EXPERIMENTAL-STUDY OF NATURAL-CONVECTION HEAT-TRANSFER BETWEEN AN OUTER HORIZONTAL CYLINDRICAL ENVELOPE AND AN INNER CONCENTRIC HEATED SQUARE CYLINDER WITH 2 SLOTS

This paper presents the results of an experimental study of natural co nvection heat transfer between a horizontal cylindrical envelope and a n internal concentric heated square cylinder with two slots. The inter nal cylinder was a hollow one with horizontal slots on its top and bot tom surfaces. The ratio of slot width S to the side height H was 0.061 2 and 0.3878. The ratio of the envelope inner diameter D-0 to the side height H was 2.653. Air was used as the working fluid. The range of R ayleigh number was 1.77 x 10(2) similar to 8.72 X 10(6) for S/H = 0.06 12 and 1.32 x 10(2) similar to 6.25 x 10(6) for S/H= 0.3878. The resul ts show that there are three different heat transfer regimes in differ ent Rayleigh number regions, i.e. pure conduction regime, transition r egime and convection regime. The average heat transfer results were co rrelated into two empirical equations. Comparison was made with the no n-slotted case. It is found that slots of the internal cylinder can si gnificantly enhance the heat transfer.