Compressed air is air that has been pressed into a volume smaller than it normally occupies. Because compressed air exerts a pressure, it performs work when released and allowed to expand in a suitable machine to its normal free state. Compression efficiency is the ratio of calculated isentropic work requirement to actual thermodynamic work requirement. Usually expressed as a percentage, the compression efficiency accounts for all thermodynamic and fluid friction losses within the compressor cylinder. It is the ratio of the theoretical horsepower to the actual indicated horsepower.
Mechanical efficiency is expressed as a percentage and accounts for all mechanical friction losses.
Overall efficiency is the product of the Compression Efficiency and the Mechanical Efficiency. Brake horsepower is the horsepower required to drive the compressor at rated conditions. Moisture separators are devices for collecting and removing moisture precipitated from the air or gas during the process of cooling. Return to index Economy of Compressed Air A number of factors make up the total cost of compressing air. The IAC has recommended several changes in the use of air compressors at manufacturing facilities that have reduced the cost of using compressed air.