Avoiding Common Pitfalls in Cooling Tower Pump Intake Design Related to Hydraulic Performance

Cooling towers are an attractive method to provide cooling water to power plants and other process cooling applications. The use of cooling towers versus once-through cooling significantly reduces the amount of water drawn from rivers and lakes, which is particularly important in many regions in the Western United States where water availability is a problem. Cooling towers also eliminate thermal pollution due to cooling water discharges into and greatly reduce the amount of water withdrawn from natural bodies of water. Despite these advantages, cooling towers provide special challenges with regard to the design of cooling water pump intake structures. These challenges must be addressed to ensure a reliable flow of cooling water with a minimum expenditure of power in order to maximize the plant capacity and efficiency. Design factors such as footprint, civil constraints, increases in plant capacity requiring increased cooling flow, and off-design operation can all affect the flow hydraulics and therefore negatively affect the performance of the pumps. In this paper, general hydraulic design guidelines and performance acceptance criteria for pump intakes based on Hydraulic Institute Standards are outlined. Case studies from physical model studies of cooling water pump intakes are presented which may provide insight into likely problems and design flaws that engineers should be aware of while designing cooling tower pump intake structures. Examples of measures to avoid or remedy the commonly-encountered hydraulic problems derived from hydraulic model studies are discussed.