Temperature dependence of thermophysical properties of disodium hydrogenphosphate dodecahydrate

The temperature dependence of thermophysical properties was evaluated for disodium hydrogenphosphate dodecahydrate, which is used in long-term, supercooled thermal energy storage (Super-TES). Super-TES stores thermal energy at temperatures lower than the melting point of the phase-change material, which reduces heat loss from the storage system. Although the degree of supercooling depends not only on the intensive material properties, such as phase-change temperatures, but also on extensive properties, such as the total material volume, except for distilled water and metals there is insufficient information in the open literature on supercooling phenomena to develop heat storage devices. A promising material for Super-TES applications is disodium hydrogenphosphate dodecahydrate. The thermophysical properties of disodium hydrogenphosphate dodecahydrate are evaluated, and its suitability for Super-TES applications is clarified. We found that in the liquid phase the hydrate density and viscosity decrease monotonically with increasing temperature. We also found that the specific heat in the liquid phase (3.45 kJ/kg . K) and the thermal conductivity in the solid phase (1.01 W/m . K near the melting point) were twice as large as reported in the open literature. This indicates that this hydrate is useful for storing both latent and sensible heat, for reducing heat loss from energy storage systems, and for efficiently exchanging energy between heat sources and the hydrate.