NATURAL CONVECTION HEAT TRANSFER AROUND TWO HEATED CYLINDERS IN AN ISOTHERMAL ENCLOSURE INCLUDING THE EFFECT OF WALL CONDUCTANCE

A numerical study has been conducted for natural convection heat transfer for air around two vertically separated horizontal heated cylinders placed inside an isothermal rectangular enclosure having finite wall conductances. The interaction between convection in the fluid filled cavity and conduction in the walls surrounding the cavity is investigated. Results have been obtained for Rayleigh numbers (Ra) between 10(3) and 10(6), dimensionless wall thickness ((W) over bar) between 0.5 and 1.375 and dimensionless wall-fluid thermal conductivity ratio ((alpha) over bar) between 0.01 and 5.0. The results indicate that wall heat conduction reduces the average temperature differences across the cavity, partially stabilizes the flow, and decreases natural convection heat transfer. The overall heat transfer coefficient for both cylinders is correlated with CRan for different (W) over bar and (alpha) over bar.