US2146352A - Heat exchanger - Google Patents

Description

J. H. ROHRER- HEAT EXCHANGER Feb. 7, 1939,

Filed Feb. 4, 1957 r Inventor: Jo'slbhflkokrer;

.9 LTMM Q Patented reb.1,;19'f39 j UNI-TED, s rArEs PAT-Eur oFI-ucs 2.146.352 m'r momen Josiah 11.1mm, Philadelphia, Pa., smiof one-half to Day and Zimmermann, Incorporated..

Marylan Philadelphia, Pa, a corporation of Application February 4, 1931, Serial is. 12am V 2 claim. (01. 257-262) a 1 I This invention relates to heat exchangers and more particularly to a tube construction which may be readily assembled in accordance with the area of the exterior surface available for contact A with the hot gases passing thereover. In the structures of this type the tube and the fins mounted thereon usually have different coefficients of expansion and, upon heating, small spaces develop between the interior surfaces of the fin blocks and the adjacent exterior surface of the tubes on which they were mounted. These spaces reduce very sharply the efiicacy of the heat transfer from the gases passing over the exterior surfaces of the fin blocks to the fluid in the interior of the tubes. In addition to this objection-the heat exchangers of this type are,

also objectionable because the assembly of the unit can not be accomplished without the dimculties arising from the necessity for. shrinking I 7 these are wholly unsuitable with the high pressures and temperatures employed in-the econ-- omizers for modern steam generating plants.

The sheet metal constructions also usually have spaces in the interiorinwhichboiler scale may collect, with resultant decrease of heat transfer, and inaddition, the fluid carrying interior space, by reason of its construction, cannot be cleaned. v

with heat exchangers or economizers of the types heretofore available also, the structure could not readily be assembled in its entirety at I the place of installation, but must be assembled, f shipped to the place of use and thus subjected to possible injury. It is an object of objectionable features heretofore encountered.

It is also an objectfiof the present invention to provide an economizer which may be readily assembled from unit parts and in desired siau.

the present invention to providea tube construction forheat exchangers or economizers which'overcomes the difficulties and It is also an object of the present invention to provide a heat exchanger or economizer which is simple in construction, and which has a large heat transfer surface on the exterior and a suitable heat transfer surface in the interior thereof with the outer surface shaped to effect substantially uniform heat transfer to the inner surface.

It is a further object of the present invention I Y to provide an economizer composed of a plurality of units and preferably unit forgings which may be quickly and easily assembled by welding.

It is a further object of the present invention to provide a heat exchanger or economizer which may be assembled in accordance with the heat transfer requirements.

It is a further object of the present invention J to provide an economizer which will be satis-- factory at high pressures and temperatures.

It is a further object of the present invention to provide a heat exchanger or economizer having exposed surfaces which are particularly adapted to receive a coating or covering forregulating and controlling the heat transfer characteristics.

Other objects of the invention will appear from the annexed specification and claims.

The nature and characteristic features of the invention will be more readily understood from the following description, taken in connection with the accompanying drawing forming part hereof, in which:

Figure 1 is a'front elevational view of an economizer or heat exchanger assembly embodying the .main features of the present invention;

Fig. 2 is a vertical central sectional view of a heat exchanger unit forging prior to assembly, illustrating certain details of construction;

Fig. 3 is ahead elevational view of a preferred form of heat exchanger unit which may be employed in the heat exchanger assembly;

Fig. 4 is an end elevational view of a modified form ofheat exchanger unit which may be employed in the heat exchanger assembly;

. Fig. 5 is an end elevational view of a further modified form of heat exchanger unit which may be employed in the heat exchanger assembly; and

lustrative m 1 y. and that various modifications a Fig. 61s a. fragmenary view partly in elevation urse, be understood that the deand changes may be made in the structure disclosed without departing from the spirit of the invention.

Referring more particularly to Fig. 1 of the drawing, it will be seen that the preferred assembled form of the heat exchanger or economizer of the present invention includes a plurality of headers Ill, a plurality of connecting tubes H, a plurality of heat exchange units l2 and a plurality of return bends IS.

The headers It) may be of any desired construction with suitable space in the interior thereof for the passage within the header III of the fluid to be heated, and may be of metal withplugs i4 threaded therein opposite the connecting tubes II.

The connecting tubes ll may also be of any preferred construction, and these connecting tubes are secured in any preferred manner to the headers III.

The heat exchange units I2, which are of particular importance in connection with the present invention, may be made in a number of different shapes but are each constructed in one piece as forgings or otherwise weldable units. The assembly may include units I! all of the same external shape or may include units of different external shapes, as hereinafter more fully referred to.

The preferred form of heat exchanger unit forging is illustrated in detail in Figs. 2 and 3, and includes an inner cylindrical surface I! for direct contact in the assembly with the liquid to be heated. I

The unit forging If as illustrated in Fig. 2 is provided at the extremities of the inner surface II with chamfered portions IQ for welding. This unit forging I2 is accordingly suitable for use as an intermediate unit of the assembly by being arranged in co-axial relationship with other and similar unit forgings and with the inner surfaces II in alinement. 4

The unit forging I2 is also suitable as an end unit of a series terminating adjacent a header in for connection to one of the connecting tubes ll, or as the other end unit of a series of units terminating at one of the return bends I! for connection thereto.

The chamfered portions i8 permit of welding the units together end to end in any desired manner but are particularly suitable for flash welding in the assembling of the heat exchanger at the place of installation from headers l0. return bends I3 and unit forgings II.

The heat exchange unit I! is constructed, as referred to above, as a forging of a single body of metal and is preferably provided with a portion I! extending outwardly and generally perpendicular to the end to end axis of the unit to provide a fin, flange or rib. This flanged portion I! has the surfaces thereof which face toward the ends of the unit I! preferably shaped substantially in accordance with the uniform heat transfer characteristic curve of the forged metal.

The portions of the surface of the flange il, indicated at ll, which are relatively close to the interior surface ll, extend substantially toward each other and represent the flatter portion of the curve, while the portions of the surface of the,

shaping of the surfaces of the flange l1 provides for a substantially equal distribution of the heat absorbed at the exterior surface of the flange l1, and including surfaces l8 and i3, and passing through the walls of the unit to the interior surface i5, so that a substantially uniform temperature prevails along the interior surface [5 of the unit i2.

The heat exchanger unit i2 is also preferably shaped in end elevation as illustrated in Fig. 3, the bounding edge portion of Fig. 3 being composed of straight portions 2i and 22'connected by suitablecurved portions 23. Therespective edges 20 in an assembly including units of this character are thus substantially bounded by pairs of parallel planes. Inplace of the conformation shown in Fig. 3, the edge portion may be generally circular in outline as shown in Fig. 4, at 20' and in theassembly of units of this character therespective edges 20 are bounded by a cylindrical surface.

The edge portions may also, if desired be made as a segment, as shown in Fig. 5, at 20", with a portion of the projecting flange or fin omitted and the remaining portion of the interior space i5 enclosed by awall 24 of substantially uniform thickness.

As has been heretofore indicated, the economizer or heat exchanger of the present invention may be assembled by weldingtogether, as by means of the welds 25, a plurality of the forged units i2, the adjoining chamfered portions l6 being united by the welding so that the thickness of the wall at the place of welding 'is not de creased by the welding, as indicated in Fig. 1. To one end unit of the series a connecting tube Ii for connection to the header i0 is welded, the other end of the series being welded to a return bend II. The other end of the return bend i3 is also welded to another series of assembled forgings l2 which are welded together in the same manner, and are connected to another connecting tube II and to another header iii.

The fluid to be heated in the econcmizer is passed in a direction generally opposed to that of the flow of the hot gases passing over the exterior surfaces, so that if the hot gases pass downwardly from the top, the liquid to be heated is introduced at the lowermost header l0, passes successively through one tube loop to the next header i0, and, in the same manner to the uppermost header i0.

It is frequently found desirable, after instal- 1 lation, and particularly where the tubes are exposed to radiant heat tovary or change the i heat transferring capacity and the tube construction of the present invention is particularly suitable for this purpose.

' After assembly if it is desired to reduce the heat transferring properties of the tube construction, a coating of refractory material 28 in plastic condition may be applied upon the exterior of the assembly or a portion thereof. A relatively large surface for adherence and support of therefractory material 26 is provided with the construction of the present invention. It is desirable, in some instances, however, to

- lock the refractory material 28 in place and for gases flowing over the exterior surfaces to liquid to be heated flowing within the interior. The apparatus of the present invention is, however, equally suitable for transfer of radiant heat, or for transfer in the opposite or outward direction through the walls of the heat exchanger, so that heat may be transferred from a hot liquid passing' within the interior to a cooler gas passing over the outer surface.

I claim:

1. A heat exchanger comprising an assembly of similar units united end to end by welds, each unit having an interior fluid contact passage arranged in alinement with similar passages in the adjoining units, each of said units having an outer gas contact face, said outer faces each comprising a plurality of curved surfaces meeting similar curved surfaces of adjoining units at the ends of the unit, said curved surfaces extending outwardly from their ends and towards each other to provide an outwardly extending flange,

vtinuous curved surfaces.

said curved surfaces terminating in an outer edge distant from the interior passage, and refractory material disposed in spaces defined by sa'i-Elcon- 2. A heat exchanger. having a plurality of similar units assembled in series to form a tubular section having an interior fluid contact passage arranged in alinement with similar passages in the adjoining units, each unit including a forged single body of metal having an outer gas contact face, said outer gas contact face including a plurality of curved surfaces extending from the 1 flanges, and refractory locking spaces formed insaid curved surfaces.

JOSIAH H. ROHRER. 20

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