US3644975A

US3644975A - Method of manufacturing a heat exchanger

Info

Publication number: US3644975A
Application number: US887826A
Authority: US
Inventors: Keiichi Kimura
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-12-24
Filing date: 1969-12-24
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28

Abstract

Method and apparatus for mounting fins unto pipes for a heat exchanger comprising the steps of placing a predetermined number of pipes into the orifices of one or more fins, the outer diameter of the pipes being less than the orifices, sealing liquid in said pipes, and heating said liquid to a superheated vapor to expand said pipes so as to expand the outer diameter of the pipes to tightly fit within the orifices.

Description

United States Patent Kimura [54] METHOD OF MANUFACTURING A HEAT EXCHANGER [72] lnventor: Keiichi Kirnura, 2-304, Osakabe, Yao,

{apan [22] Filed: Dec.24,1969

[21] Appl.No.: 887,826

Related US. Application Data [63] Continuation-impart of Ser. No. 649,325, June 27,

1967, abandoned.

[52] U.S.Cl ..29/l57.3V, 29/1573 A, 29/421,

[51] Int. Cl ..B2ld 53/02 [58] Field of Search ..29/157.3 A, 157.3 V, 421; 113/118 A [56] References Cited UNITED STATES PATENTS 2,119,960 6/1938 Price ..l13/118 R Feb. 29, 1972 2,458,189 1/1949 Morgan 29/1573 A/H X 3,432,905 3/1969 Monroe. ..29/157.3 A

3,572,073 3/1971 Dean ..29/421 X FOREIGN PATENTS OR APPLICATIONS 10,986 7/1916 Great Britain ..29/421 Primary ExaminerJohn F. Campbell Assistant Examiner-Donald C. Reiley, lll AttarneyMoonray Kojima [57] ABSTRACT Method and apparatus for mounting fins unto pipes for a heat exchanger comprising the steps of placing a predetermined number of pipes into the orifices of one or more fins, the outer diameter of the pipes being less than the orifices, sealing liquid in said pipes, and heating said liquid to a superheated vapor to expand said pipes so as to expand the outer diameter of the pipes to tightly fit within the orifices.

9 Claims, 7 Drawing Figures Patented Feb. 29, 1972 3,644,975

3 Sheets-Sheet 1 INVENTOR KEHCH/ KWURA AT T.

Patented Feb. 29, 1972 3,644,975

5 Sheets-Sheet 2 INVENTOR KEHCHI KHIURA ATT.

Patented Feb. 29, 1972 3,644,975

3 Sheets-Shet 5 INV-ENTOR KEHLH KIMURA g ATT.

METHOD OF MANUFACTURING A HEAT EXCHANGER RELATED APPLICATIONS This application is a continuation-in-part application to application Ser. No. 649,325, filed June 27, 1967, and to be abandoned shortly.

This invention relates to the method and device for manufacturing a heat exchanger provided with such fins, for example, as thermal radiation plates or endothermic plates substantially usable for the fundamental elements of a heating and cooling apparatus, an air-conditioning apparatus, a condensing unit or the like.

conventionally speaking, it is a matter of common practice that a heat exchanger is manufactured by thermally sealing these fins to heat-exchanging pipes so as to enhance the thermal conductivity of the whole system. Accordingly, many attempts and experiments have so far been made for the purpose of satisfying the above-mentioned practical requirements for manufacturing the heat exchanger; and especially the proposition has been made, for instance, firstly of the method that either liquidlike oil or air is sealed into a continuity of pipe under high pressure so as to cubically expand said pipe and fix the fins thereto; in the second place, the method that liquid sealed in the pipe is condensed until this pipe is cubically expanded and rigidly secured to the fins, as is taught by the US. Pat. No. 2,458,189; and thirdly, the method as is disclosed in the US. Pat. No. 2,119,960 that liquid is sealed into a pipe under high pressure and at the same time heated until the fins are thennally sealed to the pipe. However, according to the above-mentioned first method in which either oil pressure or air pressure is used to inflate the pipe, it is necessary to provide a large scale pipe swelling equipment and the technical deficiency is fatally brought about that accuracy of thermal sealing is not altogether securable substantially because of the frequent occurences that the force to cubically expand the pipe fails in coming up to a satisfactory extent.

According to the second method in which liquid is congealed until the pipe is cubically expanded, it is impossible to distribute the cooling effect of a refrigerant over the fixed overall length of the pipe. Thus this second method fails to secure the uniformity of the cubic expansion of the pipe, giving rise to the deficiency that the fins cannot be fixed in uniformity to the pipe and consequently necessitating a large scale pipe cooling equipment in order to obtain the completely uniform cooling effect upon the pipe.

The third method may have the advantage over the first method in that the liquid sealed under pressure is heated until the pipe is cubically expanded. However, as has been specified in the U8. Pat. No. 2,119,960, the liquid is preferably heated to an extent not exceeding the boiling point. Thus this third method is merely employable for the purpose of heating a liquid feed conduit connected to the pipes which heats the liquid body; this is partly because said method prevents the fins from being overheated and partly because it can provide a better convenience where the liquid body is heated to a desirable value, that is, to such a temperature not exceeding the boiling point. Therefore, it is easily understood that said third method intends in essence to inflate the pipe mainly by utilizing the high pressure or superhigh pressure under which the liquid is forcibly sealed into the pipe; due to this, the heating operation is merely an essence auxiliary to this method. This will also be easily comprehended from the fact that when this third method is applied, the cubic expansion of the liquid is very a little expected since the temperature of the liquid to be heated is exclusively limited below the boiling point. However, in order to seal the liquid into the pipe under high pressure or superhigh pressure which is the main element of the third method for inflating the pipe, said method needs installing a large scale pipe swelling equipment just like in case with the first method and what is more such an equipment takes very troublesome operations. Thus the defect of said first method cannot still be eliminated by this third method.

The present invention aims at disrooting the deficiencies caused by the above-mentioned conventional methods for cubically expanding the pipe; and the method of this invention is to produce vapor by effectively heating the liquid sealed in the pipe and cubically expand the pipe by using the endlessly continued cubic expansion of this vapor, without employing the method of swelling the pipe by forcibly sealing the liquid into the pipe under pressure.

Especially the principal objective of the invention is to provide the method of effectively and easily manufacturing a heat exchanger by use of either the thermal radiation plates or endothermic plates inserted through the heat-exchanging pipes so that the water in the pipe is vaporized with high effect and promptness to cubically expand the pipe by means of said endlessly continued cubic expansion of the vapor.

Another objective of the invention is to provide the method of an economical-type heat exchanger in which the thermal radiation plates or endothermic plates to be inserted through the pipes can be heated with more highly enhanced efficiency than the conventional method thereby to increase in a heating effect; and the thermal energy produced while said plates are being heated is utilized in the most effective manner. Further another objective of the invention is to provide such an easily operable device of much simplified structure that can continuously carry out the above-mentioned method of manufacturing a heat exchanger with high efficiency and promptncss.

As has been referred to above, it is a well known art in general to thermally inflate the heat exchanging pipe by heating the liquid sealed in this pipe. However, this pipe inflating method depends exclusively upon the cubic expansion of water and therefore it is impossible to expect a favorable result of cubically expanding the overall length of the pipe in uniformity merely by using this expansive power of the liquid or water. Conversely, according to the method of the present invention, it has no need of forcing the liquid into the pipe under such a high pressure as to give the cubic expansive power to the liquid, since the liquid sealed in the pipe is promptly and effectively changed into vapor by absorbing the thermal energy from the fins regularly spaced on the pipe with the result that the pipe is inflated by the cubic expansion of the vapor.

When the method of this invention is carried out, the fins are preferably heated by blowing a hot blast; but they are not to be heated directly by means of a burner or the like. According to this invention, the pipe is inflated equally through its full length thereby making it possible to manufacture a heat exchanger in such a manner that during the inflation of the pipe even a single part of this pipe is not transformed nor damaged.

The device by which the foregoing and other objectives of the present invention are accomplished and the method of their accomplishment will be readily understood upon reference to the accompanying drawing, and the novelty and characteristics of the invention are as pointed out in what is claimed.

In the accompanying drawing:

FIG. 1 is a diagrammatical illustration of a device to be used for embodying the method of the present invention,

FIG. 2 is a side elevation showing a base pattern of such an unfinished heat exchanger that has not been conveyed to be thermally sealed, and in this elevation fins are shown in lines,

FIG. 3 is a side elevation showing another type of the base pattern of an unfinished heat exchanger as against the base pattern shown in the FIG. 2,

F16. 4 is a plan view of a fin to be used in this invention,

FIG. 5 is a cross-sectional view taken on line V-V thereof,

FIG. 6 is a plan view showing another type of a tin to be used in the invention and,

H6. 7 is a cross-sectional view taken on line Vll-Vll thereof.

Setting forth one of the methods of the present invention with reference to the accompanying drawing, a desired number of heat-exchanging pipes 1 and l are provided with a plurality of regularly spaced fins (which will be referred to hereinafter) having holes of a little larger diameter than the outer diameter of said pipes. With exemption of the two pipe opening ends 1' and 1" which serve for an inlet and an outlet for a refrigerant respectively, all the other pipe opening ends are connected with bend pipes 3 by means of welding or the like in such a manner that said pipes form a single passageway for the refrigerant running from said inlet as far as said outlet.

If circumstances require, hairpin pipes 4 may be replaceable with the bend pipes. In this case, frame means 5 and 6 are mounted on both ends of the base pattern of a heat exchanger as shown in FIG. 3, and secured to each other by means of nuts 8 and supporting rods 7 tightened each other. In the second place, one of said two pipe opening ends 1' and 1" is closed and water or any other suitable kind of liquid is forcibly injected from the other pipe opening end. After injection, said other pipe opening end is closed thereby sealing the injected water or liquid in the pipe. This injection is made possible by increasing the pressure of preferably about 25 Kg/cm. for instance by means of a pump P. This forcible injection of water or liquid under increased pressure is necessary, not for cubically expanding the pipes nor for promoting the inflation of the pipes, but for eliminating air bubbles from the water to be injected, which otherwise will prevent the pipe from being effectively swelled. Said pump or other substitute means is not necessarily required for the above-mentioned purpose. As has been mentioned above with reference to FIG. 2 and 3, the unfinished fins 2 in which water is sealed forms a base pattern A of a heat exchanger unfinished or in the making which has still not been secured to the pipes 1. For conveniences sake of the following explanation, the base pattern of a heat exchanger unfinished or in the making will be called merely the base pattern in abbreviation hereinafter. Thus this base pattern that will be worded in the following paragraphs is to be noted all as designating the above fully named content.

In case of forming this base pattern A, it is desirable to immerse the pipe 1 in a tank of a Trichlene or the like prior to connecting this pipe 1 with said bend pipe 3 as is clearly shown in FIG. l, so that both the inner circumferential surface and the outer circumferential surface of the pipe 1 are thoroughly cleansed and removed of fat. Secondly, the base pattern A formed in the above-mentioned manner is placed on a conveyor system 10 and transferred through a hot blast furnace 11 whereby the pipe 1 and the water sealed therein are heated together from the outside of the base pattern A until the temperature of the water exceeds the boiling point. The temperature at which the pipe 1 is heated in the hot blast furnace 11 is subject to the diameter and thickness of the pipe 1, and in a general way, it is most suitable to be about 230-270 C. The time when the base pattern A is conveyed through the hot blast furnace 11 is also subject to the diameter and thickness of the pipe 1, and in a general way, it is most suitable to be between and 40 minutes. Incidentally, our experiments have obtained the best result for instance when the base pattern A composed of the copper-make pipe of 0.4 m./m. thick and in diameter was conveyed in half an hour through the hot blast furnace 11 heated up to 250 C. By using the hot blast furnace 11, the method of this invention provides such advantages that it is possible not only to readily and controllably secure a high-temperature necessary for inflating the base pattern A but as well to heat the outer surface of this base pattern A at a uniform temperature, without having a bad influence upon the fins 2. As the whole body of the base pattern A is heated from the outside in said manner, each surface of the fins 2 mounted in the base pattern A is heated over its maximum area; by this endothermic agency of the fins 2, the thermal energy is effectively and equally conducted into the water sealed in the pipe 1 whereby the water commences to be boiled simultaneously.

When the water has been overheated enough to exceed the boiling point, it begins to be gasified into a saturated vapor with the result of increasing in its cubic volume. And if said saturated vapor still continues to be heated, it will be changed from the dry saturated vapor into a superheated vapor; and if furthermore heated, this superheated vapor will endlessly continue to increase in its cubic volume. Thus the aim of the present invention is at inflating the pipe by using the peculiar nature of the superheated vapor that tends to boundlessly swell.

According to the method of this invention, therefore, it is remarkable enough that the cubic expansion of the pipe of such a small diameter for example, as a quarter inch is made quite possible in an easy and exact manner which has so far been accepted as being technically beyond the conventional methods. This is possible because the base pattern A, or more in particular, the fins 2, is heated from the outside so that the thermal energy is very effectively conducted from the fins direct to the pipe 1 through the heating surface area of the fins 2. Further this invention provides the advantages in that the pipe portion with which the fins are in contact can be very effectively inflated because it is the endothermic agency of the fins that is used for inflating the pipe, and that the bend pipe or any similar curved portion with which the fins are out of contact is restrictively inflated to less extent than said pipe portion which is in contact with the fins; consequently said bend pipe is prevented from such an unnecessary inflation as to be distorted or broken down.

After the pipe 1 has been inflated enough to rigidly connect the fins 2 therewith, the pipe 1 and the fins 2 are gradually cooled by means of a blower or in a water cistern 62; and then the opening ends 1' and 1" of the sealingly closed pipe 1 are opened to drain the water sealed in this pipe 1. This drainage of the water is accomplished, for example, by forcing the highpressure air into the pipe from one of said opening ends 1' and 1''. In the second place, the waterdrained pipe 1 undergoes a deliberate overhaul and then is dried by means of a desiccator whereby a heat exchanger is completely manufactured.

What is to be remarked in this respect is the employment of the fins 2 having the constructions shown in FIG. 4 thru 7; this employment of said fins 2 is especially imperative in the method the present invention since the latter aims at making the best of the endothermic agency of the pipe 1 which ahsorbs the thermal energy conducted from the fins 2. Namely, the fins 2 shown in FIG. 4 and 5 are provided with protrusions 15 of almost triangular shape regularly spaced between the holes 2' of the fins 2 through which the pipes are inserted. Each of said protrusions 15 has a slot 16 or a crevice provided along the base of said triangle opposed to the vertex thereof. The positional direction of these protrusions 15 is not especially limited; but it is desirable to dispose these protrusions 15 in such a position that each vertex of these triangles orients in the direction where the heated air or the cooled air is passing.

Said slot 16 serves as an opening communicating with closely spaced neighboring fins 2. When the fins 2 formed in this manner are conveyed into the hot blast furnace 11, they spread out the flow of the hot blast and disperse same through each vertex of the triangular protrusions 15 of the fins 2; and a certain quantity of the dispersed hot blast passes through the slot 16 and is exchanged with the hot blast flowing over the neighboring fins 2 thereby to cause a turbulent current of air within these fins 2 with the result of enhancing the heatexchanging effect to secure a very high-endothermic agency of the fins.

In addition, the heating surface per unit area is greatly increased due to the formation of said protrusions 15 so that, coupled with said endothermic agency of the fins 2, the water sealed in the pipe 1 is heated effectively in a very short time, and consequently the practical utility of the present invention is enhanced more definitely. in place of the above-mentioned fins 2, those fins having the constructions shown in FIGS. 6 and 7 are also able to secure the same effect that has been mentioned above. Namely, the constructions of said fins 2 in FIGS. 6 and 7 are different from that of the above-mentioned fins 2 in that a plurality of semispherical protrusions 17 are formed in a regular space between a plurality of holes through which the pipes 1 are inserted, and that slots 18 are formed so as to connect the mutually neighboring protrusions 17. Said semispherical protrusions 17 are formed on the fins 2 in order to provide thereon as the largest heating surface area as possible and at the same time help the flow of the hot blast pass swiftly from every direction. Further said slots 18 are formed in order to provide on a single fin 2 with a plurality of independent heating surfaces; therefore, due to the slots 18 for interconnecting the protrusions 17, the heating surface of each independent unit thus produced therefore has, so to speak, a combination of many miniature fins.

Accordingly, when the fin 2 form in this manner is adopted, the hot blast is spreaded out and dispersed through the protrusions 17 of this fins 2, though not exchanged with the hot blast flowing over the neighboring fins 2, thereby securing the same high heat-exchanging effect that has been referred to above. On the top of that, this fin 2 can obtain the same result that is obtainable when several miniature fins or several tens of miniature fins are used in combination, and secure a by far higher heat exchanging efficiency than that of the conventional single unit-type fin, consequently inflating the pipe in a very short time with the same high efficiency as has been just mentioned.

The method of the present invention is practically made applicable because the base pattern A is fonned in the beginning and then heated from the outside so as to cubically expand the pipe by use of the endothermic agency of the fin and also because said fin is formed in the above-mentioned manner. The employment of such a fin makes it possible to secure a highly efficient function especially when a heat exchanger is just in manufacture and when such a heat exchanger is practically in use. In case the protrusions are formed on the fin, they work to enhance the hardness of the fin surface. Further it is to be noted that by applying the thermal inflation to the present invention, the device for manufacturing a heat exchanger can be not merely constructed in much simplified structure but as well operated in an easy manner.

This invention is not altogether restricted within the constructions disclosed herein, since what have been disclosed in this specification are not to limit the purview of the invention but rather illustrative of the invention.

What is claimed is:

l. A method of manufacturing a finned-tube-type assembly heat exchanger comprising the steps of A. providing a plurality of fins, each of said fins substantially consisting of a flat sheet of metal having therein a plurality of holes of particular diameters and a plurality of raised portions located in the vicinity of said holes;

B. providing a plurality of lengths of pipe and assembling said fins and said lengths of pipe by means of fitting said lengths of pipe through said fins, said lengths of pipe having diameters smaller than said diameters of corresponding holes;

C. interconnecting said pipes to form a single passageway;

D. closing tightly one end of said interconnected pipes;

E. filling said interconnected pipes with liquid;

F. closing tightly the other end of said interconnected pipes;

G. heating at least said fins thereby to transmit heat from said fins to said pipes until said liquid is heated above its boiling point and converted to superheated vapor thereby to enlarge the diameter of said pipes by cubic expansion of said vapor and tightly bind the outer peripheries of said pipes to the inner peripheries of said holes;

H. cooling the expanded assembly; and

l. removing said liquid from the assembly.

2. Method of claim 1, wherein said raised portions of said fins are generally shaped to have three sides with one side being separated from said sheet, and the other two sides being joined together and adjacent to respective ones of said holes.

3. Method of claim 1, wherein said raised portions are semispherical in shape and located between selected pairs of said holes and wherein said sheet contains slots between selected pairs of said semispherical shaped raised portions.

4. Method of claim 1, wherein said pipes are hairpin-type pipes or bent pi es. I

5. Method 0 claim 1, wherein said filling of said closed Interconnected pipes with said liquid is done under pressure of about 25 KgJcm. thereby to remove air bubbles from said closed interconnected pipes.

6. Method of claim 1, wherein prior to said heating said pipes and said fins are cleaned.

7. Method of claim 1, wherein said liquid is water and said heating is at a temperature within the range of between 230 and 270 C. for a period of between 20 to 40 minutes.

8. Method of claim 1, wherein said pipes are of copper or copper alloy, and said fins are of aluminum or aluminum alloy.

9. Method of claim 1, wherein said heating is accomplished by circulating hot air unto at least said raised portions of said fins.

Claims

1. A method of manufacturing a finned-tube-type assembly heat exchanger comprising the steps of A. providing a plurality of fins, each of said fins substantially consisting of a flat sheet of metal having therein a plurality of holes of particular diameters and a plurality of raised portions located in the vicinity of said holes; B. providing a plurality of lengths of pipe and assembling said fins and said lengths of pipe by means of fitting said lengths of pipe through said fins, said lengths of pipe having diameters smaller than said diameters of corresponding holes; C. interconnecting said pipes to form a single passageway; D. closing tightly one end of said interconnected pipes; E. filling said interconnected pipes with liquid; F. closing tightly the other end of said interconnected pipes; G. heating at least said fins thereby to transmit heat from said fins to said pipes until said liquid is heated above its boiling point and converted to superheated vapor thereby to enlarge the diameter of said pipes by cubic expansion of said vapor and tightly bind the outer peripheries of said pipes to the inner peripheries of said holes; H. cooling the expanded assembly; and I. removing said liquid from the assembly.

4. Method of claim 1, wherein said pipes are hairpin-type pipes or bent pipes.

5. Method of claim 1, wherein said filling of said closed interconnected pipes with said liquid is done under pressure of about 25 Kg./cm.2 thereby to remove air bubbles from said closed interconnected pipes.

7. Method of claim 1, wherein said liquid is water and said heating is at a temperature within the range of between 230* and 270* C. for a period of between 20 to 40 minutes.