STUDY ON LATENT HEAT OF FUSION OF ICE IN AQUEOUS SOLUTIONS - EFFECTS OF CONCENTRATION AND TEMPERATURE OF AQUEOUS SOLUTION -

In dynamic type of ice thermal energy storage system, fluid ice slurry, which has high ability of cold energy transportation, is used as a phase change material. Many types of ice slurries formed from various aqueous solutions are used in practical applications, since each one has its own advantages. The characteristics of ice slurries, such as formation, transportation, melting, and storage, have been investigated by many researchers. Moreover, the thermophysical properties of ice slurries such, as latent heat are needed. In this study, the variation of enthalpy per unit mass of ice, generated by melting of ice in aqueous solution, was defined as "effective latent heat" of fusion of ice in aqueous solution. The formulation for calculating the effective latent heat by using thermophysical properties of the aqueous solutions was proposed, considering the effects of freezing-point depression and dilution heat. In the experiment, pure ice was put into ethanol solution, and temperature variations of the solution due to melting of ice were measured. The effective latent heat of fusion was calculated using an energy balance equation. It was confirmed that the effective latent heat of fusion obtained by the measurements agreed well with that by the calculation. Additionally, the effects of the concentration and the temperature of the aqueous solution on the effective latent heat of ice in aqueous solutions were investigated. As a result, it was clarified that the effective latent heat of ice in aqueous solution is affected by both concentration and temperature of the solution.