Pseudocritical heat transfer inside vertical tubes

Heat transfer to fluids with pressures slightly above the critical is strongly influenced by the variation of the fluid properties occurring in the so-called pseudocritical region. The heat transfer can either be improved or reduced, depending on the flow conditions. The improvement is due to the enhanced heat transport caused by the increased heat capacity of the fluid. In the case of reduced heat transfer the turbulence is weakened by gravitational effects. In the present paper the heat transfer due to the complex interaction between gravity and turbulence in the so-called pseudocritical region is predicted by a numerical solution of the conservation equations for a turbulent pipe flow. The numerical results are compared with published experimental data for an electrically heated vertical pipe with the fluid R12.