Free Convention Heat Transfer from an Isothermal Horizontal Thin Strip: the Influence of the Prandtl Number

Simultaneous free convection above and below a uniformly heated horizontal plate has been widely investigated, both in the case of an isothermal surface, and of a uniformly heated surface, but always assuming only air as fluid (Pr=0.7). Nevertheless, there are works dealing with horizontal plates whose results show that the Nu dependence on Pr may not be simply expressed by a power law with the same exponent of the Gr one. So it was considered useful to study the Prandtl number influence in the case of the isothermal horizontal strip. Results show that, while for the lower surface of the strip the Nu dependence in Gr can be expressed by a power law with an exponent close to the Gr one, for the upper surface the exponent is sensibly different. Correlating equations related to the investigated situations are proposed.