Numerical simulation of radiant floor cooling systems using PCM for naturally ventilated buildings in a hot and humid climate

This study constructs a coupled simulation model of heat balance analysis and computational fluid dynamics (CFD) for naturally ventilated buildings with installed phase change materials (PCMs), and demonstrates a modeling method for the thermal storage effect of PCM in the simulation. Then, the constructed model was applied to a sensitivity analysis to clarify the key parameters of a radiant floor cooling system using PCMs. The simulation was conducted for the target building, where the radiant floor cooling system was installed, and the results were validated with field measurements in the hot and humid climate of Indonesia. The results showed that the coupled simulation model can evaluate both the temperature and heat balance of PCMs in naturally ventilated buildings, where air temperature and air flow distribution are not uniform, with higher accuracy. The temperature and heat flux on the floor surface showed good correlations between the simulation and mea-surement, with the root mean square errors of 0.3-0.5 degrees C and 4.0 W/m2, respectively. In particular, coupling with radiative heat transfer calculation increased the simulation accuracy in terms of floor surface and PCM temperatures by 0.3 degrees C when the surface temperature difference between the floor and the other surfaces, i.e., the wall and ceiling, was considerable owing to the thermal storage effect of the PCMs. The following sensitivity analysis showed that a PCM thickness of 6 mm and ventilation during nighttime are the optimum settings for the radiant floor cooling system under the given hot and humid conditions.