  We consider a laminar Blasius boundary-layer flow above a slightly heated
horizontal plate and study the effect of polymer additives on the heat
transport. We show that the action of the polymers can be understood as a
space-dependent effective viscosity that first increases from the zero-shear
value then decreases exponentially back to the zero-shear value as one moves
away from the boundary. We find that with such an effective viscosity, both the
horizontal and vertical velocities near the plate are decreased thus leading to
an increase in the friction drag and a decrease in the heat transport in the
flow.
