US1961792A - Heat exchanger - Google Patents

Description

Patented June 5, 1934 UNITED STATES PATENTOFFICEA assignor to ltekuperator,

Gesellschaft mit beschrinkter Haftung, Dusseldorf, Germany Application August 6, 1932, Serial No. 627,264 In Germany August 22, 1931 2 Claims.

The principal problem connected with the construction of heat exchangers for high temperatures consists in reducing the temperature of the highly heated parts of the surfaces of the heat 5 exchangers to as low a degree as possible. This is most effectively carried out by increasing the co-efllcient of heat transmission of the heat absorbing medium.

According to the invention such an increase in the co-eilicient of heat transmission is obtained without any special auxiliary agent '(which always acts as a pressure absorber) by utilizing the impact effect of the heat absorbing medium which may leave the actual heating surface at a great speed.

This positive impact eflect' has not hitherto been useful as protection for the heating surface for the reason that the surfaces impinged upon by the heat-absorbing medium do not form the part of the surface most highly heated, but are for the most part or even entirely out of the zone of action of the heating gases or of the radiation of these gases.

According to the invention the stream of the heat absorbing medium impinges upon those parts of the heating surface of the preheater which are endangered either by the high temperature of the heating medium or by their small resistance to heat. Such danger exists principally in the neighbourhood of those-parts 'of the heating surface of, for example, steel recuperators which are first impinged upon by the stream of heating gas and which at the same time are' exposed to the radiation of the walls of the heating gas supply channel or heating chamber. i

' It is not essential when the temperature is high that the part of the wall that is to be protected should be actually impinged by the stream of heat absorbingmedium; if, for example, the part. of the heating surface en'-' dangered is the wall or a channel it is sufficient if one of the other walls of the channelifbe cooled by impact action: the wall endangered which is not directly impinged uponby the heat absorbing medium gives up so much heat to the cooled wall by radiation; when the temperatures are high, that the action is almost as if the wal 5 were itself cooled by-impinging action. The accompanying drawing illustrates diagrammatically by way of example some'methods of carrying out the invention.

. Figure 1 is a sectional elevation ofpart of a heat exchanger provided with tubular elements.

Figure 1 is a cross-section on the line 1' 1 of Figure 1.

Figure 2 is a sectional elevation of part of av heat exchanger provided with plate elements.

Figure 2 is a cross-section taken on the line 2 -2 of Figure 2.

Figure 2 is a plan view taken on-the line l -2" of Figure 2.

Figure 3 is a sectional elevation of a modified form ofheat exchanger provided with plate elements.

Figure 3' is a cross-section on the line 3"?! of 3.

In Figure 1 the medium to be heated (air or the like) is passed through the tubes 1 in the direction indicated by the arrow; these tubes open into a collecting chamber z from which the medium to be heated is withdrawn through the pipe 3 and conveyed to the place where it it to be used. 7

The collecting chamber 2 in the chamber 4 through which the stream of heating gas flows is so disposed that its walls, particularly the upright wall 5, is traversed by the stream of heating gas before the latter flows past the tubes l 3 in parallel streams. The already heated stream of the heat-absorbing medium impinges upon the wall 5 on the inside as it is deflected into the channel 3, whereby as hereinbefore de.-' scribed, a large co-efilcient of heat transmission is obtained which reduces the temperature of the wall and in addition, by reason of the considerable withdrawal of heat, reduces the temperature of the stream of heating, gas so that. the stress on the tubes 1 is reduced without heat 9 being lost for heating purposes.

Similar conditions prevail in the heat exchanger illustrated in Figure 2, which is shown as a plate exchanger. The heating elements, which are formed from plates 6, connect at the end 7 into collecting chambers 8, the walls 9 of which are exposed to the stream of heating gas and on which the heated stream impinges on the inside and is deflected. The collecting chambers 8 are in, communication witli'one another by means of a transyersely disposed channel/10; the outer wall ofwhich is first completely or partly passed over by the stream or heating gas before it meets the surfaces 9. The heat-absorbing v medium impinges upon the inner wall of the channel 10 and this very considerably assists to secure the desired effect.

Figure 3 illustrates an example of the case hereinbefore mentionedoigindirect cooling by impingement. The wall 12 is cooled by impinge-v 11 0 ment, while the wall 11 is endangered by the too intense transmission of heat from without. Notwithstanding this; when the temperatures are high the impinging action exerted on the wall 12 produces an effective cooling of the wall 11, as the wall 11 radiates its heat to the wall 12 to such an extent that its temperature cannot rise much above that of the wall 12.

I claim:

1. A heat exchanger for heating gases, comprising a plurality of parallel conduits formed* between the plates, a header at the delivery end of each conduit receiving the gas to be heated from the said conduit, and a delivery pipe at the one end of and connecting the said headers, the heating gases of highest temperature being caused to flow transversely over the surfaceof the delivery pipe and over and between the surfaces of the said headers, the said surfaces being cooled by the impinging thereon of the gases to be heated as they are diverted on impinging upon the inner-side of the said surfacesof the headers and upon the innersurface of the saiddelivery pipe. i

2. A heat exchanger for heating gases, according to claim 1, in ,which the surfaces of the delivery pipe over which flows the heating gases of highest temperature, are cooled by radiation .to those parts of the surface of the delivery pipe upon which the gases being heated impinge as they leave the headers. j

. ALFRED SCHACK.

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