gas expansion calculation

[dmrgt03]

I am flowing 100 sccm gas through 10 orifii of diameter 0.016". The gas is either B2H6 or BF3.

I want to do a gas expansion calc to determine a minimum pressure gradient needed to establish a sonic front.

 

[sailoday28]

Are you stating that the flow is choked? If the flow is adiabatic and secondaly a perfect gas with constant specific heats, then stagnation Temp must be stated.

To determine the pressure drop, either upstream stagnation pressure or downstream static pressure must also be given.

 

[dmrgt03]

If we are talking ideal gas, isenotropic flow, with M=1 then clearly it is choked flow. Stagnation temp would be 300 K.

In this case, downstream static pressure is 6, 8, or 10 mTorr.

 

[sailoday28]

For choked ISENTROPIC-flow-perfect gas, constant specific heats

The crictal pressure ratio of upstream STAGNATION PRESSURE to downstream STATIC PRESSURE =
[(GAMMA+1)/2] RAISED TO POWER [1/(GAMMA-1)]
WHERE GAMMA IS RATION OF Cp/Cv