The experimental study of natural convection within the space of a bundle of rectangular sections

The primary goal of the studies was to determine the natural convection occurring within the space of heated section bundles and the effect of this phenomenon on the intensity of overall heat flow. The tests were performed for square sections, dimensions 40 × 20 mm, wall thickness 2 mm. The quality tests, despite the fact that the critical value of the Rayleigh number was exceeded in the heated sections, did not demonstrate a proceeding convection. This situation was confirmed by the quantitative tests. The latter showed that the direction of the section heating, which determines the possible occurrence of the convection phenomenon or its lack, does not affect the intensity of the total heat flow. It was also pointed out that, for the range of the Rayleigh number which occurs during the heating of square sections of the side dimensions up to 80 mm in a chamber furnace, the heat flow related to the occurrence of free convection can be expressed as an intensification of the thermal conductivity in the liquid. For that purpose, one can apply a simple criterion dependence resulting from the similarity theory and the dimensional analysis.