粘性流体中の単一気泡からのガス吸収速度に及ぼす圧力振動の影響

抄録

The understanding of mass transfer process is important in many industries. Many researchers report that gas absorption rate depends on non-dimensional numbers such as Sherwood number which can be correlated by Reynolds number and Schmidt number. We study gas absorption rate around a bubble in viscoelastic fluid under pressure-oscillating field. Applying the pressure-oscillation at several hundred Hertz to the fluid is effective for enhancing bubble rising velocity. Due to continuous bubble expansion and contraction, complex flow structures may occur alternately in the vicinity of the bubble. Accordingly, fluid viscosity around the bubble is lower than that of bulk liquid, which may affect gas absorption rate. The experimental results show that pressure-oscillation at 50 Hz enhances the absorption rate of CO₂ gas up to about 2 times faster than natural rising condition (i.e., without pressure oscillation) . We used the spherical model and estimated shear viscosity on the surface of the bubble. We estimated enhancement of Sherwood number of the bubble by pressure oscillation and found that these enhancement is very close to that of gas absorption rate by pressure oscillation.