An experimental study of heat transfer by laminar natural convection between an electrically-heated vertical plate and both Newtonian and non-Newtonian fluids

Natural convection from a vertical electrically-heated plate (90 mm x 79 mm ) to both Newtonian and non-Newtonian fluids has been studied experimentall y for conditions of constant surface heat flux. For Newtonian fluids, a ver y wide range of viscosities (10 000-fold), of densities (1000-fold), and of Prandtl numbers (2500-fold) has been covered. The effect of shear-thinning non-Newtonian behaviour has been investigated using fluids with power-law indices from 0.48 to 0.81. Over this very wide range of conditions, the mea sured vertical temperature profile at the surface of the plate, and its dep endence on the heat flux, has been found to conform well to theoretical pre dictions. The values of the coefficients in the well-established relations between Nusselt, Grashof and Prandtl numbers have then been evaluated and t hey have been shown to compare well with theoretical predictions and experi mental results of other workers. (C) 1998 Elsevier Science Ltd. All rights reserved.