Forced-convection gas-to-wall heat transfer in a packed bed for high-temperature energy storage

Measurements of the gas-to-wall forced-convection heat transfer coefficient in a packed-bed, high-temperature, thermal energy storage system were carried out. The maximum temperature attained was 1,000degreesC. Effects of media property variations with temperature were incorporated along with detailed uncertainty analysis. Results were correlated in terms of Nusselt number, Prandtl number, and Reynolds number. The operating fluid during energy storage was flue gas and air during recovery, making this more applicable to industrial waste recovery and similar systems. Similar studies used air for both storage and recovery and developed correlations from experiments at either room temperature or slightly above. Few associated results with corresponding uncertainty margins. Due to substantial uncertainties associated with the measurements of this heat transfer coefficient, it is significant to note that no firm conclusions can be reached on the validity or otherwise of existing similar correlations for which the uncertainty margins were not reported.