
SAE AIR1168/1A
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
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Thermodynamics of Incompressible and Compressible Fluid Flow
Hardcopy , PDF
25-02-2025
English
11-04-2019
The fluid flow treated in this section is isothermal, subsonic, and incompressible.
DocumentType |
Standard
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Pages |
156
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PublisherName |
SAE International
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Status |
Superseded
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SupersededBy | |
Supersedes |
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. At higher velocities and for large loss coefficients (Kt and 4fL/D), compressible flow analysis should be used.
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