Heat storage and release behavior in a thin vessel heat storage unit using salt hydrate latent heat storage material

Abstract

Recently, there has been considerable interest in heat storage materials. Among them, sodium acetate trihydrate (melting point: 58 °C; latent heat: 264 kg/kg) is a suitable latent heat storage material for recovering and using exhaust heat in a temperature range lower than 100 °C, which is discharged in homes and factories. The purpose of this study was to investigate the heat storage and release behavior of sodium acetate trihydrate in a thin-vessel heat storage unit (160 mm × 130 mm × 4.8 mm) made of glass and polycarbonate. The sodium acetate trihydrate in the unit was heated or cooled by flowing water in water channels (width: 1 mm) disposed on both sides of the heat storage unit. From the experimental results, performance deterioration was evident in the heat storage and release process of sodium acetate trihydrate due to phase separation during heat storage and supercooling during heat release. Therefore, a thickener and a nucleating agent were added to sodium acetate trihydrate to suppress phase separation and supercooling effects. The results revealed that the thickener and nucleating agent were unevenly distributed in the case of repeated heat storage and release. The heat transfer numerical simulation adopting the lumped capacitance model was confirmed to be useful for investigating the melting behavior of sodium acetate trihydrate.