A numerical and experimental study of the laminar flow and heat transfer characteristics of a cylinder in cross-flow is presented. The computational technique used is a stream function-vorticity formulation of the laminar flow steady state incompressible Navier-Stokes and energy equations and uses a Gauss-Seidel over-relaxation technique to obtain stream function and temperature distributions. Calculations are presented for an isothermally heated single tube in a duct with different blockage ratios. The variation of local Nusselt number, pressure and also isotherm and streamline contours are predicted with Reynolds number of 120 and 390. For the Reynolds number of 390, the local Nusselt number distributions are shown to be similar to those obtained through measurement of the local heat flux from the surface of a tube using a micro-foil heat flow sensor. (C) 1998 Elsevier Science Inc. All rights reserved.