Properties of potassium acetate dihydrate as a latent heat storage material

Hydrated salts are promising latent heat storage materials because of their high heat storage density per unit volume. However, few hydrated salts have melting points in the temperature range suitable for cooling and air conditioning (273‒303 K). In this study, the relationship between the temperature and the hydration number of potassium acetate hydrate and its potential applicability as a latent heat storage material were investigated. From direct observation of potassium acetate aqueous solution, the generally accepted crystallization properties of 0.5 and 1.5 hydrated salts were confirmed. It was also suggested that potassium acetate dihydrate would crystallize upon cooling the solution to 229 K. The melting point of the dihydrate was 291 K, and its heat of fusion was 135 kJ/kg. This heat of fusion is intermediate position among those of six other hydrated salts that have melting points within the range of 285‒294 K. Potassium acetate dihydrate thus has comparable potential to those salts for application as a latent heat storage material for cooling and air conditioning.