INFLUENCE OF PRANDTL NUMBER AND SLOT HEIGHT ON FREE-CONVECTION IN A NARROW SLOT

An experimental investigation of free convection in a two-dimensional rectangular open cavity (the Hele-Shaw cell) was carried out using an IR imager. The effect of Prandtl number and of the height of the worki ng cavity on heat transfer at Rayleigh numbers varying from 4 x 10(2) to 10(8) was studied. Water, alcohol, and transformer oil were used as working liquids. The experiments were conducted with a constant densi ty of heat flux at one of the end walls of the cavity and under isothe rmal conditions at the other. An increase in the mean Nusselt number f or alcohol and transformer oil is observed in a rectangular cell and f or water in a shallow cavity with an aspect ratio of 0.5. Correlations are obtained for the local and mean Nusselt numbers for the three liq uids and different heights of the working cavity. Also presented are t he values of dimensionless temperature and distribution of the local N usselt number on the heated wall. The findings presented supplement th e data obtained during a study of heat exchange in a rectangular cavit y filled with a porous medium.