Latent heat storage systems (LHSS), using solid–liquid phase change materials (PCMs), are attracting growing interest in many applications. The determination of the thermophysical properties of PCMs is crucial for selecting the appropriate material for an LHSS and for predicting the thermal behavior of the PCM. In this context, the thermophysical characterization of four paraffins (RT21, RT27, RT35HC, RT50) at different temperatures, including the solid and liquid phases, is conducted in this investigation. This work is part of a strategic technological brick in the CERTES laboratory of the Paris Est University to build a database for phase change material properties. It contains the measurements of the thermophysical, optical and mechanical properties. It will serve as input for the numerical simulations to study the behavior of PCMs in LHSS. The temperatures and the latent heats of the phase transitions as well as the thermal dependence of the specific heat of the paraffins were evaluated by differential scanning calorimetry (DSC). In addition, the DSC measurements under successive thermal cycles revealed good reliability of the paraffins. Thermogravimetric analysis (TGA) was performed, and the results highlighted the thermal stability of the paraffins. Moreover, the evolutions of the thermal conductivities and diffusivities with temperature were measured simultaneously using the hot disk method. A discontinuity of the thermal conductivities was observed near the melting temperatures. Furthermore, the measurements of the densities of the paraffins at different temperatures were carried out. The volume changes and the coefficients of thermal expansion were assessed. The obtained outcomes of this study were compared with the available bibliographical data.

Urban densification intensifies urban heat islands (UHIs), leading to higher temperatures in cities which negatively affect residents’ health and comfort and increase energy consumption for air conditioning, thereby raising carbon emissions. Reducing UHIs is therefore essential. Phase change materials (PCMs) are a promising solution, as they can store and release significant amounts of thermal energy during phase transitions. Selecting paraffins with suitable properties is crucial for effective application. In this study, three paraffins (RT28HC, RT31, and RT35HC) with phase change temperatures of 28 °C, 31 °C, and 35 °C were characterized to evaluate their potential for summer UHI mitigation. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and measurements of thermophysical properties and density were performed. Results showed that RT28HC and RT35HC exhibit relatively simple and efficient phase transitions, while RT31 has a more complex mechanism with a wide phase change temperature range. During limited summer day–night temperature variations, RT31 may not fully crystallize, reducing the effective utilization of stored energy. These findings highlight the importance of selecting paraffins with appropriate phase change temperatures and thermal properties to optimize the performance of PCMs for urban heat mitigation.