Abstract
A computational model of a single gas microbubble immersed in a liquid of ethanol–water mixture is developed and solved numerically. This complements earlier binary distillation experiments in which the ethanol–water mixture is stripped by hot air microbubbles achieving around 98% vol. ethanol from the azeotropic mixture. The proposed model has been developed using Galerkin finite element methods to predict the temperature and vapor content of the gas microbubble as a function of its residence time in the liquid phase. This model incorporates a novel rate law that evolves on a time scale related to the internal mixing of microbubbles of 10–3s. The model predictions of a single bubble were shown to be in very good agreement with the existing experimental data, demonstrating that the ratio of ethanol to water in the microbubble regime are higher than the expected ratios that would be consistent with equilibrium theory for all initial bubble temperatures and all liquid ethanol mole fractions considered and w...
Highlights
The progressive depletion of fossil-based fuels coupled with the negative effects caused by their emissions on the environment, has motivated the search for renewable sources of energy
It was found that the enrichment of ethanol in the vapor phase is higher than the expected ratios of the equilibrium theory at short contact times for a range of initial bubble temperatures and liquid ethanol compositions
It was found that vaporization is faster than heat transfer to the liquid and that maximum evaporation occurs after a very short contact time
Summary
The progressive depletion of fossil-based fuels coupled with the negative effects caused by their emissions on the environment, has motivated the search for renewable sources of energy. As the depth of the liquid layer increases, sensible heat transfer becomes more significant leading to a reduction in vaporization as well as raising the temperature of the liquid mixture.[22] Following these findings, we have conducted experiments on the separation of an ethanol−water binary liquid mixture with superheated air microbubbles generated by a fluidic oscillator such as those shown in Figure 117,23−25 using a laboratory scale rig (see ref 26 for the details of the experimental procedure and the equipment used). A sensitivity study to investigate the effect of the main parameters governing the process is presented in section 3, while in section 4 conclusions of this study are drawn
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