Chillers transfer heat collected from the building loop to the cooling-tower loop. This warm water is pumped to the tower where its temperature is lowered by evaporative cooling; then it’s circulated back through the chiller. Chiller manufacturers have determined the most efficient operating conditions with regard to the cooling-tower return-water temperature. If the existing system doesn’t target this temperature, then the controls should be adjusted to do so.
The cooling tower is the working part of the condenser-water loop. It has one or more large fans and pumps which use copious quantities of energy. Good energy-saving projects are to reduce the fan speed by installing a variable-speed drive or two-speed motor, or to reduce the pump energy use by installing a bypass valve to take a portion of the water flow out of the cooling-tower loop (the pump head is reduced).
Both projects maintain, through controls, a constant temperature of water supplied to the condensing side of the chiller, thereby increasing its efficiency.
Another noteworthy part of a cooling-tower study is to be sure the proper water flow passes through the tower and across the fill. If the flow is out of balance, there will be much less evaporative cooling, and the fan will have to run longer—often at full speed—to cause sufficient cooling. This can be quite costly.
__________
Excerpt from Energy Conservation Projects.