New dimensionless correlation-equations for laminar free convection heat transfer in real gases with high wall-fluid temperature differences

Two-dimensional steady free convection heat transfer between isothermal vertical flat plates and real gases, also at thermodynamic states characterized by a compressibility factor significantly different than unity, was studied theoretically by taking into account the actual temperature-dependence of the physical properties of the fluids investigated. The laminar boundary-layer governing equations were solved numerically by a control-volume formulation of the finite-difference method, for significantly wide ranges of variability of the gas pressure, of the wall temperature, and of the free stream temperature. Numerical simulations were executed for air, carbon dioxide, and methane. The dimensionless heat transfer data obtained from computations were correlated by two general equations that, in contrast with other correlation-equations available in the literature, may be assumed as independent of the fluids specifically considered and, even more important, cover almost the whole vapor region. (C) 2003 Elsevier SAS. All fights reserved.