The effect of crystal size on the thermal energy storage capacity of thickened Glauber's salt

Abstract

Data are presented which demonstrate that a significant increase in thermal energy storage with thermal cycling can be obtained in thickened Glauber's salt phase change mixtures by controlling the size of Na 2SO 4 and Na 2SO 4·10H 2O crystals. This has been done in two ways: (1) by the addition of crystal habit modifiers such as an acrylamide acrylic acid copolymer (AACP) or sodium hexametaphosphate [SHMP (NaPO 3) 6] and (2) by using a polymeric polycarboxylic acid (PCA) thickener that is more effective than attapulgite clay. Thermal energy storage capacities ranging from 67 to 82 per cent of ideal have been obtained for as many as 1600 thermal cycles by using the habit modifiers and PCA as a thickener.