US2229344A - Countercurrent heat exchanger - Google Patents

Description

Jan. 21, 1941. o' SCHNEID R 2,229,344

- COUNTERCURRENT HEAT EXCHANGER I Filed Nov. 19, 1938 M i M 2 INVENTOR Oiflo Jc/zneider ATTORNEY5 Patented Jan. 21, 194i UNITED STATES COUNTERCURRENT HEAT ExonANGaa Otto Schneider, New York, N: Y., assignor of onehali. to Robert Schwarz, White B lains, N. Y.

Application November 19, 1938, SeriaLNo. 241,629

2 Claims. (oi. 252-236) An object of theinvention is to provide a, 'countercurrent heat-exchangen/which may be readily disassembled for cleaning and repair and is readily reassembled and which involves indil vidual elements of low cost and largely of standard construction.

Another object is to provide a heat exchanger of the above type in which relative expansion under'temperature change is allowed for, 'without the possibility of leakage or undue strain on the connections, despite the elimination of the stufl-' ing box commonly provided for that purpose.

In the accompanying drawing in which is shown one of various possible embodiments of the several features of the invention: Fig. 1 is a view in longitudinal cross-section of one embodiment of heat exchanger.

Fig. 2 is a sectional view on a larger scale show ing one of the connecting mounting elements for of the tube spacing struc-' to be heated is passed. The steam, water or other heatingmedium is admitted through an inlet duct l3 near one end of one outer tube "1- and I escapes through an outlet duct I4 near the corresponding end of the other .outer tube, a tube l5 of the diameter of said ports, being welded at its ends to'said outer tubes near the U-tube connection therebetween. Accordingly the steam or hotwater must pass substantially the lengths of the respective outer tubesjfor effective heating of the fluid passing through the inner tubes. The

construction thus far described is that of a substantially conventional countercurrent heater.

According to the present invention, the bundle oi inner tubes I2 is attached at one end atthe flange (not' shown) of the inlet or outlet as the case may be, for the water or other fluid 66 to be heated.

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To render the assembly of inner tubes readily demountable from the outer tube, the opposite plate that carries the opposite ends 01 said inner tubes I2 is made up of two parts 2| and 22. The inner part constitutes a disk peripherally threaded at 23 and of diameter slightly smallerthan the bore of the outer tube "I. That disk'is encircled by an annulus 22 threaded over said carryin 'disk. The extremities of the inner tubes are flanged or flared over the disk 2| as at 25 exact 10 ly as at the opposite end. The annulus 22 rests against a flanged ring 26 corresponding to ring l8 7 at the opposite end. A similar flange 21 is welded to the end of the U member and the two flanges 26 and 2! with the interposed annulus 22 are 15 clamped together in a secure assembly by means of bolts 28. I order to render the threaded connection between the disk 2| and the annulus 22 particularly secure, especially where high steam pressure is 20 used, it is desirable to form a conical seat therebetween for which purpose, the end face or disk 2| is bevelled at' 29 and seatedagainst a corresponding conical ledge 30 at'the inner periphery of the "annulus 22. If desired a soft metal gasket 5 (not shown) might be interposed. It is also desirable to cover the threads with graphite, which will serve to-fill the minute interstices between the coacting threads 23 and to prevent binding or rusting together of the threaded connection.

The construction as thus far described, admits of ready disassembly by removal of the bolts 28 and of the U.-;connection I. The annulus '22 may now be readily screwed oil? the threaded disk 2| and the entire assemblage made up of carrying plate l1 and the bundle of inner tubes l2 withcarrying disk 2| may readily be withdrawn from the outer tube and cleaned and repaired as desired and may thereupon readily'be re-assembled. The stufling box commonly used to allow for diflerential heat expansion between the outer steel tubes [2 and the inner copper or brass tubes 12 is eliminated by the presentinvention. Such relative expansion is allowed for, even'though both ends of the outer and inner tubes are rigidly connected together, without possibility of relative movement thereat. According .to the present inventiomthe simple expedient is resorted to, of outwardly bowing the metal of the outer tube III to form a narraw bead or hollow flange .01 greatly enlarged diameter, preferably oi! diameter approximately twice that of the outer tube. That 7 flange may have parallel wallsil and 32 with a toroidal perimeter 33. Preferably as shown, the tube III is made in two sections, flared at their abutting ends and welded together at 34. Thus even in the absence of any relatively slidable parts, relative expansion and contraction. are adequately allowed for without strain on any of the threaded connections.

The long, small inner tubes might in the ab sence of other precautions come into contact with each other with consequent reduction of the effective heating surface under the expansion thereof, due to heating and under the mechanical impact of the steam. To obviate this difilculty, one or more tube spacer units may be provided, preferably spaced about four feet apart. In the case of a tube eight feet "long, a single spacer would be provided near-the middle. ispreferably made up of a narrow, thin metal ring 35 of diameter'smaller than the inner diameter of the outer tube and larger than the bundle of inner tubes. That ring has welded to one edge thereof and-in edge to edge relation thereto, a series of parallel narrow, thin metal strips 36 which extend as chords thereagross. A series of like strips 31 is similarly welded to the opposite edge of thering, but said latter strips extend at an angle as shown to the first set of plates. Preferably anumber of these strips protrude as at 38 beyond the periphery of the ring 35 and serve to sustain said ring in spaced rela-- tion relative to the outer tube. Each small, inner tube will be lodged near its middle in the rectangular frame determined between two pairs of intersectingmetal strips 36, 31 as shown in plan view in Fig. 3. Accordingly, this spacer device will preclude any possibility of contact between the inner tubes.

The two sets of metal spacer strips 36 and 3I are spaced from each other as shown by the thickness of the ring 35, to avoid the greater reduction in cross-sectional area and impedance to steam flow which would be incurred if the two sets of strips were in a common plane,

The pre-heater though illustratively shown in the drawing as a two-unit device may, of course, be made with but a single outer tube section or with three or more such sections depending on requirements. The outer steel tube may be of inner diameter usually between two inches and twelve inches. The inner tubesof copper or brass are usually of inch outer diameter and wall thickness of .040 inch. The device may thus be embodied in preheaters of capacity as'small as or smaller than,5 0,000 B.'t.- u. per hour and as large as or larger than 12,000,000 ,3. t. u. per hour.

With the use of the present invention, the removal of accumulation, such as boiler scale which impairs heat exchange and greatly lowers This spacer the efliciency of the device is rendered so easy that in practice, cleaning may be resorted to at very frequent intervals and the. device readily maintained at maximum efliciency.

The pre-heater may be used in a wide variety of applications and is advantageous as a hot water heater in dwellings, for hot water heating, baths and laundries among other relations.

The tube spacer as shown by itself in Figs. 3 and 4 is not claimed herein, but is part of the subject-matter of my copendlng application, Serial No. 369,589 filed Dec. 11, 1940.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in-the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent isi 1. A countercurrent heat exchanger of the type comprising an outer tube havingilanges at the ends thereof, a bundle of smaller inner tubes having small, clearance with respect to said outer tube, perforated end plates retaining said inner tubes, one of said end plates being larger than the bore of said tube and sustained by one of said flanges, the other plate being slightly smaller in diameter than the bore of said outer tube and slightly larger than that of said bundle and protruding in assembled relation beyond the other said flange, said smaller plate having an annulus threaded thereabout and bolts through said annulus firmly pressing the same against said latter flange.

2. A countercurrent heat exchanger of the type comprising an outer tube having flanges at the ends thereof, a bundle of smaller inner tubes having small clearance with respect to' said outer tube, perforated end plates retaining the same, one of said end plates being larger than the bore of said tube and sustained by one of said flanges, the other plate being slightly smaller in diameter than the bore of said outer tube and slightly larger than that of said bundle and protruding in assembled relation beyond the other said flange, said smaller plate having an annulus threaded thereabout and bolts through said annulus firmly pressing the same against said latter flange, said annulus having a seat near its outer face snugly engaged by the corresponding beveled edge of the smaller plate.

o'r'ro SCHNEIDER.

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