An Experimental Investigation of Natural Convection From an Isothermal Horizontal Plate

An investigation of natural convection from a heated, upward-facing, square, horizontal plate to a surrounding gas medium is described in this paper. The results of the experimental investigation provide an improved correlation for the natural convection regime by accounting for variable property effects and extend the applicable Rayleigh number (Ra) range of the correlation over previous research. The large Rayleigh number regime is emphasized. The value of the Richardson number (Ri) at which combined convection influences become important is also determined. The ratio of the plate wall temperature T_w to the ambient temperature T_∞ is incorporated into the Nusselt number correlation in order to account for variable property influences. A cryogenic heat transfer tunnel, with test section temperatures that are varied between 80 K and 310 K, is used to help deduce the influences of the relevant parameters. The ranges of the dimensionless parameters investigated are 2 × 10⁸ < Ra < 2 × 10¹¹ and 1 < T_w/T_∞ < 3.1.