Dear all, I have a hard time in understanding the fundamentals of convection. Lets say we blow a fan over a hot surface. From fluid mechanics, I know that there is a velocity boundary layer due to the viscosity and no slip condition. The velocity gradient is kinda parabolic. Ok, lets now follow ONE particular hot molecule. This hot molecule is conducted at the surface-fluid interface. Then my question here is does it move to the right or does it move in a parabolic motion. I guess the problem stems in my understanding of boundary layer. I mean what happens next. Moreover, is it suppose there is a convection current always. If yes, how is it possible in this case. Thanks a lot to whoever contributes.