Experimental and numerical study of laminar mixed convection from a horizontal isothermal elliptic cylinder

The problem of laminar mixed convective heat transfer from a horizontal isothermal elliptic cylinder has been experimentally and numerically investigated. The test elliptic cylinder has major and minor diameters of 70.3 mm and 34.9 mm respectively with an axis ratio of 0.496. The buoyancy due to the temperature difference between the cylinder surface and incoming air produces a Grashof number of 2.1 × 106. Via the incoming cold air velocity, the generated Reynolds number varies from 145 to 1322.8. Hence, the corresponding Richardson number is in the range of 1.2-100. The combined effect of both upward natural convection and the forced convection has been executed for angle of attack from 0° (assisting flow) to 180° (opposing flow) with an interval of 30°. The numerical solution via the finite volume method (FVM) has been accomplished to validate the obtained experimental results. The numerical results are validated by previous experimental results which show good agreement. Results are presented in the form of average and local Nusselt number around the circumference of the elliptic cylinder. In addition, new empirical correlation is obtained for the average Nusselt number as a function of Richardson number and the attack angle.