Alwan Hibatullah

But, if we focus on heat transfer, is that necessary? because as I said, there is a difference in temperature value between the heat flux that propagates from the solid to the fluid and the heat flux that is applied directly to the fluid

I'm still confused there, as if when heat propagates from solid to fluid, the temperature on the walls of the fluid becomes stuck and cannot flow properly even though the temperature at the outlet is appropriate.