Thermal energy simulation of PCM-based radiant floor cooling systems for naturally ventilated buildings in a hot and humid climate

This study investigated the applicability of a thermal energy simulation (TES) for a naturally ventilated building in which a phase change material (PCM)-based radiant floor cooling system was installed. The TES was conducted to determine influential factors to maximize the thermal storage effect of PCMs in the building throughout a year in a hot and humid climate. First, the thermal properties of a full-scale PCM product were measured using the heat flow method. This measurement clearly captured the hysteresis of the PCM depending on the heating and cooling rates; thus, the enthalpy-temperature curve under slow heating and cooling rates was determined for the TES. Based on the results of the PCM measurement, the EnergyPlus-based TES model was validated by comparing it with the results of field measurement at a full-scale experimental building with natural ventilation in Indonesia and a computational fluid dynamics (CFD) simulation coupled with the heat balance analysis. Good correlations (up to R2 = 0.99) were observed in the air and floor surface temperatures between the measurement and TES simulation. Additionally, the TES had a similar accuracy as the coupled CFD, which considers spatial wind and temperature distribution. The results of the annual simulation showed that the proposed PCM-based radiant floor cooling system with night ventilation achieved a thermal comfort period of up to 68.5% a year. Furthermore, a reasonable annual average utilization rate of approximately 70% can be determined to maintain a low floor surface temperature throughout a year.