Factories use heat exchangers or chillers to regulate an area's temperature. The machine absorbs heat from an area that produces it and carries it to a different location. The medium that carries the heat is a refrigeration fluid that absorbs and releases heat as it experiences differing pressures. A standard formula for finding a chiller's cooling capacity from its flow rate in gallons per minute determines the cooling rate in British Thermal Units (BTUs) per hour. One refrigeration ton is a cooling rate of 12,000 BTUs per hour.

Multiply the exchanger's flow rate in gallons per minute by 500, a conversion constant. For example, if 350 gallons flow through the unit each minute: 350 × 500 = 175,000.

Multiply this answer by the fluid's temperature change as it passes through the heat exchanger. For example, if the fluid rises 21 degrees Fahrenheit in temperature: 175,000 × 21 = 3,675,000. This is the chiller's cooling rate, measured in BTUs per hour.

Divide this rate by 12,000, which is the number of BTUs per hour in a ton: 3,675,000 ÷ 12,000 = 306.25. This is the unit's cooling rate, measured in tons.