Investigation of high-enthalpy organic phase-change materials for heat storage and thermal management

The growing interest in phase-change materials (PCM) is related to their possible role in thermal energy storage and thermal management. The choice of materials depends strongly on the required temperature range, whereas the latent heat of solid–liquid phase transition has to be as high as possible. Among other organic PCM, sugar alcohols have gained some attention due to their availability and certain advantageous properties. However, the thermal processes in these materials still require investigation. In the present work, we focused on the materials with solid–liquid phase change within 80 °C–100 °C. A comprehensive literature survey was conducted to elucidate the available sugar alcohols relevant to this range. It was found that the use of pure materials of this type is not very practical, because of their scarcity in the required range and their specific features, like difficulties with crystallization and solidification. On the other hand, based on the literature, we have discerned three eutectic mixtures of erythritol with other organic materials, namely, erythritol–xylitol, erythritol–urea and erythritol– trimethylolethane (TME). In all those cases, it is remarkable that while the components commonly have rather high melting temperatures, the eutectic mixtures had the phase transitions in the required range. Still, each of these mixtures has its own peculiar features, especially at cooling and solidification. An extensive experimental study was performed to provide detailed visualization of these major processes. The results revealed the melting temperature and latent heat of the mixtures to be: 84 °C and 190 J g−1 for erythritol–xylitol, 82 °C and 227 J g−1 for erythritol–urea. Erythritol–TME has two phase transitions at 82 °C and 97 °C, with total latent heat of 198 J g−1. Based on the present findings, the erythritol–urea mixture is the best PCM candidate for the melting range within 80 °C–100 °C.