Experimental investigations of charging/melting cycles of paraffin in a novel shell and tube with longitudinal fins based heat storage design solution for domestic and industrial applications.

Abstract

Due to vulnerability of solar energy based technologies to weather fluctuations and variations in solar thermal irradiance, thermal energy storage (TES) systems with their high thermal storage capacity offer a sustainable solution. In this article, experimental investigations are conducted to identify thermal performance of latent heat storage (LHS) unit in connection with solar collector during charging cycles. LHS unit is comprised of novel geometrical configuration based shell and tubes with longitudinal fins heat exchanger, paraffin as thermal storage material and water as heat transfer fluid (HTF). In order to overcome the effect of low thermal conductivity of paraffin, the effective surface area and overall thermal conductivity for heat transfer is significantly improved by employing longitudinal fins. Moreover, the vertical orientation of longitudinal fins supports natural convection, which can assure rapid charging of paraffin in LHS unit. In experimental tests, the focus is on probing the heat transfer mechanism and temperature distribution in entire LHS unit, the influence of inlet temperature and volume flow rate of HTF on phase transition rate and mean power. Experimental results revealed that natural convection significantly influences the phase transition rate. Therefore, enthalpy gradient is noticed between PCM at top, central and bottom positions in LHS unit. Likewise, the phase transition rate and mean power of LHS unit is significantly increased by a fraction of 50.08% and 69.71% as the inlet temperature of HTF is increased from 52 oC to 67 oC, respectively. Similarly, it is concluded that volume flow rate of HTF has a moderate influence on thermal performance; however the influence declines with an increase in inlet temperature of HTF. Due to significant enhancement in thermal performance, the novel geometrically configured LHS tank can accumulate about 14.36 MJ of thermal energy in as less as 3 hours. Furthermore, a broad range of domestic and commercial energy demands can be fulfilled by simply assembling several LHS units in parallel sequence.