Refrigeration Terms and Definitions

Activated alumina is a granular Zeolite material frequently used as a desiccant media in Pressure Swing Adsorption driers. It is commonly used to dry compressed air, which becomes saturated as it’s compressed.

A unit of gas flow representing the actual volume of fluid flowing past a reference point. While frequently referred to as “CFM,” the two are not interchangable for compressible fluids. ACFM refers to the volumetric flow rate at ambient temperature and pressure. Mass flow will vary as temperature and pressure change.

A material with the ability to hold a fluid on its surface or within pores without causing a chemical or physical change to the adsorbed material.

The amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. Heating power is frequently given in terms of BTU/Hr. 1,000 BTU/Hr is approximately equal to 293 Watts.

A material used to adsorb oxygen, frequently used to generate nitrogen from compressed air.

A phase change from gas to liquid that results from cooling a vapor-gas mixture below the saturation temperature at a given pressure.

A type of HVAC system that uses constant air volume at variable temperature to maintain temperature in a space. Typically less precise control of temperature and lower overall system efficiency than VAV systems.

Unit of volume equal to 100 cubic feet. Frequently used to describe bulk gas or bulk gas equivalents. Liquid Nitrogen is frequently measured in CCF, or the amount of gas that will result when the liquid fully boils off. In liquid form, one CCF of Nitrogen is slightly more than a gallon.

A unit of rate of volumetric fluid flow. While often used alone with regard to incompressible fluids, such as water, CFM alone is not descriptive of compressible fluid flow, such as air, nitrogen, or any other gas, without additional information (see SCFM, ACFM).

Desiccant is a material that adsorbs water vapor. It is frequently used to decrease relative humidity in air.