Range temperature is the difference between the hot water entering the cooling tower and the cooled water leaving the tower, representing the actual heat removed by the tower. This value is determined by the chiller or system load, not the tower design. A higher range indicates greater heat rejection demand, while range remains constant regardless of ambient conditions or tower capability.
Calculation and Application
Range is calculated simply as inlet water temperature minus outlet water temperature. For example, water entering at 95°F and leaving at 85°F represents a 10-degree range. This 10-degree temperature differential directly correlates to the heat load in BTU terms: a 10-degree range with 1,000 gallons per minute equals approximately 83 tons of cooling. Range values typically fall between 8-15 degrees Fahrenheit in commercial HVAC applications.
System Design Considerations
Range is independent of wet bulb temperature, unlike approach temperature which varies seasonally. Larger chiller loads produce higher ranges, requiring towers sized accordingly to maintain acceptable outlet temperatures. The combination of range and approach determines the required inlet temperature. If cooling demand increases 20%, range increases proportionally unless water flow increases, which would reduce range but require larger equipment. Understanding range versus approach is essential for proper tower selection and load calculations.