Chemical heat pumps using a dispersion of a metal salt ammoniate in an inert solvent

Abstract

The decomposition and the formation of metal salt complexes can be used in chemical heat pump reactions for solar heating, cooling and energy storage. In this research we have shown that both the decomposition and the formation of CaCl 2·8NH 3 can be carried out effectively as a slurry or suspension in an inert solvent. The reaction rates are increased by an order of magnitude over use of a packed bed and the reactions appear to be essentially stoichiometric. These increased rates are attributed to (1) a greater concentration of ammonia in the solvent, (2) greater surface area of the dispersed solids, and (3) better heat and mass transfer. Three solvents ethylene glycol, heptanol, and decane were considered and the results showed that the nature of the solvent is important. Only heptanol was satisfactory but most likely other alcohols could be used. In order for the system to have practical solar application, the volume of the solvent must be kept to a minimum or separated from the suspension.