A new inlet device that enhances thermal stratification during charging in a hot water storage tank

Solar thermal energy systems are generally provided with a water storage tank. In this tank, thermal stratification takes place naturally, although it is considerably affected by the turbulence and mixing created by the water inflow and outflow. Consequently, thermal stratification is directly influenced by the inlet configuration. This study compares the effect of two water inlet devices in a hot water storage tank during a thermal charge process: a sintered bronze conical diffuser (SBCD) and a conventional inlet elbow (E). The evolution of the temperature recorded by the thermocouples, the 1-MIX number, as well as the thermocline evolution and other related parameters (shape, thickness and height of midpoint) are used to quantify the performance of the stratification. The results obtained show that the SBCD favours water stratification during thermal charging with both low and high flows. The evolution of the dimensionless height of the midpoint of the thermocline can be used to quantify the volume of water affected by the mixing produced by the turbulence generated by the water flow through the inlet device. (C) 2013 Elsevier Ltd. All rights reserved.