This study presents a numerical investigation of heat transfer in supercritical CO2 and water turbulent flow in a circular tube. To solve two-dimensional grid systems, RSM turbulent models were used. The effect of mass flow rate and pressure on heat transfer coefficient, flow acceleration and buoyancy parameter were investigated. The numerical results demonstrated that increasing the mass flux causes to decrease buoyancy and flow acceleration. In addition, an increase in pressure results in a decrease in buoyancy and flow acceleration terms. Finally, a new correlation is proposed to enumerate the effect of flow acceleration and buoyancy on heat transfer phenomena in a vertical upward flow of a supercritical fluid. (C) 2016 Elsevier B.V. All rights reserved.