7.3.4.1 Energy Aspects of the Poiseuille Flow
As far as the temperature of the fluid is concerned, we have that it has to be constant in time and its distribution is given by the temperature diffusion Equation 7.63. In this case, assuming that the duct walls are completely insulating under a thermal point of view and at the same temperature of the incoming fluid, the heat is generated by viscous dissipation all along the motion, so that a distributed heat source exists that depends on the velocity field. The viscosity generated heat is removed from the system by the flowing liquid exiting from the output duct section that will result to be at higher temperature with respect to the liquid entering from the input section.
This is not an important ...