Buoyancy effects on heat transfer and temperature profiles in horizontal pipe flow of drag-reducing fluids

We have studied the extent to which buoyancy effects in horizontal pipe flo ws of drag-reducing viscoelastic fluids cause distortions to both laminar a nd turbulent temperature profiles. In the case of laminar flows, these dist ortions may lead to variations in Nusselt numbers that are larger than thos e seen for Newtonian pipe flows under similar conditions. In the case of tu rbulent drag-reducing flows, the effects of buoyancy can also be large and may in turn result in large errors in estimated Nusselt numbers if not prop erly accounted for. These errors are quantified and recommendations are mad e on how to reduce them. (C) 2000 Elsevier Science Ltd. All rights reserved .