US2578917A - Tubeflo section - Google Patents

Description

W. BISCH TUBEFLO SECTION Dec. 18, 195] @Mace W. BISCH TUBEFLO SECTION Dec. 18, 195] 2 SHEETS--SHEET 2 Filed June 12, 1946 w m mu m we gm mM m L? um@ w /Mv lavailability of such apparatus.

of comparatively thin -have suiilcient the tubes apart not less than about one-fourth :inch and excess metal .of the fins is a considerable ymalte the overall weight Patented Dec. 18, 1951 UNIT-ED STATES PATE-Nr omer.

TUBEFLO SECTION William Bisch, Holmdel,

Griscom-Russell `Comp a corporation of VDelavv N. 5J., assigner to The any, New York, vN. Y., are

Application June L12, 1946, Serial No. 676,178 2 Claims. (Cl. 257-241) .This invention .relates to heat exchange apparatusand, .more particularly, to an .improved .constructionof .heat exchanger.

In many industrial .operations .it is essential .that heat .be economically transferred from .a .comparatively hot .fluid .to a fiuidof lower temperature. For example, the eflcient operation of a petroleum refinery .often depends .upon the in such -a y.plant -the :temperatures .of both .the hot uid andthe cooler luidare comparatively high, although 4a large temperature difference `exists `between them. Also, one or .both .of these uids may -be subjected .to very high pressure. -For such work, therefore, it is necessary .to have `heat exchange apparatus which will .withstand the pressures encountered and at the same .time

be capableof operation withoutdisability by reafson -of' different degrees .of expansion vaccompanying widely diering temperatures in closelyadjacentlparts.

In `United States Patent No. 2,013,187, yissued September 3, 1935, to Joseph Price,.and assigned 'to the same assignee-as the presentapplicaticn,

.there Yis'described andclaimed a heat exchanger of the type under consideration which .is formed metal tubes, pairs'of such upon them alarge number vare spaced slightly apart .tubes-having threaded of metal plates 'which .fromoneanother and uniformlydistributed along -the tubes.

Ymate `and rigid heat exchanging Contact -with The tubes are expanded into intitheseplates.

'Although heat exchangers constructed as just described have had a high degree of commercial success, flarge -numbers or" them having been manufacturedand beingnow in use, nevertheless such construction `possesses certain disadvantages. For-example, the metal plates `or ns connecting the tubes Imust have sufiicient strength to withstand vthe expansion process and consequently theyare usually made of .ferrous metal, and this metal interposes a rather high resistance to the heat transfer. Moreover, in order forrthe fins to .strength it is necessary to space is vrequired at the ends Consequently, the weight factor and tends to andsides of the hns.

heavier than desired. Furthermore, this `construction .is .limited as to the vpermissible temperaturediierence between the .tubes'because of the expansion strains set vup inthe plates which -are lockedsecurely to the tubes by the expand- `of the heat exchanger ying process.

Va heat exchanger in heat exchange devices -oi elevation, with shown in longitudinal section,

tance between machine .and smaller tube,- out increasing the tubes.

The object of .the present invention is to overcome these difficulties and .provide a tube-to-tube and temperatures and having greatly reduced .resistance to heat transfer and which is compact and easy to clean.

Another object of the invention is to provide a heat exchanger in which the stresses of ei:- pansion and contraction are substantially eliminated, even when operating .with uids widely different in temperature.

Another object ofthe invention is to provide a heatrexchanger in .which tubes of different size may `bee-employed Without reducing the efliciency of heat transfenand ythereby enabling the proper velocity ratio .between the two fluids to be maintained.

A furtherobject of the invention is to provide 'which the heat conduction is substantially thelsameas'though the passages for the hot andcold uids were bored in a solid lmetal block.

AA still .further object of `the invention is the provision of an improved method of lconstmcting the type described.

The invention will be understood by considerving the-accompanying drawings and the appende edclaims, -a preferred formof the invention and two modifications thereof .being illustrated in these drawings in order to exemplify thecarryingout-of rthe invention. In these drawings:

Eig. l isa view ineentral longitudinal section Yof' Athe preferred form .of heat exchange unit or l showing a `another modication; and

Figs. 7 and 8 are cross-sectional views taken on lines 'I-1 and 8--8 respectively, of Fig. 6.

Referring to these drawings, there is illustrated a heat exchanger having two U-shaped or hairpin-shaped tubes indicated generally by reference numerals I and 2 (Figs. 1 and 3). Each of the U-shaped tubes I and 2 may be formed in any suitable manner, for example, by bending upon itself a piece of metallic tubing of approximately twice the desired length of unit, bringing the two open ends together and forming two parallel legs Ia and Ib and 2a and 2b, respectively, connected at their opposite ends by integral return bend portions Ic and 2c. These tubes are preferably comparatively thin walled and may conveniently comprise seamless drawn tubes of steel or other suitable metal.

The open ends of tubes I and 2 are permanently secured in any suitable manner, for example by welding 3, toa connection ange fi. Both of these U-shaped tubes extend toward the right from connection flange 4 in substantially parallel relation. Hence, a single central pocket and four outer pockets or spaces exist and extend from end to end of the elongated tubes. Elongated core strips or filler strips 5 of generally triangular shape in cross section are placed loosely within each of the four outer pockets, and a single four-cornered core strip 5 is located within the central or inner pocket. These may be put in place either by springing apart the outer cr right-hand ends of the two tubes I and 2, or they may be inserted before the tubes are welded to flange ll.

A metallic casing 1, preferably cylindrical in form and sealed at its right-hand end as indicated in Fig. 1, surrounds the two U-shaped tubes I and 2 and holds the outer filler strips 5 in place. In the drawings the' clearance spaces between the outer surfaces of the tubes and filler strips and the interior of casing 1 have been purposely exaggerated for the sake of clearness. It is the intention, however, to have the casing fit over these parts with the smallest practicable amount of clearance which will permit the assembly of the L;

casing and tubes. The inner or lefthand end of casing I is provided with a flange 8 and both flanges 4 and 8 may be bolted to a header 9 by means of a single ring of mounting bolts as indicated by numeral I0. It will be understood that 'i header 9 contains fluid passages which connect with the open ends of the respective U-shaped tubes I and 2 for the purpose of conducting one of the heat exchange iiuids through one of these tubes, tube I for example, and the other fluid through tube 2.

The core strips 5 and 6, in order to facilitate the transfer of heat between the legs Ia and Ib of tube I and the legs 2a and 2b of tube 2, may be made of copper aluminum, or a suitable alloy, although they may also be made of steel. In order to bring about intimate heat conducting contact between the surface of the several tube legs Ia, Ib, 2a, 2b, and the surfaces of the cores 5 and 6 in contact with them, the interior of casing 'I not occupied by the tubes and core strips, is filled with an interstitial material II which is liquid a1; the operating temperature of the heat exchange apparatus, although it may be solid at ordinary room temperature; that is to say, it may solidify after the apparatus has been in operation and is shut down and allowed to cool. Material II, however, preferably has a vaporization point which is substantially above the operating temperature of the apparatus so that there will be no vapor formation within casing 1. A number of metals are suitable for this purpose, mercury, tin, lead, and zinc, and alloys of two or more of these metals being examples. Also certain non-metallic materials may be used. One such material is available under the trade name of Dowtherm and consists of a mixture composed of about 26.5% diphenyl and 73.5% diphenyl oxide.

In view of the fact that the liquid interstitial material II provides a path of good heat conductivity between the metal of each of the tubes and the metal of the core strips 5 and 5, it is not important to have the core strips preformed to t closely the curvature of the various tubes. As shown in Fig. 4, the core strips may contact the surfaces of the tubes at certain points but not at others, and if the unit is operated in horizontal position as shown, the core strips will rest upon the upper portions of the tubes and fall away from them along the lower sides of the tubes, the intervening spaces being automatically filled with the molten material I I at the operating temperature of the apparatus. It is desirable, however, to preform core strips 5 and 6 so as to fill as much of the interior space of casing 1 as possible in order to reduce the amount of the more expensive material II required.

In order to reduce heat loss from the heat exchange unit to the surrounding atmosphere, it may be lagged or provided with a suitable covering I2 of insulating material shown in Fig. l.

In the modiflcation shown in Fig. 5 the heat exchange unit is constructed exactly as described in connection with Figs. 1 to 4 inclusive, except for the fact that the core strips 5 and 6 are omitted and the interstitial material II,` which is in the liquid state at the temperature of operation of the apparatus, fills all of the space within casing I not occupied by the U-shaped tubes I and 2.

In the modification shown in Figs. 6-8, the hairpin or U-shaped tubes I3 and Iii cross one another at the ends thereof remote from the connection iiange 4. That is the elbow or return bend portion MC passes through the elbow portion IBC. Flattening the inner elbow IIIC, or both elbows ISC and IAC as shown, eliminates a bulge or enlargement beyondthe lateral dimensions of the tube bundle leg portions I3a and Ilia which would otherwise occur. In this form of the improved heat exchanger element the legs may be nested into contact with each other as shown in Fig. '7 resulting in a generally oval structure when the core strips 5m are assembled with the tubes. Inner cores I5 may be included if desired. Casing 'Im is preferably oval in crosssection. In other than these respects the construction of this modification is like that described in connection with Figs. 1-4 inclusive.

It will be understood that the casings 'I and 'Im may, if desired, be made in some other shape than shown, that is to say, square rectangular, hexagonal, etc., instead of round or oval; also that various numbers of U-shaped tubes I, 2 and I3, I4 may be included in a single casing. It will be also understood that the tube or tubes to carry one of the heat exchange iiuids may be of smaller diameter than the tube or tubes for the other heat exchange fluid, thus enabling the iiuids to pass through the apparatus at the proper velocity ratios.

In carrying out the improved method of producing the novel heat exchanger of the invention, straight tubes of preferably seamless drawn material such as steel, and each one exactly like the other except that certai smaller in diameter than molten state is then poured into the casing and caused to illl all of the spaces within the same not occupied by the tubes a nd core strips. The

whole is then allowed to cool, after which a suitable connection ange or flanges may be applied to the ends of the tubes.

By means of the present i changer unit has been provided which is well 5 tubes in close association, said casing containing united by said liquid with the contiguous surface of said llers.

2. A composite heat exchanger unit including two substantially parallel juxtapositioned prefabricated metallic U-shaped tubes, a plurality WILLIAM BISCI-I.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name

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