block obtained from the structure illustrated in Fig. 31;
Fig. 33 is a perspective view illustrating a wlnding o~ the conventional anisotropic heat conductive block illustrating in Fig. 32 onto a surface of a pipe~
~ Fig. 34 is a perspective view illustrating a method of making a conventional anisotropic heat conductive sheet to a piling body;
Fig. 3$ is a front view illustrating a device for measuring~a~heat transmission ratio of the heat ;30~ exchanger.
DESCRIPTION t:) F THE PREFERRED EMBODIMENTS
The present~invention will now be described in detail with reference to the accompanyin~ drawings illustrating embodiments of a pin-fin type heat ~exchanger and a method of manufacturing ~he pin~fin type heat exchanger in accordance with the present invention.
Pigure 3 illustrated an embodiment of a pin-fin :

_ 7 _ 1 31 6qO7 type heat exchanger in accordance with the present invention.
As shown in Fig. 3, the heat exchanger 1 includes a pipe 2 formed in a S-like shape, and composed of several straight pipe portions 2a arranged in parallel to each other and U-shape pipe portions 2b conn~cting alternate ends of the straight pipe portions 2a. Wire-like heat conductive elements 3 bent in a corrugated shape in a lengthwise direction are arranged over almost the entire lo area of the pipe portion 2a, and a curved tops 4 at one side of the wire-like heat conductive elements 3 having a corrugated shape are fixed to surfaces of the pipe 2 through which a fluid passes.
As shown in Fig. 4, a pipe formed by bending piping into an S-like shape can be used in place of the pipe 2 illustrated in Fig. ~. Further, a pipe 2 having a cylindrical shape, as illustrated in Figs. 3 and 4, may be used, and as shown in Fig. 5, a pipe 12 composed of several straight flat pipes 12a and flat pipes 12b having a U-shape and connecting two adjacent pipes 12a may be used. A pipe assembly composed of the pipes 2 and the pipes 12 also may be used.
~ ~ ~ The heat exchanger shown in Figs. 3 and 4 is mainly ;~ ~ used as a shell and;tube type heat exchanger~ and the total area o~ fins of this heat exchanger can be remarkably enlarged compared with a conventional heat exchanger equipped with an ever-fin or the like. When this heat exchanger is used to transfer heat from ; boiling water, the foam maintaining ability of foam 3~ ~ generating nucleus~is~very good, and thus the heat ~-transfer efficiency is ~increased.
Another embodiment of~the heat exchanger ln accordance with the present~invention is illustrated in Figs. 6(A) and 6(B)O~ As shown in Figs. 6(A) and 6(B), in thls~heat exchanger 6a, a plurality of straight pipes 12a ha~ing~a ~lat section are arranged in parallel and spaced from each other, and both ends of the .
v 1 3~ 6~07 straight pipes 12a are supported in headers 7 and 7' through which a fluid can be passed from one of the straight pipes 12a to another straight pipe 12a. Fach of the spaces between adjacent straight pipes 12a is provided with a wire-like heat conductive element 3 formed in a corrugated shape. The corrugated heat conductive element 3 comprises a curved top 4 and a straight portion 5. The curved tops 4 of both sides of the corrugated heat conductive el0ment 3 are fixed to the surface of the pipe 12a. Note, although only one of the corrugated wire-like heat conductive elements 3 is illustrated in Fig. 6(A) and 6(B), a plurality of corrugated wire-like heat conductive elements 3 are arranged in parallel and spaced fxom each other behind the corrugated wire-like heat conductive element 3 shown in the drawings, and are fixed to the pipes 12a, respectively.
This piling type heat exchangers can be applied to a domestic cooler, a car cooler or the like and can be made very compact compared with a conventional heat exchanger equipped with plate-fins.
The curved tops 4 at both sides of the corrugated ; heat conductive elements 3 are fixed to the surface of the pipe 12a in the heat exchanger 6a illustrated in ~ Fig. 6(A) and 6(B), the curved tops 4 at one side of a corrugated heat conductive element 3 are fixed to a surface at a side of a pipe 12a in a heat exchanger 8 illustrated in Fig. 7 respectively, and the curved tops 4 at each side of two corrugated heat conductive 30~ elements 3 are fixed to surfaces at both sides of a pipe 12a~in a heat exchanger 8 illustrated in Fig. 8, respectively.
As shown in Fig. 6(A) to Eig. 8, the flat pipe 12a is used for the piling type heat exchanger, but as shown Ln Fig. 9, lt lS posslble to provide a piling type heat exchanger la using a cylindrical pipe 2 and headers 7 and 7'.

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As a wire-like heat conductive element used in a heat exchanger in accordance with the present invention, a fine wire of a pure metal such as silver, copper, aluminum or the like, a fine wire of an alloy or a fine metal wire obtained by plating a solder or a tin onto the above-mentioned fine wire, can be used.
A wire-like heat conductive element having an optional sectional shape can be used, but it is preferable to use a wire-like heat conductive element having a sectional shape close to a circle, to reduce pressure 106s when the wire-like heat conductive element is used as a pin-fin m~mber of the heat-exchanger.
Preferably, a heat conductive ratio of a wire-like heat conductive element is 0.038 cal/cm.sec.~C or more, and a wire-like heat conductive element having a suitable heat conductive ratio may be selected according to the application of the heat exchanger.
Various surface treatments, such as a hydrophilic treatment, a rust-proofing treatment, a ceramic coating 2n or the like may be optionally applied to the wire-like heat conductive element at any stage during the manufacture of the heat exchanger.
As can be seen from the above description, the features of the heat exchanger in accordance with the ~present invention are that a fin is formed of a plurality of wire-like heat conductive elements arranged in parallel and spaced from each other, and having a corrugated shape, and curved tops of at least one side of the corrugated heat conductive elements are fixed to the pipe of the heat exchanger.
The following description is of a heat transfer mechanism of the heat exchanger in accordance with the present invention and of a conventional heat exchanger.
:
Figure 10(A) is an enlarged front view of a part of the heat exchanger having the corrugated heat conductive eIements in accordance with the present invention, and FigO 10(B) is an enlarged sectional view of the part ~o 1 3 1 6qO7 illustrated in Fig. 10(A). Figure ll(A) is an enlarged front view of a part of the conventional pin-in type heat exchanger, and Fig . 11 (B) iS an enlarged sectional view of the part illustrated in Fig. ll(B). In the drawings, Fl denotes an outside fluid and F2 a pipe-side fluid.
The outside fluid F1 enters the heat exchanger 6 or 101 from a side marked ~'IN~ and is exhausted from the h0at exchanger 6 or 101 at a side marked "OUT", and at this time, heat from the outside fluid F1 is transferred through the heat conductive elements 3 or pins 104 and the pipe 12a or 103 to the pipe-side fluid F2.
In the conventional heat exchanger 101, since there is no member of part in the pipe 103 obstructing a fluid flow passing from "IN" to "O~T", a boundary layer 106 of the outside fluid F1 is generated in an area defined between surfaces of the pipe 103 and a chain line 105 as shown in Fig. ll(B).
: In the heat exchanger 6 in accordance with the present invention, since the curved tops 4 having a length of L are arranged along the surface of the: :
:: : pipe 12a as shown in Fig. 10(A), a fluid flow passing from ~IN" to "OUT" is obstructed by the curved tops 4:at a: position near to the:surface of the pipe:12a, so that a turbulent flow 9 is generated, compared with thak of the conventional heat exchanger, as shown in Fig. 10~B).
Therefore, a thickness of a boundary layer on the surface of the:pipe 12a is thinner than in the case of the~conventional heat exchanger, or the boundary Layer 3n; is removed from the surface of the pipe 12a. As a : result, the~heat transfer efficiency per unit surface area of the heat conductive material in the heat exchanger in accordance with the present invention is : greater than that of:the conventional heat exchanger.
: : 35 ~ ~ Further, since it is difficult for the boundary ~: layer to be generated:or be maintained on ~he surface of : the pipe 12a in the heat exchanger .in accordance with 13~907 the present invention, the heat tra~sfer efficiency on the surface of the pipe, which does not contribute to the heat transfer operation in the conventional heat exchanger, is improved. This ensure a higher heat transfer efficiency of the heat exchanger in accordance with the present invention.
~ o increase the heat transfer efficiency such that a pressure loss of the outside fluid is minimized, preferably a diameter d (mm) of the wire-like heat conductive element and a contacting length L (mm) between the curved top of the wire-like heat conductive element and the pipe satisfies the following e~uation.
1 < L/d _ 9 When L/d is equal to 1.0 or less than 1.0, although a total heat transfer efficiency of the heat exchanger is increased, the pressure loss of the outside fluid in the heat exchanger is increased, and therefore, a blowing force of a fan used in the heat exchanger must be increased.
When Ltd is more than 9.0, although the pressure loss of the outside fluid is reduced, a turbulent effect caused by the curved tops of the wire-like heat conductive elements fixed~to a surface of the pipe is ; also reduced. Furtherj a total surface area of the wire-like heat conductive~elements per unit volume of the heat exchanger i8 reduced, and as a result, the total heat trans~er efficiency of the heat exchanger is ; lowered.
Preferably, the~siæe~of the~wire-like heat ~ ~ ~ 3 n conductivè element and the density of the plurality of ; ~ wire~-like heat conductive element satisfies the following equation.
0.25 < X < 2.5 0.5 <~XY < 2.5 35~ Wherein, X stands for a circumstantial length o~
; the wire-like heat conductive element and is expressed as mm, and Y;stands for a density of the wire-like heat , - 12 - l 3 1 69 07 conductive elements on the pipe and is expressed as a number per mm.
An example of a corrugated sheet used to form the pin-fin type heat exchanger in accordance with the present invention, described in detail later, is illustrated in Fig. 12. As shown in Fig. 12, five wire-like heat conductive elements 3a, 3b, 3c, 3d and 3e are arranged in a corrugated shape in the sheet 22a.
The five heat conductive materials 3a, 3b, 3c, 3d and 3e are embedded while spaced from each other into a temporary fixing material, e.g., a plastic sheet 11. In the present application, a distance bet~een two adjacent heat conductive elements is defined as Z2 , as shown .n Fig. 12. Each heat conductive element is bent into a corrugated shape and a distance between a center point of a curved top 4 of a heat conductive element and a center point of an adjacent curved top 4 of the same element, i.e., a distance between two adjacent parallel portions 5a and 5b of the: heat conductive elements 3a, is defined as Zl / as shown in Fig. 12.
The density Y1 of the heat conductive elements expressed as a number of elements per mm in a lengthwise direction of the heat conductive elements is calculated from the ~alue Zl~and the density Y2 of the heat conductive elements expressed as a number of elements :
per mm in a direction perpendicular to the lengthwise direction of the heat conductive element is calculated from the value Z2 The symbol Y used in the above equation~is defined as a mean value of Y1 and Y2.
30 ~ Preferably, Yl~ and~Y2 represent 0.2 per mm to 10 per mm, respectively, under conditions satisfying the above e~uations. ~ ~
When X is less than 0.~25, the diameter of the wire-like heat conductive element is too small, and the 35 ~ mechanical properties of the heat conductive elements are correspondingly reduced, and thus the processing efficiency at the time of manufacture of the heat :

,: . . ~
, , ' : .:

- 13 ~ l 3 1 6q 07 exchanger is lowered. Namely, the production efficiency of the heat exchanger is lowered.
When X is more than 2.5, the diameter of the wire-like heat conductive element is too large, which reduces the number of heat conductive elements that can be arranged on an unit length of the pipe, and thus a problem arises in that the efficiency of the pin-type heat exchanger is lowered.
When XY is less than 0.5, the total surface area of the wire-like heat conductive elements is too small, and thus it is impossible to obtain a high heat transfer efficiency.
When XY is more than 2.5, although a wire-like heat conductive element having a large surface area can be used, since the distances between the heat conductive elements arranged in parallel, i.e, the distances Z~
and 22 in Fig. 12, become too small, the pressure loss of the outside fluid is increased.
More particularly, in the heat exchanger illus-trated in Figs. 3, 4 and 9, in which a plurality ofwire-like heat conductive elements are arranged around the entire circumferential surface of the pipe, preferably the following equations are satisfied:
0.25 _ X _ 0.95 0.5 _ XY _ 2.5 Further, in the heat exchanger illus ration Figs. 5 to 8, in which a plurality of the wire like heat conducti~e elements are arranged or an upper face and/or a lower face of the pipe, preferably the following 0 equations are satisfied:
.3 < X _ 2.5 0.5 _ XY _ 1.6 ; The method of manufacturing the heat exchanger in accordance with the present invention is now described 35~ in detail.
An~example of an apparatus for manufacturing a sheet composed of a plurality of wire-like heat - 14 _ 1316q~7 conductive elements and a temporary fixing material is illustrated in Fig. 13.
A plurality of packages of wire-like heat conductive elements 3 are arranged in a creel 13. Each heat conductive element 3 is withdrawn from the packages by a pair of heated press rolls 14 and 14', the heat conductive element 3 is passed through an eyelet plate 15, a front reed 16, and a tensioning bar 17 to apply an uniform tension to each heat conductive elements 3, and then the heat conductive elements 3 are arranged in a state in which substantially the same pitch is fixed between adjacent heat conductive elements by a guide roller 18 having a plurality of grooves and an arranging reed 19.
A sheet 11 of a soluble resin is withdrawn from a sheet roll 11', and supplied through two guide rolls 20 and 21 to the pair of heated press rolls 14 and 14'.
The sheet 11 and the plurality of the heat conductive elements 3 are piled together and pressed under heating by the pair of heated press rolls 14 and 14', and then united by embedding the heat conductive elements 3 in the sheet 11.
~` The united sheet 22 composed of the soluble resin sheet 11 and the heat conductive elements 3, i.e., an anisotropic heat conductive;sheet, can be obtained by applying two solublé resin sheets to the heat conductive elements 3 from both sides thereof and then pressing under heating. Further, a part of the cross section of each heat conductive element 3 may be embedded in the 3~ soluble resin sheet 11.
The united sheet 22 is wound, through a pair of delivery rollers 23 and 23~, onto a winding roll 24.
Various sheets of a substance capable of being dissolved, decomposed or burnt by a heat, chemicals or the like~can be used. For example, a sheet of a cellulose group, a polyester group, or a cellulose ;~ derivative, a sheet of the c~llulose derivative, and a , ' ";''-' ' ~. , , - 15 _ 1 3 ~ 69 07 cellulose pulp or the like, can be used. A sheet manufactured by coating or laminating a polyvinyl alcohol on a sheet formed from a mixture of a carboxy-methyl cellulose and the cellulose pulp also can be S used. Further, it is possible to optionally combine the above-mentioned sheets. Note, a sheet made of the cellulose pulp is most preferable, due to the easy processing thereof.
A width and a thickness of the soluble sheet can be optionally selected, but a sheet having a width of between 0.5 m and 1.5 m and a thickness of between 10 ~m and 200 ~m i5 preferable, due to the easy processing thereof.
Although the wire-like heat conductive elements 3 are embedded in the soluble sheet 11 under the heat and pressing conditions described on the basis of Fig. 13, these elements 3 also can be fixed by coating an adhesive capable of being dissolved, decomposed or burnt by heat, chemicals or the like on the soluble sheet.
Various adhesives, for example, a polyvinyl alcohol group, a polyester group, an ethylene.vinyl acetate group, a protein group, a cellulose derivative group or the like can be used. ~
Further, the fixing of the plurality of wire-like ; 25 heat conductive elements 3 arranged in parallel and spaced from each other can be carried out without using the soluble sheet, as showm in Fig. 14. Namely, first the plurality of the wire-like heat conductive elements 3 is withdrawn in a direction of an arrow 25, and other wire-li~e heat conductive elements 26 manu-factured from the same substance as~that of the heat conductive elements 3 are~piled in a direction perpendicular to the direction o the arrow 25 on the plurality of the wire-like heat~conductive element 3, and then fixed spot welding at each cross pQint 27 of the two heat conductive elements 3 and 26.
Further, a yarn having a thermoplastic property or :: : :

' 16 13~6907 a the~moadhesive property can be used in place of the heat conductive material 26 in Fig. 14.
Next, the plurality of the wire-like heat conductive elements fixed in parallel and spaced from each other are molded into a corrugated shape by a corrugate molding machine generally used to mold a corrugated fin of a conventional corrugated plate-fin type heat exchanger, or by a pleat molding machine commercially supplied for making a pleated textile lo goods. For example, when using the corrugate molding machine, the plurality of the wire-like heat conductive elements fixed in parallel and spaced from each other are compression molded in a corrugated shape by a pair of corrugate press plates, and when a diameter of the wire-like heat conductive element i.s thin, e.g., 200 ~m, an accordion type pleat molding machine may be used.
The obtained wire-like heat conductive elemerlts 22a having the corrugated shape (hereinafter, referred to as a corrugated and united body) are illustrated in Fig. 15. Although the densities Y1 and Y2 are the same in all portions of the corrugated and united body 22a illustrated in Fig. lS, if necessary, the density Y
and Y2 may be partially changed in the corrugated and ~; ~ united body 22a according to the~application of the heat exchanger.
The heat exchanger 1 illustrated in, e.g., Fig. 3, or the heat exchanger 6 illustrated in,~e.g., Fig. 5, are manufactured from the corrugated and united body 22a.
~30 ~When~manufacturing the heat exchanger l illustrated in Fig.~ 3,~the corruga~ted and united~body 22a is cut along à lengthwise direction thereof, i.e., along the ; line 25 in Fig. 15, to produce a tape-like corrugated and~united body 27 having a width W as shown in Fig. 15.
~ The~heat exchanger l can be obtained by spirally winding ; the tape-like corrugated and united body 27 around a circumferential surface of the pipe 2 as shown in . .

' ;

Fig. 19. If necessary, the tape-like corrugated and united body 27 is further cut along a direction perpen-dicular to the lengthwise direction of the corrugated and united body 22a, i.e., along the line 26 in Fig. 15, to provide a corrugated and united body unit 27a having a width W and a length G as shown in Fig. lS. In this case the length G is determined such that the length G
corresponds to a length of the circumerential surface of the pipe 2. The corrugated and united body unit 27a is illustrated in Fig. 16. The heat exchanger 1 can be obtained by joining each corrugated and united body unit 27a to the circumferential sur~face of the pipe 2.
Before joining the corrugated and united body to the surface of the pipe, it is necessary to remove the temporary fixing material, e.g., a soluble resin covering curved tops of the wire-like heat conductive elements, to expose the surface of heat conductive element. Figure 17 illustrates an example of a corrugated and united body 28 to be used for the heat exchanger 6 illustrated in Fig. 5, from which the soluble resin 11 covering both curved tops 4 of the wire-like heat conductive material 3 has been removed by ~h1. The value of ~h1 may be between 0 and 1 mm. This resin removing treatment may be applied to the corrugated and united body before or after cutting same.
The process of joining the corrugated and united body to the pipe will now~be described.
irst, the joining process in a manufactured of the heat exchanger 1 illustrated ln Fig. 3 will be 30 ~ described. As shown in Fig. 18, a circumferential surface of a pipe 2 lS ~ applied with a solder lO to produce a solderlng pipe 29. The solder applying treatment may be performed by any known method, e.g., a ~coating method, a dipping method~or a vapor deposition method. The solder is optionally selected according to a material constituting the pipe and a material of the wire-like heat conductive element. For example, when ~ ` ~

the pipe and the wire-like heat conductive element are manufactured from copper, a solder composed mainly of lead and tin may be used. If necessary, a resin having a high heat conductivity may be used. The coating of solder may be applied to the curved tops 4 exposed from the resin 11 or to both portions, i.e., the pipe 2 and the curved tops 4.
As shown in Fig. 19, the tape-like corrugated and united body 27, the curved tops of which at a side opposit~ to the circumferential surface of the pipe 29 are exposed, is spirally wound on the pipe 29. The thus obtained wound body 30 is placed for e.g., 30 min, into an oven (not shown) at a temperature of e.g., 165C, to firmly braze together the circumferential surface of the pipe 29 and the curved tops 4 of the corrugated and united body, to thereby produce a pipe fin assembly 31 as shown in Fig. 20.
Since the temporary fixing material, i.e., the soluble resin 11, still remains in spaces betw~en the wire-like heat conductive elements 3 in the fin-pipe assembly 31, the soluble resin 11 is removed by using the appaxatus illustrated, for example, in Fig. 21.
Namely, the fin-pipe assembly 31 is placed on a moving ,:
belt 32 and hot water 33 at a temperature of about 100C
~: ~ 25 i8 poured over the fin-pipe assembly 31 to completely remove the soluble resin ll from the spaces.~ As shown in~Fig. 22(A) and 22(Bj, when the resin is completely removed~from the spaces, an exposed fin-pipe asse~bly 34 ~ is obtained.
; 30 The solder may be~removed by dipping the fin-pipe assem:bly 31 into a vessel~holding hot water.
It is~preferable to apply a surface treatment to ` the exposed fin-pipe assembly 34 to provide a hydro-philicity to the exposed fin-pLpe assembly 34 or to ~35 increase a corro ion resistance of the exposed fin-pipe assemb1y~34. For~example, when aluminum is used as a material of the plpe 2 and the wire-like heat conductive . .~

- 19 1316qo7 elements 3, a film having a good corrosion resistance may be formed on the surface of the exposed fin-pipe assembly 34 by treating same with a chemical, e.g., a chromate, a phosphate or the like, and then covering the film with another film of an organic substance or an inorganic substance by applying an inorganic substance, such as fine particles of a silicate, a silica or the like, or an organic substances, such as a polyvinyl alcohol, an acrylic group resin or the like, to provide a hydrophilicity.
An embodiment of the heat exchanger 37 manufactured by bending the exposed fin-pipe assembly 34 into a S-like shape, and connecting an inlet 35 of a pipe-side fluid and an outlet 36 of the pipe-sid~ fluid to the ends of the pipe 2 of the exposed fin-pipe assembly 34 is illustrated in Fig. 23.
The ioining process in a manufacture of the heat exchanger 5 illustrated in Fig. 5 will be described hereafter.
First, a flat pipe 12 having a size and a shape illustrated in Fig. 24(A) and 24(B) is prepared. In the drawings, J denotes a length of the pipe 12a, K a width of the pipe, ~ a thickness of the pipe, and M a thickness of metal plate constituting the pipe 12a.
Although the flat pipe 12a in which opposite portions 12c and 12d in a sectional view are parallel is illustrated in Fig. 24(B), a pipe having an elliptic cross section may be used in place of the flat pipe 12a for the heat exchanger 5 illustrated in Fig. 5.
As shown in Fig. 25, a corrugated and united body unit 27a is prepared b~ cutting the corrugated and united body 22a illustrated in Fig. 15. In this case, a :
length J' and a width K' of the corrugated and united body unit 27a may be shorter than that of the corre-sponding portions of the pipe 12 illustrated in F1gs. 24(A) and 24(B~. The curved tops 4 at both sides of the corrugated and united body 27a are removed.

~ 20 - 1 3 1 69 0 7 Flat portions 12c and 12d of the flat pipe 12a are applied with a solder 10 to prov-de a ~oldering pipe 38.
The solder may be applied in the same manner as described for Fig. 18.
Figure 27 illustrates a method of assembling the corrugated and united body units 27a and the soldering pipes 38 to obt~in a piling body 39 constituting a heat exchanger having headers 7 and 7' (see Fig. 6(A) and 6(B)) or a U-shape pipe 12b tsee Fig. 5). As shown in Fig. 27, several corrugated and united body units 27a and several soldering pipes~ 38 are alternately piled by an implement 41 and are fixed to each other under a pressure of, for example, about 2 kg per cm2, to produce a piling body 39. The piling body 39 is placed for, e.g., 30 min, in an oven at a temperature of, e.g., 165C, (not shown) to firmly braze together the surface of the soldering pipe 38 and the curved tops 4 of the corrugated and unit body unit 27a, to thereby produce a fin-pipe assembly.
A soluble resin 11 remaining in spaces between the wire-like heat conductive elements 3 in the fin-pipe assembly is removed in the same manner as described for Fig. 21. The thus obtained an exposed fin-pipe ~ assemble 45 is connected to a header 7, as shown in `~ ~ 25 Fig. 29, and the header is connected to both sides of the exposed fin pipe assembly 45, and the headers and the~exposed fin-pipe assemble 45 are brazed together by a solder. The header 7 includes several connecting pipes connecting adjacent flat pipes 12, an inlet of a 30 ~ pipe-side fluid, and an outlet~of the pipe-side fluid.
It is preferable to apply a surface treatment to the exposed fin-plpe assembly 45 to provide hydro-philicity thereto and to improve the corrosion resistance, in the same manner as described for the manufacture of the heat e*changer 1.
The pressure used to obtain the piling body 39 depends on manufacturing conditions for the corrugated ~' , - 21 ~

and united body unit 27a, e.g~, the diameter of the wire-like heat conductive elements, the pitch of the heat conductive elements, the thickness and the material of the soluble resin sheet, or the like. Of course, the pressure musk not be such that the corrugated and united body unit 27a is buckled by the pressure and temperature in the oven and the joining between the pipes and the curve tops of the wire-like heat conductive material is weak.
Figure 28 illustrates a method of assembling the corrugated and united body units 27a and a soldering pipe having an S-like shape to obtain a piling body 40.
When preparing the soldering pipe 42, preferably a distance h2 between adjacent parallel portions of the soldering pipe 42 is smaller than the height h1 of the corrugated and united body units 27a. The corrugated and united body units 27a are inserted into spaces between the adjacent parallel portions of the soldering pipe 42 having the S-like shape, and the units 27a and the pipe 42 are arranged in an implement 43. In that time, spacers 44 are inserted between the adjacent : parallel portion of the soldering pipe 42 so that the distance h2 becomes the~distance h1 after applying a pressure to the units 27a and the pipe.42. The piling 25 ~ body 40:is obtained by carrying out a heat treatment on : the implement 43 with the units 27a and the pipe 42, similar to that described for Fig. 27.
A heat exchanger using the flat pipe having the S-like shape can be obtained by connecting an inlet of a pipe-s:ide fluid and~an outlet of the pipe-side fluid to ends of the flat pipe.:
Since a fin of the heat exchanger in accordance ~ with the present invention is formed by corrugating the : wlre-like heat conductive elements, a heat exchanger having a desired~excellent heat transfer efficiency can .
be obtained by suitably determlning the diameter of the wire-like heat conductive elements and the density . . .

thereof. Also, since the wire-like heat conductive element is used and the corrugating operation is used to make the corrugated and united body, it is possible to manufacture a fin having a precisely arranged density of the wire-like heat conductive elements. Further, since -the fin includes the plurality of curved tops, a heat exchanger having the excellent heat transfer efficiency and less pressure loss can be obtained.
Since in the method of manufacturing the heat exchanger in accordance with the present invention the corrugated and united body is joined to the pipe instead of fixing each pin on a surface of a pipe as a con-ventional heat exchanger, it is possible to easily manufacture the heat exchanger having an excellent heat transfer efficiency.
Examples The present invention will be explained further by means of examples which in no way limit the invention.
An united sheet is manufactured from a plurality of wire-like heat conductive elements and a sheet of soluble resin by an apparatus illustrated in Fiy. 13, a corrugated and united body is manufactured by corru-gating the united sheet, and curved tops of the wire-like heat conductive elements in the corrugated and united body are exposed by removing the soluble resin on the curved tops.
; The manufacturing conditions when making the corrugated and united body are as follows Wire-like heat conductive element Shape in Cross Section: Circular Diameter: 200 ~m~
Material: Copper Number of bobbins of wire-like element: 500 ~ Feeding of Wire-like element: Withdrawing in direction perpendicular to bobbin axis while rotating bobbin ' .

Running speed of wire-like element: 1 m/min Reed: 25.4 pieces per 1 inch, i.e., pitch of reed: 1 mm Soluble resin sheet- Poly~inyl alcohol film supplied from Soko seiren Co., Ltd, thickness: 200 ~m Heated press roller Temperature: 200C
Press: 20 kg/cm Corrugating machine: ~ccordion pleat machine supplied from Toyo Rokisha Height of corrugation: 8 mm ~ xample 1 To manufacture a heat exchanger having a structure similar to that illustrated in Fig. 3, a circular pipe having a diameter of 7.94 mm and produced from a copper plate having a thickness of 0.30 mm was prepared. A
tape-like corrugated and united body was wound around the circular pipe as shown in Fig. 19 and placed in an oven to braze the tape-like corrugated and united body ~to the circular pipe to produce a fin-pipe assembly.
~The soluble resin in the fin-pLpe assembly~was removed, and an inlet and~an outlet of a pipe-side fluid are provided at~both ends of the circular~pipe, ~hereby a :
heat~exchanger similar to the~heat exchanger illustrated in Fig. 3 was obtained. A value of L/d of this heat exchanger was~4, X was 0.628 and Y was 1 per mm.
Example 2 To manufacture a heat exchanger having a structure simi~lar to~that illustrated in~Fig. 5,~several 30~ corrugated~and`unL~ed~body units~were arranged in spaces between~adjacent flat~pipes ha~ing a minor axis of 5 mm and~a major~axis of~12.~7 mm in cross section and made of a copper plate having a~thickness of 0.65 mm, respectively, by a ji~ illustrated in Fig. 27, and 35 ~ placed~in an oven to braze the~corrugated~and united body units to the flat pipes to produce a fin-pipe assembly. The soluble resin in the fln-pipe assembly '.
:
, was removed, and a header including an inlet and art outlet of a pipe-side fluid was provided at both ends of the flat pipes, respectively. Thus a heat exchanger similar to the heat exchanger illustrated Fig. 5 was obtained. Note that the values of I./d, X and Y of this heat exchanger were the same as that of the heat exchanger of Example 1.
To manufacture comparative examples of a heat exchanger, a united sheet was manufactured by the same method as used for manufacturing the united sheet for the above-mentioned examples of the heat exchanger in accordance with the present invention, except that two soluble resin sheets having a thickness of 500 ~m were used.
Eleven united sheets 22 were piled and pressed by an apparatus illustrated in Fig. 30 to produce an anisotropic heat conductive structure 46 (see Fig. 31).
The sheets were pressed for 30 min at a temperature of 175C. This s~ructure~46 was cut along a line II to II
to form an anisotropic heat conductive sheet 47 having a thickness of 8 mm as shown in Fig. 31.
A soluble resin of both sides o~ the anisotropic heat conductive block 47 was removed to expose both ends of a heat conductive material included in the aniso-tropic heat conductive block 47 (see Fig. 32~.
Comparative Exantple 1 A heat exchanger having the same structure asthat of Example l was manufactured by the same method as that used to manufacture the~example shown in 30 Fig. 33, except that the anisotropic heat conductive sheet 47 was used.
Comparative Example 2 A heat exchanger having the same structure as that of the Example 2 was manufactured by the same method as that used to manufacture Example 2 as shown in Fig. ~4, except that the anisotropic heat conductive sheet 47 was used.

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In the Comparative Examples 1 and 2, a value ~/d was 4, X was 0.628 and Y was 1 per mm. Those values are the same as of the Examples.
To compare the ~haracteristics of the heat exchangers of the Examples ad the Comparative Examples, a heat exchange ratio and pressure :Loss were measured by a device illustrated in Fig. 35.
A cross section of a fluid passage of a heat exchanger 51 in the measuring device 50 was 300 mm x 300 mm. The air flow was calculated by an air speed measured by a hot wire anemometer 54 and the cross section. A pressure loss ~p of the heat exchanger 51 was obtained by a manometer 55 by measuring a static pressure difference between a front of the heat exchanger 51 and a back of the heat exchanger 51 in an air flow direction 56. Hot water was supplied to an inlet 52 of the heat exchanger 51 and exhausted from an outlet 53, and returned through a flowmeter ~not shown) to a controller (not shown~ by which the temperature of the hot water was controlled. A heat transfer quantity of the water QW was calculated from the water flow, temperature at the inlet 52, and temperature at the :: : : ::
outlet 53.;
The heat exchange ratio K was calculated from~he following equation K - Qw/(Ao-~Q)~ ~
Wherein Ao stood for a total heat transfer area, and ~Q stood for~a mean temperature difference between the air and~the hot water.
30 ~ ~ Table l~shows the~heat exchange ratios and pressure losses in the~Examples and the Comparative Examples when the measurement is made~at an air speed of 1 m/sec by he above measuring device.
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- 2~ -Table 1 Comparative Comparative Example 1 ExaDIple 1 Example 2 Example 2 Heat 1.18 1 1.21 Exchanging Ratio Pressure Loss Shape of Pipe clrcular n Flat n * The numbers of Bxamples in Table 1 are expressed as a ratio to the measuring value of the comparative examples, i.e., 1, or 2 respectively.

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Claims

1. A pin-fin type heat exchanger comprising a pipe through which a fluid can flow and on a surface of which a fin is arranged, wherein said fin is comprised of a plurality of wire-like heat conductive elements arranged in parallel and spaced from each other, said wire-like heat conductive elements having corrugated shape formed by bending said heat conductive elements in a lengthwise direction and having curved tops arranged at at least one side of the corrugated heat conductive elements and fixed to the pipe.

2. A pin-fin type heat exchanger according to claim 1, wherein the following equation is satisfied.
1 < L/d ? 9 wherein L is a contacting length between the pipe and the curved top of the corrugated heat conductive element and is expressed as mm, and d is a diameter of the heat conductive element and is expressed as mm.

3. A pin-fin type heat exchanger according to claim 1, wherein the following equation is satisfied.
0.25 ? X ? 2.5 0.5 ? XY ? 2.5 wherein X is a circumferential length of the wire-like heat conductive element and is expressed as mm, and Y is a density of the heat conductive elements when arranged on the pipe and is expressed as a number of elements per mm.

4. A pin-fin type heat exchanger according to claim 1, wherein the curved tops arranged at one side of the corrugated heat conductive elements are fixed to the pipe and the curved tops arranged on another side of the corrugated heat conductive element are free.

5. A pin-fin type heat exchanger according to claim 1, wherein the curved tops arranged on the one side of the corrugated heat conductive material are fixed to the pipe and the curved tops arranged on another side of the corrugated heat conductive elements are fixed to another pipe spaced from said pipe.

6. A pin-fin type heat exchanger according to claim 4 or 5, wherein the pipe has an S-like shape.

7. A pin-fin type heat exchanger according to claim 1, wherein a plurality of straight pipes having both ends open and arranged in parallel to each other are used, and both ends of the straight pipes are connected and held by a header through which the fluid can pass, respectively.

8. A pin-fin type heat exchanger according to claim 1, wherein a plurality of straight pipes having both ends open and arranged in parallel to each other are used, and both ends of the straight pipes are connected by a U-shape tube, respectively.

9. A method of manufacturing a pin-fin type heat exchanger having corrugated pin-fins, wherein said method comprises a step of arranging a plurality of wire-like heat conductive element in parallel and spaced from each other, a step of temporarily fixing the plurality of wire-like heat conductive elements in an arrangement such that they form a sheet constituted of the wire-like heat conductive elements and a temporary fixing material, a step of shaping the sheet in a corrugated state, a step of joining curved tops of the wire-like heat conductive elements applied on at least a side of the corrugated sheet to the pipe, and a step of removing the temporary fixing materials.

10. A method according to claim 9, wherein said temporary fixing material is a resin.

11. A method according to claim 10, wherein said resin is a soluble resin.

12. A method according to claim 11, wherein said soluble resin is a substance capable of being melted by heat.

13. A method according to claim 11, wherein said soluble resin is a substance capable of being decomposed by heat.

14. A method according to claim 11, wherein said soluble resin is a substance capable of being burnt by heat.

15. A method according to claim 11, wherein said soluble resin is a substance capable of being dissolved by a chemical.

16. A method according to claim 11, wherein said soluble resin is a substance capable of being decomposed by a chemical.

17. A method according to claim 9, wherein a resin is used as the temporary fixing material, said method further including a step of removing a resin of the wire-like heat conductive material on the curved tops applied on at least a side of the corrugated sheet.