Theoretical and experimental investigations of inlet stratifiers for solar storage tanks

A rigid stratifier is investigated theoretically with Computational Fluid Dynamics and experimentally with Particle Image Velocimetry and temperature measurements. The stratifier consists of a main tube with three circular openings. The stratifier is mounted inside a 144 l water tank. During a tank charge test, the investigations show that cold tank water is sucked into the stratifier through the lowest opening. The mixed fluid enters the tank through the top opening. To illustrate the influence of mounting flaps working as “non-return valves” at the stratifier openings, the experiment is repeated with the stratifier with flaps. The results show that the “non-return valves” reduce the unwanted flows into the lowest opening. To quantify how well the stratifier with the flaps works for other flow rates more tank charge tests are carried out. Based on a stratifier efficiency it is found that the stratifier is most efficient for flow rates between 5 l/min and 8 l/min.