US3482626A

US3482626A - Heat exchanger

Info

Publication number: US3482626A
Application number: US700804A
Authority: US
Inventors: Nathan R Gainsboro; Robert A Weisberg
Original assignee: Sweco Inc
Current assignee: Sweco Inc
Priority date: 1968-01-26
Filing date: 1968-01-26
Publication date: 1969-12-09
Anticipated expiration: 1986-12-09

Description

Dec. 9, 1969 N. R GAINSBORO ETAI- HEAT EXCHANGER Filed Jan. -26, 1968 Fm. J.

V INVENTORS. 505667 A. [ME/55656 BQ/A THAN 6 GEM/55066) M 7'70E/V6V United States Patent 3,482,626 HEAT EXCHANGER Nathan R. Gainsboro and Robert A. Weisberg, Los Angeles, Calif., assignors to Sweco, Inc., Los Angeles, Calif., a corporation of California Filed Jan. 26, 1968, Ser. No. 700,804 Int. Cl. F28d 7/00 US. Cl. 165-155 10 Claims ABSTRACT OF THE DISCLOSURE An apparatus for the transfer of heat between a first fluid and a second fluid, comprising an outer shell, an inner shell for the flow of the first fluid, first inlet means for the first fluid near one end of the inner shell, and first outlet means for the first fluid near the other end of the inner shell, a pipe longitudinally disposed in the inner shell for flow of the second fluid, second inlet means for the second fluid near the first outlet means for the first fluid, a plurality of tubes longitudinally extending along the outer circumference of the pipe, one end of each of the tubes communicating with the pipe near the first inlet means, and second fluid passing in the tube counter current to the second fluid within the pipe.

This invention relates to heat exchangers of the type useful in transferring heat between two confined fluids. The invention is more particularly directed to a device having improved operating characteristics during high temperature and high pressure exchange processes.

In numerous industrial operations, it is desirable that heat be efliciently transferred from a comparative hot fluid to a fluid of lower temperature. During certain processing operations, the efficiency of the operation often depends to a large extent upon the completeness with which the heat content of different fluids is interchanged at different stages of their flow. The mechanical construction of the heat exchanging device employed for this purpose is an important item since this construction determines the thermal efliciency as well as the mechanical integrity and reliability of the device. In general, an efficient heat device should be constructed to provide for control of expansion strains, accessibility for maintenance and fluid-tight joints between the component parts thereof. In certain processes, it is desirable or essential that one or both the fluids between which an exchange of heat is desired be handled at a comparatively high temperature and pressure and, accordingly, the heat exchange device should be capable of withstanding high pressures and high temperatures without danger of leakage or rupture.

When the fluid passing through the tubes is under relatively high pressure and low temperature in relation to high temperature fluid surrounding the tubes, the numerous components of the conventional heat exchangersare subject to a high degree of expansion or contraction which may ultimately cause such components to fail.

Due to the corrosive and fouling properties of the fluids passing within and about the tubes of the heat exchanger, it also becomes advantageous to employ a heat exchanger which can be easily dismantled for cleaning and repairing purposes.

It is, therefore, an object of this invention to provide an improved heat exchanger for certain high temperature and high pressure processes.

It is another object of this invention to provide an improved heat exchanger which eliminates the necessity of employing a tubesheet, channel and channel cover.

Still another object of this invention is to provide an improved heat exchanger, which may be easily disman- See tled for removal, replacement, repair or cleaning of its component parts.

With the above objects in mind and other objects which may hereinafter appear, reference is directed to the drawings accompanying the specification in which:

FIGURE 1 is a side section view of the heat exchanger unit of this invention; and

FIGURE 2 is a section view of the heat exchanger of FIGURE 1 taken through 2-2 of FIGURE 1.

The above and other objects of the invention are accomplished by a heat exchanger for the trans-fer of heat between the first fluid and a second fluid, comprising an outer shell, an inner shell for the flow of the first fluid, first inlet means for the first fluid near one end of the inner shell, first outlet means for the first fluid near the other end of the inner shell, a pipe longitudinally disposed in the inner shell for flow of the second fluid, second inlet means for the second fluid near the first outlet means for the first fluid, a plurality of tubes longitudinally extending along the outer circumference of the pipe, one end of each of the tubes communicating with the pipe near the first inlet means whereby the second fluid passing in tubes is countercurrent to the second fluid within the pipe and co-current to the first fluid passing in the inner s ell.

The heat exchange device, as shown in FIGURE 1, consists of a horizontally positioned, elongated, cylindrical outer shell 10 having a generally dome-shaped cover 11 welded, bolted or otherwise suitably secured to the end of the shell. The covers central area is provided with an opening of substantially smaller diameter than the shell 10. A cylindrical insulating pipe 12, afflxed in a suitable manner to the opening, projects horizontally from the cover and terminates with an inward-1y projecting flange 13. Passing through, and concentrically disposed within the insulating pipe 12, is an inlet pipe 14. The circular flange 13 of the insulating pipe 12 circumvents and is aflixed by welding or other suitable means to the outer wall of the inlet pipe 14. The inlet pipe 14 communicates with and is aflixed by welding or other suitable means to a conical pipe section 15 of expanding diameter. Gusset plates 16 secure the open conical pipe 15 to the cover 11. The cover 11 is secured to the outer shell 10 by virtue of bolts 17 which pass through holes in a circular flange 18 provided on the cover, into corresponding openings in a circular flange 19 provided on the shell 10, the end of the bolts being provided with nuts 20. Because the open conical pipe 15 is securely aflixed to the cover 11, the pipe 15 remains with the cover .as an integral part thereof when the cover 11 is removed from the shell 10.

Concentrically disposed within the outer shell 10 is an elongated cylindrical inner shell 25 which extends from a point at the periphery of the pipe section 15 to the opposite end of the outer shell 10, terminating with the opening 26 at the end of the inner shell 25.

The end of the pipe section 15 nearest the inner shell 25 is provided with a horizontal circular flange 27 of sufficient diameter to permit the peripheral walls of the inner shell 25 to overlap the flange 27. It should be observed that the flange 27 of the pipe section '15 is not welded or otherwise securely affixed to the walls of the inner shell 25. By this arrangement, the pipe section 15 may be easily removed from its communication with the inner shell 25 by removing the cover from the outer shell as the pipe section 15, as previously mentioned, is an integral part of the cover 11. As an alternative, however, the flange 27 may be welded or otherwise aflixed to the wall of the inner shell.

A pipe positioned transverse to the shells 10 and 25, as generally indicated at 28 in FIGURE 1, passes through and is welded or otherwise suitably secured to the outer and inner shell and and, by virtue of a substantially 90 bend portion 29, extends, concentrically disposed within the inner shell 25, to a point near the pipe section 15. The end of the elongated portion of the pipe 28 is provided with a dome-shaped cover 31. Disposed over the cover 31 and aflixed thereto by welding or other suitable means is a conical shaped deflector cover 32. The deflector cover 32 functions as a means to maintain the incoming fluid at a constant velocity. Concentrically disposed within the transverse and. 90 bend portion of the pipe 28 is an inner pipe 33. The inner pipe 33 is provided with the inlet opening 34 at its upper end. The upper peripheral end of the outer pipe 28 converges upon the external walls of the inner pipe 33 and is welded or otherwise suitably secured to such wall, thus eliminating any opening at the upper end of the outer pipe. 28. Communicating with the transverse portion of the pipe 28 is a horizontal pipe 35 which is welded to or fabricated as an extension of the Walls of the outer pipe 28. The outer pipe 28, by virtue of the bend portion 29 being concentrically disposed within the inner shell 30, extends to a point near the pipe section 15. The peripheral end 39 of the substantially horizontal portion of the inner pipe 33 terminates in an outwardly projecting circular flange 40. The flange is either welded or otherwise affixed to such pipe or provided as a fabricated extension of the end of such pipe. The outer periphery of the flange 40 is welded to the inner wall of the pipe 30. By virtue of the flange 40, fluid flowing within the inner pipe (as indicated by the arrows 41 and 42) continues to flow into the pipes elongated portion 30 while the fluid flowing within the transverse and bent portions of the outer pipe 28 (as indicated by the arrows 43 and 44) is prevented from flowing into the outer pipes elongated portion 30.

As best shown in FIGURE 2, circumferentially positioned about the elongated portion 30 of the pipe 28 and remaining Within the confines of the inner shell 25, are a plurality of tubes 50. The tubes extend substantially the entire length of the pipe 30 and are parallel to the pipe 30.

As best shown in FIGURE 1, the end of each tube 50 nearest the deflector cone 32 (by virtue of provided bend portions 51, FIGURE 1) communicates with the elongated pipe 30 through the openings 52, thus enabling fluid flowing through the pipe 30 to pass into each of the plurality of tubes 50. The opposite ends of the tubes 50, which extend just past the flange 40 of the inner pipe 33, communicate with the outer pipe 28 by virtue of the bend portions 53.

Extending longitudinally on the tubes 50 are fins 54 (FIGURE 2) which are preferably straight or substantially straight. Each fin 54 may lie in a plane, passing through or parallel to the axis of the tube 50, or each fin 54 may be curved to form a long pitch helix so that each fin is Wrapped around its tube a few times in the length of the fin 54. It should be observed that any type of fin arrangement may be provided on the tubes 50, depending upon the type of heat exchange operation. Further, as an alternative, bare tubes may be employed.

Although only one layer of tubes 50 is shown as being circumferentially disposed about the elongated portion 30 of the pipe 28, any number of layers of such tubes may be provided depending upon the thermal efliciency that is desired for the particular heat exchange process. As shown in FIGURE 1, the bend portions 51 and 53 of each of the tubes 50 communicate with the elongated portion 30 of the pipe 28 at locations about the pipe such that the bend portions at one end of the pipe 30 are staggered with respect to the remaining bend portions at the same end of the pipe. Staggering the location of the bend portions relieves any structural stress upon the pipes elongated portion 30 which would otherwise exist if the openings 52 of the bend portions 51 and 53 were circumferentially positioned about the elongated portion 30 of the pipe 28 in an aligned plane corresponding to a cross-section of 4 such elongated portion. The staggered bend portions 51 and 53 need not be positioned in any particular pattern unless a pattern may be desirable in order to reduce fabrication costs.

The heat exchanger, as heretofore described and shown in FIGURES 1 and 2, may be dismantled whereby the cover 11 and pipe section 15, as an integral unit, is detached from the outer and inner shell 10 and 25. This provides easy access to the plurality of tubes 50 and the fins 54 for cleaning and repair.

It should be observed, however, that any means for detaching one portion of the outer and inner shell 10 and 25 from the remaining portion may be provided at any location upon such shells as the primary purpose for detaching the shells is merely to expose either all or a por tion of the tubes 50 and the fins 54 for cleaning and repair purposes.

The heat exchanger, as above described, may be varied by other arrangements. For example, the device as shown in FIGURE 1 by which the heat exchanger is in a horizontal position may be varied whereby it is operated in a vertical position. This many be accomplished merely by rotating the device of FIGURE 1 in a clockwise position. Such varied arrangement, although not alfecting the operational process of the device, may prove useful where space is a critical factor.

The heat exchanger functions to effect heat exchange between fluids. Fluid at an extremely high temperature is projected into the inlet pipe 14 and, when striking the deflector cone 32, the fluid flows longitudinally within the space provided between the horizontal pipe 30 and the inner shell 25. Because of the extreme temperatures, the deflector cone, which receives the initial force of the projected fluid, is preferably made of Incoloy. However, any suitable material may be employed which is tolerant of high temperature and has a high erosion resistance.

The finned tubes 50, which are located circumferentially about the pipe 30 and within the inner shell 25, are exposed to the projected fluid which flows within the space where the tubes are positioned. The fluid continues to flow through the channel provided between the pipe 30 and inner shell 25 within which the tubes 50 are disposed, and ultimately passes from the opening 26.

Disposed between the inner shell 25 and outer shell 10 is a suitable insulating matetrial such as a light weight castable refractory. By insulating the outer shell 10 from the extreme temperature subjected to the inner shell 25, the outer shell 10 need not be constructed of Incoloy or other special metals as would ordinarily be required. The inner shell 25, pipe 28 and other surfaces which are exposed to the high temperature fluid entering the inlet pipe 14 may be constructed of any material which will with stand the high temperature of such fluid, such as for example Incoloy.

The heat exchanger described and shown in FIGURES l and 2 is arranged to enable the fluid entering the inlet pipe 14 to pass through the heat exchanger and out the outlet opening 26 at a relatively high velocity.

Although various fluids may be passed through the tubes 50 and within the space between the inner shell 25 and the pipes elongated portion 30, it is generally preferred to pass a hot gaseous fluid such as efliuent from a chemical reactor or cracking furnace through the shell 25 and to cool this gas by passing a liquid cooling medium such as water or some other liquid through the tubes 50.

The cooling fluid flows into the opening 34 of the transverse inner pipe 33 through its bend portion and into the outer pipes elongated portion 30. The fluid then passes into the plurality of tubes 50 by virtue of the bend portions 51 which communicate the tubes 50 with the pipes elongated portion 30 through the openings 52.

The fins 54, FIGURE 2, as previously described, are located upon the tubes 50 so that a large heat absorbing surface may be presented to the fluid passing through the shell 25. Although integral fins may be used, it is preferr'ed in certain cases to employ separate fins formed of a metal of high thermal conductivity, such as copper or an alloy of copper, and to anchor these fins to the outer surfaces of the tubes, as shown in FIGURE 2.

As the fluid passes within the tubes 50, it abstracts considerable quantities of heat from the high temperature fluid passing through the shell 25. Most commonly, steam would be generated in the tubes.50 in which case the heat exchange device of this invention would be a waste heat boiler.

By virtue of the bend portions 53 of the tubes 50 communicating with the outer pipe 28 through the openings 52 which are located just beyond the flange 40, the fluid passes into the outer pipe 28. It should be observed that the heated fluid passing into the outer pipe 28 (as indicated by arrow 43) is isolated from the fluid within the inner pipe 33 by the walls of the inner pipe which are concentrically disposed within the transverse and bend portions of the outer pipe 28. As the cooling fluid passes through the inner transverse pipe 33 and bend portion thereof, the heat absorbed fluid passes in the opposite direction within the space between the outer and inner transverse pipe 28 and 33 to ultimately become discharged by way of the outlet opening 56.

As above described and shown in FIGURE 1, the fluid intended to be cooled which enters the inlet pipe, travels in a path countercurrent to the cooling fluid within the pipes elongated portion 30. However, as an alternate, the fluid intended to be cooled may travel cocurrent with the cooling fluid within the elongated portion by having the inlet opening located where the outlet opening 26 is positioned for the device of FIGURE 1. It is referred that the fluid to be cooled enter near the end of the heat exchanger opposite the end that the transverse pipe 28 is located. Having the inlet opening for the fluid intended to be cooled near the same end that the transverse pipe 28 is located would impair the flow of the incoming fluid resulting in reduced efliciencyduring the heat exchange operation because the incoming fluid would strike the transverse pipe 28 before such fluid had an opportunity to become exposed to the tubes 50.

It should be observed that the pipes elongated portion 30 is suspended within the inner shell by virtue of having only the transverse portion of the pipe 28 affixed by welding or other suitable means to the outer and inner shell and 25.

Where the pipes elongated portion is relatively long in relation to its diameter and the velocity of the fluid entering the inlet pipe relatively high, vibrations are set up in the elongated portion 30 as a result of the incoming fluid striking the deflector cover 32 which is provided at the unsecured end of the elongated portion 30. The vibrations set up in the elongated portion 30 might cause the tubes 50 and fins 54 to knock against the inner shell, resulting in damage to the tubes and fins unless means are provided to stabilize the elongated portion 30. As shown in FIGURE 2, extending between the inner wall of the inner shell and outer wall of the pipes elongated portion and aflixed thereby by welding or other suitable means are a plurality of centering guides 57. The centering guides 57 are positioned at spaced intervals circumferentially about the elongated portion 30 and are aligned in a manner which will not impair the flow of the fluid passing within the space between the inner shell 25 and elongated portion 30. The centering guides 57 need not necessarily extend the entire longitudinal length of the elongated portion 30 but may merely be provided at spaced intervals.

It should be observed that any supporting means may be employed to extend between the elongated portion and shell at any location upon the elongated portion to retain such portion in its suspended position, provided such supporting means does not impair the flow of the incoming fluid or the efliciency of the tubes 50 and their attached fins S4.

The heat exchange device of this invention as above 6 described and shown in FIGURES 1 and 2 may be employed with other devices which are commonly utilized with heat exchangers for the recovery of the cooled fluid and also recovery of the cooling fluid which, upon absorption of a considerable quantity of heat during the heat exchange operation, is often saturated with steam.

While particular embodiments of this invention have been shown and described, it is not intended to limit the same to the exact details of the construction set forth and it embraces such changes, modifications and equivalents of the parts and their formation and arrangement as come within the purview of the appended claims.

We claim:

1. An apparatus for the transfer of heat between first and second fluids and for providing relatively even flow paths for said fluids, comprising shell means for receiving said first fluid, said first shell means being elongated and having an inlet end and an outlet end,

elongated pipe means positioned within said shell means,

the major portion thereof being substantially unaffixed with respect to said shell means for allowing relative expansion and contraction in the longitudinal direction of said shell means and pipe means, said pipe means having an inlet end and an outlet end,

deflection means coupled with said pipe means near the inlet end of said shell means for enabling said first fluid to remain at a substantially constant velocity when flowing into said apparatus,

a plurality of elongated tube means disposed about the outer periphery of said elongated pipe means in a layer substantially coaxial therewith, each of said tube means having an inlet end coupled with and communicating with the outlet end of said elongated pipe means and having outlet ends, and

outlet means coupled with the outlet ends of said tube means for providing an outlet for said second fluid.

2. An apparatus as in claim 1 wherein the inlet end of said elongated pipe means is positioned near the outlet end of said shell means, and substantially only said outlet means aflixes the inlet end of said pipe means with respect to said shell means.

3. An apparatus as in claim 1 including fins secured to the periphery of each of said tube means,

said fins being substantially parallel with the respective tube means.

4. Apparatus as in claim 1 including fins secured to the periphery of each of said tube means, said fins extending from one end to the other of each of said tube means in a helical fashion.

5. An apparatus as in claim 2 including centering guide means coupled between said shell means and said elongated pipe means at least near the inlet end of said shell means and the outlet end of said elongated pipe means, said guide means being securely affixed to one of said shell means or elongated pipe means and substantially unsecurely aflixed with respect tothe other of the shell means or elongated pipe means to reduce vibrations of the outlet end of said elongated pipe means while allow ing relative expansion and contraction between said shell means and said elongated pipe means.

6. An apparatus as in claim 2 wherein the outlet end of said elongated pipe means includes a plurality of apertures respectively communicating with said tube means, the inlet ends of said tube means being bent to communicate with said apertures while the major portion of each of said tube means is disposed substantially parallel to said elongated pipe means.

7. An apparauts as in claim 2 wherein said outlet means comprises substantially coaxial pipe means extending through said shell means transverse to the longitudinal direction of said shell means and pipe means, said coaxial pipe means having an inner pipe coupled with the inlet end of said elongated pipe means and an outer pipe affixed to said shell means, the outlet ends of said tube means communicating through the space defined between said inner and outer pipes of said coaxial pipe means.

8. An apparatus as in claim 7 including centering guide means coupled between said shell means and said elongated pipe means at least near the inlet end of said shell means and the outlet end of said elongated pipe means, said elongated pipe means thereby being securely afiixed to said shell means substantially only by said outlet means.

9. An apparatus for the transfer of heat between first and second fluids and for providing a relatively even flow path for said fluids, comprising shell means for receiving said first fluid, said shell means being elongated and having an inlet end and an outlet end,

elongated pipe means positioned within said shell means and being substantially unafiixed with respect to said shell means for allowing relative expansion and contraction in the longitudinal direction of said shell means and pipe means, said pipe means having an inlet end and an outlet end,

a plurality of elongated tube means disposed about the outer periphery of said elongated pipe means in a layer substantially parallel therewith, each of said tube means having an inlet end coupled with and communicating with the outlet end of said elongated pipe means and having outlet ends, and

outlet means coupled with the outlet ends of said tube means for providing an outlet for said second fluid and for afiixing an end of said elongated pipe means to said shell means, said outlet means comprising coaxial pipe means including an outer pipe affixed to said shell means and an inner pipe afiixed to the inner end of said elongated pipe means for supply ing said second fluid to said elongated pipe means, the outlet ends of said tube means communicating with the space defined between said inner and outer pipes of said coaxial pipe means to provide an outlet for said second fluid.

10. An apparatus as in claim 9 including centering guide means coupled between said shell means and said elongated pipe means at least near the inlet end of said shell means and the outlet end of said elongated pipe means, said elongated pipe means thereby being securely aifixed to said shell means substantially only by said outlet means.

References Cited UNITED STATES PATENTS 2,600,595 6/1952 Wilson 165155 2,870,997 1/1959 Soderstrom l6-5--155X FOREIGN PATENTS 162,776 4/1958 Sweden.

30 ROBERT A. OLEARY, Primary Examiner THEOPHIL W. STRE-ULE, Assistant Examiner US. Cl. X.R.