US2872163A

US2872163A - Heat exchanger

Info

Publication number: US2872163A
Application number: US545085A
Authority: US
Inventors: Norman H Ranstead
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1955-11-04
Filing date: 1955-11-04
Publication date: 1959-02-03
Anticipated expiration: 1976-02-03

Description

Feb. 3, 1959 N. H. RANSTEAD HEAT EXCHANGER Filed Nov. 4, 1955 //V VE/V TOR: Norman H Ransiead ATTORNEY:

' AGE/VT- HEAT EXCHANGER Norman Ranstead, Des Plaines, Ill., assignor to Universal 011 Products Company, Des Plaines, Ill., a corporation of Delaware Application November 4, 1955, Serial No. 545,085

4 Claims. (Cl. 257-230) This invention relates to a method for disposing heat exchange tubes carrying relatively cool fluid in indirect heat exchange with the heating medium. In particular, this invention relates to a method for supporting heat exchange tubes in an unusually hot environment.

Heat exchange tubes, particularly in direct fired heat exchangers, are subjected to an extremely hot environment. Although good heat exchange is effected with a high temperature differential between the furnace and the fluid being heated, there are some inherent diificulties characteristic of extremely hot heaters. One difliculty is supporting the tubes passing through the heater. As is well known, metal loses its strength rapidly as the temperature increases therefore requiring the metal tube sup ports to be of expensive high alloy material in order to withstand the conditions of operation. Even the finest of alloys, however, suffer embrittlement and oxidation even though they retain their structural characteristics at high temperatures and it is therefore a continuous problem to maintain heater tubes supported. Besides the difficulty of maintaining the supports in operative condition, in high temperature heaters it is necessary to insulate the metal shell from the interior of the heater in order to construct the shell of ordinary carbon steel. Insulation is usually ceramic or earthen in nature and includes such materials as fire brick, fireproof cement, alumina blocks, etc. To obtain material having insulating and heat-resistant qualities, however, one must sacrifice physical strength since these materials although capable of supporting their own weight, cannot be used structurally to any great extent. It is therefore necessary to attach the tube supporting members to the outer metal shell of the heater and in doing this a path for conducting heat at high temperatures directly through the insulation is provided via the tube support. There results a hot spot on the metal shell at the point where the tube supporting member is attached and this hot spot is a source of weakness, rapid oxidation and danger.

It is an object of this invention to provide a simple but extremely effective means of overcoming the difficulties associated with supporting heat exchange tubes in high temperature environments. In eifect, this invention provides for a cool supporting member which is obtained by disposing some of the heat exchange tubes to be used within the shell in such a manner and in such a shape as to have structural strength and to employ the thus disposed tubes as support members for longer and differently disposed tubes.

In one embodiment this invention relates to the method for disposing heat exchange tubes in a vessel which comprises externally supporting some of said heat exchange tubes, passing the latter tubes substantially horizontally through the shell of said vessel in tube-supporting relationship with the interior of said shell and supporting other heat exchange tubes on the first of said tubes.

This invention may be better described with reference to the accompanying drawing which shows one embodiment thereof and which is intended to be illustrative rather N I 2,872,163 C Patented Fees, 1959 than limiting upon the broad scope of the invention. Figure l of the drawing is a sectional plan view of one suitable arrangement of heat exchange tubes within a vessel and Figure 2 shows a partial sectional elevation view of the vessel of Figure 1.

Referring to Figure 1, there is shown a circular vessel 11 in which heat exchange tubes are disposed. The vessel 11 is insulated with insulating material 12 so that the iron shell 11 may be relatively cool with respect to the inside temperature in chamber 13. In this particular embodiment, horizontally disposed

tubes

14, 15 and 16 which run parallel to the cylindrical shell 11 are in the interior of the vessel in chamber 13. As here shown, the outlets and inlets of

tubes

14, 15 and 16 are adjacent. The tubes are bent to conform with the interior contours of shell 11 and extend half way around. A U-bend then causes the tubes to double back to the outlet, which is disposed immediately below the inlet. This arrangement allows for thermal expansion by permitting the U-bend end of the tubes to move freely.

Tubes

14, 15 and 16 are long and have an extended length within chamber 13 in order to have sufficient heat transfer area to obtain the desired temperature of fluid flowing therein. It is therefore necessary that these tubes be supported within chamber 13 since the high temperature conditions therein would cause

tubes

14, 15 and 16 to lose their structural strength and warp or break when in operation; To that end,

tube supporting members

17, 18, 19 and 20 are employed and shown herein spaced apart aroundthe periphery of the vessel 11 although more or less supports may be used spaced at closer intervals. In Figure 2 the shape of the latter tube supporting members is better illustrated. In Figure 2 member 17 is shown to be relatively short in length and disposed'vertically within the chamber. It is preferred that the center portion of member 17 does not bear against the interior wall of the vessel so that the insulation will not be disturbed by its thermal expansion. It may be noticed from Figure 2 that tube 17 is externally supported by support member 21, which may be of any suitable shape, and passes through holes in the chamber wall which may be insulated as shown herein with insulating cement or loose packing of some well known variety. The pictured external support wherein the tube is supported by a flange is preferred since this support provides for a cool attachment to the vessel wall and furthermore permits this invention to be used on a pressure vessel, since the flange seals the interior of the vessel from the atmosphere.

In this embodiment, it may be seen that tube 17 which carries cool fluid to be heated will remain relatively cool because of cooling effect of the fluid passing therethrough and therefore will retain most of its structural strength. It may also be seen that tube 17 is supported by support member 21 which is connected to the outside of vessel 11 and therefore remains cool and unaffected by the temperatures within chamber 13. This arrangement not only provides for the support of tubes in heat exchange relation but also provides a heating means for the fluid that cools the supports. t

' As hereinbefore stated, Figures 1 and 2 are intended merely to illustrateone embodiment of this invention which is typical of a class included within its broad scope. Therefore, the vessel 11 may be square, rectangular, oval or any other shape and may contain one or more walls within to break the heater into segments. It may be direct fired and if so may be of the upshot, downshot or horizontally fired type and it may be heated by radiation from a glowing ceramic wall, by radiation from a direct flame, by convection from hot gases or any combinations thereof. The heater may also be employed in indirect heat exchange with a hot fluid. The method of this invention may also be employed as a cooling means.

Therefore in a catalytic cracking process wherein spent catalyst is reactivated by oxidizing carbonaceous deposits from the surface thereof, the regeneration zone frequently requires cooling in order to prevent the temperature from becoming so high as to deactivate the catalyst. The regeneration zone also represents a heat source which may conveniently be used to supply process steam for other applications. T this end the process of the present invention provides a very suitable means for disposing heat exchange tubes within a catalyst regenerator vessel inasmuch as the temperature within such a vessel is extremely high, in the range of 1400 F., and the size of modern catalyst regenerators is of such magnitude that long heat exchange tubes are required and these heat exchange tubes require support at frequent intervals along their length. From the above illustrations it may be seen that this invention may be adapted to virtually any heat exchanger.

The various heat exchange tubes illustrated in the embodiment of Figures 1 and 2 and in other embodiments of this invention may be independent of each other or arranged serially. Therefore, the cooling fluid flowing through

support member

17, 18, 19 and 29 may be passed into

lines

14, and 16 for further heating and in this embodiment all of the tubes may be in series so that all of the fluid passes through all tubes or in various parallel arrangements. For example, one third of the fluid passing through tubes 17 through may pass through each of tubes 14 through 16. In other modifications each of the tubes may be in parallel so that diflerent fluid passes through each and in fact, some of the tubes might be employed for generating steam by passing Water therethrough and others may be employed, for example, for heating a petroleum fraction to be processed. It will, of course, be preferred that the coolest fluid pass through

support members

17, 18, 19 and 20 inasmuch as these members require structural strength whereas the

elongated tubes

14, 15 and 16 are supported, however, various arrangements may be made to adapt this invention to the particular needs of the process.

In the embodiment herein shown, particularly in Figure 2,

tubes

14, 15 and 16 are disposed within the interior loops of support member 17 and therefore, restricted from free expansion although as herein shown, suflicient distance is left between the tubes so that expansion may be effected, the tubes may be supported merely by laying on the upper surface of tube 17 when desired and tube 17 may have more or less loops than as shown herein. It is preferred that the supporting member formed by tube 17 be relatively short in order to be structurally effective, however, depending upon the material of which it is constructed, the conditions of use and other considerations, tube 17 may be longer, shorter, formed with varying contours or otherwise modified to better perform its function of supporting other internal heat exchange tubes.

In a preferred embodiment, support member 17 i a vertical, externally supported coil composed of a series of short horizontal tube members arranged in a vertical plane and connected in series with U-bends. The long, horizontal heat exchange tube coils are then supported on the short horizontal tube members of the externally supported coil, as pictured in Figure 2. This arrangement is particularly suitable for regenerator vessels and radiant heating zones where the interior of the vessel need not be filled with tubes, but where the heat exchange tubes are disposed along the wall of the vessel.

I claim as my invention:

1. A heat exchange apparatus comprising a chamber, a plurality of spaced coils Within said chamber, means for supporting said coils externally of the chamber, each of said coils comprising relatively short horizontal tubular members disposed in a vertical plane in the chamber and said coils as a group having corresponding tubular members positioned in the same horizontal plane in the chamber, means for passing cooling fluid through said coils, and a plurality of relatively long horizontal fluid conduits supported in a horizontal plane on said corresponding tubular members and disposed substantially at right angles to said corresponding tubular members.

2. A'heat exchange apparatus comprising a chamber, a plurality of spaced coils extending inwardly from the periphery toward the interior of said chamber, means for supporting said coils externally of the chamber, each of said coils comprising relatively short horizontal tubular members disposed in a vertical plane in the chamber and said coils as a group having corresponding tubular members positioned in the same horizontal plane in the chamber, means for passing cooling fluid through said coils, and a plurality of relatively long horizontal fluid conduits adjacent the periphery of the chamber supported in a horizontal plane on said corresponding tubular members and disposed substantially at right angles to said corresponding tubular members.

, 3. A heat exchange apparatus comprising a cylindrical chamber, a plurality of spaced coils extending radially from the periphery toward the center of said chamber, means for supporting said coils externally of the chamber, each of said coils having relatively short horizontal tubular members disposed in a vertical plane in the chamber and said coils as a group having corresponding tubular members positioned in the same horizontal plane in the chamber, means for passing cooling fluid through said coils, and a plurality of relatively long horizontal fluid conduits supported in a horizontal plane on said corresponding tubular members, said conduits being disposed adjacent and parallel to the periphery of said cylindrical chamber and substantially at right angles to said corresponding tubular members.

4. The apparatus of claim 1 further characterized in that said coils have at least two groups of corresponding horizontal tubular members disposed in dilferent horizontal planes in the chamber and in that horizontal fluid conduits are supported on each of said groups of tubular members.

References Cited in the file of this patent UNITED STATES PATENT S,

386,579 Engel July 24, 1888 1,139,548 Lovekin May 18, 1915 1,652,037 Merckle Dec. 6, 1927 1,720,768 Spreen July 16, 1929 1,801,467 Uhle et al. Apr. 21, 1931 2,165,258 Hardgrove July 11, 1939 2,268,730 Vagt Jan. 6, 1942 2,456,564 Muller Dec. 14, 194-8 2,660,410 Hofmeister Nov. 24, 1953 2,762,635 Lorber Sept. 11, 1956 FOREIGN PATENTS 310,695 Great Britain May 2, 1929 121,581 Sweden May 4, 1948