Compressed Air System

Compressed air is the most expensive utility in most factories and the one nobody measures — roughly 8 kW of electricity for 1 kW of useful work. The three power figures below bracket the problem: isothermal is the thermodynamic floor, isentropic is a single uncooled stage, and the gap between them is exactly what intercooling buys.

Free air delivery is measured at INLET conditions, not at discharge — a compressor rated "10 m³/min" delivers that much atmospheric air, which becomes about 1.25 m³/min at 8 bar. Discharge temperature is per stage; above roughly 180 °C mineral lubricants start to break down, which is the real reason large machines are multi-stage. Receiver sizing here is for pump-down hold time; sizing to limit compressor starts per hour usually gives a larger vessel. Condensate assumes the aftercooler leaves the air saturated, which is what a real one does.