How to Calculate GPM to BTU Tonnage

Factories use chillers to maintain optimum conditions.

An industrial chiller pumps refrigeration fluid to lower an area's temperature. This helps to cool equipment, increasing its efficiency. The area's temperature drop is the effect that you can most easily measure, but this corresponds to an energy transfer, which is measured in British Thermal Units (BTUs) per hour. The greater the chiller's flow rate, measured in gallons per minute (GPM), the greater the rate of energy transfer.

Instructions

1. Calculate the fluid's temperature change as it goes through the chiller. If, for instance, fluid enters the device at 72 degrees Fahrenheit and leaves at 55 degrees Fahrenheit: 72 - 55 = 17 degrees.

2. Multiply this answer by the flow rate through the device, measures in gallons per minute. With a flow rate of 320 gpm: 17 --- 320 = 5,440.

3. Multiply this answer by 500, a constant conversion factor: 5,440 --- 500 = 2,720,000. This is the chiller's total power, measured in BTUs per hour.

References

• Stanford University; Chilled Water Plant Pumping Schemes; James J. Nonnenmann
• Austin Community College; Carrier Water Piping Systems; 1986

Resources

• T.J. Snow Company, Inc: Chillers
• American Hermetics: Selection Guide