temperature gain in the flow field due to solar radiation
 

I want to simulate temperature distribution due to the heat gain by the solar radiation in the transparent pipe.
i defined the velocity inlet, and outflow BC. and semi transparent wall with transmissivity of 1.
and defined the absorption coefficient for the fluid.
and solar ray tracing model.
but I don't see any temperature increase, and total temperature at the outlet is exactly equal to the inlet temperature.
can anyone tell me what is the problem?, i put many times on it, and I am tired of searching on the internet.

a few questions just to know more about your setup..

what velocities are you getting? how long (e.g. minutes) are you running your simulations? can you show your geometry?

Thank you so much for the reply, in fact i have tried the steady solution, you think i should try unsteady??
the geometry is a simple cylindrical pipe. i defined inlet velocity as 0.1 [m/s].
I attached the velocity magnitude profile. if you need another information please tell me. thanks.
Attachment 12466

could the temperatures are not changing due to the effective cooling at velocity 0.1m/s?