Natural convection experiments on a heated horizontal cylinder in a differentially heated square cavity

Natural convection heat transfer from a heat generating horizontal cylinder enclosed in a square cavity, where a temperature difference exists across its vertical walls has been experimentally investigated for the range 2×104<Racyl<8×104 and a Pr of 0.71. Temperature and cylinder Nusselt number measurements were taken for a range of θ*. θ* is defined as a ratio of cylinder and cavity Grashof numbers. It has been found that at the lower values of Racyl, the heat transfer from the cylinder compares well with correlations available in literature. As Racyl increases however, it deviates away and the overall heat transfer from the cylinder is increased when compared to these correlations due to the interaction from the cavity. 2D-PIV measurements of the flow structures inside the compartment were conducted. They show an increased interaction between the flow structures generated by the cylinder and by the cavity with increasing θ*, corresponding to the increase in the heat transfer from the cylinder. It is observed that the recirculation generated by the temperature gradient imposed on the cavity is broken down as the plume from the cylinder becomes stronger and a transition process is observed, whereby the flow transitions from being dominated by the temperature difference across the cavity to that dominated by the temperature difference due to the cylinder.