Numerical simulation of the migration of hot gases in open vertical shaft

The problem associated with the migration of hot gases in open vertical shaft has been numerically investigated. Model predictions based on the same experimental conditions have shown to yield good agreement with the measurements. The effects of non-dimensional parameters such as the Grashof, Reynolds and Biot numbers governing the flow and thermal fields are investigated in detail. The results indicate that hot gases flow upward over the entire cross section of the shaft when the Grashof number is small at a fixed Reynolds number. However, a thin boundary layer is developed along the vertical wall with a pronounced recirculation cell within the interior region of the vertical shaft as the Grashof number increases; similar characteristics are also observed at fixed Grashof number and different Reynolds numbers. Turbulent flow predictions revealed significantly different flow structures in comparison to the flow at laminar conditions. The time taken by the hot gases from the inlet to the top exhaust and temperature at the exhaust are analytically and numerically estimated. The gas exhaust temperature has a strong dependence on the Grashof and Biot numbers.