Effects of Bubble Interactions on Liquid Phase Mass Transfer Coefficients in Three Types of Bubble Columns

抄録

This work investigates a mechanism and degree for bubble interactions such as bubble clustering, coalescence and breakup to affect the liquid phase mass transfer coefficient k_L. Our previous k_L data for a normal bubble column (NBC), internal loop airlift (ILBC) and external loop airlift (ELBC) are compared with k_LS for single bubbles and k_L,BF in the bubble flow (BF) at a fixed mean bubble diameter d_B. Our correlations of k_L∝ε_G^0.1 (NBC and ILBC) and k_L∝ε_G^0.2 (ELBC) have been found to arise from the relationship for gas holdup ε_G=0.5(d_B/l)³, where l is the mean distance between the adjacent bubbles. The reported k_L,BF values were reproduced by the Higbie model with the average bubble slip velocity of (gd_B/2)^0.5. A factor F=k_L,CTF/k_L,BF is defined to quantify an effect of the bubble interactions on k_L,CTF in the churn-turbulent flow (CTF). The reported correlation gives F=0.5Eo^3/8, where Eo=gd_B²ρ_L/σ. Eo<6.4 and Eo>6.4 have been found to give the clustering regime and the coalescence and breakup regime, respectively. Our k_L,CTF data (NBC and ILBC) satisfied F=0.5Eo^3/8. F=k_L,ELBC/k_L,BF for the ELBC roughly correlates as F=1.3.