Bubble dynamics and mass transfer characteristics from an immersed orifice plate

Abstract

BACKGROUND: Bubble dynamics plays an important role in performance enhancement of multiphase reactor. The formation of the bubbles at the orifice is critical for the dynamics of bubbles and the mass transfer process during the rising stage. However, few studies have focused on the detailed changing characteristic of bubble formation and its relationship with mass transfer.RESULTS: The evolution of the bubble dynamics from millimeter to micrometer-sized immersed orifice plates is in situ visualized. Bubble inrush is observed from the orifices with diameters below 421 ∼m, resulting in significant fluctuation on the gas-liquid interface. The base of the leading bubble varies with the orifice diameter. Smaller orifice is preferred to produce more trailing bubbles with smaller size. The inrush time of the trailing bubble is prolonged with decreasing orifice diameter and increasing gas velocity. The inrush time and diameter of the latter trailing bubble are higher than the former at a certain gas velocity. The volumetric mass transfer coefficient (K L a) is obtained by measuring the bubble volume during the rising process using chemical absorption of carbon dioxide (CO 2 ) with sodium hydroxide (NaOH). Increasing gas velocity, decreasing orifice diameter and bubble inrush make an apparent positive impact on the K L a.CONCLUSIONS: The bubble inrush happens at micrometer orifice. Decreasing orifice diameter and increasing gas velocity are important to intensify oscillation of the leading bubble and increase the frequency of bubbles with high specific interfacial area, which are conducive to the enhancement of the volumetric mass transfer coefficient.

Experimental Study on Bubble Dynamics and Mass Transfer Characteristics of Coaxial Bubbles in Petroleum-Based Liquids

“…Gómez-Díaz et al analyzed the impact of liquid viscosity on the volumetric mass transfer coefficient using pure carbon dioxide as the gas phase and different concentrations of carrageenan aqueous solution as the liquid absorption phase. Shi et al examined the influence of orifice diameter and superficial gas velocity on bubble dynamics and mass transfer in NaOH aqueous solutions. Different literature sources presented the drag model of the bubble in experiments calculated with the Reynolds number ( Re ), Weber number ( We ), and Morton number ( Mo ). − They are defined respectively as italicRe = ρ normall d normale U μ normall italicWe = ρ normall d normale U 2 σ italicMo = g μ normall 4 ( ρ l − ρ g ) ρ normall 2 σ 3 in which ρ l and ρ g are the density of liquid and gas, respectively; μ l and σ are the liquid viscosity and the liquid surface tension, respectively; U is the bubble velocity; and d e is the bubble equivalent diameter.…”

“…Gómez-Díaz et al 14 analyzed the impact of liquid viscosity on the volumetric mass transfer coefficient using pure carbon dioxide as the gas phase and different concentrations of carrageenan aqueous solution as the liquid absorption phase. Shi et al 15 examined the influence of orifice diameter and superficial gas velocity on bubble dynamics and mass transfer in NaOH aqueous solutions. Different literature sources presented the drag model of the bubble in experiments calculated with the Reynolds number ( Re ), Weber number ( We ), and Morton number ( Mo ).…”