Heat accumulator with an enlarging expansion area

Details Heat accumulator with an enlarging expansion area Heat accumulator with an enlarging expansion area

1990-12-07

1993-06-08

Davis, Jr., Albert W.

Heat exchange

Regenerator

Heat collector

165133, F28D 2000

Patent

active

052170624

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a heat accumulator comprising a storage container having an interior space for accommodating storage medium, with the interior space including a solidification area in which the storage medium is located following a solidification process and an expansion area in which the storage medium can expand during the melting process.
Such heat accumulators are known. Herein, high-purity nickel, high-alloy steels, nickel-cobalt or nickel-cobalt alloys or nickel-niobium alloys are used as container materials. The problem with such storage containers is that the volume of the storage medium increases in the order of magnitude of from 20 to 30% during the transition from the solidified to the completely liquid state. This results in mechanical problems, above all, during the charging of such a heat accumulator as the storage medium immediately adjacent to the storage container starts to melt in the area of wall surfaces of the storage container and expands with respect to its volume by the aforesaid amount but is prevented by the core of still solidified storage medium located above it from expanding into the cavities formed during the solidification. Consequently, such storage containers are subjected to high mechanical stresses owing to the pressure increase during the charging cycle. Problems are also caused by the corrosion of the materials from which the storage containers are made and, therefore, in all, only storage containers with walls of very thick and sturdy design can be used, but this makes such a heat accumulator unattractive.
The object underlying the invention is, therefore, to so improve a heat accumulator of the kind described at the beginning that low mechanical stresses occur and hence the storage container can be of structurally simpler and cheaper design.
This object is accomplished in accordance with the invention with a storage container of the kind described at the beginning by wall surfaces of the storage container adjacent to the storage medium being made of a material which is not wettable by the storage medium.
Hence the advantage of the inventive solution is to be seen in that the solidified storage medium is prevented from adhering to the wall surfaces by a choice of material for the wall surfaces which is not wettable by the storage medium, that at the beginning of the charging process, i.e., at the beginning of the liquefaction of the storage medium, the possibility is created for the increase in volume of the liquefying storage medium to be compensated by the core of still solidified storage medium being displaced relative to the wall such that the liquefied storage medium can enter the expansion area so that, in the end, no or only slight mechanical forces act upon the storage container. Therefore, the storage container can be of mechanically considerably less sturdy and simpler and hence also less expensive design.
It is particularly advantageous for the solidification area to widen towards the expansion area, i.e., to exhibit an increasingly larger cross-section in the direction towards the expansion area. Hence in addition to the lack of adherence of the storage medium to the wall surfaces, the widening of the solidification area towards the expansion area causes the core of still solidified storage medium to became displaced at the beginning of the charging process and the liquefied storage medium to enter the expansion area.
Within the scope of the present invention, it has proven particularly advantageous for the solidification area to widen conically towards the expansion area.
In order to also prevent the still existing, firm core of solidified storage material from tilting during the displacement, thereby possibly causing at least for a short time until further solidified storage medium has liquefied, an increase in pressure in the area of the liquefying storage medium, it is particularly advantageous for the part of the expansion area adjoining the solidification area to have essentially at least the same cross-section as a transition from the solid

REFERENCES:
patent: 4241782 (1980-12-01), Schoenfelder
patent: 4696338 (1987-09-01), Jensen et al.
Japanese Patent Application Abstract, Application No. 58-153263, Patent Abstracts of Japan, M-399, Jul. 24, 1985, vol. 9.
Patent Abstracts of Japan, vol. 8, No. 166 (M-314) (1603), Aug. 2, 1984; and JP, A 5960185 (Toshiba K.K.) Apr. 6, 1984.

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