Investigation of Thermal Properties of Na2HPO4 Hydrate Slurries for Evaluating Their Use as a Coolant in Absorption Chillers

摘要

The thermal characteristics of inorganic disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O) slurries in a water/ethylene glycol mixture were investigated in an attempt to reduce the size of absorbers in absorption chillers. In order to find the optimal concentration of Na2HPO4·12H2O and the optimal weight ratio of ethylene glycol to the mixture for cooling the absorber, solubility, phase change temperature, and latent heat were measured. The obtained results indicated that the hydrate slurry has an appropriate phase change temperature and sufficient concentration at the working temperature of the absorber when the hydrate concentration and the weight ratio of ethylene glycol to the mixture are set to 50 wt% and 0.4, respectively. Under this condition, the particle characteristics of the slurries were also measured. The particle size was found to be rather small, and it increased gradually. Thus, inorganic Na2HPO4·12H2O can be used as a cooling medium of the absorber in an absorption chiller.