Compositions – Frost-preventing – ice-thawing – thermostatic – thermophoric,...
Patent
1987-05-14
1989-01-03
Wax, Robert A.
Compositions
Frost-preventing, ice-thawing, thermostatic, thermophoric,...
568852, 568868, C09K 506
Patent
active
047955805
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a latent heat storage material on the base of multivalent aliphatic alcohols of the general formula ##STR1## i.e. such ones with unramified hydrocarbon chain and one hydroxyl group per C-atom. Furthermore the invention concerns a preferred use of this material.
Latent heat storage materials are used in numerous heat transfer processes as means of heat storage. They possess a melting point, which lies in the working temperature range of the heat transfer process, so that they during warm-up change over from the solid to the liquid phase, and during cool-down return to the solid phase, thus likewise absorbing and releasing again latent heat (heat of fusion). In comparison with so-called capacitive heat storage materials (i.e. such ones, on those the state of aggregation does not change in the range of working temperature, so that only sensible heat is absorbed and released again) latent heat storage materials have with that the advantage, that they make possible the storage of a larger amount of energy within a narrow range of temperature at a relatively small requirement of volume.
In general latent heat storage materials should possess a melting enthalpy as high as possible, at which it particularly depends upon the volumetric (i.e. to the volume related) specific melting enthalpy, in order to create a maximum of storage capacity per volume unit of storage plant. Besides this they must be cycle proof, i.e. the phase transition solid-liquid-solid must retain reversible reproduceable over a long period of times and should not be affected by chemical reactions, demulgations or the like effects. Furthermore important criteria could be the solidification behaviour (e.g., the formation of a metastable melt, the quantity of volume change during phase transition, or the form of cristallisation) and the compatibility with construction materials, the physiological harmlessness and the availability to acceptable costs. It has proved difficult until now, to find latent heat storage materials, which accomplish the whole of this criteria in an optimal manner to the respective application.
Many of the so-far known latent heat storage materials have been developed to be used in the domain of room heating and possess accordingly melting points in the range of domestic water. Besides anorganic substances, like salt hydrates and salt mixtures (which are oftenly corrosive and less cycle proof) organic substances including some alcohols have already been proposed likewise for that purpose. Thus the DE-A No. 28 56 374 describes the use of simple alcohols like stearyl alcohol, hexadecanol or octanediol as latent heat storage material for solar heating systems. The melting enthalpy on a volume base of these simple alcohols however is comparably small by reason of their low density. Furtheron the DE-A No. 27 47 664 describes the use of xylitol (that is an alcohol according to the common formula A mentioned at the beginning with n=5) as latent heat storage material for heat packs or for heating systems which work with solar energy or electrical night current. Compared to simple alcohols xylitol possesses a higher specific melting enthalpy on a volume base, but forms during cool-down a marked metastable melt, which even at room temperature still is permanent and which could only be brought to cristallisation by additional means as the use of nucleation agents, rubbing or ultrasonic affection. This may be useful for the provided application of the DE-A No. 27 47 664, but is not so in the most other cases.
Another special application of latent heat storage materials is the use within heat protection systems for borehole probes in deep geotechnical wells. In this case the point is to keep an electronic measuring unit, which is placed in a dewar-like heat-shield, at a low temperature (i.e. between 70.degree. and 125.degree. C.) on an utmost period of time, while a measuring-log is run in a borehole at a rinsing-water temperatures up to 200.degree.-300.degree. C. For that usually cartridge-like latent heat sinks ar
REFERENCES:
patent: 4295517 (1981-10-01), Guex
patent: 4304798 (1981-12-01), Clapp et al.
Brimacombe et al., "Alditols and Derivatives" in The Carbohydrates, Pigman et al., Ed., Academic Press, New York, 1972, pp. 479-518.
Grunewald Glen R.
Lampe Thomas R.
Wax Robert A.
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