The objective of this paper is to obtain an excellent structure of a Rotational hydrodynamic cavitation reactor (RHCR) by a numerical method and then to investigate the cavitating flow characteristics of the optimized RHCR experimentally. The RNG k-ε turbulence model combined with the Zwart cavitation model was applied to analyze the influence of the straight blade number, the baffle position and the baffle shape on the pressure field, bubble distribution and turbulence kinetic energy of the RHCR. The results show that compared to the original model, an RHCR with a straight blade number of 6, a baffle position of 0. 74 and a triangular baffle offers better cavitation performance. Moreover, the energy performance and the cavitation development process of the optimized RHCR were studied experimentally. The results indicate that the multiscale bubbles are induced by straight blades and baffles of the optimized RHCR, accompanied by the twice quasi-periodic shedding dynamics in one cycle. The findings of this study have positive significance for the design and optimization of RHCRs.

In recent years, many of research have been focused on energy production in the chemical processes such as crude oil upgrading during the collapse of cavitation micro bubbles generated sonolytically. For maximum efficiency of sono-reactors, the effect of various physical and operational parameters must be determined. In present work, cavitation active zone and the effect of various physical and operational parameters on sono-reactor efficiency has been quantified with CFD simulation of acoustic wave propagation in water bulk. With an ultrasonic probe tip of diameter 13 mm, the pressure distribution has been simulated for different probe positions and the effect of probe depth in water has been investigated. Comparison with experimental results has clearly established the correctness of the numerical simulations. The results show for finding of optimum sono-reactor design the highest intensity of acoustic cavitation and produced cavitational energy can be predicted by CFD simulation reasonably.

Biodiesel is a bio-renewable fuel derived from vegetable oils and animal fats with less environmental pollution than fossil fuels. This research aims to design, fabricate, and evaluate a hydrodynamic reactor for biodiesel production. According to the fluid characteristic, the rotor and stator were designed and the electric engine was chosen. The cavities of the rotor were designed for optimal cavitation. The effect of reaction time and Rotational speed were examined to assess the reactor. Speed rotor Rotational speed of hydrodynamic cavitation reactors can intensify the transesterification reaction by increasing the occurrence of cavitation in the space between the rotor and the stator. Therefore, to investigate the effect of this variable on biodiesel production efficiency, three levels were selected (2000, 2500, and 3000 rpm). As the Rotational speed of the hydrodynamic reactor increases, the cavitation operation increases, and as a result, the conversion percentage rises too. This experiment indicated that the rise of residence time from 30 s to 60 s increases methyl esters yield, but following the time up to 60 s, the methyl esters yield has no significant changes. The results showed that the biodiesel produced from waste oil in the hydrodynamic reactor could be a suitable alternative to diesel.

In this study, experimental cavitation erosion is carried out on different types of Rotational models (gray cast iron, aluminum 1100, aluminum 6061 and chromium stainless steel) at constant Rotational speed, temperature and cavitation number in a cavitation closed tunnel. The weight loss rate and the behavior of corrosion were analyzed with SEM and optical microscopes. The effect of the Rotational speed variation on the cavitation erosion was evaluated for models of different materials. The findings significantly showed that the diameter of the holes is independent from Rotational speed and with increased Rotational speed, the number of the holes and the cavitation erosion escalate. The study revealed that chrome stainless steel model has a higher resistance against cavitation erosion. The relationships between weight loss rate and Rotational speed are further presented.

hydrodynamic cavitation (HC) with an orifice as the cavitating device was used to study the degradation of methyl orange dye. The operating parameters of the process, such as pH and inlet pressure, were optimized. The effect of hydroxyl radical promoters like Fenton oxidation and hydrogen peroxide (H2O2) on the extent of degradation was also investigated. It has been observed that acidic conditions (pH 2) favor the degradation of methyl orange. The combined effect of hydrodynamic cavitation with hydrogen peroxide was investigated at the solution’s natural pH and an optimized solution pH 2. Maximum degradation of 99.2% was observed at natural pH, whereas complete degradation of methyl orange dye was observed at pH 2 with 8 ml/L of hydrogen peroxide addition. The hybrid process of HC/Fenton and HC/H2O2 showed the highest efficiency for the degradation of methyl orange with a minimum energy requirement (0.11 kWh) and operational cost (USD $ 0.0062/L).

In this paper, the effect of presence of nano-microbubbles on flotation recovery of chalcopyrite fine particles (-38+5mm) has been studied. Comparative flotation tests were performed both in the presence and absence of nano-microbubbles (conventional flotation) to evaluate recovery changes of chalcopyrite. Methyl IsoButyl Carbinol (MIBC) was used as frother and Potassium Amyl Xanthate (KAX) as collector at pH= 10. Nano-microbubbles were generated using a nano-microbubble generator based on cavitation phenomenon in venturi tubes. Changes in size distribution, zeta potential and stability of nano-microbubbles were measured as a function of time. Results showed that the interval between generation time and 10 minutes after that, simultaneous with reduction of the absolute value of zeta potential increased the average size of nano-microbubbles from 358 nm to 13.24 mm. The results in the presence of nano-microbubbles showed increased flotation recovery of chalcopyrite fines by 16-21% and reduction of chemicals reagent (up to 75% of collector and 50% of frother). In addition, the effect of nano-microbubbles on promoting the recovery of ultrafine particles (-14.36+5 mm), has been higher than fine particles (+14.36-38 mm).

An 1D hydrodynamic model has been simulation and developed for gas hold-up and liquid circulation velocity prediction in air-lift reactors. model is based on momentum balance equations and has been adjusted to experimental data collected on a pilot plant reactor equipped with two types of gas distributors and using water as the liquid phase.The model equations described previously constitute a set of non-linear equations which are solved by an iterative procedure (v.b) (c plus). This model has also been combined with mass transfer and the kinetics of a chemical reaction to yield a complete model of the performance of a reactor.

Introduction: Many pollutants in industrial wastewaters, such as dyes, can't be removed easily by the conventional physical, biological and chemical purification processes, because of their complexity and intractability. Therefore, it is necessary to find an effective treatment technology that can degrade complex biorefractory molecules or can breakdown them into smaller molecules which can be further degraded by conventional methods. cavitation is one such recent technique which has been extensively studied for the treatment of complex wastewater due to its ability of generating highly reactive free radicals. hydrodynamic cavitation has a potential of application on larger scale due to its capability in generating hydroxyl radicals at ambient condition, easy scale up and less material cost making it more economical to employ. The purpose of this study was application of hydrodynamic cavitation process for removing Reactive Black 5 and optimization the affecting parameters (pH, inlet pressure, hole diameter and initial concentration of dye) based on the amount of efficiency and energy consumption. Material and methods: In this research, removal of Reactive Black 5 with the use of hydrodynamic cavitation process was studied. 8. 25 liters of colored solution was examined in each test. The cavitation was produced by orifice plate and pump. In order to optimize process, various trials were performed in pH of 3 to 11 and also using different orifice plates with hole diameter of 2, 3, 5 and 7 mm at inlet pressures of 2, 3, 4 and 5 bar and dye concentration of 30, 50 and 100 ppm. Due to the constant voltage of urban electricity, the electric current was measured as an indicator of energy consumption by ammeter. Results and discussion: According to the results by reducing the pH, dye removal was increased and orifice plates with larger hole diameter in upper pressures had better efficiency. It was observed that increasing the initial concentration of dye resulted in decreasing dye removal efficiency. The orifice with 7 mm hole diameter at 5 bar inlet pressure yielded the highest efficiency, but by involving the amount of energy consumed and considering the process efficiency to energy consumption, the orifice with 7 mm hole diameter at 4 bar inlet pressure was chosen as the best. The pH of 3, orifice with 7 mm hole diameter at 4 bar pressure and initial concentration of 30 ppm (with regards to pump energy consumption obtained from measuring the electrical current and the efficiency of process) were selected as optimum conditions. In these conditions after 120 minutes, 38. 21% dye removal was obtained using hydrodynamic cavitation. Conclusion: hydrodynamic cavitation has a potential of application on larger scale due to its capability in generating hydroxyl radicals at ambient condition. It was found that the energy consumption was an effective factor in selecting the optimum conditions. By reducing the initial dye concentration and pH, dye removal was increased and orifice plates with larger hole diameter in upper pressures had better efficiency.

The textile industry wastewater causes serious environmental problems due to its high toxicity and color. Therefore, it is necessary to find an effective treatment technology for removing organic dyes from wastewater. cavitation is one such modern technique which has been considered for the treatment of complex pollutants because of its ability to generate highly reactive free radicals. Up to now, researchers have mostly focused on qualitative interpretations and related scientific techniques, and there has been no quantitative cost analysis for pollutant control in textile industries for decision making purposes. Future studies need to focus on the cost analysis of more processes in textile wastewater treatment, such as advanced oxidation and combined and biological processes. Thus, this research was conducted with the aim of investigating and comparing various single and combined processes using the hydrodynamic cavitation (in a single system and with a specific contaminant) to remove reactive black 5 dye. hydrodynamic cavitation (HC) was applied by using an orifice plate with a 7 mm hole diameter at the inlet pressure of 4 bars. Single processes, photocatalysis, photolysis, adsorption and combined processes, cavitation + photolysis, cavitation + photocatalyst and cavitation + photocatalysis were investigated in dye elimination and each of them was optimized by changing the various parameters (pH, TiO2 nanophotocatalyst concentration, irradiation power and dye concentration) and their best efficiency was obtained. In addition, considering the cost of energy and the nanophotocatalyst consumed by the processes, along with the process efficiency, processes were ranked by defining the index of efficiency to cost ratio. In the studied processes, efficiency increased as pH reduced, however, in the case of the photolysis process, efficiency increase at the highest level of the basic pH was significantly higher than acidic pH. Increasing the nanophotocatalyst concentration up to an optimum level resulted in efficiency increase. The decolorization rate increased as the irradiation power increased. The processes efficiency decreased with an increase in the initial concentration of the dye. In terms of efficiency, cavitation + photocatalysis, photocatalysis, cavitation + photolysis, photolysis, cavitation + photocatalyst, cavitation and adsorption processes, with the dye removal efficiencies of 83, 60, 52, 49, 43, 38 and 13% were placed first to seventh. This is while, considering both efficiency and cost consumption, photolysis process and then processes of cavitation + photolysis, cavitation and photocatalysis were ranked first to fourth, respectively with the best ratios. hydrodynamic cavitation is a promising approach for dealing with industrial pollutants and the combination of this process with other advanced oxidation processes yields desirable results. Considering the parameters of energy and the cost of consumed nanophotocatalyst in the comparison of processes is very important and the output efficiency of the process should not be the only criterion. Paying attention to the substantial costs of nanophotocatalysts such as nanotitanium dioxide, combined techniques (e. g., the combination of cavitation with other advanced oxidation processes) lead to less consumption of nanomaterial and lower operational costs and are therefore cost-effective.

The performance of internal combustion engines can be improved by optimizing fuel spray characteristics. However, high injection pressures and small nozzle diameters in modern fuel injectors result in cavitation flows inside the nozzle, making it difficult to accurately characterize vapor bubble formation and growth. In this review, we explore the influence of cavitation flow on spray formation and examine the effects of geometric and operational factors. We discuss the experimental techniques used to generate a cavitation map and the mathematical models used to describe the behavior and magnitude of the bubble. We also investigate the impact of cavitation on spray properties, including the enhancement of liquid jet fragmentation due to the collapse of cavitation bubbles near the nozzle output. We present a multidimensional cavitation-coupled spray model and discuss the effect of cavitation on spray angle. While experimental work is effective, theoretical analysis can also provide insights into the impact of cavitation flow on spray characteristics. Our review concludes that the spray angle increases during the growing cavitation and super cavitation regimes, but decreases significantly following the cavitation flip. The string cavitation is observed when the position of the needle valve shifts or at a lower needle lift and the spray cone angle increases significantly. Overall, this review provides an inclusive overview of cavitation flow and its influence on spray formation and will aid in the development of more efficient internal combustion engines.