Melting performance enhancement of PCM based thermal energy storage system using multiple tubes and modified shell designs

In this paper, experimental and numerical investigations are performed for heat transfer enhancement in a horizontal Latent Thermal Energy Storage System using multiple heat transfer tubes and modified shell designs. Stearic acid is used as phase change material and it is placed in the annulus of steel shell and copper tubes carrying water as the heat transfer fluid (HTF). A single Y-fin HTF tube, used as Base Case, is split up into 2 - 5 tubes with different arrangements while ensuring constant mass of the PCM. The vertical double tube and triple tube V-configuration improve the average heat transfer rates by 33.6% and 23.7%, respectively, as compared to the Base Case. The corresponding complete melting times is also reduced by 27.7% and 21.7%. Additionally, elliptic and triangular shell design modifications are proposed for double and triple tube arrangements, respectively. Both configurations increase the average heat transfer rate by 85% which results in reduction of the complete PCM melting time by 50% with respect to Base Case of Y-fins single tube arrangement. In comparison to the Base Case, an increase in HTF temperature of 5.6% improves the average Nusselt number by more than 37% for both the cases. Additionally, the correlations for melting Fourier number and average Nusselt number are also developed.