Vice President & COO
PE, ASHRAE Presidential Fellow, LEED AP BD+C, BEAP, MCIBSE
Open Cooling Tower Design Considerations
ASHRAE Journal, February 2016
The design decisions made in selecting and sizing cooling towers and their components has a direct impact on the performance of the overall chiller water plant. A cooling tower’s long-term performance is a function of the details of design for the cooling tower and its supporting components.
This month, I point out some common problems that must be addressed in cooling tower selection and the design of condenser water systems. These problems can impede the system’s ability to perform reliably and efficiently. These are all examples from actual facilities that I have designed, peer reviews I have performed on designs by others, or retrofits of systems designed by others.
Principle of Operation
Evaporation is a cooling process. Cooling towers use the internal heat from water to vaporize the water thus removing heat from the water. Sensible heat that changes temperature is also responsible for a small part of the cooling tower’s operation. A cooling tower’s purpose is to expose as much water surface area to air as possible to promote the evaporation of the water. In a cooling tower, approximately 1% of the total flow is evaporated for each 10°F (6.9°C) temperature change. Range and approach are two important terms used in the discussion of cooling towers.