US2539886A - Tubeflo section - Google Patents

Description

Jan. 30, 1951 w. BISCH 2,539,886

TUBEFLO SECTION Filed Nov. 16, 1945 2 Sheets-Sheet l INVENTOI? William fl/scfi BY M M Mi d M HIS ATTORNEYS W. BISCH TUBEFLO SECTION Jan. 30, 1951 2 Sheets-Sheet 2 Filed Nov. 16, 1945 lNVE NTOR BY I Q4 $4 014 H I 5 ATTORNEYS UNITED STATES ATENT OFFICE TUBEFLO SECTION William Bisch, Holmdel, N. 1., assignor to The Griscom-Russell Company, New York, N. Y., a corporation of Delaware Application November 16, 1945, Serial No. 629,050

3 Claims;

This invention relates to heat exchange apparatus and, more particularly, to an improved construction of heat exchanger.

In numerous industrial operations it is desirable or essential that heat be economically transferred from a comparatively hot fluid to a fiuid of lower temperature. Thus, for example, in oil refinery work the efficient operation of the plant often depends upon the completeness with which the heat content of different fluids is interand sides of the fins. The weight of the fins conchan ed at different stages of their flow. Not insequently is a considerable factor and tends to frequently the temperatures of both the hot fluid make the heat exchanger heavy. Furthermore, and the (300 81 flu a e ot y pa at e y the center-to-center distance betwee the tubes h gh but also a comp r v ly large t p ra u is fixed by the expanding machine and prohibits difference exists between them. The mechanical the use of tubes of different size in the same unit construction of the heat exchanging device emwithout increasing the resistance to heat flow ployed under such conditions and for such purb t t tubes pose is an important item, since this construction The present invention aims, more specifically, determines the thermal efficiency and economy to overcome these difficulties and to provide a of operation as well as the adaptability of the tube-to-tube heat exchanger adapted for use at device to various installations. high pressures and temperatures having a greatly In general, an economical heat exchanging dereduced resistance to heat transfer and which vice should provide the maximum thermal effiis lighter in weight, more compact, easy to clean ciency consistent with reasonable initial and and tends to keep itself clean. maintenance costs and should be constructed to Another object of the invention is to provide provide for easy cleaning of the fluid passages a heat exchanger of the type described in which a fluid-tight J' between its Component tubes of different size may be employed without parts. In certain processes it is desirable or eS- reducing the efficiency or" heat transfer, and sential that one or both of the fluids between thereby enabling the proper velocity ratio bewhich an exchange of heat is desired be delivered tween the two fluids to be maintained. n t O y at comparatively high temperature b A further object of the invention is the provia at comparatively high pressure, and accolflsion of an improved method of constructing heat ingly the heat exchanging device should be capaexchanging devices of the type described. the of withstanding high pressures at high tem- The invention will be understood from a conpelatures Without danger Of leakage p sideration of the accompanying drawings and of The primary object of the present invention is a the appended claims, certain modifications being to provide an improved heat exchanger for efillustrated for the purpose of exemplifying the iecting the transfer of heat between various invention. In these drawings: kinds of fluids at extremely high pressures and Fig. 1 is a side view of a heat exchanger unit temperatures without danger of leakage or rup- 40 constructed according to the preferred emboditure. ment of the invention;

In United States Patent 2,013,187, issued Sep- Fig. 2 is an enlarged view, partly in elevation tember 3, 1935, to Joseph Price and assigned to and partly in section, of the right hand end porthe same assignee as the present application, tion of the device shown in Fig. 1; there is described and claimed a heat exchanger Fig, 3 is a, cross-sectional iew taken on line device of the type in question which is con- 3 3 of Fig 1; structed with comparatively thin metal tubes of i 4 is a i il t Fig, 1 01 a modified steel or other suitable material, such tubes passform of t, exchanger it; i t o p n in a plurality metal Figs. 5 and 6 are views showing steps in the p ates, t e plates being Spaced 3 and manufacture of the preferred embodiment of the formly along the tubes. The tubes are expanded into intimate heat exchanging contact with the plates by drawing an expanding device through the tubes.

Whi1e heat exchangers of such construction have reached a high degree of commercial success, large quantities of them having been manufactured and being new in use, nevertheless the construction possesses limitations. For example, the tubes cannot nest against one another but must be spaced apart, and, in order for the fins to have sufiicient strength it is necessary for the tubes to be spaced apart not less than about inch and excess metal is required at the ends invention;

Fig. '7 is a cross-sectional View of a modification;

Fig. 8 is a cross-sectional view of another modification; and

I Fig. 9 is a side view of one of the tubes used in the modification shown in Fig. 8.

A Referring to the drawings, particularly Figs. 1 and 2, the heat exchanger unit of the invention comprises generally a plurality of tubes or pipes T1, T2, T3 and T4 arranged side by side and nested against one another in parallel relation leaving spaces or pockets between them extending lengthwise substantially from end to end of the unit. In these pockets are elongated strips or bars forming cores C1 and C2 of good heat conducting material such as copper, aluminum or a suitable alloy. The cores may also be made of steel. The tubes and cores are secured together throughout their length by brazing or welding, thereby uniting their contacting surfaces to provide paths havinglow resistance, to the conduction of heat between the tubes.

Tubes T1, T2, T3 and T4 are preferablycomparatively thin walled and may conveniently comprise seamlessdrawntubes of steelor other suitablemetal. The elongated strips. or bars which form the cores may take various shapes, and asshown in Figs. 2 and 5 may comprise four outer core strips C1 within the lengthwise pockets between-the tubes, and two inner core strips C2 of smaller cross-sectional area within the internal spaces or pockets. This results in two of the tubes-for example tubes T2 and T4,

being in-contact with one-another, and the other I twotubes Ti and- T3 being spaced apart from each otherbut in. contactiwith-each of the tubes T2 andTa. The cross-sectional shape of the device is approximately that of an ellipse.

The outer core strips Cr are preformed with curved inner surfaces which conform to the curvature of the tube surfaces. The-apex l at the intersection between these curvedsurfaces is preferably flattened as shown in Fig.- 5 to facilitate manufacture of" the core strips and their assembly with the tubes.- strips C2 surfaces. Their apexes-Z are blunted or flattened in a similar manner to'the-apexes-i of'core strips C1. As shown in Fig. 5, small airspaces exist between the-apexesl of-the outer cores C1 and the apexes- 2 of the innercores C2. These are eliminated during the brazingor welding operations, as will'be mentioned further below, so' as to provide contiuous metallic-paths for the how of heat between the-tubes.

Arrangement is made for one or more of'thetubes to carry a comparatively hotfluid, and-for the remainder of the tubes to-carry a comparatively cool fluid. It is generally preferred to employ each unit of the heat exchanger as a double pass heat exchange device, although this ar rangement is not essential to theinvention.

Thus in the disclosed embodiment means are provided for passing a comparativelyhot fluid through the tubes-T2 and-T4 in succession and for passing a: comparatively-cool fluid-through the tubes T1 and'Ts in succession. The comparatively hot and coolfluids maybe conducted to the tubes by the use of a stationary-headt- The inner core 1 are preformed with substantiallyequalsides of the-samecurvatureas thetube As indicated at 1 in Fig. 2 the flange-- At the opposite end of the heat exchanging device the return connections 5 and 6 may convenientl comprise return bends formed of the same material as the tubes and welded to these tubes as indicated at 9 and I0, respectively. To accommodate these connections the outer ends II of tubes T2 and T4, respectively, are offset so that. the outer return bend iencompasses the inner return bend-5. To facilitate the offsetting of tubes T2 and T4 a strengthening fin or flange i2 is provided to surround the heat exchanger tubes as shown in Figs. 1 and 3. Fin I2 is of sufficient strength to Withstand the bending stresses accompanying the formation of the offset'portions in the ends II.

In the heat exchanger unit as thus constructed, theflow path foreach of the fluids has substantially uniform area from ingress to egress, tending to'kcep the unit clean, that is, free of scale or deposit from the fluid passing through it. Also in case suchv deposit does accumulate through extended usethe flow. passagesarenot: difficult to clean.

It will be understood that head 3.contains-.ingross and egress channels.(not shown). for. conveying the respective fluids to and from the twopairs of tubes. Thusthe comparativelyhotfluid. may flow into the end oftube T2 from head. 3; then through the tubeto the returnbendkand thence through tube T4 back to head 3'r where it enters an egress channel therein. Alsosthe comparatively cool fluidmayenter tube T1 from a separate inflow channel in head. 3 and flow through tube T1, return bend--5 and tubeTa .Where. it enters a fourth channel in head 3: The heads 3. may be constructed, for example, as-shown-in the previously mentioned U. S=- Patent, and any desired number of the heat exchanger unitsmay. be. assembled to form-a heat eXchange-apparatus-of. any desired capacity as disclosed in thatpatent. Thus a plurality of suchunits-maybe assembled in series relation by employing heads. as. disclosed in that patent. It will be understood that the heat exchanger unitsof the-present. invene tion-may be constructed of-tubes of any.:desir.ed. length to. suit-a particular. installation; A150,; as; disclosed in that patent, theheat exchangeunits can be made in sections wherev it. is desirable, to. employ a unit .of. extreme... length...

The modified form of heat. exchanger .unit/ shown inFig. 4-is like thatof Fig. 1.excep t-that. bands l3or Mare employedtostrengthem the; unit; that is, to assistthebrazingor, weldingfii. tubes and core stripsin holding. the.v imitate: gether. The type of band indicatedl at 1343011..- sists of afewturns of binding. wire,.while.the type shownat 14- consists .ofa metal striphaving. its ends joined by brazing, welding, or..the, like. A given unitmay-be.;.provided with. either type; applied in. suitable spaced relation. throughout its length.

In-regard to the mcthod ofmanufacturing the heat exchanger-- unit, when the core stripsandtubes are to be secured togetherby brazing or. hard soldering; the inner surfaces of the. core. strips C1 are provided-'with-a coating-of appro priate welding metal having a fusin temperature; which is lower than that of thetube or core ma-. terial. Such-coating is indicatedat l5.in Fig. .5, andthe inner core strips 02 are coatedaallover; with a layerl6-of similar welding metal. The various parts, includingthe four'tubes', the..fo.un core strips-C1 andthe'two-core strips.C2 are; assembled in parallel relation as shown in .Fig. 5.,-v and temporary binding wiressuch as; indicated at I! are applied at suitable intervals throughout the length of the bundle to hold the parts together. It will be understood that with the parts thus assembled, the surfaces of the tubes T1, T2, T3 and T4 will not necessarily be precisely tangent to one another or in contact with one another as shown in Fig. 5, but at least some of the tubes will be apt to be held in slightly spaced relation from their neighbors by the thicknesses of the core strips C1 and C2.

With the parts assembled as shown in Fig. 5 thy are subjected to a brazing temperature in any suitable manner as, for example, by placing the entire bundle in an oven, or by passing the bundle through a continuous brazing apparatus adapted to apply brazing temperature to a portion only of the bundle at a given time. In Fig. 6 the relative positions of the tubes and core strips are shown after the brazing operation has been completed and the parts united thereby into a unitary structure, and the temporary binding wires ll removed.

During the brazing operation appropriate pressure is applied to bring the four tubes into tangential contact with one another throughout their length as shown in Fig. 6. Such pressure may be applied either by means of the binding wires IT or by other external and appropriate means. The apexes l and 2 of the respective core strips C1 and C2 disappear during the brazing operation and the brazing metal flows into and fills the vacant spaces or interstices shown in Fig. 5 adjacent these apexes. This causes the coatings I5 and I6 of the brazing metal to become somewhat thinner as shown in Fig. 6. The contacting surfaces of the respective tubes and core strips are united in intimate rigid contact throughout the extents of their surfaces and throughout the length of the heat exchanger unit.

When the parts of the heat exchanger unit are to be united by means of welding instead of brazing, the parts are assembled in a bundle similar to that shown in Fig. 5, but the coatings l5 and I6 of welding metal are omitted from the core strips. Then the assembled bundle is subjected to a welding operation, preferably in a continuous welding machine, causing the parts to be Welded together as shown in Fig. 7. From this figure it will be understood that the interengaging surfaces of the core strips CW1 and CW2 are united by the welding of the surface metal of these strips and that of the respective tubes as indicated at [3 and H. The metal of the core strips, while in the liquid condition fills the interstices between the tubes and cores, thus providing all metal heat flow paths between adjacent tubes.

Referring now to Figs. 8 and 9, there is here illustrated a further modified form of the invention. In this embodiment each of the tubes T5, T6, T7 and T8, one of which is shown in side view in Fig. 9, has circular end portions 29, and between these end portions are heat conducting cores CI, a portion or" each core being integral with the metal of the tube. These core portions CI have flat interengaging surfaces 2! extending lengthwise of the tubes and the thickness of these integral core portions CI varies as may be seen in the cross-sectional view in Fig. 8 in such manner that the four tubes can be nested together with their respective flat surfaces 2! in engagement with one another. These several surfaces are united by films of welding metal 22 to compipe the t bes. into a unitary structure.

Tubes-T5 and T7 are in cross section substantially the shape of a modified pentagon with one rounded corner, and tubes T6 and Ta are in cross section substantially trapezoidal with one rounded corner. With their fiat sides in engagement with one another as described, and as shown in Fig. 8, the general outline of the unit in cross section is that of a parallelogram with rounded corners similar to the other forms of heat exchange unit previously described.

The metal added along the central portions of the tubes and extending outwardly beyond the circular outlines (Fig. '7) of the end portions 20 of the tubes serves as core material forming paths between the several tubes for the transfer of heat in a manner similar to the heat transfer in the other embodiments of the invention.

It will be understood that the end portions 20 may be secured in a connecting flange similar to flange 6 in Fig. 1 and that at the opposite end of the unit, the proper tubes may be connected'together by return bends similar to return bends 4 and 5.

By means of the'present invention there has been provided a compact heat exchanger unit which is comparatively light in Weight and is well adapted for use at both high pressures and high temperatures and which provides for the efficient transfer of the heat from the comparatively hotter fluid to the cooler fluid.

Although in the described embodiments two tubes are provided for hot fluids and two for cooler fluids, the number of tubes employed for each fluid may be varied as desired, and the invention is not limited to the number of cool and hot tubes shown. Thus the units may be of the single pass type with one or more tubes for each fluid and no return flow. When a plurality of passes is to be employed, two or more tubes are used for the hot fluid and two or more tubes for the cooler fluid. Different numbers of tubes may be used for the difierent fluids. For example, the unit may comprise three tubes for carrying one fluid and six tubes for carrying the other.

Also, the tube, or tubes, for carrying the hot fluid may be of different size from the tube, or tubes, for carrying the cooler fluid. In this way the fluids may be caused to flow at different velocities to establish the maximum rate of heat transfer between the two fluids for any particular installation. When either pair of tubes, for example tubes T1 and T3 is made smaller in diameter than the other pair T2 and T4, the cross section of the elongated outer and inner core strips may be modified correspondingly but the length of the path of heat conduction from tube to tube through the cores is not increased. Consequently, there is no change in the rate of heat transfer due to an increase in the length of'the path of heat conduction from one tube to another. Should it be found desirable to do so, the diameter of one of the four tubes or of one of each pair of the tubes may be reduced or increased as required to produce the desired fluid velocity in that particular tube.

It should be understood that the embodiments of the invention selected for illustration are but typical of various forms in which the invention may be carried out and that the invention is not limited to the details of construction disclosed except in so far as set forth in the appended claims.

In the present application the filler strips and tubes are restrained against relative longitudinal movement under the forces of expansion and com 7 traction, whereas-in applicants-Patent No. -2,4 43,- 295. issued J we 15,, 1948; the pants: are. not; so: he, strained Iclaim;

L; A; built-up. heat exchanger element including four substantially parallel; originally discrete prefabnicatecl thin-wall. seamless. metallic tubes;. two at said. tubes: being: in, contact,- with each otheriand also. in contact'lseparatelyiwith each of: the other two tubes, said .foux tuhesthns form,- ing two= inner interstitial; spaces. of substantially triangular cross-section and; four outer interstitial: pockets. of substantially triangular: crosssection', and triangular prefabricated; metak filler strips-rot substantially triangular crossesectien; disposed to: occupy substantiallyall; the, freespace. in saidi spaces and pockets,v said-- tubes and, said strips being united. structurally: and thermally by: a. continuous metallic. bond.- applied: during: f abnication. of the element to. unite alli contiguous prefabrieat'ed metal 1 surfaces.

2: A built-up heat. exchanger element; includ; ing four substantially parallel originally discrete; prefabricated metallic. tubes, two of said tubes being in mutual contact; and, also in contact separately with, each ofthe. other tubes; and. a plurality of prefabricatedl metal fillers, positioned, to fillsubstantially all of the space between the outer, walls of said. tubes along, substantially the entire lengths thereofllsaidl tubes andfillers being united structurally andthermally by acontinuous metal bond applied; during fabrication of. the element 8 to..unite. all; contiguous. metal surfaces; and pre: vent. relative. longitudinal.v movement thereof).

3. A..built.-.up heat exchanger element asudefined; in claim 2; in which, each of said prefabricated. metal fillers isintegral with a prefabricated metallic tuba.

WILLIAM BISCH.

REFERENCES- CITED The following referencesare of record in the file ofthis patent:

UNITED STATES PATENTS Number: Name Date 1,779,706 J'acobus Oct. 28,1930 1,841,762- Samesreuther Jan. 19, 1932 2,000,906 Turner May" 14', 1935 2,013,187 P-rice Sept. 3-, 1935- 2 046381- Priee July 7, 1936 2,119,451 Turner May 31, 1938 2,122,521 Goddard July 5, 1938 2,146,823 Karmazin Feb; 14, 1-939 2,268,369 Askin- Dec. 30, 1-941 2 ,270,864 Blais Jan. 27, 1942- 2,313,315 Blais Mar. 9, 1943 2,443,295 Bisch June 15, 1948- FOREIGN PATENTS Number Country Date 336,755 Great, Britain Oct. 23,, 1930- 7921166 France Oct. 28, 1 5.

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