Experimental and mathematical modeling of an air-PCM heat exchanger operating under static and dynamic loads

Abstract

The building sector is one of the biggest contributors to world energy consumption and greenhouse gas emissions, and consequently global warming. Latent heat thermal energy storage systems in general and phase change materials (PCM) in particular have received considerable attention as a mean of improving thermal management in buildings. These materials can be used to store and release heat in passive or active way. This paper describes an active air-PCM heat exchanger unit designed using a mathematical model developed in this work. The model was implemented in Matlab software, applying two dimensional explicit finite difference method. The advantage of this comprehensive model over previous models is the inclusion of natural convection in the melted PCM, the thermal mass of PCM container's wall and the effect of PCM volume expansion. In addition, the model was validated under both static and dynamic loads. For the dynamic load testing, solar energy was used to charge the PCM through an air solar collector. The results showed a good agreement between the model and experimental measurements, with an average deviation of less than 8%. The model was then used to study the effect of airflow rate and orientation of the heat exchanger on the performance of the unit. In addition, the experimental measurements confirmed the potential of the designed unit to satisfy the heating demand of a residential building at electricity price peak and shift it to off-peak hours.