Abstract
Thermal characteristics of laboratory- and practical-scale latent heat thermal energy storage tanks using the shell-and-tube heat exchangers have been investigated experimentally and theoretically. Commercial paraffin wax (melting point ≈ 49°C, thermal conductivity = 0.21 W/(m·K)) as the thermal energy storage material is packed in the tanks. Cloths made of high conductive carbon fibers (thermal conductivity = 190 W/(m·K)) are installed in the tanks to strengthen the contact between the carbon fibers and the heat transfer tubes and enhance the heat transfer rate in the tanks. Experimental results show that carbon-fiber cloths of only 1 vol.% remarkably improve the heat transfer rate in the tanks. Moreover, the thermal characteristics are improved with increasing volume fraction of carbon fibers. In addition to the experiments, a numerical model describing the heat transfer in the tanks using the carbon-fiber cloths has been developed to predict their thermal characteristics. The numerical heat release rates agree well with experimental ones under various experimental conditions for laboratory- and practical-scale thermal energy storage tanks. Optimum volume fractions of carbon fibers added in the tanks is also discussed.
