A Transient Buoyancy-Driven Convection Experiment for Surfaces in Air

Abstract

A novel, transient experiment for buoyancy-driven convection from surfaces in air is described in this paper. The experiment is applied to a heated, vertical (37 mm high), copper plate which is allowed to cool in still air and in a partial vacuum. The recorded temperature histories are reduced using numerical methods. The result is an average emissivity of 0.42 and a heat transfer correlation of Nu_H = 1.59 Ra_H^0.175 in the Rayleigh number range 31 300 to 242 500. A scale analysis shows that the transient heat transfer result may be compared with a steady-state correlation.