A study of electroconvection in the presence of a gravitational field

Abstract

Measurements were made of the electroconvective heat transfer coefficient in gases (Ar, O2, N2O, and Freon-22); liquid (distilled water); and a colloidal suspension (α-Fe2O3 in distilled water) from a single Pt wire (diameter = 0.025 mm) mounted along the axis of a Cu cylinder (diameter = 53 mm). The measurements were carried out as functions of electric fields (dc and ac) and pressure in the Earth's gravitational field. The measurements reveal a complicated interaction between the electric-field gradient and thermal convection. Measured heat-transfer data are correlated by dimensional analysis. The data are compared with the empirical correlation relation and analytical expression and are well correlated over the range of Rayleigh numbers from 1.2 × 107 to 4.5 × 108. An empirical correlation relation has, also been proposed to evaluate the efficiency of convection and the results for dc and ac fields are presented.