Molecular alloys for storing and restoring thermal energy by pha

Details Molecular alloys for storing and restoring thermal energy by pha Molecular alloys for storing and restoring thermal energy by pha

1993-05-04

1999-12-07

Lieberman, Paul

Compositions

Frost-preventing, ice-thawing, thermostatic, thermophoric,...

165 10, 16510421, 16510417, 524488, 524489, C09K 506

Patent

active

059977620

DESCRIPTION:

BRIEF SUMMARY
The invention relates to compositions useful as phase-change materials for storing and restoring thermal energy by latent heat.
Thermal energy may be stored in two main forms, namely sensible heat and latent heat.
Storage of sensible heat in a material results in an increase in its temperature or in the case of restoration in a reduction of its temperature.
In contrast with storage by sensible heat, storage by latent heat is performed isothermally if the material is pure, or with some variation in temperature in the case of mixtures: the main factor being the phase change of the material.
Phase change materials (PCMs) are thus compounds capable of storing and restoring thermal energy by means of their phase transitions, most frequently solid-to-liquid transitions, but also solid to solid transitions.
When heated the material takes calories from the external medium and reaches a temperature T.sub.tr (transition temperature), passing from phase 1 to phase 2 by heat absorption. When the transition is completed, its temperature can rise again.
If the material is cooled, the converse transition takes place: at T.sub.tr the material passes from phase 2 to phase 1 and restores to the external medium the energy which it had previously stored, while remaining at the temperature T.sub.tr. The energy involved is the variation in phase change enthalpy H.
Widely used PCMs are formed by ice and saline hydrates. Certain eutectics have also been proposed. However, these materials have the disadvantage of operating at a single, non-adjustable temperature. A number of them, more particularly the saline hydrates, are corrosive and melt irregularly, frequently causing segregations which are difficult to control and which make the materials behave poorly in thermal cycling.
It has also been proposed to use organic compounds such as fatty acids, paraffin waxes or certain paraffin wax mixtures for the storage of energy.
Thus, French Patent 2 368 529 discloses the use of paraffin wax mixtures which are solid at 25.degree. C. as PCMs. However, the aim of that patent is to improve the thermal properties of such mixtures by the addition of metals, their oxides or their silicates. The example given relates to improving the thermal properties of an 82/18 mixture of n-docosane
-tetracosane by the addition of magnesium oxides, alumina, emery, kaolin and aluminium in the proportion of 25 to 55% by weight.
However, this patent does not consider the advantage of the mixture of paraffin waxes as such, or the conditions to be combined to enable it to meet the demands of a given application at a defined temperature.
Applications W087/03290, EP 0 344 013 and EP 0 344 014 disclose polyolefine composites containing phase change materials formed more particularly by mixtures of paraffin waxes of C.sub.14 or above. These composites are intended for the storage of solar energy.
The paper given by Salyer at the 15th North American Thermal Analysis Society Conference, Cincinnati, Ohio, Sep. 21-24, 1986, relates to the analysis of crystalline paraffinic hydrocarbons more particularly intended for the storage of solar energy. Mixtures of commercially available paraffin waxes are studied as regards their properties as phase change materials for this application.
That study relates to mixtures of alkanes in given proportions and formed by odd chains--i.e., chains with an odd number of carbon atoms (referred to hereinafter as Cni) (mixtures C15/C19, C17/C19); even chains--i.e., with an even number of carbon atoms (referred to hereinafter as Cnp) (mixtures C14/C16, C16/C18, C16/C20); even and odd chains (C16/C17, C18/C19) or by Cni or Cnp of longer chains (>C20). Ternary mixtures are also reported (C16/C17/C18; C17/C18/C19; C16/C18/C20; C17/C19/C21; C14/C17/C20 and C16/C19/C21), all used in the concentration 0.25/0.50/0.25.
Similarly, Salyer reports on the results obtained with synthesised multi-component mixtures corresponding to commercially available products.
However, the conditions used for the measurements do not allow a proper assessment of the

Affiliated with

Also associated with

Rating

Molecular alloys for storing and restoring thermal energy by pha does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Molecular alloys for storing and restoring thermal energy by pha, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular alloys for storing and restoring thermal energy by pha will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-820094