DISPLACEMENT EFFICIENCY OF WATER IN A CYLINDRICAL TANK

The objective of the present study is to improve the design of a cylindrical water supply tank in order to achieve better displacement efficiency of old water in a cylindrical tank. The present paper describes the results of an experimental study of the flow pattern and the residual concentration of old water in a tank. The effect of the shapes of the inlet and outlet pipes on the displacement efficiency of old water in the tank was investigated. The displacement efficiency of old water in a tank that has inlet and outlet pipes at one end of the tank (Type 2) is better than that in a tank that has inlet and outlet pipes at the center of the tank (Type 1). The displacement efficiency of water inside the tank that has an inlet pipe with a diverging nozzle and an outlet pipe with a circular baffle plate (Type 5) is better than that of the other tank. The replacement efficiency of old water with new water in the tank depends on the location, the length of the inlet nozzle, and the diameter of the baffle plate. The entrainment of the old water to the jet of new water is found to decrease with the addition of the diverging nozzle, and the baffle plate is found to prevent the diffusion of old water.