Performance analysis of an improved PCM-to-air heat exchanger for building envelope applications - An experimental study

The applications of PCM-to-air heat exchangers (PAHXs) face operational challenges regarding the local climatic conditions. One of the main issues is the insufficient cooling potential during the phase change material (PCM) solidification process. In order to increase the cooling charging power of the system, in this study, a unique PAHX type is proposed for building envelope applications. The objective is to magnify the thermal radiation losses from the PCM panels to the nocturnal sky during the solidification process. Two real-scale prototypes were designed and constructed to monitor the effect of radiative cooling on the PAHX thermal behavior during solidification. Accordingly, the cooling performance was investigated for different operational scenarios. In addition, specific key performance indicators were defined to analyze the system charging performance. The experimental results proved that exposure to the clear sky during solidification increases the charging power of the system due to the maximized thermal losses by radiation. The results confirmed that the sky condition and the ambient air temperature profile are key factors in determining the cooling potential of the system. It was shown that making use of the radiation thermal loss to the clear sky increased the charging energy by up to 22% of the proposed PAHX application.