A scale analysis for natural convective flows over vertical surfaces

► A new scale analysis is performed for natural convection from a vertical plate. ► Boundary conditions of constant temperature, constant heat flux, and convective heating analyzed. ► A new combination of Boussinesq and Prandtl number proposed to correlate data. ► Correlation is valid for all Prandtl numbers and covers all three boundary conditions. ► Known results for very low and very high Prandtl numbers recovered from proposed correlation.