PHASE CHANGE MATERIAL FORMULATIONS FOR LOW TEMPERATURE HEAT STORAGE APPLICATIONS

A phase change material which has a solid/liquid transition temperature in the range of from 5 °C to 15 °C, without the problem of incongruent melting or supercooling, has a formulation comprising a mixture of sodium sulphate decahydrate, borax (sodium tetraborate decahydrate), fumed silica, ammonium chloride, potassium chloride, calcium sulphate, and water in excess of the stoichiometric quantity included in the hydrates. A phase change material which has a solid/liquid transition temperature of about 58 °C, and which does not exhibit incongruent melting or supercooling, has a formulation comprising sodium acetate trihydrate, tetrasodium pyrophosphate decahydrate, fumed silica, and water in excess of the stoichiometric quantity included in the hydrates. The solid/liquid transition temperature of the second material can be lowered by the addition of either urea or lithium acetate dihydrate.