Solar-driven melting dynamics in a shell and tube thermal energy store: An experimental analysis

The integration of an array of two evacuated-tube solar collectors with a latent thermal energy storage system has been accomplished, in order to study the heat transfer characteristics during solar-driven melting. A shell-and-tube heat exchanger is employed for energy storage purposes, using 30 kg of paraffin RT70HC in the shell side. A tube bundle uniformly distributed accommodates 12 tube passes, allowing a total mass flow of 100-1000 kg/h of water for inducing turbulent-flow in the tube side. A Coriolis flowmeter is employed for measuring the mass flow through the tubes, and PT100 temperature sensors are used for measuring the inlet and exit temperature of the heat transfer fluid. Outside wall temperature is measured in different cross-sections of the tubes using T-type thermocouples, which capture the buoyancy plume of the PCM induced over the tubes during phase change. Vertical and horizontal temperature probe arrays in the shell characterize the thermal stratification that occurs during melting. Liquid fraction and energy storage during three different scenarios of solar irradiance are computed. The relation between the primary energy source and the heat transfer dynamics of the LTES are described, considering the constraints in terms of maximum PCM operating temperature and achievable liquid fraction. (C) 2020 Elsevier Ltd. All rights reserved.