US2259433A - Heat exchanger - Google Patents

Description

Oct. 14, 1941. w. H. KITTO HEAT EXCHANGER Filed Nov. 15, 1937 INVENTOR Zlzam H Kiflo ATTORNEY Patented Oct. 14, 1941 HEAT EXCHANGER I William H. Kitto, Canton, Ohio, assignor to The Hoover Company, North Canton, Ohio, a corporation of Ohio Application November 15, 1937, Serial No. 174,601

. 4 Claims. (01. 29-1573) This invention relates to the art of making tubular structures and more particularly to fluid heat exchangers fabricated from standard tubmg.

It is commonplace to utilize tubing of different diameters to mak heat exchangers by inserting a smaller tube in a large tube, and then bending the telescoped tubes into a desired shape. Such constructions are easily made from standard, readily obtained materials. This form of heat exchanger is very eflicient, inexpensive and free from sharp bends.

However, prior art heat exchangers of this type are subject to certain disadvantages. One of the chief difficulties is that in making the concentric tube heat exchanger, the operator has no control' over the inner tube. Consequently, in bending thetubes into a desired shape, the bending operations are directly applied to the outer tube, and only indirectly to the inner tube. As a result, the inner tube is not coaxially positioned within the outer tube, and the inner tube may lie closely against the inside wall of the outer tube adjacent the bends. Therefore, the fluid passing between two tubes is greatly impeded wher the tubes lie close together, and the'heat exchange is poorest where the inner wall of the outer tube is furtherest from the inner tube.

According to this invention, I propose simple modifications in the constructions heretofore known which permit the retention of the many desirable characteristics of concentric tube heat exchangers and yet entirely avoid the disadvantages herelnabove pointed out, as well as others of lesser importance.

It is accordingly an object of my invention to provide a new and improved heat exchanger. More specifically it is an object of fny invention to provide a heat exchanger having inner and outer tubes and means for spacing the tubes with respect to each other. Another object is to provide means for spacing the curved sections of telescoped tubes with respect to each other. A further object is to provide means for connecting a transverse tube to curved telescoped tubes. Another object is to provide methods of making heat exchangers. Other objects and advantages of the invention will be apparent in the specification and drawing, wherein:

Fig. #1 is a perspective view of the heat exchanger;

Fig. 2 is a section along the line 2-2 of Fig. 1;

Fig. 3 is a section along the line 3-3 of Fig. 1;

Fig. 4 is a section similar to Fig. 3 illustratin: another embodiment of the invention.

The heat exchanger shown in Figures 1 through 3 comprises telescoped metal tubes i0 and II coiled as indicated in Fig. 1 to provide arcuate bends l2 and i3 and straight portions 14. The outer tube Ii has its ends 15 sealed to the projecting ends of the inner tube I0. Welded to the outer tube II along the inner arc of the bend i3 is a transverse pipe i1, and a pipe I8 is welded to the opposite end of th outer tube II, and which communicate with an annual passageway is formed between the telescoped tubes 10 and Ii to provide passage for the fluid therethrough.

The arcuate bends i2 and 13 are formed by bending the telescoped tubes as a unit. In the bending operation the operator has control of the outer tube ii and can bend it into any desired degree of curvature. The inner tube in, however, is not under the control of the operator but is bent by th pressure exerted thereon by the outer tube I. In forming, for example the bend I3 as shown in Figure 3, the inner tube in tends to take a flatter arc than the outer tube ii, so that the center portion 20 in the bend of the inner tube [0 tends to bear against the center of the inner arc of the outer tube II, and the opposite ends 22 on the outer arc of the inner tube [0 tend to bear against the opposite ends 23 on the outer arc of the outer tube ii, to thereby interrupt flow of fluid in the passageway 19 and to the transverse tube [1.

One method of correcting this objectionable construction is shown in Figures 1 to 3, wherein the outer tube II is provided with longitudinally circumferentially spaced indentations 25 throughout the curved or arcuate portions thereof. These indentations bear against the inner tube ill to space it in concentric relation with respect to the outer tube l I throughout the curved portions l2 and I3. If inner tube I0 is co-axially positioned in outer tube H at the curved portions of the exchanger, the straight sections of tubes I0 and H will be retained in co-axial relation in the unbent portions H of the heat exchanger. The transverse tube H is welded, as indicated at 26 in the opening 24 to the outer tube I I, and due to the indentations 25 communicates freely with the annual passage l9.

One method of making a heat exchanger of this type consists of forming the openings 24 at desired point or points in the outer tube II for the desired number of transverse tubes l1 and I8, inserting the smaller tube III in the outer tube ll, forming groups of spaced-apart dimplesor indentations 25 longitudinally and circumferentially around the outer tube ll wherever the same is to be bentor curved, bending both tubes as a. unit into a coil so that a group of indentations is located at each bend as shown in Fig. 1, and then welding the transverse pipes l1 and I8 to the outer pipe II. If desired the dimpies may be formed in the outer tube prior to inserting the smaller tube, and the transverse pipes may b welded to the outer pipe prior to "bending the tubes into a coil.

outer tube II, to space the inner tube from the.

opening 36 to provide an uninterrupted path for fluid between the transverse pipe llv and the annular passage 19. If desired, indentations may be provided at substantially the opposite ends of the outer are on the outer tube II to space the inner tube Hi from the outer tube ll throughout the length of the bend.

Ifit is desired to form a heat exchanger employing this construction the outer tube II is provided at a certain point or points with the desired number of openings 36 and the smaller tube I is arranged within the larger tube I l and the indentations 35 are formed in the outer tube II in the vicinity of the openings 36. The two tubes are then bent as a unit into the desired shape. Due to the indentations 35 the inner tube III will be spaced from the inner arc of the outer tube II at the opening 36.

Although the indentations have, been described as located at the bent or curved portions of the tubes, it will be understood that the indentations may be distributed over straight sections of tubing as well to assure co-axial positioning of the tubes throughout the length of the heat exchanger. Where the straight sections of tubing are short, as in Figure 1, it is not usually necessary to locate indentations in the straight portions.

It will thus be apparent that the present invention provides a new and simple method of constructing a concentric tube type heat exchanger especially suited for mass production. A minimum number of dies, tools, implements,

and operations are required. The only change 'a heat exchanger construction which is very simple, economical, and highly eflicient in operation, as well as one in which the heat exchange fluids flow freely to and from the exchanger, as well as through the respective passages 01' the exchanger.

I claim:

l. A heat exchanger, comprising an outer tube, an inner tube disposed in and spaced from said outer tube, said tubes being bent to form a coiled heat exchanger, a tube connected to and extending laterally from said outer tube along the inner arc of one of said bends, and indentations in the wall of one of said tubes along said inner arc of said tube bend for spacing said inner tube from said outer tube to provide a passageway between said spaced pipes and said transverse tube to facilitate the free passage of a fluid between said laterally extending tube and said heat exchange coil.

2. That .method of constructing a fluid heat exchanger which comprises cutting lengths of tubing of different diameters into sections of predetermined length, the sections of smaller diameter tubing being longer than the sections of larger diameter tubing, inserting a section of smaller diameter tubing into a section of larger diameter tubing until the ends of the smaller tubing project beyond both ends of the larger tubing, placing groups of indentations in the surface of' the larger tubing at spaced points therealong which indentations are of sufllcient size and spaced in such manner as to retain said smaller and larger sections in a definite position with respect to one another, and then bending said tubing sections at said groups of indentations to form a coil having a substantially continuous annular fluid passage between said tubing sections from the inlet to the outlet thereof.

3. A heat exchange device comprising two continuous conduit sections one of which is of smaller diameter than the other, said smaller section being positioned within the larger section so as to provide'two fluid passageways one of which is through the smaller section and the other of which is between said smaller and larger conduits, said smaller conduit being longer than the larger conduit so as to extend beyond the ends of the latter, said conduit sections being bent into a coil, and groups of indentations in said larger conduit positioned so as to prevent the smaller conduit from contacting the inner surface of the larger conduit except at said indentations, said groups of indentations being located at the coil bends.

4. A heat exchange device as defined in the preceding claim in which the larger conduit has an opening through the side thereof, a conduit joined to the larger conduit over said opening,

and indentations in said larger conduit adjacent I said opening to hold the inner, smaller conduit away from said opening to permit the free passage of fluid through said opening.

WILLIAMH.KI'I'TO.

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