US2686044A - Heat exchanger - Google Patents

Description

10, 1954 P. E. J. M. MALDAGUE HEAT EXCHANGER 4 Sheets-Sheet 1 Filed Oct. 14, 1949 a Q w lllll lllll llwlllll 0 6 P HWHW m m H 1+ iv i ||l ||||L|:||:||.. 11| 1r l- 0, 1954 P. E. J. M. MALDAGUE 7 2,686,044

HEAT EXCHANGER Filed Oct. 14, 1949 4 Sheets-Sheet 2 Aug. 10, 1954 P. E. J. M. MALDAGUE HEAT EXCHANGER 4 Sheets-Sheet 3 Filed Oct. 14, 1949 x... axzjeu 4 Sheets-Sheet 4 Hm I D M I 3 9 wwwwmw M 1954 P. E. J. M. MALDAGUE HEAT EXCHANGER Filed Oct. 14, 1949 Patented Aug. 10, 1954 HEAT EXCHANGER Pierre Edmond Jules Marie Maldague, Seraing, Belgium, assignor to Societe Anonyme John Cockerill, Seraing, Belgium, a Belgian company Application-October 14, 1949, Serial No. 121,347

Claims priority, application Belgium October 16, 1948 in heat exchangers with a nest of tubes the transmission of heatis effected between a stream of fluid circulating through the interior of the tubes and another stream of fluid circulating over the outside ofthe tubes. The tubes forming the nestof tubes are secured in a fluid-tight manner in tubular plates by means of swaging or ramming. In many applications it is indispensable that the tubes forming the nest of tubes may be replaced individually in the case of deterioration;

the easy replacement of each tube individually is only possible when the axis of the tubes is at constant curvature and at constant torsion, that is to say, that from a technical point of view this axis is either straight or curved along an arc of a circle.

In these exchangers, it is also desirable for the coefficient of thermal transmission to be as high as possible so that it is possible to reduce the surface of heat transmission and consequently, the

cost of the apparatus. It is also necessary to take care that the streams of fiuid passing through the apparatus are subjected to the minimum possible loss in load so that the mechanical power dissipated in the apparatus is at a minimum. Finally it is desirable that irregularities in temperature of the various parts of the apparatus do not cause the appearance of considerable stresses in the metal.

Up to the present time it has not yet been possible to obtain simultaneouslyall the desiderata referred to above.

The present invention has for its principal object to provide a method of construction of heat exchangers with a nest of tubes which simultaneously produces a satisfactory transmission of heat, a low loss of load in connection with each of the streams of fluid, low stresses due to thermal planatory description set out hereinafter With' reference to the accompanying drawings of some forms of construction of heat exchangers according to the invention.

Figures 1 and 2 are diagrammatic illustrations of tube contours and derivation thereof. Figure 3 1 Claim. (01. 257-224) 2 is a diagrammatic longitudinal section illustrating tube layer disposition. Figure 4 diagrammatically illustrates the arrangement of tubes in a layer. Figures 5, 6 and '7 diagrammatically illustrate an arrangement of tubes having a noncylindrical central portion. Figure 8 is a side elevation of a heat exchanger. Figure 9 is a section taken along the line A-A of Figure 8 and Figure 10 is a section taken along the line B-B of Figure 8. V

Fig. 1 shows diagrammatically the outer contour of the nest of tubes of a heat'exchanger according to the present invention.

The surface, casing of the nest of tubes, is a cylindrical surface of revolution about the axis a, the generating line of this cylindrical surface being the line b. The volume in which is contained eral shape converging from-the section 3 to the section 4.

Fig. 2 shows a straight cylinderidentical with that in Fig. l, included'bet-ween the sections 2 and 3, this cylinder being extended in Fig. 2 up to the sections and 4 in Fig. 1. The section iii is the middle section of Figs. 1 and 2.

The straight line segment 0 in-Fig. 2 represents the line, in the plane of'the drawing, of a semi plane at right angles'to the plane of the drawing passing through the points'5'and t and through the point of intersection of the axis a in the section It, the intersection of this semi-plane with the'cylinder of Fig. 2 being the semi-ellipse shown in Fig. 2 after folding in the plane of'the drawing. The points '1', 8 and 9 of the folded semi-ellipse d are folds at the respective piercing pointslt and 9 of the semi-ellipse inthe respective sections 2, ill and 3. The-curve e in Fig. Z-indicates an arc of a circle of correct size, defined by the three points if, 8' and 9, and limited-at H and E2. The segment 0 of Fig. 2 also representsthe projection, in the plane of the drawing, of the arc of circle e brought into the secant plane of the I section thus obtained from the generating line b,

comprised between the sections 2 and 3, being generally approximately and not rigorously a straight line. From a sectional point of view, this latter approximation is without practical importance, as the difference between a straight cylinder and the actual cylinder comprised between the sections 2 and 3, is comprised within the tolerance of manufacture. When a predetermined tolerance is adopted for the dimensions of a true cylinder between the sections 2 and 3, it is possible to take this tolerance into consideration in drawing the arc of circle e, so that this is not defined rigorously by the points I, 8', and 9 but may deviate therefrom within limits defined by the admitted tolerances.

The method of generation of the surface shown in Fig. 1, by the rotation of an arc of circle about an axis, constitutes the principle of construction of heat exchangers with a nest of tubes according to the invention. In apparatus 'according to the invention the various layers of tubes are obtained in such a manner that all the axes of the tubes constituting a layer are contained within a cylindrical surface obtained in the manner shown in Figs. 1 and 2, the various layers having the same axis a and the same median plane i9.

Fig. 3 shows a section, through an axial plane, of the various cylindrical surfaces containing the layers of tubes constituting the nest of tubes according to the invention, the lines 1 indicating the track of these surfaces in the plane of the drawing. The sections l, 2, 3 and 4 of Fig. 3 are those defined in Figs. 1 and 2.

Fig. 4 shows the arrangement of the tubes in a layer, according to the invention, the tubes being curved along an arc of a circle e defined in Fig. 2 and the terminal sections I and 4 being those defined in Figs. 1 and 2.

The method of construction of the nests of tubes according to the invention, may adapt itself to apparatus of very diverse dimensions, by reason of the freedom of selection which exists for the respective positionings of the sections i, 2, 3, ti and i9 and of the points 5 and 6, defined in Fig. 2. In particular, it is possible to obtain a nest of tubes in which the straight cylindrical portion comprised between the sections 2 and 3 is of zero value.

This last particular case may be obtained in the following two ways.

In the first way, the tubes having only a slight or zero curvature and each layer of tubes then has the shape of a hyperboloid of revolution, as shown in Fig. 6 in which the lines it represent the axes of the tubes forming a layer. In the second way, all the tubes forming the layer have a determined curvature and their axes are located in axial planes of the nest. Fig. 5 shows aview or" such a layer of tubes, the lines g indicating the axes of the tubes forming this layer.

Other constructions of nests of tubes, according to the invention, can be obtained by juxtaposition of the partial elements, taken from the constructions above described. For example, it is possible to arrange the curved tubes in the arc of a circle in such a manner that their axes g are contained in one plane, as shown in Fig. 5, and a number of planes of tubes of this type may be juxtaposed in such a manner as to obtain a nest of tubes of arbitrary section varying arbitrarily.

The nest of tubes, according to the invention, obtained as above described, are secured in a known manner by swaging or by ramming in tubular plates. The tubular plates are more frequently plane but they may be arched.

In the case of heat exchangers with a nest of tubes which are to resist a high pressure, the nests of tubes, according to the invention, lend themselves particularly well to the construction of arched tube sheets, as the surface of these arched tube sheets may be substantially rectangular to the axes of the tubes, as indicated diagrammatically in Fig. '7, in which the lines 2' indicate the axes of the tubes and a indicates an arched tube sheet.

Fig. 8 shows, descriptively and not in any way in a limiting sense, an improved heat exchanger according to the invention. The lines I and the tubular plates define the position or" the nest of tubes according to the invention, of which a tube 70 is shown. The casing 11. consists of a straight central cylindrical section and two end truncated sections into which the admission and outflow of fiuid in circulation to the outside of the tubes takes place through the tubular members p and q. The fluid circulating in the interior of the tubes is guided by the tubular members r and s bolted in a known manner to the plane tubular plates m. The axis a of the apparatus is also the axis of the nest of tubes according to the invention. The detail of the arrangement of the tubes in the respective sections A-A and BB of Fig. 8 shows that the cross sectional passage of fluid outside the tubes of the nest is appreciably greater in the inlet and outlet sections of this fluid than in the central cylindrical section.

What I claim is:

A heat exchanger comprising in combination a pair of end plates, a series of tubes extending in longitudinally adjacent relationship and mounted between said end plates to form a bundle body having a generally cylindrical central portion of substantial length and divergent end portions, the center line of each of said tubes constituting an arc of a circle throughout its length facing concavely inwardly toward the central longitudinal axis of said bundle body, said tube center lines being each disposed in planes forming equal acute angles with said central axis.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,125,758 Stack Jan. 19, 1915 1,655,086 Blending Jan. 3, 1928 1,869,973 Lucke Aug. 2, 1932 2,346,822 Clancy Apr. 18, 1944 FOREIGN PATENTS Number Country Date 1,136 Australia Dec. 30, 1931 of 1931 3,792 Great Britain Dec. 14, 1872 of 1872 112,222 Great Britain Jan. 3, 1918 563,894 Germany Nov. 11, 1932 570,115 Great Britain June 22, 1945

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