Experimental investigation on nucleating agent for low temperature binary eutectic salt hydrate phase change material

Abstract

The melting enthalpy and melting temperature have a significant impact on the latent heat that results from phase change materials (PCMs) used for thermal energy storage. Among the PCMs that are currently on the market, inorganic salt hydrates have greater thermal conductivity and latent heat than organic PCMs. However, the problem of salt hydrates' degree of supercooling limits their use in energy storage devices. Using sodium carbonate decahydrate (SCD) and sodium phosphate dibasic dodecahydrate (SPDD), a low temperature inorganic-inorganic eutectic salt hydrate PCM with a higher melting enthalpy and intended phase transition temperature is developed in this research study. The eutectic SCD/SPDD salt hydrate PCM eutectic point and the eutectic composition of salt hydrate PCMs to operate at low temperature range is numerically determined using Schrader equation. By numerical methods we obtain the 68 wt% of SCD with 32 wt% of SPDD to exhibit eutectic SCD/SPDD composite with eutectic melting temperature of 26.2 °C and melting enthalpy of 210.6 J/g. The synthesised eutectic PCM are characterised to explore their chemical stability, latent heat, melting point and their shortcoming due to degree of supercooling. A good way to get around the problem of the supercooling degree is to disperse the nucleating agents. In order to assess the type and degree of supercooling, the produced eutectic PCM composition is experimentally evaluated at 1–10% utilising borax, alumina, and sodium sulphate dodecahydrate as nucleating agents. However, for building cooling applications PCM with minimal degree of supercooling, with the ability to release low enthalpy during discharging is an advantage.