This study aims to reveal the temporal and spatial heat transfer performance and the transition process from a steady axisymmetric separated flow to a chaotic flow of an isothermally heated sphere placed in a uniform, downwardly directed flow by experimentation and transient 3D numerical simulation. Experiments were carried out using air with a Grashof number of 3.3 x 10(5) and with several Reynolds numbers up to 1900. Four types of flow patterns appear showing that the chaotic flow around the sphere is a spatiotemporal chaos by the calculation of a set of Lyapunov exponents from the calculated time series of temperatures. (C) 2010 Elsevier Ltd. All rights reserved.