Temperature distribution inside hot-water storage tanks of solar collectors

Abstract

An analytical-experimental investigation into the temperature field inside the hot-water storage tank of a solar collector is carried out. A transient two-dimensional semi-infinite cylindrical length model with time and space boundary conditions dependency is selected. Conduction and convection heat transfer modes in the axial direction together with conduction in the radial direction are considered. Good agreement between theoretical and experimental predictions is verified. The radial direction temperature dependency disappears for axial lengths greater than one quarter of the tank depth for most practical operating conditions especially for low inflow velocities and low inlet to outlet temperature ratios. The axial conduction term in the governing equation can be dropped out for inflow velocities greater than a certain critical value without disturbing the theoretical consequences. Temperature profiles in the axial direction can be assumed to be linear especially for high inflow velocities as well as low temperature differences at inlet and outlet of the storage tank.