Mixing of Complex Fluids with Confined Impinging Jets

Lead Research Organisation: University of Manchester
Department Name: Chem Eng and Analytical Science

Abstract

Confined Impinging Jets (CIJs) have been shown to be highly efficient continuous mixers, offering a strong alternative to more traditional and less efficient industrial mixing technologies such as mechanically stirred vessels. In these devices, two or more liquid streams are injected into a confined space by opposed jets. Under appropriate conditions, a hydrodynamic instability promoted by the rapid deceleration of the impinging streams allows for mixing to be achieved rapidly and without moving mechanical parts. When compared to stirred vessels, CIJs can offer a more efficient utilisation of energy for mixing by providing higher and more uniformly distributed energy dissipation rates in the flow.

CIJs mixers can prove to be a suitable solution to intensify continuous processes that require a rapid homogenization of streams. Nonetheless, the impact that the complex rheological properties of non-Newtonian fluids can have on the mixing performance is not yet fully understood. Additional studies to offer a more robust and intensified operation of CIJs mixers for processing complex fluids are, thus, still crucial.

This project will focus on the computational and experimental study of the flow dynamics and mixing performance of shear-thinning and viscoelastic fluids in CIJs. Numerical simulations of the flow will be obtained with Computational Fluids Dynamics (CFD). Advanced experimental techniques, such as Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV), will be also used for the characterization of the flow and mixing.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509565/1 01/10/2016 30/09/2021
1918337 Studentship EP/N509565/1 18/09/2017 30/09/2020 George Fletcher
 
Description Derivation of the Reynolds number for the Carreau-Yassuda constitutive equation, which represents power law fluids with zero shear viscosity, infinite shear viscosity, a relaxation time and a power law slope between the two aforementioned viscosities through calculation of the pressure drop through a pipe. This model well represents real world shear-thinning fluids. The Reynolds number definition widely used is only appropriate for non-Newtonian fluids and specific viscoelastic fluids (Boger fluids).

It was found through examination of the dynamic behaviour simulated through CFD of the fluids that the typical characteristic length used to compute the Reynolds number may be inappropriate, as the critical Reynolds number did not match between the different fluids. Using the chamber width has tentatively been found to be a more appropriate length to use as the critical Reynolds number becomes similar for all fluids used. Further investigation showed that using this length, the characteristic frequency of the driving instability also correlated well with the new Reynolds number definition. For Newtonian fluids this simply causes the Reynolds number to change by a constant factor due to the ratio of the inlet width and the chamber width which is why this definition has not previously been considered, however, for shear thinning fluids, this is not the case.
Exploitation Route Once published, the newly developed criteria for the driving parameter of the system will lead to improved process design techniques for mixing and reaction processes within the pharmacological and plastics areas either by additional academics or directly by industry.
Sectors Chemicals,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description Mixing 16 Main Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Full presentation at the 16th European Conference on Mixing during one of the sessions on mixing of complex fluids. Presented research outcomes to that point to experts from industry and academia from across the world. The conference also provided the opportunity to meet the leading minds in the field.
Year(s) Of Engagement Activity 2018