Numerical study of heat transfer characteristics of rectangular latent heat thermal energy storage unit

In the latent heat thermal energy storage (LHTES) system, adding fins to the phase change material (PCM) is a commonly used technique. Its primary role is to direct heat flow and enlarge the heat exchange area, and this method is anticipated to significantly enhance energy storage effectiveness. This research delves deeply into the overall influence of multiple design factors on the thermal performance of a rectangular phase change thermal energy storage unit, employing a two-dimensional advanced numerical computational model for precise analysis. The factors considered include the number of circular tubes, rotation angle, eccentricity, fin quantity, fin length, and the inlet temperature of the heat transfer fluid (HTF). The findings indicate that the melting time of the three-tube system equipped with fins is cut down by around 54.3 % in comparison to the one without fins. This clearly shows the crucial role that fins play in boosting thermal conductivity. Moreover, there exists an optimal eccentricity of D = 0.24, which improves the melting performance by 64.7 % compared to the case with no eccentricity. The LHTES unit with eight fins can not only maintain good heat transfer performance, but also effectively improve the energy storage effectiveness. In addition, when the inlet temperature increases from Ste = 0.11 to 0.35, the total melting time is decreased by 68.2 %. The findings will greatly facilitate the rectangular multi-tube LHTES units with fins towards more extensive engineering practice applications.