This simulation models compressible flow of air through a reversible nozzle/diffuser. The inlet pressure P₁, the exit velocity u₂, and the exit temperature T₂ are calculated from mass and energy balances and that the entropy change is zero. The air exits as a free jet at atmospheric pressure (P₂ = 101.3 kPa). Set the outlet diameter d₂ and inlet velocity u₁ with the sliders. When d₂ < d₁, the device acts as a nozzle, with the inlet pressure higher than the exit pressure (P₁ > P₂) in order to provide the energy needed to accelerate the air through the nozzle. When d₂ > d₁, the device operates as a diffuser, and the exit pressure is higher than the inlet pressure (P₁ < P₂). When “plots” is selected, the outlet velocity or outlet temperature is plotted as a function of outlet diameter for compressible air flow (blue) and incompressible air flow (green). Air is assumed to behave as an ideal gas and all flow is subsonic.

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About:

This simulation was made at the University of Colorado Boulder, Department of Chemical and Biological Engineering.  Author(s): Rachael L. Baumann

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