INFLUENCE OF ELEVATED PRESSURE ON THE STABILITY OF BUBBLY FLOWS

The effect of elevated pressure on the stability of the homogeneous bu bbly flow regime in a gas-liquid bubble column is examined. Experiment s were performed in a 0.15m diameter bubble column operated at pressur es in the range 0.1-1.3 MPa with nitrogen as the gas phase and water a s the liquid phase. The transition from homogeneous to heterogeneous f low regime was determined by two procedures. The first procedure invol ved visual examination of the swarm velocity vs gas velocity curve to determine the transition point. In the second procedure the transient pressure signals were monitored by high-frequency pressure transducers and the instability point determined by analysis of the chaotic featu res. The two major findings of the work were: (a) increased system pre ssure reduces the bubble swarm velocity of the homogeneous dispersion, (b) increased system pressure results in a significant increase in th e gas holdup at the instability point. The stability theory of Batchel or (1988, J. Fluid Mech. 193, 75-110) and Lammers and Biesheuvel (1996 , J. Fluid Mech. 328, 67-93) has been used to provide theoretical supp ort to these observations. (C) 1997 Elsevier Science Ltd.