Inlet nozzles primarily determine droplet size in Taylor vortex devices
DOI: 10.1063/10.0001795
Inlet nozzles primarily determine droplet size in Taylor vortex devices lead image
Taylor-Couette flow (TCF), characterized by vortices in turbulence, is widely used to study hydrodynamic instabilities that occur in mixing and extraction in applications ranging from drug development to remediation practices.
In the multiphase processes of these applications in which immiscibility matters, the size and spatial distribution of dispersed phase bubbles, droplets or particles play a crucial role in TCF device performance.
To better understand the flow conditions that produce various droplet size distributions (DSD) in liquid-liquid TCF, Campbell et al. employed a Taylor vortex reactor to study two operational parameters on DSD: the inner cylinder angular velocity and the inlet flow rate. Results showed that the average droplet size and distribution are determined primarily by jet breakage dynamics at the inlet nozzle tips.
The researchers filled the vertical semi-batch reactor with deionized water before injecting hexane through four nozzles at a continuous rate. They used a digital camera to identify and measure the droplet diameters.
DSD patterns, based on Reynolds numbers, transitioned from a single-peak distribution at low cylinder rotation speeds to a double-peak distribution at intermediate speeds. At the largest rotation speeds considered, the double-peak distribution became right-skewed.
From these observations, the researchers determined that the average droplet diameter and the DSD depends on the jet inlet Reynolds number much more than on the cylinder rotational speed.
“We found that if a specific droplet diameter is required for a Taylor-Couette reactor application, the inlet Reynolds number is the key operating parameter for obtaining that diameter, with the droplet diameters remaining relatively unchanged over a large range of cylinder rotational speeds,” author R. Dennis Vigil said.
Source: “Droplet size distributions in liquid-liquid semi-batch taylor vortex flow,” by Charlton Campbell, Michael G. Olsen, and R. Dennis Vigil, AIP Advances (2020). The article can be accessed at https://doi.org/10.1063/5.0018065 .
