Cavitation Reactor Research Articles

Erratum

Journal of Food ScienceVolume 73, Issue 2 p. vii-vii Free Access Erratum This article corrects the following: Inactivation of Food Spoilage Microorganisms by Hydrodynamic Cavitation to Achieve Pasteurization and Sterilization of Fluid Foods P.J. Milly, R.T. Toledo, M.A. Harrison, D. Armstead, Volume 72Issue 9Journal of Food Science pages: M414-M422 First Published online: October 25, 2007 First published: 20 February 2008 https://doi.org/10.1111/j.1750-3841.2007.00701.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In Inactivation of Food Spoilage Microorganisms by Hydrodynamic Cavitation to Achieve Pasteurization and Sterilization of Fluid Foods by Milly, et al, the following error was published in the abstract on page M414: Various high-acid (pH ≥ 4.6) fluid foods were processed in a hydrodynamic cavitation reactor to determine if commercial sterility can be achieved at reduced processing temperatures. Sporicidal properties of the process were also tested on a low-acid (pH < 4.6) fluid food. The text was incorrect and should have read: Various high-acid (pH ≤ 4.6) fluid foods were processed in a hydrodynamic cavitation reactor to determine if commercial sterility can be achieved at reduced processing temperatures. Sporicidal properties of the process were also tested on a low-acid (pH > 4.6) fluid food. We apologize for this error. Reference Milly PJ, Toledo RT, Harrison MA, Armstead D. 2007. Inactivation of Food Spoilage Microorganisms by Hydrodynamic Cavitation to Achieve Pasteurization and Sterilization of Fluid Foods. J Food Sci 72(9): M414- M422. Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Volume73, Issue2March 2008Pages vii-vii ReferencesRelatedInformation

Inactivation of Food Spoilage Microorganisms by Hydrodynamic Cavitation to Achieve Pasteurization and Sterilization of Fluid Foods

Hydrodynamic cavitation is the formation of gas bubbles in a fluid due to pressure fluctuations induced by mechanical means. Various high-acid (pH < [corrected]/= 4.6) fluid foods were processed in a hydrodynamic cavitation reactor to determine if commercial sterility can be achieved at reduced processing temperatures. Sporicidal properties of the process were also tested on a low-acid (pH > [corrected] 4.6) fluid food. Fluid foods were pumped under pressure into a hydrodynamic cavitation reactor and subjected to 2 rotor speeds and flow rates to achieve 2 designated exit temperatures. Thermal inactivation kinetics were used to determine heat-induced lethality for all organisms. Calcium-fortified apple juice processed at 3000 and 3600 rpm rotor speeds on the reactor went through a transient temperature change from 20 to 65.6 or 76.7 degrees C and the total process lethality exceeded 5-log reduction of Lactobacillus plantarum and Lactobacillus sakei cells, and Zygosaccharomyces bailii cells and ascospores. Tomato juice inoculated with Bacillus coagulans spores and processed at 3000 and 3600 rpm rotor speeds endured a transient temperature from 37.8 to 93.3 or 104.4 degrees C with viable CFU reductions of 0.88 and 3.10 log cycles, respectively. Skim milk inoculated with Clostridium sporogenes putrefactive anaerobe 3679 spores and processed at 3000 or 3600 rpm rotor speeds endured a transient temperature from 48.9 to 104.4 or 115.6 degrees C with CFU reductions of 0.69 and 2.84 log cycles, respectively. Utilizing hydrodynamic cavitation to obtain minimally processed pasteurized low-acid and commercially sterilized high-acid fluid foods is possible with appropriate process considerations for different products.

Intensification of esterification of acids for synthesis of biodiesel using acoustic and hydrodynamic cavitation

Cavitation results in conditions of turbulence and liquid circulation in the reactor which can aid in eliminating mass transfer resistances. The present work illustrates the use of cavitation for intensification of biodiesel synthesis (esterification) reaction, which is mass transfer limited reaction considering the immiscible nature of the reactants, i.e., fatty acids and alcohol. Esterification of fatty acid (FA) odour cut (C 8–C 10) with methanol in the presence of concentrated H 2SO 4 as a catalyst has been studied in hydrodynamic cavitation reactor as well as in the sonochemical reactor. The different reaction operating parameters such as molar ratio of acid to alcohol, catalyst quantity have been optimized under acoustic as well as hydrodynamic cavitating conditions in addition to the optimization of the geometry of the orifice plate in the case of hydrodynamic cavitation reactors. Few experiments have also been carried out with other acid (lower and higher)/methanol combination viz. caprylic acid and capric acids with methanol with an aim of investigating the efficacy of cavitation for giving the desired yields and also to quantify the degree of process intensification that can be achieved using the same. It has been observed that ambient operating conditions of temperature and pressure and reaction times of <3 h, for all the different combinations of acid (lower and higher)/methanol studied in the present work, was sufficient for giving >90% conversion (mol%). This clearly establishes the efficacy of cavitation as an excellent way to achieve process intensification of the biodiesel synthesis process.

Intensification of oxidation capacity using chloroalkanes as additives in hydrodynamic and acoustic cavitation reactors

The effect of the presence and absence of the chloroalkanes, dichloromethane (CH 2Cl 2), chloroform (CHCl 3) and carbon tetrachloride (CCl 4) on the extent of oxidation of aqueous I − to I 3 - has been investigated in (a) a liquid whistle reactor (LWR) generating hydrodynamic cavitation and (b) an ultrasonic probe, which produces acoustic cavitation. The aim has been to examine the intensification achieved in the extent of oxidation due to the generation of additional free radicals/oxidants in the reactor as a result of the presence of chloroalkanes. It has been observed that the extent of increase in the oxidation reaction is strongly dependent on the applied pressure in the case of the LWR. Also, higher volumes of the chloroalkanes favour the intensification and the order of effectiveness is CCl 4 > CHCl 3 > CH 2Cl 2. However, the results with the ultrasonic probe suggest that an optimum concentration of CH 2Cl 2 or CHCl 3 exists beyond which there is little increase in the extent of observed intensification. For CCl 4, however, no such optimum concentration was observed and the extent of increase in the rates of oxidation reaction rose with the amount of CCl 4 added. Stage wise addition of the chloroalkanes was found to give marginally better results in the case of the ultrasonic probe as compared to bulk addition at the start of the run. Although CCl 4 is the most effective, its toxicity and carcinogenicity may mean that CH 2Cl 2 and CHCl 3 offer a safer viable alternative and the present work should be useful in establishing the amount of chloroalkanes required for obtaining a suitable degree of intensification.

Conceptual design of a novel hydrodynamic cavitation reactor

Hydrodynamic cavitation has been increasingly used as a substitute to conventional acoustic (or ultrasonic) cavitation for process intensification owing to its easy and efficient operation. In this paper, we have put forth conceptual design of a new kind of hydrodynamic cavitation reactor that uses a converging–diverging nozzle for generating pressure variation required for driving radial motion of cavitation bubbles. Moreover, the reactor uses externally introduced bubbles of a suitable gas (argon or air) for cavitation nucleation. This design differs from earlier designs used by researchers where an orifice plate is used for creating cavitating flow. The new design offers a good control over two crucial parameters that affect the cavitation intensity produced, viz. rate of nucleation and nature of pressure variation driving bubble motion. Using numerical simulations of bubble dynamics and associated heat and mass transfer, trends in cavitation intensity produced in the reactor are assessed with varying design parameters. The results of simulation show that the externally introduced bubbles undergo transient motion in the flow through the nozzle generating moderate cavitation intensity. On the basis of results of simulation, some recommendations have been made for the effective design and scale up of the new kind of hydrodynamic cavitation reactors using concept introduced in this paper.

Dynamics of cavitational bubbles and design of a hydrodynamic cavitational reactor: cluster approach

In the present work, a cavity cluster of predetermined size has been considered to study the bubble dynamics in the hydrodynamic cavitation reactor. The effect of different operating and system parameters on the cavitational intensity has been numerically investigated. The yield of any cavitationally induced physical/chemical transformations depends not only on the collapse pressure of the cavities but also on the active volume of cavitation within the reactor. Empirical correlations have been developed to predict the collapse pressure and the active volume of cavitation as a function of different operating parameters based on the bubble dynamics studies. Recommendations are made for designing a cavitational reactor on the basis of the proposed empirical correlations. This work is a first step towards the designing and optimization of hydrodynamic cavitational reactor with cluster approach.

A review and assessment of hydrodynamic cavitation as a technology for the future

In the present work, the current status of the hydrodynamic cavitation reactors has been reviewed discussing the bubble dynamics analysis, optimum design considerations, design correlations for cavitational intensity (in terms of collapse pressure)/cavitational yield and different successful chemical synthesis applications clearly illustrating the utility of these types of reactors. The theoretical discussion based on the modeling of the bubble dynamics equations aims at understanding the design information related to the dependency of the cavitational intensity on the operating parameters and recommendations have been made for the choice of the optimized conditions of operating parameters. The design information based on the theoretical analysis has also been supported with some experimental illustrations concentrating on the chemical synthesis applications. Assessment of the hydrodynamic cavitation reactors and comparison with the sonochemical reactors has been done by citing the different industrially important reactions (oxidation of toluene, o-xylene, m-xylene, p-xylene, mesitylene, o-nitrotoluene, p-nitrotoluene, m-nitrotoluene, o-chlorotoluene and p-chlorotoulene, and trans-esterification reaction i.e., synthesis of bio-diesel). Some recommendations have also been made for the future work to be carried out as well as the choice of the operating conditions for realizing the dream of industrial scale applications of the cavitational reactors.

Cavitation reactors: Efficiency assessment using a model reaction

AbstractAcoustic and hydrodynamic cavitation can be used for a variety of applications ranging from biological applications such as cell disruption to chemical reactions such as oxidation of organic pollutants in aqueous effluents, including biorefractory toxic chemicals. Different equipment used for cavitational effects was compared based on a model reaction (decomposition of potassium iodide resulting into iodine liberation). A correlation was developed for the prediction of the cavitational yield in terms of the cavity collapse pressure. This correlation, when used with earlier correlations for the pressure amplitude generated during the violent collapse of cavities, will help design engineers to choose particular equipment, operating conditions, and geometric parameters to achieve a desired chemical change. The developed equation relating the macroscopic reaction rates with the collapse pressure is the first of its kind reported in the literature. Pilot‐plant‐scale hydrodynamic cavitation orifice plate setup is most energy‐efficient, with significantly higher cavitational yields for the model reaction.

Modeling of hydrodynamic cavitation reactors: a unified approach

An attempt has been made to present a unified theoretical model for the cavitating flow in a hydrodynamic cavitation reactor using the nonlinear continuum mixture model for two-phase flow as the basis. This model has been used to describe the radial motion of bubble in the cavitating flow in two geometries in hydrodynamic cavitation reactors, viz., a venturi tube and an orifice plate. Simulations of the bubble dynamics in a venturi flow demonstrate the stable oscillatory radial bubble motion due to a linear pressure gradient. Due to an additional pressure gradient due to turbulent velocity fluctuations the radial bubble motion in case of an orifice flow is a combination of both stable and oscillatory type. The results of numerical simulations have been explained on the basis of analogy between hydrodynamic cavitation and acoustic cavitation.

Hybrid Cavitation/Constructed Wetland Reactors for Treatment of Chlorinated and Non-Chlorinated Organics

Mitigation strategies can be implemented to decrease chlorinated and non-chlorinated organic exposures to biota of aquatic receiving systems thereby reducing associated risks. In this work, we investigated the concept of coupling a physical/chemical reactor (i.e. a cavitation reactor) with a biological reactor (i.e. a constructed wetland) in an effort to efficiently transform PCE, TCE, and petroleum in freshwater into non-toxic chemical forms or concentrations. Rates of TCE degradation due to cavitation ranged from 0.010 to 0.026 min -1 with corresponding half-lives of 69 to 27 min. Compared to controls, degradation of petroleum in water by cavitation was not detected in these experiments. After treatment in anaerobic wetland reactors, TCE and PCE decreased by more than 99% under two flow regimes (5-d and 20-d HRT). In reciprocating constructed wetland reactors receiving petroleum, mean COD, BOD 5 , and total Zn decreased by 90.0, 88.8, and 86.8 %, respectively, in wetland outflows compared to the initial conditions (96-h HRT). Percent survival (96-h) of D. magna and P promelas increased from zero percent in initial conditions to 80.1 (± 18.9) and 80.0 (± 21.4) %, respectively, after treatment in the constructed wetland reactors. The experimental results obtained in the laboratory-scale set-up and the theoretical model for the hybrid reactor concept will be used to obtain the intrinsic kinetic coefficients for the appropriate reactors. This kinetic information will be used to scale-up the hybrid reactor model concept for the same level of pollutant removal.

Numerical investigations in the behaviour of one-dimensional bubbly flow in hydrodynamic cavitation

Hydrodynamic cavitation has been attempted as an alternative to acoustic cavitation over past few years and this form of cavitation has been proved to hold higher potential for industrial scale processes. In this work, we have tried to investigate the dynamics of the bubbly flow in hydrodynamic cavitation with the help of numerical simulations. A continuum bubbly mixture model is used to study the one-dimensional cavitating flow through a venturi. The nonlinear dynamics of the bubbles has been modeled by Rayleigh–Plesset equation. The results of the simulations show that the bubble/bubble and bubble/flow interaction through the hydrodynamics of the flow has important effect on the behavior of the bubbly flow. Effect of parameters such as downstream recovery pressure, venturi to pipe area ratio, initial bubble void fraction in liquid and initial bubble size in the flow on the dynamics of the flow has been studied. Based on the results of the simulations, recommendations have been made for an effective design and scale-up of a hydrodynamic cavitation reactor.

Engineering design methods for cavitation reactors II: Hydrodynamic cavitation

AbstractThe bubble behavior and hence the pressure generated at the collapse of the cavity for hydrodynamic cavitation depends on the operating conditions and geometry of the mechanical constriction generating cavitation. The effect of operating parameters such as inlet pressure through the system's orifice, initial cavity size, and the indirect effect of the hole diameter (it affects the frequency of turbulence in the vicinity of the orifice) on the bubble behavior was numerically studied. The bubble dynamics were simulated in two stages considering: Rayleigh‐Plesset equation up to the point of bubble wall velocity = 1,500 m/s; then the compressibility of the medium using the equation of Tomita and Shima. An empirical correlation was developed to predict the collapse pressure generated as a function of just mentioned parameters. The trends in the magnitudes of collapse pressure match the observed experimental trends for cavitation‐induced reactions. The work is an extension of the earlier analysis done for the sonochemical reactors. Some recommendations are also suggested for the design of hydrodynamic cavitation reactors based on the simulations.

Class D amplifier for a power piezoelectric load

We present a high efficiency inverter (>90%) that can drive an acoustic cavitation reactor with a 2 kW power between 10 and 100 kHz. This reactor is composed of numerous piezoelectric transducers and is particularly used to accelerate various industrial chemical reactions and destroy a variety of organic contaminants in water. The class-D amplifier or inverter is composed of power MOSFETs, type IRFP460, in a full bridge configuration driven by IR2110 circuits in bootstrap mode. The specific nature of the problem comes from the fact that, at frequencies slightly different from a resonant frequency frn, the load is mostly capacitive. The insertion of an appropriate low-pass filter in front of the load allowed an efficient solution to the problem due to the load being capacitive for harmonics. The realized system can provide nearly 2 kW to this type of piezoelectric load, with an efficiency of more than 95%

Sonochemistry: Science and Engineering

Sonochemistry is the use of ultrasound to enhance or alter chemical reactions. Sonochemistry in the true sense of the term occurs when ultrasound induces “true” chemical effects on the reaction system, such as forming free radicals which accelerate the reaction. However, ultrasound may have other mechanical effects on the reaction, such as increasing the surface area between the reactants, accelerating dissolution, and/or renewing the surface of a solid reactant or catalyst. This comprehensive review summarizes several topics of study in the sonochemical literature, including bubble dynamics, factors affecting cavitation, the effects of ultrasound on a variety of chemical systems, modeling of kinetic and mass-transfer effects, the methods used to produce ultrasound, proposed cavitation reactors, and the problems of scaleup. The objective of this paper is to present a critical review of information available in the literature so as to facilitate and inspire future research in the field of sonochemistry.