Where to Find a Spreadsheet for Choked Air Flow Calculation
To obtain a spreadsheet for choked air flow calculations , click here to visit our spreadsheet store. Intended for use in making fanno flow calculations with adiabatic compressible flow of air, you can buy a convenient spreadsheet for choked air flow calculations for a very reasonable price. This spreadsheet will also calculate the frictional pressure drop, and is available in either U.S. or S.I. units. Read on for information about a choked air flow calculation spreadsheet for compressible pipe flow.
Conditions for Choked Air Flow Calculation with a Fanno Flow Excel Spreadsheet
For flow of air in a pipe with the frictional pressure drop less than 20% of the inlet air pressure, satisfactory results can be obtained using incompressible flow calculations with the Darcy-Weisbach equation. For background information on that type of calculation, see the article, “Pipe Flow-Friction Factor Calculations with Excel Spreadsheets.” If the frictional pressure drop is more than 20% of the incoming air pressure, then Fanno Flow equations should be used, as discussed here using a Fanno Flow Excel spreadsheet.
With adiabatic compressible flow conditions, the maximum air flow rate that can pass through a pipe is that which occurs when the exit Mach number is 1.0. This is referred to as “choked flow.”
Equations for Choked Air Flow Calculations with a Fanno Flow Excel Spreadsheet
Shown below are the primary equations used in the fanno flow excel spreadsheet being discussed here for compressible flow of air in a pipe. These equations are for compressible pipe flow with negligible heat transfer with the surroundings, but including effects of friction in the flow.
- f = Moody friction factor
- L = pipe length
- D = pipe diameter
- k = adiabatic constant for the flowing air
- M = mach number
- T = air temperature
- P = air pressure
- ρ = air density
Parameters with an asterisk refer to conditions at the “choke point” in the pipe, where the Mach number is 1.
Screenshot for a Choked Air Flow Calculation Spreadsheet Using Fanno Flow Equations
The screenshot below shows part of a fanno flow excel spreadsheet for making compressible air flow calculations. These calculations are for air flow in a pipe, in S.I. units. This Excel spreadsheet and others for compressible pipe flow calculations in a fanno flow excel spreadsheet are available in either U.S. or S.I. units at a very reasonable cost in our spreadsheet store.
Bengtson, Harlan H., “Compressible Flow Pressure Drop Calculator Spreadsheet,” an online blog article