Special Issue "Controlled Hydrodynamic Cavitation: An Emerging Class of Greener Processing Technologies"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editor

Dr. Francesco Meneguzzo
E-Mail Website
Guest Editor
Institute for BioEconomy, National Research Council, 10 Via Madonna del Piano, I-50019 Sesto Fiorentino (FI), Italy
Interests: Bioactive compounds; Energy efficiency; Food; Green extraction; Hydrodynamic cavitation; Nanoemulsions; Process yield
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Special Issue Information

Dear Colleagues,

Processes including controlled hydrodynamic cavitation steps are spreading and receiving growing interest, both in the laboratory and, more slowly, in the industry. Hydrodynamic cavitation-based single-unit operation systems, and components, are proposed, designed and experimented on a weekly basis, aimed at intensifying several different processes. Technical fields benefitted by an increase in process yields include wastewater treatment, water disinfection, crude oil refining, metal ore recovery, synthesis of nanomaterials, biodiesel, bioethanol and biogas production, food processing including physical and microbiological stability, as well as extraction of nutrients and bioactive compounds, and many others.

Controlled hydrodynamic cavitation has a tremendous potential, based on its power to focus the bulk energy of the processed single or multi-phase liquid, or liquid-solid and liquid-gas mixture, into myriads of hot spots, in turn sites of unique physical and chemical phenomena on the micro and nanoscale. All of this, while preserving a relative simplicity in construction and operation.

However, the well-deserved spread at the industrial level is lagging behind, mainly due to a persistent lack of standardization, affecting the process-specific choice of the suitable devices, the structural and working parameters, the dependence of process yields on concentration and doses, just to name a few.

This Special Issue is aimed at providing an up-to-date picture of recent advances and breakthroughs in controlled hydrodynamic cavitation technologies and processes, both fundamental, including modeling and experiments, and applicative in any relevant technical field, with special focus on comparative process yields, compliance with green chemistry and green extraction principles, process-specific standardization, and scalability up to the industrial level. 

Dr. Francesco Meneguzzo
Guest Editor

Manuscript Submission Information

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Keywords

  • Hydrodynamic Cavitation
  • Modeling
  • Simulation
  • Experiments
  • Scalability
  • Standardization
  • Process Systems Engineering
  • Process yields
  • Biomass
  • Bioenergy
  • Food
  • Materials
  • Water

Published Papers (9 papers)

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Research

Jump to: Review

Article
Porous Venturi-Orifice Microbubble Generator for Oxygen Dissolution in Water
Processes 2020, 8(10), 1266; https://doi.org/10.3390/pr8101266 - 09 Oct 2020
Cited by 1 | Viewed by 827
Abstract
Microbubbles with slow rising speed, higher specific area and greater oxygen dissolution are desired to enhance gas/liquid mass transfer rate. Such attributes are very important to tackle challenges on the low efficiency of gas/liquid mass transfer that occurs in aerobic wastewater treatment systems [...] Read more.
Microbubbles with slow rising speed, higher specific area and greater oxygen dissolution are desired to enhance gas/liquid mass transfer rate. Such attributes are very important to tackle challenges on the low efficiency of gas/liquid mass transfer that occurs in aerobic wastewater treatment systems or in the aquaculture industries. Many reports focus on the formation mechanisms of the microbubbles, but with less emphasis on the system optimization and assessment of the aeration efficiency. This work assesses the performance and evaluates the aeration efficiency of a porous venturi-orifice microbubble generator (MBG). The increment of stream velocity along the venturi pathway and orifice ring leads to a pressure drop (Patm > Pabs) and subsequently to increased cavitation. The experiments were run under three conditions: various liquid velocity (QL) of 2.35–2.60 m/s at fixed gas velocity (Qg) of 3 L/min; various Qg of 1–5 L/min at fixed QL of 2.46 m/s; and free flowing air at variable QLs. Results show that increasing liquid velocities from 2.35 to 2.60 m/s imposes higher vacuum pressure of 0.84 to 2.27 kPa. They correspond to free-flowing air at rates of 3.2–5.6 L/min. When the system was tested at constant air velocity of 3 L/min and under variable liquid velocities, the oxygen dissolution rate peaks at liquid velocity of 2.46 m/s, which also provides the highest volumetric mass transfer coefficient (KLa) of 0.041 min−1 and the highest aeration efficiency of 0.287 kgO2/kWh. Under free-flowing air, the impact of QL is significant at a range of 2.35 to 2.46 m/s until reaching a plateau KLa value of 0.0416 min−1. The pattern of the KLa trend is mirrored by the aeration efficiency that reached the maximum value of 0.424 kgO2/kWh. The findings on the aeration efficiency reveals that the venturi-orifice MBG can be further optimized by focusing on the trade-off between air bubble size and the air volumetric velocity to balance between the amount of available oxygen to be transferred and the rate of the oxygen transfer. Full article
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Article
Accuracy Assessment of RANS Predictions of Active Flow Control for Hydrofoil Cavitation
Processes 2020, 8(6), 677; https://doi.org/10.3390/pr8060677 - 08 Jun 2020
Cited by 1 | Viewed by 954
Abstract
In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guided vanes. Furthermore, the effects of wall injection on both the cavitation and on the hydrodynamic performance of the guided vane are studied. The numerical simulations are performed [...] Read more.
In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guided vanes. Furthermore, the effects of wall injection on both the cavitation and on the hydrodynamic performance of the guided vane are studied. The numerical simulations are performed using OpenFOAM v1906. We used a 2D k- ω SST model for modeling the turbulence in the present set of simulations. We studied the flow for two angles of attack, viz. 3 and 9 . For the 3 angle of attack, the present numerical work is in good agreement with the previous experimental work, but for the larger angle of attack, because of flow separation, the present simulations do not capture the flow correctly. Full article
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Article
Considering the Diffusive Effects of Cavitation in a Homogeneous Mixture Model
Processes 2020, 8(6), 662; https://doi.org/10.3390/pr8060662 - 03 Jun 2020
Cited by 1 | Viewed by 694
Abstract
Homogeneous mixture models are widely used to predict the hydrodynamic cavitation. In this study, the constant-transfer coefficient model is implemented into a homogeneous cavitation model to predict the heat and mass diffusion. Modifications are made to the average bubble temperature and the Peclet [...] Read more.
Homogeneous mixture models are widely used to predict the hydrodynamic cavitation. In this study, the constant-transfer coefficient model is implemented into a homogeneous cavitation model to predict the heat and mass diffusion. Modifications are made to the average bubble temperature and the Peclet number for thermal diffusivity in the constant-transfer coefficient model. The evolutions of a spherical bubble triggered by negative pressure pulse are simulated to evaluate the prediction of heat and mass diffusion by the homogeneous model. The evolutions of three bubbles inside a rectangular tube are simulated, which show good accuracy of the homogeneous model for multibubbles in stationary liquid. Full article
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Article
Influence of Fluid Properties on Intensity of Hydrodynamic Cavitation and Deactivation of Salmonella typhimurium
Processes 2020, 8(3), 326; https://doi.org/10.3390/pr8030326 - 10 Mar 2020
Cited by 5 | Viewed by 1224
Abstract
In this study, three microfluidic devices with different geometries are fabricated on silicon and are bonded to glass to withstand high-pressure fluid flows in order to observe bacteria deactivation effects of micro cavitating flows. The general geometry of the devices was a micro [...] Read more.
In this study, three microfluidic devices with different geometries are fabricated on silicon and are bonded to glass to withstand high-pressure fluid flows in order to observe bacteria deactivation effects of micro cavitating flows. The general geometry of the devices was a micro orifice with macroscopic wall roughness elements. The width of the microchannel and geometry of the roughness elements were varied in the devices. First, the thermophysical property effect (with deionized water and phosphate-buffered saline (PBS)) on flow behavior was revealed. The results showed a better performance of the device in terms of cavitation generation and intensity with PBS due to its higher density, higher saturation vapor pressure, and lower surface tension in comparison with water. Moreover, the second and third microfluidic devices were tested with water and Salmonella typhimurium bacteria suspension in PBS. Accordingly, the presence of the bacteria intensified cavitating flows. As a result, both devices performed better in terms of the intensity of cavitating flow with the presence of bacteria. Finally, the deactivation performance was assessed. A decrease in the bacteria colonies on the agar plate was detected upon the tenth cycle of cavitating flows, while a complete deactivation was achieved after the fifteenth cycle. Thus, the proposed devices can be considered as reliable hydrodynamic cavitation reactors for “water treatment on chip” applications. Full article
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Article
Experimental Investigation of Sludge Treatment Using a Rotor-Stator Type Hydrodynamic Cavitation Reactor and an Ultrasonic Bath
Processes 2019, 7(11), 790; https://doi.org/10.3390/pr7110790 - 01 Nov 2019
Cited by 13 | Viewed by 1093
Abstract
In the present work, the sludge treatment performance of a sludge treatment using a rotor-stator type hydrodynamic cavitation reactor (HCR) was investigated. To verify the performance, a comparison with an ultrasonic bath was conducted in four experimental cases using three assessment factors. The [...] Read more.
In the present work, the sludge treatment performance of a sludge treatment using a rotor-stator type hydrodynamic cavitation reactor (HCR) was investigated. To verify the performance, a comparison with an ultrasonic bath was conducted in four experimental cases using three assessment factors. The HCR consisted of a rotor and three covers with inserted dimples resulting in variation of the cross-sectional area in a flow. The experimental cases were established using the same energy consumption for each device. Disintegration performance was analyzed with assessment factors using particle size distribution and sludge volume index (SVI), oxidation performance using total chemical oxygen demand (TCOD) and volatile suspended solids (VSS) reduction rate, as well as solubilization rate using soluble chemical oxygen demand (SCOD). As a result, the particle disintegration and oxidation performance of the HCR were generally superior to those of the ultrasonic bath. However, due to the contradictory interactions of these factors, the solubilization rate of the two devices was measured similarly as 42.3% and 41.4% for each device. Results of the current study proved that the HCR can be an effective, promising and clean sludge treatment technique for use in wastewater treatment plants. Full article
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Article
Real-Scale Integral Valorization of Waste Orange Peel via Hydrodynamic Cavitation
Processes 2019, 7(9), 581; https://doi.org/10.3390/pr7090581 - 02 Sep 2019
Cited by 22 | Viewed by 2375
Abstract
Waste orange peel represents a heavy burden for the orange juice industry, estimated in several million tons per year worldwide; nevertheless, this by-product is endowed with valuable bioactive compounds, such as pectin, polyphenols, and terpenes. The potential value of the waste orange peel [...] Read more.
Waste orange peel represents a heavy burden for the orange juice industry, estimated in several million tons per year worldwide; nevertheless, this by-product is endowed with valuable bioactive compounds, such as pectin, polyphenols, and terpenes. The potential value of the waste orange peel has stimulated the search for extraction processes, alternative or complementary to landfilling or to the integral energy conversion. This study introduces controlled hydrodynamic cavitation as a new route to the integral valorization of this by-product, based on simple equipment, speed, effectiveness and efficiency, scalability, and compliance with green extraction principles. Waste orange peel, in batches of several kg, was processed in more than 100 L of water, without any other raw materials, in a device comprising a Venturi-shaped cavitation reactor. The extractions of pectin (with a remarkably low degree of esterification), polyphenols (flavanones and hydroxycinnamic acid derivatives), and terpenes (mainly d-limonene) were effective and efficient (high yields within a few min of process time). The biomethane generation potential of the process residues was determined. The achieved results proved the viability of the proposed route to the integral valorization of waste orange peel, though wide margins exist for further improvements. Full article
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Review

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Review
Review of Evidence Available on Hesperidin-Rich Products as Potential Tools against COVID-19 and Hydrodynamic Cavitation-Based Extraction as a Method of Increasing Their Production
Processes 2020, 8(5), 549; https://doi.org/10.3390/pr8050549 - 08 May 2020
Cited by 28 | Viewed by 5753
Abstract
Based on recent computational and experimental studies, hesperidin, a bioactive flavonoid abundant in citrus peel, stands out for its high binding affinity to the main cellular receptors of SARS-CoV-2, outperforming drugs already recommended for clinical trials. Thus, it is very promising for prophylaxis [...] Read more.
Based on recent computational and experimental studies, hesperidin, a bioactive flavonoid abundant in citrus peel, stands out for its high binding affinity to the main cellular receptors of SARS-CoV-2, outperforming drugs already recommended for clinical trials. Thus, it is very promising for prophylaxis and treatment of COVID-19, along with other coexistent flavonoids such as naringin, which could help restraining the proinflammatory overreaction of the immune system. Controlled hydrodynamic cavitation processes showed the highest speed, effectiveness and efficiency in the integral and green aqueous extraction of flavonoids, essential oils and pectin from citrus peel waste. After freeze-drying, the extracted pectin showed high quality and excellent antioxidant and antibacterial activities, attributed to flavonoids and essential oils adsorbed and concentrated on its surface. This study reviews the recent evidence about hesperidin as a promising molecule, and proposes a feasible and affordable process based on hydrodynamic cavitation for the integral aqueous extraction of citrus peel waste resulting in hesperidin-rich products, either aqueous extracts or pectin tablets. The uptake of this process on a relevant scale is urged, in order to achieve large-scale production and distribution of hesperidin-rich products. Meanwhile, experimental and clinical studies could determine the effective doses either for therapeutic and preventive purposes. Full article
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Review
Controlled Hydrodynamic Cavitation: A Review of Recent Advances and Perspectives for Greener Processing
Processes 2020, 8(2), 220; https://doi.org/10.3390/pr8020220 - 13 Feb 2020
Cited by 11 | Viewed by 1721
Abstract
The 20th century has witnessed a remarkable enhancement in the demand for varieties of consumer products, ranging from food, pharmaceutical, cosmetics, to other industries. To enhance the quality of the product and to reduce the production cost, industries are gradually inclined towards greener [...] Read more.
The 20th century has witnessed a remarkable enhancement in the demand for varieties of consumer products, ranging from food, pharmaceutical, cosmetics, to other industries. To enhance the quality of the product and to reduce the production cost, industries are gradually inclined towards greener processing technologies. Cavitation-based technologies are gaining interest among processing technologies due to their cost effectiveness in operation, minimization of toxic solvent usage, and ability to obtain superior processed products compared to conventional methods. Also, following the recent advancements, cavitation technology with large-scale processing applicability is only denoted to the hydrodynamic cavitation (HC)-based method. This review includes a general overview of hydrodynamic cavitation-based processing technologies and a detailed discussion regarding the process effectiveness. HC has demonstrated its usefulness in food processing, extraction of valuable products, biofuel synthesis, emulsification, and waste remediation, including broad-spectrum contaminants such as pharmaceuticals, bacteria, dyes, and organic pollutants of concern. Following the requirement of a specific process, HC has been implemented either alone or in combination with other process-intensifying steps, for example, catalyst, surfactant, ultraviolet (UV), hydrogen peroxide (H2O2), and ozone (O3), for better performance. The reactor set-up of HC includes orifice, slit venturi, rotor-stator, and sonolator type constrictions that initiate and control the formation of bubbles. Moreover, the future directions have also been pointed out with careful consideration of specific drawbacks. Full article
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Review
Plant and Biomass Extraction and Valorisation under Hydrodynamic Cavitation
Processes 2019, 7(12), 965; https://doi.org/10.3390/pr7120965 - 17 Dec 2019
Cited by 11 | Viewed by 1736
Abstract
Hydrodynamic cavitation (HC) is a green technology that has been successfully used to intensify a number of process. The cavitation phenomenon is responsible for many effects, including improvements in mass transfer rates and effective cell-wall rupture, leading to matrix disintegration. HC is a [...] Read more.
Hydrodynamic cavitation (HC) is a green technology that has been successfully used to intensify a number of process. The cavitation phenomenon is responsible for many effects, including improvements in mass transfer rates and effective cell-wall rupture, leading to matrix disintegration. HC is a promising strategy for extraction processes and provides the fast and efficient recovery of valuable compounds from plants and biomass with high quality. It is a simple method with high energy efficiency that shows great potential for large-scale operations. This review presents a general discussion of the mechanisms of HC, its advantages, different reactor configurations, its applications in the extraction of bioactive compounds from plants, lipids from algal biomass and delignification of lignocellulosic biomass, and a case study in which the HC extraction of basil leftovers is compared with that of other extraction methods. Full article
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