Compressors are sized by which of the following requirements?

Compressors in refrigeration systems are primarily sized based on the airflow they need to handle, which is measured in cubic feet per minute (CFM). This measurement indicates the volume of air that the compressor can move and is crucial for ensuring efficient heat exchange and maintaining the desired temperature within the refrigeration system.

In industrial ammonia refrigeration, the compressor's ability to handle specific airflow is essential for optimizing the system's performance. The CFM rating is directly related to the cooling capacity and efficiency of the compressor, helping to deliver the necessary cooling effect required for the application.

Other measurements listed, such as gallons per minute (GPM) or miles per hour (MPH), do not pertain directly to the operation of compressors in this context. GPM is typically used for liquid flow rates, while MPH and kilometers per hour (KPH) are measures of speed, neither of which apply to the sizing of compressors in industrial refrigeration systems. Therefore, CFM is the correct choice as it directly reflects the airflow requirements essential for proper compressor function in refrigeration.