The unsteady, conjugate, forced convection heat transfer from a fluid sphere to a surrounding fluid flow in the presence of viscous dissipation has been analysed. The fluid flow inside and outside the sphere was considered laminar, axisymmetric, steady and incompressible. The heat balance equations were solved numerically in spherical coordinates system by a splitting finite difference method. The influence of the Reynolds, Brinkman and Peclet numbers on the heat transfer mechanism and rate was analysed for different values of the physical properties ratios (thermal conductivity ratio, heat capacity ratio, viscosity ratio and density ratio). (C) 2015 Elsevier Ltd. All rights reserved.