Physical Model Test of Water Intake Including Huge Pump Station and Drum Screen

Abstract

A physical model, built at an undistorted scale of 1:15 tested the original design of the six drum screen and nineteen cooling water pump intake connected to header bay. The capacity of origin water intake including huge pump station and drum screen is 400,000 m3/hr. The study objectives were to evaluate as-designed screen bay and pump bay performance and to propose design modifications to optimize intake flow conditions with respect to head-losses, uniformity of the approach flow, evenness of pump throat velocity distribution, and free and subsurface vortex formation. The model was built and operated in accordance with froude-number similitude. It allowed accurate representation of complex flow patterns caused by the physical geometry of the approach bay and pump bays. The major factors that can affect the selection of a concept and design development for a water intake are: a) The occurrence of dead water zones, flow separation or reverse flow b) Vortex building and air entrainment in the pump compartments c) Submerged vortices building in the pump compartments d) Low velocity area e) Strong rotational flow f) Strong cross flow appear in front of pump units g) Pre rotation in the pump suction lines. Dye injection was used to examine the stratified flow behavior along water. The existing design of the pump bays was found to produce a uniform, symmetrical flow distribution in the approach flow, weak but persistent floor and side-wall-attached submerged vortices, avoiding cross flow and reverse flow in front of the pumps and negligible swirling motion in the pump suction. Modified design includes (i) profiling low velocity area (ii) adding flow deflectors along inner walls (iii) infill area of low velocity (iv) adding suspended baffle in front of drum screens (v) adding diffuser block in front of pumps (vi) provision of floating booms in front of pumps.