Modeling the shear rate and pressure drop in a hydrodynamic cavitation reactor with experimental validation based on KI decomposition studies

Abstract

A mathematical model describing the shear rate and pressure variation in a complex flow field created in a hydrodynamic cavitation reactor (stator and rotor assembly) has been depicted in the present study. The design of the reactor is such that the rotor is provided with surface indentations and cavitational events are expected to occur on the surface of the rotor as well as within the indentations. The flow characteristics of the fluid have been investigated on the basis of high accuracy compact difference schemes and Navier-Stokes method. The evolution of streamlining structures during rotation, pressure field and shear rate of a Newtonian fluid flow have been numerically established. The simulation results suggest that the characteristics of shear rate and pressure area are quite different based on the magnitude of the rotation velocity of the rotor. It was observed that area of the high shear zone at the indentation leading edge shrinks with an increase in the rotational speed of the rotor, although the magnitude of the shear rate increases linearly. It is therefore concluded that higher rotational speeds of the rotor, tends to stabilize the flow, which in turn results into less cavitational activity compared to that observed around 2200-2500RPM. Experiments were carried out with initial concentration of KI as 2000ppm. Maximum of 50ppm of iodine liberation was observed at 2200RPM. Experimental as well as simulation results indicate that the maximum cavitational activity can be seen when rotation speed is around 2200-2500RPM.

Development of extraction technique and GC/FID method for the analysis of cannabinoids in Cannabis sativa L. spp. santicha (hemp)

“…Among all the above‐mentioned extraction methods, ultrasonication was found to be the optimal since it requires less time, energy and cost. According to literature, the shock waves generated because by cavitation are capable of breaking the chemical bonds and causing cell lysis, thus assisting the process of extraction . Moreover, the combination of localized stirring effect occurring due to cavitation along with the repeated washing of cellular components with solvent further intensified the extraction of compounds in case of ultrasonication …”

Ultrasound‐Assisted Extraction of Cannabinoids from Cannabis Sativa L. Optimized by Response Surface Methodology

“…The energy released from implosion of the cavitation bubbles brings about various physical effects such as turbulence due to circulation of solvent as well as chemical effects like free radical generation due to decomposition of water and pyrolysis of the trapped compounds. The shock waves generated because of cavitation are capable enough to break chemical bonds and cause cell lysis, thus assisting the process of extraction (Badve, Alpar, Pandit, Gogate, & Csoka, ; Iskalieva et al., ). Higher extraction in lesser time occurs due to the mechanical impact on plant cell walls caused by ultrasonic waves (Khan et al., ).…”

Hydrodynamic Cavitation: A Promising Technology for Industrial-Scale Synthesis of Nanomaterials

“…Most of the existing research relates to applications, the characteristics of HCRs have been rarely focused, which largely influences the development and application of HC technology. Even though a few researchers have made important contributions in theoretical (Sarvothaman et al, 2019), computational (Badve et al, 2015), and experimental (Zhang et al, 2018) aspects of HCRs, their cavitation generation mechanism, internal flow fields, external characteristics, and scale-up law are not well understood by utilizing experimental flow visualization, particle image velocimetry, and computational fluid dynamic methods, especially for the R-S HCRs. More importantly, the universal research and design methods (e.g., the theoretical and numerical methods for design the rotor, stator, and flow path, scale-up law, and optimization method) for HCRs have not been established yet.…”