On enhancing interfacial mass transport through microextraction in dispersed droplet systems. (April 2023)

• Record Type: Journal Article
• Authors: Trivedi, Mohit; Sharma, Aakriti; Agarwal, Kalyani; Chhabra, Rajendra P.; Nirmalkar, Neelkanth
• Is Part Of: International journal of heat and mass transfer. Volume 203(2023)
• Publication Date: 2023-04
• Subjects: Shear-thinning fluids -- Extraction -- Dispersed droplets system -- Sherwood number -- Extraction efficiency; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2022.123776
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Shear thinning behavior facilitates the augmentation in the extraction efficiency, thereby leading to the process intensification in chemical & environmental engineering. The thermodynamic equilibrium of the dispersed droplet system reaches faster in the shear-thinning environment. The present findings on the interfacial mass transfer agree well with prior experimental and numerical results. Graphical abstract: Abstract: The physio-chemical hydrodynamics and the solute transport around a translating dispersed drop are often multicomponent and multiphase systems. When such a dispersed droplet system is out of the thermodynamic equilibrium, steep momentum and concentration gradients are developed around the interface leading to rapid flow and solute transport. In broader perspectives, the dispersed droplet system has direct/indirect relevance to addressing the technological challenges in the 21 st century, namely, energy storage, hydrogen production, C O 2 capture, biofuel production, chemical analysis, diagnosis extraction, and drug delivery. Environmental engineering challenges include flotation and separation technology, inkjet printing, coatings, and paints. The most challenging issue in such applications is enhancing the transport rate from the droplet to the bulk of the fluid. In this work, we have proposed a novel method to foster the transport of solute from the drop to the bulk fluid by altering the viscosity of the bulk fluid. We have exploited the shear-thinning behavior of the fluid in bulk to reduce the viscous losses and resistances to the mass transfer. A linear thermodynamic equilibrium relation at the fluid-fluid interface is considered. The scant prior experimental results were observed to agree with the present findings. Therefore, the extensive numerical findings are presented for the ranges of pertinent parameters such as Reynolds number, ( 1 ≤ R e ≤ 75 ) Peclet number, ( 10 ≤ P e ≤ 10 3 ), internal to external fluid diffusivity ratio, ( 0.5 ≤ d r a t i o ≤ 4 ), dispersed to continuous fluid viscosity ratio, ( 0.25 ≤ μ r a t i o ≤ 4 ) and power-law index, ( 0.4 ≤ n ≤ 1 ). The drag coefficient exhibits an increase of 180 % with the increase in the μ r a t i o as well as with the n at the maximum convective regime. The Sherwood number exhibits a positive dependence on the Reynolds number, Peclet number, and the diffusivity ratio. On the contrary, the viscosity ratio lowers the transport of species from the droplet to the fluid due to the reduced internal circulations inside the droplet. Shear-thinning fluid behavior offers a higher extraction efficiency than the Newtonian fluid (upto 30 % increase in at low P e ). Finally, simple predictive correlative equations have been proposed for the drag coefficient and the average Sherwood number over the conditions considered here.