Hi,

I have a problem considering a cylinder with a moving piston, which compresses the Helium in the cylinder. I want to determine the heat flux out of the cylinder through the walls. To determine this heat flux, I use the area-averaged Wall Heat Flux for every boundary in my closed cylinder. Although I get good result for pressure and temperature (compared to measurements), the Wall Heat Flux, as a function of the piston position, gives very strange results (i.e. the profile is completely different and irrealistic). Does anyone have the same experiences when determining the Wall Heat Flux with CFX551?

Regards

Hi

What are you setting for your Wall boundary condition ? A fixed temperature ? An external Heat Transfer Coefficient ? Also are you modeling radiation in your problem ?

Regards,

Sharks

Hi,

Fixed Wall Temperature boundary condition, No radiation...

Regards

You can calculate the wall heat flux in turbulent flows: QW=(TWALL-TCENTER)*DENSITY*SPECHT*UTAU/THETA with dimensionless Temperature (universal wall function) THETA=PRTURB/CAPPA*DLOG(CTHETA*YPLUS).