Development and numerical investigation of parallel combined sensible-latent heat storage unit with intermittent flow for concentrated solar power plants

Abstract

A parallel combined sensible-latent heat storage unit with intermittent flow was developed. Heat transfer fluid (HTF) alternately flowed between two tubes for creating cyclic intermittency within a single tube to enhance the heat transfer performance. In this study, a two-dimensional transient model was established and validated with experimental data from the previous study. The effect of heat transfer fluid intermittency cycle length on the heat transfer performance was investigated and the change rule of the optimum intermittency length in different stages during the melting process was designed by a recursion method. It is demonstrated that the optimum intermittency cycle length in each stage plotted as a function of time or melting fraction has an initial non-linear regime followed by a linear regime. The critical point separating these two regimes is related to propagation of melting front. These correlations between heat transfer fluid intermittency and melting behavior provided guidance for enhancing heat transfer performance in the parallel combined sensible-latent heat storage unit. A multistage intermittent mode is recommended to further reduce full melting time by 8.73% compared with that under the continuous mode. This design can improve the charging/discharging power, thus providing better economical efficiency for concentrated solar power (CSP).