US2985434A

US2985434A - Regenerator

Info

Publication number: US2985434A
Application number: US646457A
Authority: US
Inventors: Stewart A Boring; Elio J Speca; Stephen J Zierak
Original assignee: Air Preheater Co Inc
Current assignee: Alstom Power Inc
Priority date: 1957-03-15
Filing date: 1957-03-15
Publication date: 1961-05-23
Anticipated expiration: 1978-05-23

Description

May 23, 1961 s. A. BORING ET AL 2,985,434

REGENERATOR Filed March l5, 1957 2 Sheets-Sheet 1 May 23, 1961 s. A. EQRING HAL 2,985,434

REGENERATOR Filed March l5, 1957 2 Sheets-Sheet 2 Y y 2,985,434 REGENERAToR Elio J. Speca, and!v Stephen J. Zierak,

Stewart A. Boring, x

assignors to The Air Preheater Cor- Wellsville, N.

poration, New York, NX., a corporation of New York Filed Mar. 15, 1957, Ser. No. 646,457

`1 Claim. (Cl. 257-245) The present invention relates to improvements in platel type heat exchangers utilized for the transmission .of heatj between two confined iliuids, and particularly it relates to an improved form of envelope component to be assembled in multiples for forming such a heat exchanger.

One type of heat exchange apparatus for the transfer of heat between two confined fluids comprises a plurality of spaced metallic plates forming passages through alternate ones of which a relatively hot gas lflows in heat exchange lrelationship with air or other fluid to be heated that in turn traverses the intermediate passages. In many such heat exchangers a series of envelopes are provided each comprising `a pairv of parallel plates with the space therebetween closed along one pair of opposite edges to bound the sides dof the passage for one of the fluids such as air to be heated.v -The Yenvelopes are mounted in spaced parallel relation to form therebetween the passages for a lsecond' or. heatingi fluid, thel interfenvelope spaces being closed along one pair of opposite side edges to direct theow of liuid therethrough-Euch spaced envelopes form a core that is usually enclosed within a housing that is provided with inlet andoutlet manifolds leading to and away from the gas and air passages through the heat exchanger. A, l

Heatexchangers ofthis general type are usuallyprovided with extendedsurfaee in-the form of fins' extending-into'jthe path of fluids ,and serving to increase the conduction of heat to and through the walls bounding the passages. These lfins have been formed variously from sinuously formed wires or channel members lying adjacent the passage walls in a direction generally parallel to the flow of uid. To provide good heat transfer between extended surface elements, good bonds must be provided between elements, and it has therefore been customary to braze the elements integrally together into an envelope for assembly into a composite heat exchanger.

Heat exchanger devices of the general type defined possess good heat transfer characteristics and they furthermore have adequate strength and resistance to creep and corrosion to bear up under substantial temperature and pressure. However, there is a growing demand for a plate type heat exchanger having characteristics making possible its use in regions of extrme temperature and pressure.

More specifically it may be stated that the code for pressure vessels as formulated by the American Society of Mechanical Engineers specifies that brazed pressure vessels may not be used at service temperatures in excess of 406 degrees F. Therefore a primary objective of this invention is to provide an improved -form of extended surface arrangement for a plate type heat exchanger which may safely be used at conditions of elevated temperature and pressure.

A second object of this invention is to provide a plate type heat exchanger having a minimum number of comice ponent parts which may be readily and economically assembled into an integralvunit.

It is a further object of this invention to provide a plate type heat exchanger wherein bonds between component parts thereof that are in a state of tension are v formed by a process ofwelding, while those bonds that are maintained under compression may be produced by more conventional procedures.

The invention will be best understood upon consid eration of these objects when viewed in conjunction with the accompanying drawings in which:

Figure 1 is a perspective view yof ay preferred form of heat exchange envelope defined by this invention.

Figure 2 is a transverse sectional view of a modified form of the invention.

Figure 3 is a transverse view `of a further modified form of 4the invention. Y

Figure 4 is a perspective view of a plurality of envelopes bonded into an integral heat exchanger.

As indicated in the drawings two heat exchange plates..

12 are spaced apart by a series of metallic tubes 14 having a rectangular cross section whereby opposite sides thereof abut said plates and the sides normal thereto extend perpendicularly between plates ,to provide a series of longitudinal fins extending through the passageway V15 therebetween.

The Atubes may be spaced apart as illustratedin Fig-:- ure- 1 or theyv may otherwiseybe placed in lateral abut' t thereof.

, Further variation in therpreci'se arrangement ofv'elef. ments within `an envelope may be had byteliminationof' plate. 12 entirelyvas'is illustrated in Figure 3, sincethe sides .1 8' of tubes 14 which lie in end-to-end abutment provide. a; passage wall that precludes thenecessity ofyan additional n A.wall member illustrated; byl plate y1,2;'5fof` Figure'l. i

A still further variation is shown in Figure 2 where a corrugated sheet is utilized to replace the tubular elements of Figures 1 and 3. The corrugated sheet is preferably formed with a series of substantially vertical risers 28 extending4 between crests 32 which abut the spaced plates 12 on Iwhich the sheets 16 of interrupted strip ns are positioned. Assembled in this manner the risers 28 provide a series of imperforate fins extending between plates 12 while the members 24 provide a series of interrupted strip fins on the opposite side thereof to effect an eiicient transfer of heat between fluids on opposite sides of said plates.

In assembling envelope units of the type illustrated in Figures 1, 2 or 3 no special supports or jiging xtures are required since the elements when assembled are inherently stable and the assemblies may be readily bonded into integral units by a process of brazing. As is customary, thin sheets of brazing material 34 are inserted during assembly between surfaces to be bonded and on being heated to a brazing temperature the brazing material fuses and is drawn into the interstices between abutting elements by a process of capillarity.

When certain alloy steels are used as envelope com-v ponents norm-al brazing procedures are often times not effective because of the necessity for highly critical atmospheric conditions that must be maintained in the space surrounding the envelope during the brazing operation. Therefore, in the bonding of stainless steel and other high temperature alloys, various ceramic adhesives may effectively replace the metallic brazing material as v a bonding agent and as an aid to the conduction of heat between abutting elements.

12 along a pair of opposite Ysides thereof parallel to the rows'of tubing 14 and are welded continuously" thereto;l

This lwelding operation may be readily carried out automatically as exempliiied by automatic seam welding or submerged arcwelding procedures.

After the closure bars 36 have been welded in place between sides of individualV envelopes, va series of envelopes are `joined together by welding a series of closure `bars 3 8 normal to bars 36 between ends of adjacent envelopes YinA the manner shown in Figure 4. The space between envelopes thus bonded together by weld-ing becomes `a iluid passageway 42 having a series of interrupted strip fins 24 protruding thereinto. A series of envelopes so joined together then becomes a bundle Y 4 strong-back `assembly which is sized to aiord added strength to the housing as may be required to safely contain conditions of elevated temperature and pressure.

vWhile this invention has been described with reference to the several embodiments illustrated in the drawing it is evident that various changes may be made without departing from the spiritxof the invention and it is intended that all matter contained inthe above description of envelopes which may be handled as a unit for further y assembly.l i

After assembly in'this manner the bundled elements arefenclosed in a housing having unitary sides 45 with composite sides normal thereto, the latter Vsides being built up by Welding a series of metallic strips 48 in side-to-side relationship'. 'The strips'48 are sized to extend laterally a distance equivalent to the distance between'adjacent closure bars 36 or a predetermined multiple thereof in such a manner that the welds 52 joining strips 48 together are aligned with the closure bars and may be made integral therewith by the process of welding.V

One of the composite sides of the housing isrprovided withran inlet 54 and an outlet v56 Iwhereby a fluid under highipressure may be admitted and exhausted from the series of Vpassageways 42 between envelopes that are :formed by welding the closure bars 38 between envelope walls.V Simultaneously a low pressure fluid as may be exemplified by combustion gases is directed through the passageways 15 within the series of envelopes, the difference in pressure of the two uids resulting in a force component which places the welded joints between envelopes ina state of tension while the tubes 14 together with their brazed joints are placed under compressive force. 'Ihe completed housing may be further encased in a or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What we claim is: Y

Heat exchange apparatus adapted to transfer `heat between twoconned iluids comprising in combination a series of envelopes that include unitary wallsspaced apart by ligaments and having a pair ofl side closure bars at the sides thereof parallel to the ligaments and adapted to enclose a iirst passageway therethrough for a low pressure fluid; end closure bars welded normal to the side closure bars between opposite Vends of vadjacent envelopes to providea series of interenvelope passageways for a high pressure iluidgfa metallic plate coextensive with each of said unitary walls bonded thereto and having rows of apertures therein, the material from which comprises aY series of interrupted fins attached to one side of the aperture when bent out from the surface thereof; and a hous Ving surrounding the assembled envelopes including a seriesy of plane metallic strips welded continuously along'rtheir sides to the intermediate portion of the side closure bars and spaced from the ends ofthe end closure bars to defineV ports at opposite ends of the metallic strips for the ilow of the high rpressure fluid through the inter envelope passageways; and plate members abutting opposite end walls in aseries of assembled envelopes adapted to combine with the plane metallic strips lying normal thereto and provide aA housing around the envelopes'.

References Cited in the tile of this patent UNITED STATES PATENTSA Hammond Aug. 25, 1,953