Process Cooling Using a Closed-Loop System
When used for process temperature control, a recirculating water chiller can keep the water at or below ambient temperature. Other times, dry coolers or cooling towers operate at temperatures above the wet bulb or ambient temperatures.
Chillers are an obvious choice when water costs are high, water quality is poor, or when environmental constraints prohibit the drainage of cooling water. But, they also can provide relatively quick payback in applications where temperatures must be controlled in continuous-duty operations.
In fact, any process that achieves cooling directly or indirectly through a heat exchanger with city water can benefit from using a closed-loop cooler. There are three key benefits.
1. Using city water to cool production equipment can be expensive.
In a process consuming only 3 gal/min, more than 360,000 gal can be washed down the drain each year (see sidebar, p. 56). By contrast, a chiller requires only a gallon or two of water each month to make up losses. A closed-loop system can safely and automatically cool heated liquid, then recirculate it back to the equipment. Processors do not need to purchase large quantities of water to maintain process temperature control.
2. Equipment investment is protected.
City water must be pretreated or it can lead to mineral scaling and blockages in the equipment, reducing efficiency and leading to equipment failure. A closed-loop system eliminates mineral scaling and the need for ongoing water treatment. Equipment can last longer with less unscheduled downtime for repairs or replacement.
2. Productivity can be increased because temperature fluctuations are eliminated.
Unlike fluctuations in city water temperature, a recirculating water system will hold the temperature of the water or other cooing media to within +/-1oF. This helps maintain close tolerances, resulting in more uniform, higher quality products. In addition, in machining applications, coolant life is extended and reduced evaporation improves working conditions.
Water-cooled chillers are designed for cooling water, water/glycol combinations, or other water-based fluids. The self-contained refrigeration units require only electrical power, fluid connections and a water makeup line (if used). Consider using one in your application, and stop watching your dollars go down the drain.