High-Rayleigh-number convection in a horizontal enclosure

Abstract

A review of the literature on natural convection in a horizontal layer heated from below shows the need for reliable data at high Rayleigh number ( Ra ) to determine the asymptotic Nusselt number ( Nu ) variation with Rayleigh number. The present study expands the data base by the use of an electrochemical mass transfer technique to determine the asymptotic dependence of the Sherwood number ( Sh ) on Ra at high Schmidt number ( Sc ). The results of the present study give Sh = 0.0659 $Ra^{frac{1}{3}}$ for Sc ≈ 2750, 3 × 10 9 < Ra < 5 × 10 12 . Using the heat-mass transfer analogy, this indicates the high Prandtl number variation of Nu with Ra .