Natural convection in a square enclosure with a hot source

The aim of this paper is to analyse the convective heat transfer generated by a source with three different heights (ζ). This strip is located in the middle of a square enclosure. In detail the experimental analysis was carried out using holographic interferometry, to study the effect of the heat transfer, and a 2D-PIV system, to analyse the dynamic behaviour of the phenomenon. The comparison is based both on the evaluation of the Nusselt numbers at different Rayleigh numbers and on the study of the velocity fields at the same Rayleigh numbers in different configurations. During the experimental analysis we can see how the height of the strip influences the distribution of the velocity fields and consequently the heat transfer efficiency. Three different heights are analysed: ζ = 0, ζ = 0.25 and ζ = 0.5. The study shows how the natural convective heat transfer worsens with the increase in the source height. This can clearly be seen by analysing the upper side of the strip, which was studied for each geometrical configuration, and is also confirmed by the results on the lateral sides, analysed only for ζ = 0.25 and ζ = 0.5. Finally the experimental data are compared with the results obtained through a numerical simulation performed using the volume finite software, Fluent 6.3.26. The aim of this comparison is to validate the numerical procedure, which is useful for enlarging the Rayleigh number range.