A numerical analysis of laminar natural convection in a quadrantal cavity filled with water having variable length heaters attached on the adjacent walls have been made to examine heat and fluid flow. Numerical solutions are obtained using a commercial computational fluid dynamics package, FLUENT, using the finite volume method. Effects of the Rayleigh number, Ra, on the Nusselt number, Nu, as well as velocity and temperature fields are investigated for the range of Ra from 10 3 to 10 7. Computations were carried out for the non-dimensional heater lengths on the vertical wall (m=0.2, 0.4 and 0.6) and horizontal wall (n=0.2, 0.4 and 0.6). It is observed that heat transfer increases with increase in Rayleigh number and the flow strength increases with increase in size of heater on the vertical wall compared to the bottom wall and temperature fields are also affected. In contrast, with increase in size of heater on both side of adjacent walls flow strength does not changes significantly.

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Copper surface is modified to copper oxide surface for high heat flux electronics applications. Copper oxide surface is prepared by chemical etching using NaOH and (NH 4 ) 2 S 2 O 8 . A pool boiling experiment is conducted to investigate the critical heat flux (CHF) and boiling heat transfer coefficient (BHTC). The results indicate that BHTC of all copper oxide surfaces are enhanced remarkably. Bubble dynamics are also analyzed by means of a high-speed camera. Bubble visualization demonstrates that the active nucleation sites for the copper oxide surfaces are higher than the bare copper surface.