Comprehensive thermal energy storage analysis of ceramic foam-enhanced molten salt in a shell-and-tube unit

Ceramic foam can be used to enhance the energy storage efficiency of molten salt for high-temperature solar thermal applications. However, its performance in a shell-and-tube unit is not fully understood. In this study, the energy storage performance of ceramic foam-enhanced molten salt in a shell-and-tube unit is investigated. The effects of ceramic foam configurations such as the filling height, porosity and outer diameter are studied. The results show that when the ceramic foam reaches the inner tube, the enhancement performance is remarkable, while it is insignificant in the case of below the inner tube. Although the total stored energy of the full foam-filled case is decreased by 13.6% compared to the no foam-filled case, the energy storage rate is improved by 54.9%. The variation of energy storage rate with porosity is generally regular. Ceramic foam with a small outer diameter has great enhancement performance; as the outer diameter increases, the difference in the enhancement gets less remarkable. The three factors are compared through a normalised effective porosity and the ceramic foam with varying outer diameters shows the best performance including the shortest melting time, the largest total stored energy and the highest energy storage rate. It is attributed that the ceramic foam surrounds the tube completely and concentrates around the tube, so its performance of conducting the heat of the tube is the best. The corrosion resistance of ceramic foams and the cost advantage make it a suitable thermal enhancer for molten salt in hightemperature solar thermal energy storage applications.