Question: Consider uniform-temperature laminar flow in a circular tube with a fully developed velocity profile. At some point x+ = 0 the surface temperature is raised above the fluid temperature by an amount a. It remains constant at this value until a point x+ =x1is reached, where the surface temperature is again raised an amount b, remaining constant thereafter. Develop a general expression for the surface heat flux, and for the mean fluid temperature Om, in the part of the tube following the second step in surface temperature. Use variable-surface-temperature theory.