US2537220A - Heat exchanger - Google Patents

Description

Jan. 9, 1951 H. w. HAHNEMANN HEAT EXCHANGER Filed June 7. 1948 Patented Jan. 9, 1951 land, assignor to Power Jets (Research and Development) Limited, London, England, a

British company Application June 7, 1948, Serial No. 31,524 In Great Britain August 29, 1947 3 Claims. 1,

This-invention relates to improvements in heat exchangers of the regenerative kind, 1. e. of the kind wherein a heat absorbing and transmitting matrix is moved successively into a region of hotter fluid and into a L gion of colder fluid, so as to absorb heat from the former and impart heat to the latter; v I

The matrix is generally sub-divided to form passages or cells and each of these as it is transferred from the hotter fluid to the colder fluid carries its fluid charge with it. When the two fluids are at substantially different pressures as for example in the case of a gas turbine heat exchanger, wherein the colder fluid is air delivered by the compressor at higher pressure, while the hotter fluid is exhaust gas at a considerably lower pressure, there is a. pressure loss as the passages or cells are transferred from one region to the other, and this reduces the efl'lciency of the apparatus.

The invention is based on the principle that to prevent this loss, means may be provided whereby a cell which has just left the high pressure reion is put into communication with a cell which is just about to enter the said region at a moment when both cells are out 01f from the high pressure and low pressure regions. This equalizes the pressure in the two cells to a value intermediate the two pressures and considerably decreases the above-mentioned pressure loss.

The present invention provides a particularly convenient form of such means and for this purpose a heat exchanger according to the present invention comprises two oppositely rotatable coaxial disc-like matrix members having a plurality of axially directed passages and a fluid tight partition extending between the discs and adapted to divide the space between the discs into two parts, the said partition being provided with a number of axially directed passages, so that as the disc-like members rotate, each passage in the matrix passes and enters into communication with one or more passages in the partition. The disc-like members are preferably of similar dimensions and the two parts are adapted to serve as a high pressure region and a low pressure region.

The invention is illustrated by way of example in the accompanying drawings in which:

Figure 1 is a transverse section in diagrammatic form;

Figure 2 is a section on the line IIII of Figure 1.

As shown in the drawings the apparatus comprises two disc-like matrix members I, 2, for example of ceramic material, arranged co-axially on shafts 3, 4 respectively, and adapted to rotate in opposite directions. Each disc has a number of axially directed passages I a, 2a respectively. Extending axially between the discs I, 2-, is a fluid tight partition 5 which in conjuncetion with ducts 6a, Ia, divides the space between the said discs into two chambers 6, I, and is itself provided with a number of axially directed passages 5a, so that a the discs I, 2, rotate, each passage Ia, 2a, passes and enters into communication with one or more of the passages 5 a.

The discs I, 2, rotate against the ends of cylindrical ducts 8, 9 respectively, which are each provided with fluid tight partitions I 0, II respectively, so as to divide each of the ducts 8, 9, into two semi-circular ducts respectively 8a, 8b, 9a, 9b. The discs I and 2 are driven in opposite directions, for example, by electric motors I3 and I4 through gearing I5, I6 and I1, I8 respectively.

Hotter fluid at a relatively lower pressure such as the exhaust gases of a gas turbine engine flows along ducts 8a, 9a, through those passages Ia, 2a, which are in alignment with said. ducts, into chamber I5 and are then led away through duct 5a, for example to atmosphere. Colder fluid at a relatively higher pressure such as the air delivery from a compressor of a gas turbine engine is led through duct Ta to chamber I and thence through those passages Ia, 2a, which are in communication with chamber 5 to ducts 8b, 9b, respectively, and thence through auxiliary ducting (not shown) to any desired locality such as the combustion system of a gas turbine engine. By means of the rotating discs I, 2, heat is transferred from the hotter fluid to the colder fluid.

At any particular moment some of the passages la, in disc I will be just leaving the lower pressure chamber 6 in order to enter the higher pressure chamber I While simultaneously some of the passages 2a in disc 2 will be just leaving the higher pressure chamber 1 in order to enter the lower pressure chamber 6 and these two sets of passages Ia, 2a, will be placed in temporary communication with one another as they rotate past the passages 5a. In this Way the pressure of these passages la, 2a, will be equalized and the consequent power loss upon their transfer from one chamber to the other will be minimised. Since the partition 5 may be provided with a large number of passages 5a and each disc I, 2, inay also have a large number of passages Ia, 2a, the p w loss can be reduced to very small p portions,

It is preferable to arrange for each passage 5a to be divided longitudinally into two or more parts as for example by a block l2 as shown in Figure 2 in order to prevent a passage 2a which is just leaving the low pressure chamber 6 from making communication with another passage 2a which i just about to enter this chamber, and similarly to prevent communication between two such passages la.

The efiect of the above described arrangement is to enable relatively smaller discs to be used, the heat exchanger operating more uniformly and having a higher heat transmission co-efiicient than would otherwise be possible. Furthermore, if it is desired to divide the area of the discs I, 2, into unequal portions in order further to minimise the pressure loss, this can easily be arranged without the necessity of introducing any complicated structure.

I claim:

1. A heat exchanger comprising a casing, two oppositely rotatable and axially separated coaxial disc like matrix members forming opposite end walls for said casing and each having a plurality of axially directed passages, a fluidtight partition extending between the discs and adapted to divide the casing between said discs into two chambers, said casing having a duct constituting an inlet into one of said chambers and a second duct constituting an outlet from the other of said chambers, further ducting adapted in combination with said discs to lead one fluid through some of the passages in each disc into one of said chambers and to lead another fiuid from the other chamber through other passages in each disc, the said partition being provided with at least one axially directed channel whereby as the discs rotate a passage in one disc as it moves past said channel enters temporarily into communication with a second passage in said second disc as said second passage moves past said channel whereby the pressure in said passages are equalized.

2. A heat exchanger according to claim 1 wherein the partition is provided with a number of axially directed channels and means are provided to divide each said channel longitudinally into at least two non-communicating parts.

3. A heat exchanger according to claim 2 wherein said further ducting comprises for each disc a duct closed at one end by said disc and divided longitudinally by a fluid-tight partition into two parts whereby one of said parts is adapted to communicate with some of the passages in said disc, while the other part is adapted to communicate with other passages in said disc.

HORST WOLFHARD HAHNEMANN.

REFERENCES CITED Country Date Great Britain May 9, 1927 Number

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