Conference Proceeding published 1979 by ASHRAE
Written By Carlyle S. Herrick
Sodium sulfate decahydrate was long ago identified as being a desirable latent heat storage material for domestic solar heating systems use (1). Since that time it has become well known for the difficulty involved in freezing it from liquid to solid completely (2). The hydrate melts incongruently to form two phases, a saturated liquid phase, and a solid phase (anhydrous Na SO ) which quickly settles out of the liquid. This settling action, which effectively removes the two phafes from equilibrium contact with each other, is the primary cause of difficulty. Experimental efforts to prevent the settling met with only temporary success (3). Cessation of further work was recommended unless a novel approach could be devised.
Experimental work in this laboratory has demonstrated that sodium sulfate decahydrate can be made to freeze rapidly, completely, and repeatedly when it is contained in a cylindrical vessel having the cylindrical axis both horizontal and the axis of rotation for a slow rotary motion.
Citation: Symposium, ASHRAE Transactions, Volume 85, Part 1, Philadelphia, PA
