Numerical study of PCM solidification in a triplex tube heat exchanger with internal and external fins

Thermal energy storage improves the efficiency and eliminates the mismatch between the energy supply and energy demand of solar thermal energy applications. Among the different types of thermal energy storage, latent heat thermal energy storage has gained significant attention recently because of its high energy density per unit mass/volume at nearly constant temperature. The current study numerically investigates the solidification of a phase change material (PCM) in a triplex tube heat exchanger with and without internal and external fins to enhance heat transfer during the charging and discharging of PCM. The effects of PCM freezing from the inside tube, the outside tube, and both tubes were investigated using a 2D numerical model developed with the Fluent 6.3.26 software. The pure conduction and natural convection were considered for the simulation. Different design parameters, such as the numbers of fins, fin length and thickness, and PCM unit geometries, were considered. Results indicate that Case G (8-cell PCM unit geometry) achieved complete solidification in a short time; that is, 35% of the finned tube. Experiments were conducted to validate the proposed model. Simulated results agree with the experimental results.