Investigation of the performance of a cylindrical PCM-to-air heat exchanger (PAHE) for free ventilation cooling in fluctuating ambient environments

This paper proposes the use of a cylindrical annulus composed of phase change material (PCM), referred to as a PCM-air heat exchanger (PAHE), to regulate the supplied air temperature in ventilated buildings exposed to fluctuating thermal environments. The forced convection inside the PAHE tube enhances the heat transfer between the air and PCM, and thus both the sensible and latent heat transfer contribute to reducing the air temperature fluctuations and peak cooling/heating loads. Both experiments and numerical simulations are performed to investigate the performance of a PAHE exposed to fluctuating ambient temperatures. The effects of three PAHE parameters, i.e., the flow rate through the PAHE tube, melting temperature of the PCM, external diameter of the PAHE, and the tube length on the PAHE performance were investigated numerically. Maintaining a stable inner surface temperature in the PAHE is crucial for maximizing its ability to reduce air temperature fluctuation amplitude. For this purpose, these key parameters should be appropriately selected. The cooling performance of the PAHE in a region with hot summers and cold winters region was evaluated. The simulation incorporated real meteorological data of two transitional seasons and a summer, and demonstrated a maximum reduction in air temperature of 5.4 degrees C.