Performance Study of Latent Heat TES System Integrated with Natural Circulating Solar Water Heating Unit Using Helical Type Heat Exchangers

This work was undertaken to study the feasibility of using a Thermal energy storage (TES) system with helical type copper coil heat exchangers to transfer heat from the solar collector to the storage system, to store solar energy using phase change material (PCM) and utilizing it to heat water for night time usage towards commercialization of the solar water heater. This system has a solar flat plate collector, PCM based (TES) tank with helical copper coil heat exchangers. The TES tank contains paraffin as PCM in aluminium cylinders. Water is used as heat transfer fluid (HTF) to transfer heat from the solar collector to the TES tank .Water is also used as sensible heat storage (SHS) material in the tank. The solar collector supplies hot water to the TES tank during daytime. The storage unit stores the heat in SHS material and PCM and supplies hot water via a discharge coil. The heat is transferred to PCM by natural circulation or forced circulation through the heat exchanger connected to the solar collector. Charging (heat storage) experiments are performed at varying HTF inlet temperatures to examine the effect of flow rate of HTF and discharging (heat retrieval) experiments are conducted by continuous and batch wise processes. The significance of time wise variation of HTF and PCM temperatures during charging and discharging processes is discussed. The performance parameters such as cumulative heat stored, and efficiency are also studied. The advantage of using heat exchanger in the top and bottom (inner) sides of the tank to transfer heat to and from the tank is highlighted in this paper.