Air Compressor Terms-what does it mean?
Part two of a valuable resource- A Compressed Air System Glossary:
(For Part One-see our May 07 posting)
Degree of Intercooling - The difference in air or gas temperature between the outlet of the intercooler and the inlet of the compressor.
Deliquescent - Melting and becoming a liquid by absorbing moisture.
Desiccant - A material having a large proportion of surface pores, capable of attracting and removing water vapor from the air.
Dew Point - The temperature at which moisture in the air will begin to condense if the air is cooled at constant pressure. At this point the relative humidity is 100%. The temperature to which air must be cooled, at a given pressure and water-vapor content, for it to reach saturation; the temperature at which dew begins to form.
Demand - Flow of air at specific conditions required at a point or by the overall facility.
Diaphragm - A stationary element between the stages of a multi-stage centrifugal compressor. It may include guide vanes for directing the flowing medium to the impeller of the succeeding stage. In conjunction with an adjacent diaphragm, it forms the diffuser surrounding the impeller.
Diaphragm cooling - A method of removing heat from the flowing medium by circulation of a coolant in passages built into the diaphragm.
Diffuser - A stationary passage surrounding an impeller, in which velocity pressure imparted to the flowing medium by the impeller is converted into static pressure.
Digital Controls - See Logic Controls.
Discharge Pressure - Air pressure produced at a particular point in the system under specific conditions.
Discharge Temperature - The temperature at the discharge flange of the compressor.
Displacement - The volume swept out by the piston or rotor(s) per unit of time, normally expressed in cubic feet per minute.
Droop - The drop in pressure at the outlet of a pressure regulator, when a demand for air occurs.
Dynamic Type Compressors - Compressors in which air or gas is compressed by the mechanical action of rotating impellers imparting velocity and pressure to a continuously flowing medium. (Can be centrifugal or axial design)
Efficiency - Any reference to efficiency must be accompanied by a qualifying statement which identifies the efficiency under consideration, as in the following definitions of efficiency:
Efficiency, Compression - Ratio of theoretical power to power actually imparted to the air or gas delivered by the compressor.
Efficiency, Isothermal - Ratio of the theoretical work (as calculated on an isothermal basis) to the actual work transferred to a gas during compression.
Efficiency, Mechanical - Ratio of power imparted to the air or gas to brake horsepower (bhp).
Efficiency, Polytropic - Ratio of the polytropic compression energy transferred to the gas, to the actual energy transferred to the gas.
Efficiency, Volumetric - Ratio of actual capacity to piston displacement.
Exhauster - A term sometimes applied to a compressor in which the inlet pressure is less than atmospheric pressure.
Expanders - Turbines or engines in which a gas expands, doing work, and undergoing a drop in temperature. Use of the term usually implies that the drop in temperature is the principle objective. The orifice in a refrigeration system also performs this function, but the expander performs it more nearly isentropically, and thus is more effective in cryogenic systems.
Filters - Devices for separating and removing particulate matter, moisture or entrained lubricant from air.
Flange connection - The means of connecting a compressor inlet or discharge connection to piping by means of bolted rims (flanges).
Fluidics - The general subject of instruments and controls dependent upon low rate of flow of air or gas at low pressure as the operating medium. These usually have no moving parts.
Free Air - Air at atmospheric conditions at any specified location, unaffected by the compressor.
Full-Load - Air compressor operation at full speed with a fully open inlet and discharge delivering maximum air flow.
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