Correlation for laminar natural convection between confocal horizontal elliptical cylinders

The steady-state natural convection for air bounded by two confocal horizontal elliptical cylinders has been studied numerically for the case of inner hot and outer cold isothermal surfaces. The local and average Nusselt numbers are determined over the range of Raleigh numbers from 104 to 2 × 105 for different eccentricities of the inner surface. Correlations are given for the average Nusselt number based on both the inner and the outer surfaces. Increasing the eccentricity of the inner surface increases the local Nusselt number over the entire inner surface and part of the outer surface.