[abhayachougule]

Hi All,

I am solving a Unsteady CHT problem of pressure vessel , containing gas . Gas is released suddenly from a opening, which causes sudden drop in Temp. .
Now which BC should I give mass flow outlet or pressure outlet(@ 0 gauge pressure) or any other BC? Also is it necessary to specify heat transfer coeff. at outer solid surface, as am not simulating the outer domain?


Thanks in advance.

[Hamidzoka]

you are about to solve an unsteady problem. according to the fact that outlet gas flow rate varies as the vessel pressure drops, it would be better to set a presure boundary condition at outlet. since we are sure that discharged gas has a constant atmospheric condition.
for the case of outter surface, having not isolated the vessel you should consider heat exchange of vessel with surrounding air as well.
for this purpose you can assume an averaged heat transfer coefficient.
if the vessel is installed outdoor and air blows, forced convection should be considered. an in case the vessel in installed indoor or there is no air blows free convection assumtions shall be considered.

regards

[abhayachougule]

Thanking you