US2499901A - Fin tube assembly - Google Patents

Description

March 7, 195%.? J. w. BROWN, JR FIN TUBE ASSEMBLY 2 Sheets-Sheet 1 Filed Aug. 31, 1946 INVENTOR.

N N W m B W N. H O J ATTOR/VE Y8 March 7, 1950 J. w. BROWN, JR

FIN TUBE ASSEMBLY 2 Sheets-Sheet 2 Filed Aug. 51, 1946 I INVENTOR.

I i Nil [in Iil 1] FA I Al I? I III! III III ATTORNEYS JOHN- w. BROWN JR. BY

' on the adjacent tube, that Patented Mar. 7, 1950 FIN TUBE ASSEMBLY John W. Brown,

Brown Fintube Company,

poration of Ohio Jr., Elyria, Ohio, assignor to Elyria, Ohio, a cor- Application August 31, 1946, Serial No. 694,228 2 Claims. (Cl. 257-239) This invention relates to heat exchangers and more particularly to heat exchangers in which a series of tubes are mounted parallel to each other with one commodity passing through the tubes and the other circulating over their exterior.

In order to provide a maximum heat transfer efficiency in apparatus of this kind the tubes are frequently provided with external fins as illustrated and claimed in my United States Patent Number 2,261,137 issued on November 4, 1941 and entitled Heat exchanger conductor. Such tubes are provided with a plurality of external fins that preferably extend from one end of the tube to the other and comprise a base portion and a fin portion. The base portion is secured to the exterior of the tube as by welding to insure efficient heat transfer between the tubing and fin and the fin comprises a fiat sheet portion extending outwardly from the tube to lie in the path of the commodity that circulates around the tube exterior. A heat exchanger of the type employing a series of generally parallel tubes will preferably have the tubes positioned as close to each other as may be, in order that the commodity flowing externally of the tubes may come in contact with as much tube or fin surface as possible. At the same time it is necessary to space the tubes radially of each other a sufficient distance to permit them to be mounted properly in a heat exchanger and also to insure that thefiow of the commodit on the outside of the tubes shall not be impeded by undue proximity of the fins of one tube to the fins of the next adjacent tube. Preferably the tubes should be so spaced from each other that, although the fins of two adjacent tubes lie close together, the fins of one tube do not enter within the region bounded by the outer edges of the fins is, do not intermesh. In the construction of heat exchangers with externally finned tubes it was been customary to support the finned tubes by means of spaced supports in the form of perforated plates through which the tubes extend, and by which they are. spaced, with respect to each other. The tubes generally are employed in pairs with the adjacent ends of the tubes of a pair interconnected by a return bend so that one tube provides on its interior an outgoing passage for a commodity and the other tube of a pair a return passage. In such heat exchange apparatus the supports must be placed in position before the return bends of the respective pairs of tubes are secured in place, and when the assembly is completed an inner return bend and the tubes to which it is secured cannot be replaced without dismantling the entire assembly.

Such a construction also requires that the tubes be inserted within the supports in openings of sufficient diameter to receive both the tube and the fins secured to it to permit removal of a tube through a hole in one of the supports for repairs or for other reasons. This construction, in which the holes in the supports have a diameter equal to the external diameter of the fins, requires the tubes to be spaced somewhat farther from each other than is otherwise desirable to afiord sufficient material between holes in the header.

The general object of the present invention is to provide a heat exchanger and tube assembly in which the axes of adjacent tubes are not spaced from each other a distance that is substantially greater-than the external diameter of the respective fins. Another object of the invention is to provide a heat exchanger tube assembly in which all of, the tubes may be assembled and secured together as a single unit and thereafter be mounted in the shell of a heat exchanger. Another object of the invention is to provide a tube assembly in which the outer tubes may be spread apart without dismantling the assembly to permit access to an inner tube in order that it may be repaired or replaced. Still another object of the invention is to provide a heat exchanger of simplified construction, reduced first cost and lowered cost of maintenance. An additional object is to provide a heat exchanger including a plurality of generally parallel externally finned tubes that are so strapped together as a unit that they may be retained in pro-determined spaced relation independent of any header or tube sheet with which they may be used.

Further objects and advantages of the invention will become apparent from the following description of a preferred form thereof, reference being made to the accompanying drawings. The novel features of the invention are summarized in the claims.

Referring now to the drawings: Figure 1 is a perspective of one type of heat exchanger tube that may be embodied in the present invention; Figure 2 is a side elevation of one form of heat exchanger constructed in accordance with the present invention; Figure 3 is an axial section through Figure 2 in a plane parallel to that figure; Figure 4 is a perspective showing a plurality of heat exchanger tubes, provided with external fins, and assembled as a unit; and, Figure 5 is an enlarged, fragmentary section through Figure 2 side of the tube T approximately as indicated by the line thereon.

To illustrate the type of finned tube from which a heatexchanger assembly as embodied in the present invention may be constructed reference may be made to my Patent Number 2,261,137 referred to above; Such a tube, as shown in Figure 1 of the present disclosure, may comprise a tubular member T to which a number of finned members H are secured. Each fin member is preferably of channel section and tegrally therewith, the base and fins being of substantially the same thickness. The base portions may be curved slightly to conform substantially to the outer surface of the tube and are secured to the tube T by a series of resistance welds.

may comprise a base portion [2 and upstanding fins l4 formed in- Heat transfer between a commodity on the inand on the outside may take place either through the tube wall directly or through the tube wall and the finned portions l4, the rate of heat transfer through the metallic fins and tube generally being greater than through the adJacent commodity. Although the finned members on the tube T are shown as U-shaped it will be apparent that other structural shapes, as for instance an L-shape, may be employed if desired. A simple heat exchanger employing a tube as shown in Figure 1 can consist of a single tube in which one commodity flows over the exterior and the other through the interior. For the great majority of uses it is very desirable to provide a plurality of such finned tubes secured together in generally parallel relation and mounted inside of a heat exchanger shell.

In Figures 2 and 3 of the drawings, I have illustrated a preferred form of my invention as embodied in a heat exchanger adapted to be disposed within a tank and to heat a fluid as it is withdrawn from the tank through the exchanger. In these figures there is shown a portion of a tank In in phantom outline in which the elongated steel shell of the heat exchanger is mounted by a mounting flange 2| welded thereto and secured to said tank in any well known manner. At the right-hand end of the assembly in Figure 2 the heat exchanger is shown as provided with a dished head 24 to which is secured an annular flange 26 adapted to register with 2. correspondin flange 21 secured to the end of the shell 20. Suitable bolts and nuts 28 hold the flanges together to provide an integral unit as shown in Figure 2. These flanges also secure in place a tube sheet 30 (Figure 3) to which is secured the heat exchanger tubes in a manner hereafter to be described. A partition wall 33 is secured at its ends to the tube sheet In and the interior of the wall of dished head 24 and divides the head space into two chambers 33a and 33b. Suitable sealing gaskets at the edges of the flanges prevent leakage between the head portion 24 and the shell interior and also prevent leakage to the outside atmosphere. A

The tube sheet 30 serves to divide the heat exchanger into two portions, one of which receives the commodity that is circulated on the exterior of the tubes T and the other of whichvreceives the commodity that is circulated on the interior. In the former case the commodity flows from the tank Ill into the shell 20 at the left-hand end 32 (Figure 2) as generally shown in Patent No. 2,174,318, issued September 26, 1939, to Guy T. Ellis. The commodity passes around the exterior of the tubes'flowing from the left to the right (Figure 2) and is removed through a port 34.

0 sem passage at 35 (Figure 3) and passes through chamber "a to enter through the tube sheet it into the upper tubes T of the assembly. This commodity passes through the tubes from right left and then passes through return bends 31 to return to the tube sheet from left to right through the lower tubes T. As indicated above, two tubes of a pair are connected by a respective return bend to provide both an outgoing and a return passage with respect to the tube sheet 30 for the internally carried commodity. After the commodity has returned to chamber 33b of the head portion 24 it is removed therefrom (as condensate in the case of steam) through an opening I! at the bottom.

The assembly just described provides for the exchange of heat between a commodity flowing over the exterior of the tubes T and one flowing through their interior and is illustrative of one form of the invention. It will be apparent that app ratus that differs in some respects from the form illustrated and described above may be constructed within the scope of the present invention to perform a heat exchange function.

The heat exchanger tubes T illustrated in Figure 3 are mounted in the shell 20 as an integral assembly that is supported wholly within itself and their connection to the tube sheet 30 is not necessarily for support but primarily to position the parts for operation. To this end each tube T is tightly fitted in its corresponding opening in the tube sheet and preferably expanded outwardly to enter annular recesses formed in the opening and insure that the parts are tightly secured together.

As indicated above it is preferable to have as much effective area of tubes and fins in the asbly as possible in order that the most efiicient heat transfer between the two commodities may take place. For this reason it is very desirable that the tubes be placed as close to each other as possible and yet sufilciently far enough apart so that the fins of one tube do not enter region bounded by the outer edges of the fins of adJacent tubes. Such spacing is insured in apparatus embodying the present invention by placing on various tubes a plurality, generally three or four, of straps that encircle the tube and in effect define a plurality of very short cylindrical shells about the tube and its associated external fins. The straps are preferably tack welded to the outer edges of the fins with which they contact.

A tube that has been provided with such a plurality of straps 40 (Figure 3) is mounted adjacent one or more externally finned tubes that are not so strapped. These tubes may be held close together in such relation that the adjacent fins on one tube are very close to the adjacent fins on another tube but do not overlap due to the presence of the straps 40. By judiciously positioning those tubes that have been externally strapped in a bundle of such tubes an assembly as shown in Figures 3 and 4 may be made up in which none of the fins of one tube will enter within the region bounded by the outer edges of the fins of an adjacent tube.

Such an assembly will comprise a large number of substantially parallel tubes T, each provided with a series of external fins I4 in such manner that 'none of the fins of any one tube overlap appreciably the fins of any other tube. At the same time the tubes are so closetogether that a maximum number are positioned within a given cross-sectional area and yet are held far enough apart so that the flow of a commodity over their exterior is not unduly retarded.

In order that a group of tubes may be held in position with respect to each other as described above and retained together as a single unitary assembly, a plurality of straps 45 surrounding all of the tubes are provided as shown in Figure 4. These straps, preferably three or four in number, hold all of the tubes within them firmly together as a unit and eliminate the necessity of mounting the tubes in transverse supports as has been customary heretofore. A suitable arrangement of tubes and bands is shown on an enlarged scale in Figure 5, which illustrates eight of the tubes of the assembly. As shown therein the bands 40 prevent intermeshing of the fins 01' adjacent tubes without requiring bands on every tube, while the straps 45 hold the assembly together. After such an assembly has been prepared and strapped as shown in Figure 4 the respective pairs of tubes may be connected together by the return bends 31.

Generally the outermost tubes of a bundle will form one pair connected by a return bend and then the next innermost tubes also will be connected and finally the innermost tubes. Thus, referring to Figure 4, tubes 46a and 46b will be connected together to make a pair as will tubes 41a and 41b and tubes 48a and 48b. In the assembly shown there are two pairs of outermost tubes, four pairs of tubes in the intermediate layer and five pairs of tubes in the inner layer.

Occasionally it is necessary to obtain access to the tubes of a pair, as for instance the tubes indicated at 48c and 48d. With the constructions heretofore used it became necessary to dismantle the assembly entirely in order to get at these two tubes. With the present invention it is necessary only to remove the binding straps 45 and then spread the tubes sufliciently, whether connected to the return bends or not, to attain access to any desired tube or pair of tubes.

An assembly of tubes as illustrated in Figure 4 is mounted in the shell of the heat exchanger as shown in Figure 3. In the embodiment of the invention illustrated the disconnected ends of the tubes are mounted as described above in the tube sheet 30 and the whole mounted as a unit within the shell 20 and secured in place by the bolts 28. Considerable saving in time and labor is effected by this manner of construction and unitary assembly as distinguished from heat exchangers for the same general purpose as made in the ways heretofore known in the art.

From the foregoing descrpition of a preferred form of my invention it will be evident that I have provided an eflicient and economical externally finned tube type heat exchanger in which full advantage is taken of the heat transfer capacity of the fins. Exchangers embodying my invention not only are efllcient from the standpoint of heat transfer but also are simple to assemble and maintain. They may be produced economically and rapidly and can be made of materials and in sizes and types to meet a wide variety of uses.

Various changes and modifications in my invention will be apparent to those skilled in the art. It is therefore to be understood that my patent is not limited to the preferred form of my invention described herein and that it is contemplated that changes and modifications within the scope and spirit of my invention may be made by those skilled in the art. Therefore it is to be understood that the description herein is given by way of example and not by way of limitation and that my patent is not limited to the forms described herein or in any manner other than by the appended claims when given the range of equivalents to which my patent may be entitled.

Iclaimz' 1. A heat exchanger comprising in combination, a bundle embodying a plurality of heat exchanger tubes mounted parallel to each other, said tubes having a plurality of external fins extending substantially parallel to the axes of said .tubes, an elongated heat exchanger shell surrounding said bundle of tubes and adapted to constrain a fluid to flow in a longitudinal direction over the exterior surfaces of said tubes, straps encircling certain of said tubes and the fins thereon to provide continuous annular surfaces encircling the fins on said certain tubes without substantially obstructing the flow of fluid along the exterior of said tubes, said straps engaging a fin on an adjacent tube to separate said tubes and to prevent the fins on adjacent tubes from intermeshing, and means encircling said bundle of tubes and holding the tubes therein as close to each other as said straps will permit.

2. A heat exchanger according to claim '1 wherein the straps are tack welded to the outer edges of the fins which they encircle.

JOHN W. BROWN, JR-

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Price Sept. 23, 1924 Kearney Dec. 6, 1938 Bergdoll Feb. 7, 1939 FOREIGN PATENTS Country Great Britain France Number Date Nov. 20, 193'? Sept. 12, 1922 Number

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