GAS DISSOLUTION PROCESS OF SPHERICAL RISING GAS-BUBBLES

The gas dissolution process of a spherical rising gas bubble was inves tigated experimentally and numerically. We developed an experimental s ystem that uses a charged-coupled device (CCD) camera coupled with a m icroscope to follow the rising bubble. By measuring the bubble size an d the rising speed from the bubble motion data captured by a personal computer, we could precisely estimate the drag coefficients and the Sh erwood number for the dissolution of gas bubbles at Reynolds numbers b elow 100. We also numerically estimated the drag coefficients and Sher wood number for dissolution of gas bubbles in an infinite liquid by di rectly solving the Navier-Stokes equation and the convection-diffusion equation. The experimental and numerical results are in good agreemen t. Moreover, we compared the experimental results with several propose d equations for estimating the drag coefficients and Sherwood number a nd clarified the applicable region of each equation. Finally, based on correlation with the numerical results, we present an equation for es timating the Sherwood number in the range where the Reynolds number is less than 100 and the Peclet number is greater than 1. (C) 1998 Publi shed by Elsevier Science Ltd.