The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible.With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2. Athigher velocities and for large loss coefficients (Kt and 4fUD), compressible flow analysisshould be used.
SAE AIR1168/1-1990(R2004) history
2019SAE AIR1168/1A-2019 Thermodynamics of Incompressible and Compressible Fluid Flow
2011SAE AIR1168/1-2011 Thermodynamics of Incompressible and Compressible Fluid Flow
0000 SAE AIR1168/1-1990(R2004)
1990SAE AIR1168/1-1990 Thermodynamics of Incompressible and Compressible Fluid Flow
1989SAE AIR1168/1-1989 Thermodynamics of Incompressible and Compressible Fluid Flow