LAMINAR HEAT-TRANSFER BETWEEN PARALLEL PLATES AS THE LIMITING SOLUTION FOR THE RECTANGULAR DUCT

This paper is aimed at demonstrating that the velocity and the tempera ture distributions of a Newtonian fluid in fully developed laminar flo w between infinite parallel plates with uniform wall heat flux, can be derived from the rectangular duct analysis, in H2 boundary conditions , in the limit of the aspect ratio beta tending to infinity. Hence the 2-D analytical distributions of fluid velocity and temperature for th e rectangular duct are elaborated to obtain the well known 1-D distrib utions for the slab geometry. The main outcome regards the Nusselt num ber; it is calculated for the rectangular duct, in the limit of beta - -> infinity, and coincides with the Nusselt number of the infinite par allel plates.