Entrance effects in solar storage tanks

A theoretical and experimental analysis of water jets entering a solar storage tank is performed. CFD calculations of three inlet designs with different inlet flow rates were carried out to illustrate the varying behaviour of the thermal conditions in a solar store. The results showed the impact of the inlet design on the flow patterns in the tank and thus how the energy quality in a hot water tank is reduced with a poor inlet design. The numerical investigations were followed by experiments. A test solar store, similar to the store investigated by numerical modelling was constructed with cylindrical transparent walls so that the flow structures due to the inlet jets could be visualized. With the three inlets, nine draw-off tests with different inlet flow rates were carried out and the temperature stratification in the tank was measured during the draw-offs. The experimental results were used in an analysis using the first and second law of thermodynamics. The results showed how the entropy changes and the exergy changes in the storage during the draw-offs influenced by the Richardson number, the volume draw-off and the initial tank conditions. (C) 2003 Elsevier Ltd. All rights reserved.