Experimental study on melting enhancement of phase change material by heat transfer tube orientation

Abstract

Phase change material (PCM) is beneficial for energy storage applications but suffers from poor thermal conductivity. This study emphasizes using two heat transfer tube (HTT) configurations to improve the charging behavior of PCM. The vertical and horizontal configurations of S-shaped HTT were studied with the melting characteristics to find an optimal HTT for thermal storage. An energy and exergy analysis of two HTT orientations was made using heat transfer fluid (HTF) at 80 °C and 30 LPH. The vertical configuration showed a melting time of 240 min, 17 % less than the horizontal case. Also, the maximum energy efficiency of the vertical HTT case is 54 %, but the horizontal configuration has 47 %. The average energy stored by the vertical and horizontal HTT configuration is 214 kJ and 200 kJ, respectively. The exergy efficiency of the vertical and horizontal configuration is 32.44 % and 26.33 %, respectively. The peak Nusselt and Stefan numbers for horizontal and vertical configuration are 130, 0.33, and 95, 0.44, respectively. The results show that the vertical S-shaped HTT effectively melts PCM in a storage container compared to the horizontal orientation. Such thermal energy storage systems could be used for solar thermal applications.