A computational investigation of laminar forced convection of supercritical CO2 flow in horizontal duct with plane symmetric sudden expansion and its bifurcation phenomenon are presented in this study. The computations were conducted at various Reynolds numbers for cases of different wall heat fluxes. A parameter named recirculation disturbance intensity is introduced that is aimed to shed some light on the reduction of flow stability when Reynolds number or wall heat flux increases. The Nusselt number distribution in the symmetric flow regime is presented, the variations of peak Nusselt number and its relative location are discussed. Wall friction coefficient and pressure coefficient distributions are presented and discussed. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.