In refrigeration terms, what is tonnage a measure of?

Tonnage in refrigeration specifically refers to the measure of heat transfer capacity of a refrigeration system. It indicates how much heat can be removed from a space over a certain period of time. In the context of this question, tonnage is directly related to British Thermal Units (BTUs).

One ton of refrigeration is defined as the ability to remove 12,000 BTUs of heat from a space per hour. This measurement is crucial in determining the size and efficiency of refrigeration systems; it allows for the proper sizing of equipment to meet specific cooling loads in various applications, such as commercial or industrial refrigeration.

The focus on heat transfer in BTUs per time emphasizes the continuous nature of the refrigeration process, where the system is capable of transferring a specific quantity of heat each hour. This is why the correct answer is that tonnage is a measure of heat transfer in BTUs per time.