《CORRELATION EQUATIONS FOR FREE CONVECTION HEAT TRANSFER IN HORIZONTAL LAYERS OF AIR AND WATER》.pdf

hr. .I. Hear Mass TronsJer. Vol. 18,pp.879-884. PergamonPress1975.PrintedinGreatBritain CORRELATION EQUATIONS FOR FREE CONVECTION HEAT TRANSFER IN HORIZONTAL LAYERS OF AIR AND WATER K. G. T. HOLLAND~ G. D. RArTHBYt and L. KONICEK* (Received 4 June 1974 and in revised form 21 October 1974) Abstract-New experimental measurements are reported on the natural convective heat transport through a horizontal layer of air, covering the Rayleigh number range from sub-critical to 4 x 106. When these data are combined with Goldstein and Chu’s data for air, the full set of data points are demonstrated to bear a Nusselt number dependence which is asymptotic to a l/3 power on the Rayleigh number as the Rayleigh number approaches inhnity. The asymptotic coefficient of proportionality is consistent with that predicted by a simple “conduction layer model” which is described. Knowledge of the asymptote has permitted a simple but accurate correlation equation to be obtained, valid for the full range of Rayleigh number. By extension, a similar correlation equation is also obtained for water. NOMENCLATURE flow consists of steady rolls. Subsequent increases in the constant in equation (2) [dimensionless]; Rayleigh number produces flows of increasing com- depth of fluid layer [ml; plexity