Experimental study of the resulting flow of plume–thermosiphon interaction: application to chimney problems

The quality of the surrounding air depends on the various dismissals of the combustion gases (exhaust cars, smokes of chimneys, …), their scattering in the environment. Urban development around industrial zones and overexploitation of lands near factories triggered responsible interest in the problem of pollution. In order to decrease the impact of air pollution, several chimneys have been constructed in the different industrial facilities. So the improvement of the industrial chimney range became one of the current research problems. In order to improve the industrial chimney efficiency and to increase the vertical scattering of combustion products, we studied a system that could be integrated to the industrial chimney exit. This system is essentially constituted of an open-ended vertical cylinder of larger diameter. Thermal radiance emitted by smoke heats the internal cylinder wall. The heating of the fluid at the cylinder-inlet is the cause of the thermosiphon effect around the thermal plume. To study the problem in the laboratory we simulated the plume exiting of a chimney by a disk heated uniformly by the Joule effect at constant temperature. Different configurations were studied, while acting, on the source–cylinder spacing and the cylinder height. The study of the average fields permits, in a first stage, to get better information about the mechanism of the resulting flow development, and in a second stage, to determine the spacing of the source–cylinder and cylinder height optima, for which a clean increase of fluid flow rate is obtained.