US2183160A - Heat exchanger - Google Patents

Description

12, 1939- c. D. couLTER Er AL HEAT EXCHANGER Filed Jan. 19, 1938 2 Sheets-Sheet 1 Dec, 12, 1939. c. D. COULTER l-:r AL

HEAT EXCHANGER Filed Jan. 19, 1958 2 Sheets-Sheet 2 n. NM.

EESEESBSISSSEISSS Nr IESSSEEEBESQS QESSEBBIBSSSIEBSB ESEBEBBHHBHRIBB INVENTOR` 70kg/Ica 0. Cow/fn; BY fQ/w/n A? COX.)

ATTORNEY.

Patented Dec. 12, 1939 UNITEDy STATES PATENT OFFICE Cox, Huntington Park, Calif.,

assignors to Southwestern Engineering Company, Los Angeles, Calif., a corporation of California Application January 19, 1938, Serial No. 185,710

4 Claims.

This invention relates to heat exchangers and to means for improving their eiiiciency.

It is a principal object of the invention to provide a heat exchanger of high efficiency.

An object of our invention is to provide means in a heat exchanger for directing the flow of fluid therethrough so as to result in an improved heat transfer.

Another object is to provide a heat exchanger having means for confining the flow of fluid therethrough to paths in which heat exchange may take place.

Still another object of the invention is to provide convenient means for mounting the fluid confining means in a heat exchanger.

These and other apparent objects we attain in a manner which will be clear from consideration of the following description taken inconnection with the accompanying drawings, of which:

Fig. 1 is a cross-sectional view of one form of our improved heat exchanger taken along a vertical diameter of the shell.

Fig. 2 is a sectional view of the heat exchanger of Fig. 1' taken along the line 2 2.

Fig. 3 is a cross-sectional view of our improved heat exchanger taken along the horizontal diameter 3 3 of the shell.

Fig. 4 is a cross-sectional view of an alternative form of heat exchanger employing the principles of our invention, taken along a vertical diameter of the shell.

Fig. 5 is a sectional'view of the heat exchanger of Fig. 4 taken along the line 5 5.

Fig. 6 isa sectional view of the heat exchanger of Figs. 4 and 5, taken along the broken line 6 6.

Fig. 7 is a view of the heat exchanger of Figs. 4 and 5 with the shell partially cut away along the line 1 1.

The heat exchanger in which our invention is herein illustrated as being employed includes an elongated cylindrical shell I0 with outwardly directed anges I I and I2 at the ends, a radially directed inlet I3 at one end, and a radially and oppositely directed outlet I4 at the other end. One end of the shell Ill is closed by shell cover I5 having a flange I6 which is bolted tightly against the flange Il by bolts I1. At the other end of the shell is located a relatively short cylindrical member I3, called a channel, and providing at its ends the flanges I9 and 28. Between the anges I2 and I9 is securely clamped a tube sheet 20 by action of the bolts 2l. The tube sheet 20 is a circular plate forming the terminal support for the bundle of tubes 22. The tubes 22 pass through holes bored in the tube sheet 20 and are expanded at their ends to retain them in the tube sheet. The tubes extend longitudinally of the shell for nearly its full length and terminate in a similar manner in a second tube sheet 23 forming part of a floating head. A cover 24 is bolted to the tube sheet 23 to make the tube bundle fluid tight at this end. It will be observed that the tube bundle is longitudinally fixed at only one end which permits it to freely expand and contract within the shell I0 in response to temperature changes without placing stress upon the shell.

The channel I8 is provided with an inlet 25 at the bottom, and an outlet 26 at the top. A partition 21, welded to channel I8, extends across the full diameter of the tube sheet and separates the inlet from the outlet within the channel I8. A cover plate 29 is bolted to the flange 23 to make this end of the channel fluid-tight. As a result of this construction, fluid enters through inlet 25, passes through the tubes comprising the lower half of the tube bundle 22 in the direction of the arrows shown, turns within the space between the tube sheet 23 and the cover 24returns through the tubes comprising the upper half of the tube bundle and passes out through the outlet 26.

'I'he function of the heat exchanger is to transfer heat from one iluid to another, and to this end a uid is caused to enter the shell I0 through inlet I3, pass around and between the tubes 22 and leave through outlet I4, so that heat may be exchanged between this fluid and that inside the tubes 22. In order to assure uniform transverse circulation of the iiuid around the tubes and a better contact of all the tubes with the body of fluid, the baiiies 3l and 32 are alternately located at intervals longitudinally along the tube bundle. The bailles 3| and 32 are circular sheets of about the same diameter as the shell I0 and through which the tubes 22 pass, the bailles fitting the outsides of the tubes closely to prevent iiowv of fluid through the ballles. Each of the baliles 3l has a segment cut away -at one side to provide 4a uid passage 33, and each of the alternately disposed batlies 32 has a segment cut away at the opposite side to provide a fluid passage 34. As a result of this construction, the fluid entering inlet I3 passes horizontally back and forth between the tubes in the transverse passages defined by baflles 3| and 32, and through passages 33 and 34, as indicated by the arrows, and finally leaves the shell through outlet I4. The baule nearest the tube sheet at each end of the tube bundle may, if necessary, be cut away nearest the adjacent inlet or outlet passage to afford communication between the inlet and outlet passages and the spaces adjacent the respective tube sheets.

Since the row of tubes which would ordinarily be present in the diametric position directly facing the end of partition 21 would be blocked by the partition so that fluid could not pass therethrough, we prefer to substitute solid rods 33 in this row in place of tubes. The rods are prei'- erably screwed into threaded holes in tube sheet 23 which extend only part way through the tube sheet, and at their opposite ends terminate in threaded portions extendingsomewhat beyond the bame farthest from tube sheet 20. Nuts are screwed on these threaded ends tightly against this baille. By this construction a smooth surface on the tube sheet 23 is presented to abut the end of partition 21. The rods 30 are made of suitable diameter with respect to the spacing and diameter of .tubes 22 to prevent excessive bypass of fluid through the tube bundle along the horizontal diameter of the shell, which would otherwise occur if the tubes in this row are simply omitted to leave an uninterrupted passage through the tube bundle. In place of the row of rods 30 we may substitute a plate in the same plane as the partition 21, suitably mounted, and of a thickness such that excessive bypass of fluid through the tube bundle does not take place in the space opposite the partition 21.

In order to secure a comparatively large heat transfer area in a limited space, it is desirable to employ a very large number of relatively small tubes in the tube bundle and to locate them close together. Another result following from the use of small, closely spaced tubes is that tortuous paths are provided for all the fluid from one side of the shell I0 to the other, resulting in a turbulent condition of flow in which all parts of the fluid contact the tube surfaces and may readily transfer heat to or from these surfaces. In order to still further increase the turbulence -of the flow of uid around the tubes 20, they are preferably located with their centers at the corners of adjoining squares or triangles and the tube bundle is oriented so that the sides of the squares or triangles lie at angles to the horizontal.

The condition of a large number of small, closely spaced tubes, staggered to provide tortuous paths between, while being advantageous from the standpoint of heat exchange, provides a problem by offering a high frictional resistance to the flow of fluid from one side of the shell to the other. If, therefore, a path other than thatA between the tubes and of lower resistance is offered the iluid, it will flow through this path of less resistance rather than past the tubes, and the advantage of closely spaced, staggered tubes may be partially or completely lost. Such an alternative path, we ilnd, is ordinarily provided in heat exchangers o! the general type illustrated because of the fact that a space must necessarily exist between the tube bundle and the inside ofthe shell. This space designated at the top by numeral 33 and at the bottom by numeral 36 must exist in order that the tube sheet 23 with its outwardly Vextending rim, to which cover 24 is bolted, may be withdrawn through the shell. Unless means are provided, as according to our present invention, to prevent it, a considerable quantity offluid, which should for best results flow between the tubes 22 from one side of the assenso shell Il to the other side, will rather i'low up over the tube bundle through the space 33, and down under the tube bundle through the space 33. to the other side, as shown by the dotted arrows, and thus completely avoid contact with the tubes 33. This detrimental action takes place to some extent at the open end of each of the bailes 3| and 32 in a heat exchanger not provided with means to prevent it, and is, we find, a very important cause of inemciency in heat exchangers. 'Ihe inefllciency due to this cause is, moreover. particularly great in the case of viscous fluids moving through the shell of the exchanger, and this condition exists inmany important industrial processes.

According to our invention, shrouds 31 and 33 are placed in the passages between the bailes 3| and 33. and above and below the tube bundle, so as to substantially block oil.' the spaces 33 and 33 to the transverse ilow of fluid and force all of the fluid to flow through the spaces between the tubes. The shrouds 31 and 33 preferably consist of arcuate sheets closely fitting the outside of the tube bundle, of a width substantiallythe same as the distance between baflles 3| and 33, and terminating at each end in a portion which may be bent out radially to meet the shell i3 at points near where bailles 3| and 32 are cut away. Right angular lugs 43 may be welded to the outside of each shroud adjacent each bame at the ends and middle oi.' the shroud. The shrouds are supported by bolting to the intervening baille by means of bolts 4| the lugs of adjacent shrouds. By means of this construction, iiuid tending to flow into the spaces 3l and 33, as indicated by the doted arrows in Fig. 2, is diverted into the tube bundle where heat exchange may take place. The result is that, following this construction, we have been able to construct heat exchangers with considerably higher heat transfer rates -`than have been common in the industry.

An alternative form of shroud and manner of supporting it is shown in the heat exchanger of Figs. 4, 5, 6, and '7, in which all other parts are to the shell I 3 to substantially block of! flow of iluid into the spaces 33 and 33. By making the shrouds approach the shell at a small angle, eddying of the fluid at-the juncture of shroud and shell is avoided.

In order to support the shrouds, long rods 41 may be screwed into the tube sheet 2l at one end and pass through all the bailes 3| and 32. Spacing tubes 43, of suitable inside diameter to slip over rods 41, and of a width equal to that of the shrouds, are welded to the outsides of shrouds 43 and 43, and are supported on rods 41 between the baiiles 3| and 32. 'I'he nuts 43 screwed onto the threaded ends of the rods'41 beyond the bafe farthest from tube sheet 23 are employed to tighten the entire structure of baies, rods 41, and spacers 43. The rods 41 may pass through holes in the banies 3| and 32, but preferably slots are formed in the outer edges of the baffles of suitable width and depth to accommodate the rods 41 in their operative position, but of less width than the outside diameter of spacers 43.

'I'he rods 41, then, are simply slipped into these slots, with the supported spacers and shrouds located between the bailles, and the whole structure is tightened. In this manner the shrouds 45 and 46 are firmly supported in a way that permits of their being easily and quickly removed for cleaning of the equipment.

It is recognized that the shrouds herein disclosed may be made in various shapes and may be attached to the associated parts in various ways, and that the shrouds may be applied to heat exchangers of other design, while still operating in accordance with our invention. While we have shown a heat exchanger in which fluid passes one way through part of the tubes of the tube bur/idle and returns through the remaining tubes. the invention may also be applied to a single-pass exchanger in which fluid passes only once through the tubes of the tube bundle, or to a multiplepass exchanger in which the uid flows any deslred number of times through the tubes of the tube bundle. We have illustrated our invention in connection with a heat exchanger in which l fluid within the shell, but outside the tubes, traverses the length of the unit only once; but our invention may also be applied to heat exchangers in which this uid traverses the unit more than once. Such an exchanger, for example, may be constructed with a partition on the shell diameter and with fluid passages' causing iluid to be directed back and forth down the exchanger between the banies on one side of the partition, then to be returned in a similar manner between the bailles on the other side of the partition, making a double pass through the shell.

When we have spoken of the vertical and horizontal directions and of the sides of the apparatus, it is understood that we were in no way limiting the apparatus to use in the particular orientation disclosed, but that the heat exchangers shown and described may be oriented in 'any desired direction.

It is understood that in the light of this disclosure various other changes and modifications in design and construction may be made by those skilled in the art without departing from the spirit of the invention defined inthe appended claims.

We claim as our invention:

l. In a heat exchanger, the combination of: a plurality of tubes for passage of fluid therethrough and forming a tube bundle, a shell surrounding said tube bundle and spaced therefrom, a plurality of bames transverse to said tube bundle and disposed at intervals longitudinally thereof, alternate baiiies having openings at opposite sides for longitudinal passage of fluid within said shell, said bailes havingslots in their outside edges. longitudinally extending rods residing in said slots outside of said tube bundle, spacers on said rods between said bailes and of a length substantially equal to the distance between bailes, and shrouds located between said bailies and adapted to substantially prevent transverse flow of said fluid in the space between said tube bundle -and said shell, said shrouds being attached to said spacers for support of said shrouds.

2. In a heat exchanger, the combination of: a plurality of tubes for passage of fluid therethrough and forming a tube bundle, a shell surrounding said tube bundle and spaced therefrom, a plurality of bames transverse to said tube bundle and disposed at intervals longitudinally thereof, alternate bailles having openings at opposite sides for longitudinal passage of fluid within said shell, said baiiies having slots in their outside edges, longitudinally extending rods residing in said slots outside of said tube bundle, shrouds located between said bailles and adapted to substantially prevent transverse flow of said fluid in the space between said tube bundle and said shell, and means for supporting said shrouds on said rods.

3. In a heat exchanger, the combination of: a plurality of tubes for passage of iluid therethrough and forming a tube bundle, a tube sheet supporting said tubes at one end thereof, a partition abutting said tube sheet, a shell surrounding said tube bundle, a plurality of transverse baihes arranged to cause fluid to pass transversely back and forth across said tube bundle, means longitudinally spacing said baiiles from one another and from said tube sheet, solid rods taking the place of tubes opposite said partition, said rods being of such diameter as to prevent excessive bypass through said tube bundle in the space opposite said partition, and means on the ends of said rods retaining said baiiies and said tube sheet in assembled relation.

4. In a heat exchanger, the combination of: a plurality of tubes for passage of iluid therethrough and forming a tube bundle in which the tubes occupy positions characterizing a regular geometrical pattern, a tube sheet supporting said tubes at one end thereof, a partition abutting said tube sheet, a shell surrounding said tube bundle, a plurality oi transverse bellies arranged to cause uid to pass transversely back and forth across said tube bundle, means longitudinally spacing said baii'ies from one another and from said tube sheet, members occupying the tube positions opposite said partition and supported in said tube sheet in holes therein extending only partially therethrough. said members being of such diameter as to prevent excessive bypass through said tube bundle in the space opposite said partition, and means on said members in engagement with one oi' said baiiies for retaining said bailes and said tube sheet in assembled relation.

CLARENCE D. COUIIIER. 'EDWIN R.. COX. p

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