KC-84-07-2 -- Open-Loop Evaporative Cooling for Winter Chiller Plant Optimization PDF

In colder weather, cooling towers can replace centrifugal chiller machines as a source of chilled water. When wet-bulb temperatures go below 40°F (4.5°C), the chilled and condenser water circuits are combined, using an integral strainer for keeping the system free of particulate contamination. The cooling towers are used as a refrigerating machine, thereby saving the electrical power needed to run a chiller during cooler weather.
Existing building conditions provide for a constant off-season load of 500 tons (1758 kilowatts), with a maintained chi11ed water temperature of approximately 43°F (60°C). Temperatures are held constant by varying the tower fan speed, and the chilled water flow rates. Using data from the United States Weather Service, a yearly operating time of 2500 hours can be expected. This translates to an annual operating savings of $87,500 and a project payback of less than two years for this installation.