Experimental and Numerical Study of Mixing in a Horizontal Hot-Water Storage Tank

Thermal mixing and stratification are explored experimentally in a horizontal cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70 cm long and 24 cm in diameter. The study is conducted in a transient mode, namely, the tank is filled with hot water, which in the course of operation is replaced by the tap water in a stratified way or by mixing. The flow rates of 2, 3, 5 and 7 liters per minute are explored. Temperature of hot water is usually about 55 °C, while the tap water is about 20 °C. In the experiments, both flow visualization and temperature measurements are used. The effects of port location and deflector installation are examined. The experimental results are presented in a dimensionless form, as the normalized outlet temperature vs. dimensionless time. Three-dimensional transient numerical simulations, done using the Fluent 6 software, provide an additional insight in the process of mixing inside the tank.