  The Latent heat storage technology is being used worldwide to bridge the gap
between supply and demand of energy. The material store energy during the
charging process (melting) and releases energy during the discharging process
(solidification). In spite of having various advantages such as high storage
energy density, it suffers from the fact that most Phase Change Materials
(PCMs) commonly used have a very low thermal conductivity, hence, very slow
charging /discharging times. In the current work, a shell and tube type heat
exchanger with phase change material on the shell side and heat transfer fluid
on the tube side are considered. The effect of flow rate and inlet temperature
of heat transfer fluid on melting and solidification times are investigated
with single and double pass (counter and parallel) arrangements of Heat
Transfer Fluid (HTF). The major difficulty encountered in the melting of the
PCM is the accumulation of solid (unmelted) part at the bottom during the
charging process, while the liquid part remains at the top during the
discharging process, which decreases the efficiency of the system to quite a
great extent. In this study, an attempt has been made to improve the efficiency
of the system by considering two configurations (double and triple tube) of the
shell and tube heat exchanger and it is found that the latter case has better
performance.
