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 l/min, 3 l/min, 5 l/min, and 7 l/min are explored. Temperature of hot water is usually about 55 degrees C, while the tap water is about 20 degrees 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 versus 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.