Effects of PCM arrangement and natural convection on charging and discharging performance of shell-and-tube LHS unit

The low thermal conductivity of phase change material (PCM) seriously weakens the heat charging and discharging rates of latent heat storage (LHS) system. High efficient performance enhancement method is urgently needed. In present study, three-dimensional simulation models with and without natural convection were established for a shell-and-tube LHS unit to investigate the effects of PCM arrangements and natural convection on the charging and discharging performance. The results show that compared ot the commonly used shell-and-tube LHS unit with PCM in shell side, the LHS unit with PCM in tube side can significantly enhance heat storage rate under the same working conditions and overall dimensions. Natural convection has significant effects on charging performance, espeically when PCM is arranged in tube side. When natural convection is neglected, PCM melting time can be reduced by 25.4% and latent heat storage rate can be enhanced by 36.6% with PCM arranged in tube side. When natural convection is considered, PCM melting time can be reduced by 34.4% and latent heat storage rate can be enhanced by 54.2% with PCM arranged in tube side. However, natural convection has little effects on discharging performance even if for the model with PCM in tube side.