Performance evaluation and analysis of a vertical heat pipe latent thermal energy storage system with fins-copper foam combination

As one of the most promising thermal storage techniques, latent thermal energy storage (LTES) using phase change materials (PCMs) is gaining importance. However, as is well known, most PCMs still suffer from the poor thermal conductivity for both the solid and liquid phases. To overcome this drawback, a combination of fins and copper foam based on the heat pipe (HP) heat exchanger is proposed and applied. The thermal performances, including the liquid fraction, the exergy transfer rate, the evolution of solid-liquid interfaces, and temperature distributions are evaluated by a two-dimensional numerical model considering natural convection. The results indicate that the combination shows a greater enhancement performance than using either copper foam alone or fins alone, and the best enhancement can be achieved with a specific fin volume ratio (gamma(fin) 0.5) when the total volume fraction is fixed. Besides, the exergy analysis further suggests that increasing the total volume fraction accelerates the phase change rate by improving the effective thermal conductivity, but meanwhile, the impact of natural convection is gradually reduced. This study illustrates an effective method for enhancing the heat transfer of LTES by combining different techniques.