Gas dispersion phenomena and mixing characteristics under gas injection through slot nozzle submerged in water

Abstract

Bubble dispersion and mixing behaviour in a bath with gas injection through a slot nozzle was studied by a cold model. A high speed video recording system was used to measure the bubble diameter and the size of plume cross sectional area. The mixing time was measured by using an electrical conductivity method. Measurements were conducted under various gas flow rates and bath depths. Comparison of mixing time was examined between a slot nozzle and a single circular nozzle. The results were discussed in terms of specific power of injected gas. At lower gas flow rates, the bubble size distribution was not changed with the vertical distance. At higher gas flow rates, the bubbles detached at the nozzle coalesced immediately and became large. It was found that the slot nozzle led to an increase in plume cross sectional area as compared with a single circular nozzle. The mixing time for the slot nozzle was smaller than that for the single circular nozzle. The plume cross sectional area for the slot nozzle was larger than that for the single circular nozzle. The increase in the plume cross sectional area was connected with the decrease in the mixing time. Effects of the experimental variables on the mixing time were quantitatively examined.