Heat transfer performance of a finned shell-and-tube latent heat thermal energy storage unit in the presence of thermal radiation

Abstract

Phase change materials can emit and absorb radiation, so the role of thermal radiation on melting process becomes prominent with the recovery of medium-high temperature waste heat and the development of concentrating solar power. In the study, a numerical analysis on the heat transfer performance of finned shell-and-tube latent heat thermal energy storage (LHTES) units was conducted where the influence characteristics and mechanism of thermal radiation were particularly emphasized. Also the effect of three fin parameters was examined. Results show that the radiation heat transfer rate is nearly one order of magnitude smaller than total heat transfer rate. However, thermal radiation lengthens the phase interface length and enhances the heat transfer of the lower part, accelerating the melting process considerably, with the liquid fraction enhanced by 7.9% and melting time shortened by 23.3% for the base case. The increase of fin length or fin number weakens the role of thermal radiation. As fin number increases from 4 to 48, the maximum radiation enhancement factor reduces from 7.3% to 1.2%. A fin structure with the angle of 0°, dimensionless length of 1.0 and number of 48 is recommended for improving the heat transfer performance of shell-and-tube LHTES units.