I have done one analysis using star in which rho, mu and Cp are temperature dependant. Oil is flowing through a closes channel and heat flux is applied at channel's walls. The temperature rises as oil passes through it. The area of the channel varies. If I plot temp vs length plot of the oil. It is non linear and has high temperature at location where velocity is low. But at exit velocity suddenly reduces, and to my surprise temperature also suddenly drops. How this is happening? My model contains RFR (channel is rotating). I have extended boundaries at inlet and exit. Kindly guide.

Thanks

if you have pressure boundary at outlet and recirculation there, it can happen, dependent on what temperature you have specified at pressure boundary

Yes you are right I have pressure boundary at outlet. I have given zero gradient there. But it is far away from actual outlet (since it is extended). How to specify pressure BC without temperature? Now I specified same temperature as inlet at pressure (out)BC. But in overall analysis is following q=m*cp*dt. Kindly guide.

Dang..... you guys are smart.