Hello

I am solving a transonic heat transfer problem in concentric pipe heat exchanger. Hot air entering in the inner pipe are at 500m/s at 1173 Kelvin and their Mach # is 0.7283. Gases are leaving into the atmosphere.

I can apply two boundary conditions at the inlet as fluent manuals guides me. Mass flow inlet or Pressure inlet. But in both Boundary condition i need to specify the Static pressure at the inlet, which i don't have.

Is there any genius who can help me in making the initial guess for static pressure. I am also facing a problem in achieving balance of continuity equation. What could be the REASONS ?

With Regards

Ejaz Ahmed

For supersonic flow you can consider Mass flow inlet as the boundary condition. But if you consider it then you have to be very careful about static pressure otherwise it always gives some problem in the continuity equation. good luck

"PRESSURE-INLET" boundary condition gives you the posibility to specify both total and static(supersonic/initial gauge) pressure. That means the program calculates the initial velocity field using ecuation:

ptot/pstat=(1+(k-1)/2*M^2)^(k/(k-1))

where k=1.4, M= Mach number.

So if you know the Mach number, then you can easily calculate coresponding static pressure.

Best whishes, Razvan

Dear Razvan

Bundle of thanks for ur responce. I have velocity and static temperature data at inlet. Neither i have static or total pressure at the inlet. Now i cannot apply mass or pressure inlet boundary condition.

Is there any possiblity to solve this problem having the given data.

I am looking to trace the pressure mean while

with regards

Ejaz Ahmed

some how now i am assuming the static pressure on the basis of friction loss in one meter pipe.

thanx for the contributors

Ejaz Ahmed