US3249156A

US3249156A - Fin-on-tube type heat exchanger

Info

Publication number: US3249156A
Application number: US360606A
Authority: US
Inventors: Thomas A Mcgrew
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1964-04-17
Filing date: 1964-04-17
Publication date: 1966-05-03
Anticipated expiration: 1983-05-03

Description

May 3, 1966 T. A. M GREW FIN-ON-TUBE TYPE HEAT EXCHANGER Filed April 17, 1964 INVENTOR.

THOMAS A. McGREW BYW t-us ATTORNEY United States Patent M 3,249,156 FIN-ON-TUBE TYPE HEAT EXCHANGER Thomas A. McGrew, Fern Creek, Ky., assignor to General Electric Company, a corporation of New York Filed Apr. 17, 1964, Ser. No. 360,606 3 Claims. (Cl. 165-181) The present invention relates to heat exchangers and is particularly concerned with a heat exchange coil of the fin-on-tube type comprising a plurality of parallel tubular sections passing through a plurality of transversely disposed parallel fins.

Heat exchangers of the fin-on-tube type employed, for example as condensers or evaporators in refrigeration equipment comprise connected parallel passes of tubing for conducting the refrigerant and a plurality of thin metal fins which are designed to increase the heat transfer between the refrigerant and the air passing through the heat exchanger. The design of a commercially acceptable heat exchanger requires the consideration of a number of factors. The heat flow between the tubes and the fin structure is dependent upon the area contact of the fin material with the surfaces of the tube. In order to increase this contact and hence the heat transfer rate, the use of relatively thick and strong fin material and/or the bonding of the fin material to the tube by means of solder or the like is indicated. However, both thick fin materials and the soldering operation involve an increased cost of the heat exchanger. Also, it is not practical at present to use soldering or brazing materials with aluminum fin stock. Heat transfer between the fin material and the air circulated over the heat exchanger is a function more of fin surface area than fin thickness. Therefore within limits, it is desirable to use a relatively large number of relatively thin fins both for increasing the heat exchange area and also for limiting the material cost of the heat exchanger.

It is a primary object of the present invention to provide a new and improved heat exchanger particularly characterized by an optimized fin construction from the standpoint of cost and heat transfer requirements. Further objects and advantages of the present invention will become apparent from the following description and features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of the present invention, there is provided a fin-on-tube heat exchanger comprising a plurality of spaced fins including a plurality of spaced openings for receiving the tube components of the heat exchanger. Each of the fins is corrugated over its entire area and the pattern of corrugations is designed to provide maximum strength in the fin material at the tube openings and in the remaining areas between the tube openings to facilitate manufacture of the heat exchanger. These results are obtained primarily by a corrugation pattern that provides continuous corrugations radially extending from one tube opening to each adjacent tube opening.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

FIGURE 1 is a general view of a fin-on-tube heat exchanger embodying the present invention;

FIGURE 2 is an enlarged view of a portion of the heat exchanger of FIGURE 1 illustrating the corrugated fin pattern or structure of the present invention; and

FIGURE 3 is an edge view from line 3-3 of FIG- URE 1.

Referring to FIGURE 1 of the drawing, the illustrated fin-on-tube heat exchanger comprises tubing formed into a sinuous or serpentine shape to provide a plurality of Patented May 3, 1966 parallel passes 1 connected by return bends 2, each of the latter serving to connect two of the passes. For a low cost, lightweight heat exchanger, the tubing is preferably composed of aluminum as are also the fins 3 which are operatively associated with the passes 1 in order to obtain a good heat transfer between the fins and the passes.

In accordance with the present invention, each fin 3 contains a plurality of openings 4, each of which is adapted to receive one of the passes 1. These openings, as illustrated in FIGURE 2, are preferably arranged in one or two parallel rows with the openings in each row spaced from one another and spaced from the openings in the remaining rows. More specifically for two rows, the tube receiving openings 4 and hence the tube passes 1 contained within these openings are so arranged that the openings in one row are aligned with the openings in the other row or in other words, as viewed in FIGURE 2, the tube openings 4 in the upper row are directly above corresponding tube openings in the bottom row.

This configuration of the tube openings within the fin 3 permits a corrugated pattern in the fins 3 which is designed to provide maximum strength for the individual fins even though they may be made of relatively thin material, such as .005 inch aluminum sheet.

More specifically, while corrugated fin structures having various corrugation patterns have previously been used or proposed for strengthening purposes or for the purpose of improving the heat transfer between the fin surfaces and the air circulating over and between the fins, the fins of the present invention are characterized by a corrugation pattern which optimizes fin construction on the basis of material cost and strength and heat transfer requirements.

The fin of the present invention is shown in detail in FIGURES 2 and 3 of the drawing illustrating a portion on one fin in which the tube openings are arranged in two parallel rows with the openings in one row directly opposite the openings in the other row or, in other words, are arranged so that four adjacent openings comprising two from each row are at the four corners of a rectangle.

The corrugated pattern for the fins 3 is a repetitive pattern, the unit pattern of which is defined by the rectangle. The unit pattern includes a plurality of continuous corrugations extending radially from each tube opening to the adjacent tube openings in the same row and in the adjacent row and this series of corrugations defining the perimeter of the unit pattern area encloses an inner area in which the fin material is corrugated to provide a plurality of intersecting curved corrugations defining concentric rectangles having relatively concave sides.

More specifically, the fin material between any two adjacent tube openings is provided with one or more relatively straight corrugations 8 extending radially from one tube opening directly to an adjacent tube opening and a plurality of

curved corrugations

9 and 10 of increased curvature which also extend radially from one tube opening and radially into an adjacent tube opening. These

continuous corrugations

8, 9 and 10 between adjacent openings may be described as having substantially the same shape and arrangement as the magnetic lines of force between unlike magnetic poles. These continuous corrugations extending radially from each tube opening provide maximum pressure strength for the fin material defining the tube opening and thereby permits maximum pressure contact between the tube and fin material for good heat transfer properties. Also, as will be described more fully hereinafter, they provide maximum rigidity for the fin material between adjacent tube openings to facilitate assembly of the fins and the passes 1 without distortion or bending of the fins.

The central area of the unit corrugation pattern, that is the area within the series of corrugations extending continuously from each tube opening to an adjacent tube opening is also corrugated or rigidized by a plurality of interconnecting corrugations 11 and 12 defining concentric or rectangles having concave sides whereby these areas of fins 3 are also strengthened.

Since the fins 3 are characterized by a repetitive pattern of corrugations, the corrugations such as 9a and 10a correspond to

corrugations

9 and 10 but terminate in the various edges of the fin material as indicated in FIGURE 3 of the: drawing while one or more of the corrugations such as 11 terminate as corrugations 11a in the edges of the material. Thus the corrugations 9a, 10a, 11a and comparable corrugations strengthen the edges of the fin material and permit the use of a thinner fin stock insofar as these areas are concerned.

Preferably the corrugated fins are manufactured by pressing fiat fin stock between platens having surfaces designed to provide the desired corrugated patterns and at the same time or subsequently punching the fin openings 4 and the slots 14 connecting each of the openings to an edge of the fin stock. The purpose of the slots 14 is to permit assembly of the tube passes 1 Within the openings 4 employing any of the well known means for accomplishing this result. For example, the passes 1 may be flattened or made into an oval configuration of a dimension such that they can readily be inserted through the slots 14 and into the tube openings 4. Thereafter, either by hydraulic means or by applying suitable pressure to the exposed surfaces of the tube contained within the openings 4, the tube passes are pressed into a circular configuration and in tight engagement with the adjacent edges of the fin material defining the openings 4. In this process, the radially extending

corrugations

8, 9 and 10 provide maximum fin strength in these areas to resist any forces resulting from the deformation of the tube passes 1 and thereby to provide an intimate contact between the fin edges and the passes.

Alternatively the notches or slits 14 can be omitted and various straight pieces of tubing corresponding to the passes I inserted into the openings 4 and thereafter connected by return bends to provide the finished heat exchanger.

Due to the fact that a thinner fin material can be used when provided with a corrugated pattern of the present invention, relatively low cost heat exchangers can be produced using lightweight material such as aluminum. The overall irregular fin surface provided by the corrugations also provides for a greater heat transfer rate between the fin surfaces and the air circulated over the heat exchanger while the corrugated edges of the tube openings in contact with the passes 1 provide maximum contact between the passes and the fins without use of soldering materials or the like. The

continuous corrugations

8, 9 and 10 between the various tube passes provides maximum rigidity in the fin structure for resisting the pressures which may be applied to the passes 1 after assembly in the openings 4 for the purpose of deforming these passes into intimate engagement with the fin edges.

While the invention has been described with reference to a particular embodiment thereof it will be understood that it is not limited thereto and intended by the appended claims to cover all such modifications as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A heat exchanger comprising a plurality of spaced fins each including openings for receiving the tube components of said heat exchanger,

said openings being positioned so that each set of four openings form the four corners of a rectangle,

each of said fins having a repetitive pattern of corrugations over substantially the entire area thereof,

a unit pattern of said corrugations being defined by said rectangle,

said unit pattern including a series of corrugations extending radially from each of said openings and terminating in an adjacent opening.

2. A heat exchanger of the fin-on-tube type comprising a plurality of spaced fins each including spaced openings for receiving the tube components of said heat exchanger,

said openings being positioned whereby four of said openings form the four corners of a rectangle,

a unit pattern of said corrugations being defined by said rectangle,

said unit pattern including a series of corrugations extending radially from each of said openings and terminating in an adjacent opening,

the central area of said unit pattern comprising a plurality of intersecting curved corrugations defining concentric rectangles having concave sides.

3. A heat exchanger comprising a plurality of spaced fins each including at least one row of spaced openings for receiving the tubular components of said heat exchanger,

each of said fins having a corrugated pattern over sub stantially the entire area thereof and including continuous corrugations extending between adjacent openings extending radially from said adjacent openings and having substantially the same shapes and arrangement as the magnetic lines of force between unlike magnetic poles.

References Cited by the Examiner UNITED STATES PATENTS 1/1905 Humphrey. 10/ 1925 Modine.

1/1933 Caldwell 165-182 X N. R. WILSON, Assistant Examiner.

Claims

1. A HEAT EXCHANGER COMPRISING A PLURALITY OF SPACED FINS EACH INCLUDING OPENINGS FOR RECEIVING THE TUBE COMPONENTS OF SAID HEAT EXCHANGER, SAID OPENINGS BEING POSITIONED SO THAT EACH SET OF FOUR OPENINGS FORM THE FOUR CORNERS OF A RECTANGLE, EACH OF SAID FINS HAVING A REPETITIVE PATTERN OF CORRUGATIONS OVER SUBSTANTIALLY THE ENTIRE AREA THEREOF, A UNIT PATTERN OF SAID CORRUGATIONS BEING DEFINED BY SAID RECTANGLE, SAID UNIT PATTERN OF SAID CORRUGATIONS BEING DEFINED BY TENDING RADIALLY FROM EACH OF SAID OPENINGS AND TERMINATING IN AN ADJACENT OPENING.