Fundamentals of Refrigeration: Rate

Rate is the quantity of something measured against something else. For refrigeration, the “something else” will always be a unit of time. When length is measured against time, the result is a speed or velocity measurement. Examples include miles per hour and feet per minute.

When volume is measured against time, the result is a flow rate such as cubic feet per minute, CFM, or gallons per minute, GPM.

When measuring the heat within a substance, we often use British Thermal Units or BTUs. Heat transfer rate is often expressed as BTUs per minute or BTUs per hour.

Every refrigeration professional must be familiar with the unit called a “ton” or a “ton of refrigeration”. In a refrigeration context, a ton is a rate measurement and is equivalent to 12,000 BTU per hour.