Passive scalar transport in turbulent channel flow of viscoelastic dilute polymer solutions exhibiting drag reduction (DR) is studied using direct numerical simulations for DR values up to 74.0%. DR is accompanied by the stabilization of low-speed streaks in the buffer layer that are primarily responsible for the streamwise heat transport. Moreover, as DR increases, the Reynolds stress and the root mean square fluctuations in the wall-normal and spanwise velocity components decrease. Thus, as DR is increased, streamwise heat flux increases, whereas both wall-normal and spanwise heat fluxes decrease. Consequently, for large DR values, the flow acts as a highly efficient heat pump. The turbulent Prandtl number, defined as the ratio of the eddy diffusivities of momentum to heat, increases from its Newtonian limit of unity to a value that exceeds the molecular Prandtl number for DR = 74.0%. This experimentally well documented phenomenon is predicted using first-principle simulations for the first time in this work. (c) 2005 American Institute of Chemical Engineers.