cooling water flow rate control 1

[etchyHA]

hi every one

well i have a project contains 3- water cooled chiller and 3-cooling towers at and i ve been asked to make a schematic dwg for these equipments ,to control the cooling water flow rate i will use three way valve my question is where is the best location to put is it before the cooling water pumps on OUT line of the cooling tower and the by-pass line connected to the IN line of the cooling tower which i think it is wrong cuz this may cause cavitation problem or should i put it after the pumps to assure +ve NPSH of the constant speed cooling water pumps?

 

[ChasBean1]

The bypass is usually put at the towers, bypassing water from the cooling tower inlet (aka condenser water return) to the cooling tower outlet (cws). Its purpose is not flow control but temperature control. If it's a cool day and you need chiller operation, you still could drop to too low a cws temperature by just shutting off tower fans because water still cascades over the tower baffles. The bypass gives improved cold weather temperature control.

The sequence of operation is if all tower fans are off and cws temperature drops below set point, modulate the cooling tower bypass valve toward bypass to maintain cws temperature.