A NUMERICAL STUDY OF HEAT-TRANSFER DUE TO AN AXISYMMETRICAL LAMINAR IMPINGING JET OF SUPERCRITICAL CARBON-DIOXIDE

The physical properties of a supercritical fluid vary markedly as the temperature and the pressure approach its critical point. In this paper, heat transfer due to an axisymmetric laminar impinging jet onto a flat wall surface of uniform temperature is analyzed numerically, taking into account the temperature- and pressure-dependence of all physical properties of supercritical carbon dioxide. Numerical solutions are obtained for the jet Reynolds numbers 500-2000, the jet pressures 7.4-8.4 MPa, the jet mouth-to-surface distances 1-4 times the jet nozzle diameter, and the temperature difference between the jet mouth and flat wall from 10 to 150 K. The differences between the supercritical pressure and the atmospheric pressure for the flow field and the temperature field are investigated. Also, the effects of the pressure and the temperature of the jet, the jet mouth-to-surface temperature difference and the jet Reynolds number on the heat transfer characteristic are examined. A correlating equation of estimating the value of the local Nusselt number for the supercritical carbon dioxide from the constant-property solution is proposed and the agreement between the present correlation and numerical results is within 10%.