I have modeled a heated isothermal cylinder in natural convection and for some reason the total tmeperature is lower than the static temperature how is this possible?

What kind of solver are u using. You must check the values of density or specific heat. Sonce its a convection problem, i think you are having a variable density, i guess the density values are going negetive during iterations. If this is the problem, you can enforce a bound on density values to be more than zero. Hope this helped Mahesh.R

I know that statis temperature is what you measure. I forgot what is total temperature but I know that it is static temperature powered by something (velocity or.....)

Static Temperature is the temperature that you measure. Total temperature is the temperature of the flow if it were brought to rest adiabatically.

Total temp is the static temperature the fluid would reach if it were brought to rest isentropically

Thanks Andy for correcting that, i forgot it was isentropically and not adiabatically

My maximum temp at the inlet of a valve is 545C and the flow is adiabatic flow.I need a temperature downfall but during analysis it takes 545c as the min temp and i hav a high temp variation.I am getting resonable pressure values but high temp variation.

Its a sonic flow inlet Static pr: 181.428 bar Static temp:545c outlet: normal speed: 654m/s