US2091119A - Heat exchanger - Google Patents

Description

@M /fwyww M/wf HEAT EXGHANGER Filed Jan. 11, 1936 E. C. SAI NT-,JACQU ES Aug. 24, 1937.

Aug 24, 1937 v E. c. SAINT-JACQUES 2,091,119

v HEAT EXCHANGER Patented Aug. 24, 1931 UNITED STATES HEAT EXCHANGER Eugne Camille Saint-Jacques, Paris, France Application January 11, 1936, Serial No. 58,747

In France January 14, 1935 3` Claims.

`This invention relates to surface heat exchangers, and more particularly to such devices used to transmit heat fromone ilowing fluid to another flowing fluid, said iluids being either in.`

` the liquid or gaseous states.

'Ihe principal object of the invention is to improve the eflciency of, and the rate of heat transmission in, heat exchangers of the tubular type, in which the `heat-conveying iiuid must first transmit heat to the metallic walls of the tubes, which walls then transmit the heat to the iiuid to be heated.

A further object of the invention is to provide special improved types of tubular heat exchangers in which the length of travel of the fluid is considerably longer than the actual length of the tubular channels composing said heaters, and the time of contact available for conveying heat from one fluid to the other is correspondingly lengthened.

A still further object is to provide a special concentric multitubular heater, in which a helical and swirling motion is imparted to the heatconveying and heat-absorbing fluids passing therethrough.

One of the principal defects-of tubular heat exchangers of existing types lies in the fact that the greater part of the iluids'between which heat is to be exchanged ilows through the central 130 portion of the cross-section of the tubes, while the fraction of said fluids which is in contact with, or in the immediate neighborhood oi, the metallic walls of the tubes is materially retarded by friction against said walls, its rateof ow being so reduced thereby that it serves more as a heat insulator than as a heat conveyor. Thus the major portion of the iluids moves under conditions which do not favor a high rate of heat transmission. By the use of my invention,

40 these defects are avoided as all parts of-the iluid are brought into contact with the coniining wall during passage through the apparatus.

Further details and advantages of the invention will appear from the inspection of the ac- ,companying drawings, which are given by way of example, and are not to be considered as limiting in any degree the scope of the invention.

Said drawings show two of the preferred embodiments of the invention. In these drawings:

Fig. 1 is a longitudinal cross-section of the first embodiment, the spacing disks and central core being shown in elevation;

Fig. 2 is a longitudinal cross-section of the second embodiment;

, 2 and 3.

Flg. 3 is an elevation of the second embodiment;

Fig. 4 is a plan oi the latter.

Fig. 5 is a sectional view on the line V-V ofl Fig. 1.

In the example shown in Fig. 1, a is the central core member inserted in the center of an inner tubular heaterelement b which is closed at both ends. Said core member a bears at suitable axial intervals a plurality of spacing disks c machined to iit slidingly inside tube b, said disks c being provided with numerous radial inclined slotted passages c1 overlapping one another. Tube b is iixed by means of spacing collars d comprising slanting guide vanes within a corrugated metallic caslng e also closed at both ends. As mentioned above, said spacing collars may optionally be replaced by a continuous helical baffle. 'I'he total structure may be completely inclosed in a heat-insulated tube g within whichl may slide the inner heater tube b.

Said inner heater tube b is shown provided with tangential inlet and outlet tubes. h1 and ha for the hot gases; the corrugated casing e is likewise provided with tangential inlet and'outlet tubes i1 and i: for the cold gases, said inlet and outlet tubes being also located at the ends of said casing.

Under these conditions., the hot gases enter tangentlally through inlet h' into one end of tube b, and acquire inside the latter a rapid' helicoidal motion, the pitch of which is maintained substantially constant by the passage of said gases through the slotted passages in disks c. Said gases are finally evacuated through outlet h2 at the oppositeend of tube b. In a like manner, the cold gases follow a helicoidal path between tubes b and e. V

This heater may be connected to provide contra-now of the hot and cold gases, by setting the cold gas inlet at the opposite end from that of the hot gases; or, on the contrary, for parallel ilow, by connecting the hot and cold gas inlets at the same end of the heater. Furthermore, a mixed parallel and contra-flow arrangement may be obtained by feeding the gases to be heated into the casing e at both ends of the same, in

two opposed streams, and evacuatlng said gases at the center, either by a single outlet tube, or by two separate outlet tubes, as shown in Figures In the variant illustrated in Figs. 2 to .4, a is the `central core; b the inner heater tube concentric lar and concentric with both a and b, and within which iiow the cold gases. h1 and ha are the tangential inlet and outlet tubes for the hot gases which are located at the ends of tube b; i1 and i1', 5 i2 and i2' are respectively the tangential inlet and outlet tubes for the cold gases, the first located' at the ends, the latter on both sides of the middleI point, of the casing e, so as to give the mixed parallel and contra-how arrangement described hereabove.

A sheet metal helix k winds around central core a, its outer edge bearing against the inner surface of tube b. A second sheet metal helix l winds around tube b, its outer edge bearing 'against the inner surface of casing e. The pitches of the two helices 1c and Imay optionally be either equal or different. The helices may have multiple threads.

The heater may be designed so that the helical baiiies k and l being simply slipped over the core a and tube b respectively, tube a may be rapidly removed, and then tube b, so as to release baii'les K and l for cleaning. For this purpose, it will be sufilcient' first to 'remove the bottom plates m which close the ends of tubes b and e.

The operation of this heater is identical with that of the device illustrated in Fig. 1.

It is evident that the same device may be connected to give pure contra-flow or pure parallel flow, by placing at the end of the casing e opposite to that of the inlet of the hot gases, either the cold gas inlet'or the cold gas outlet. n

By means of the helicoidal and swirling motion imparted to the hot fluids on the one hand and to the cold iluids on the other, these terms being used relatively, a longer path and greater length of contact is insured for given overall dimensions than in any known type of heat exchanger, without having to resort to complex baiiiing which 40 causes excessive pressure drop through'the heater.

Furthermore, the maximum rate of heat transmission by conduction is insured through the medium of the spacing disks interposed between the central core and the inner heater tube. Said spacing disks become highly heated by the hot gases passing through their slotted passages, and

they then transmit this heat to the walls of the inner heater tube.

'Ihe use of an outer casing comprising a corrugated outer wall has the advantage of avoiding excessive gas velocities suchas would occur in a tube having a smooth inner surface along which the gases would flow tangentially; the corrugations of the casing actually force the molecules of gas to remain longer in contact with the inner heater tube, and also serve to reduce the thickness of the veins of gas and to produce velocity changes and turbulence therein, as they pass from one corrugation to another, all of which 50 factors contribute to accelerate the diffusion of the heat throughout the mass of said gases and so to raise the rate of heat transfer. Furthermore, the corrugated casing constitutes a heat-conducting body of considerable mass and large contact surface, which helps to convey heat to the gases flowing against it. While I have described a preferred embodiment of my invention, it is to be understood that changes in the form, proportions used and minor details of construction may be made without departing from the spirit vof the invention and the scope of the appended claims. I claim:

1. A heat exchanger of the class described comprising, in combination, a central core member, a

plurality of tubular members inclosing said core member and substantially concentric with respect to the same, said tubular members being closed at both ends, tangential inlet and outlet connections for feeding iiuid into and evacuating same from each of said tubular members, spacing means interposed between said tubular members and between the latter and said central core member, to maintain the same in fixed space relation with respect to each other and to said central core member, said spacing means being provided with suitable apertures to allow said fluids to ow through them from one end to the other of said tubular members.

2. A heat exchanger of the class described comprising, in combination, a central core member, a plurality of tubular members inclosing said core member and substantially concentric with respect to the same, said tubular members being closed at both ends, the outermost member having corrugated sheet metal walls, means for admitting a fluid into and evacuating same from said innermost tubular member, means for admitting.a uid into and evacuating said fluid from said outer tubular member, baille members inserted between said central core member and the innermost tubular member, and between said innermost tubular member and said outermost tubular member said baille members having radially inclined slotted passages therein, for thepurpose of imparting to said fluids helical motion from the fluid inlet .to the fluid outlet in each tubular member, and for maintaining said tubular members in fixed space relation with respect y spect to each other and to said central core member, the vanes being suitably inclined to allow said fluids to iiow through them from one end to the other of said tubular members.

EUGNE cAMnLE sanar-JACQUES.

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