Glauber's Salt Composites for HVAC Applications: A Study on the Use of the T-History Method with a Modified Data Evaluation Methodology.

Phase change materials (PCMs) can be utilized in buildings for peak load shifting in air conditioning systems, and the use of salt hydrate-based PCMs can reduce the cost of thermal energy storage devices. Glauber's salt is an economical salt hydrate PCM with a melting point of around 32 °C. However, the desired melting range typically falls between 18 and 22 °C for building air conditioning applications. Although many researchers have characterized Glauber's salt and its composites with modified melting points, enthalpy-temperature curves for composites of Glauber's salt and NaCl are unavailable. In this study, we report the melting and solidification enthalpy-temperature curves for two different composites of Glauber's salt and NaCl with a melting point of 21 °C obtained by the T-history method. Both composites contain NaCl to suppress the melting point, borax to reduce supercooling, and sodium polyacrylate as a thickener to enhance cyclic stability. The first composite with 12 wt.% NaCl demonstrated 139 kJ·kg of latent heat of fusion, and the second composite with 9 wt.% NaCl demonstrated 171 kJ·kg. Both the composites have high volumetric energy densities compared to their organic counterparts with similar melting points.