Assessment of Tandem Venturi on Enhancement of Cavitational Chemical Reaction

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Hoseyn Sayyaadi
Keyword(s):  
Chemical Reaction ◽  
Oxidation Process ◽  
Flow Characteristics ◽  
Chemical Oxidation ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Hydrodynamic Cavitation ◽  
Operating Pressure ◽  
Local Pressures ◽  
Second Category

The collapsing phenomenon of cavitation bubbles generates extremely high local pressures and temperatures that can be utilized for the chemical oxidation process. This process is carried out in cavitation reactors. A Venturi tube is one of the most common forms of hydrodynamic cavitation reactors, which is suitable for industrial scale applications. In this work, the hydraulic performance and efficiency in chemical reaction of a new form of hydrodynamic cavitation reactors, which is called “tandem Venturi,” were studied and compared with the conventional type of the single Venturi. The tandem Venturi is used for enhancement of the chemical reaction of hydrodynamic cavitating flow. The reaction enhancement is useful especially for the reaction of aqueous solutions not containing volatile organic compounds (VOCs). The operating pressure, inlet pressure, flow rate, and consequently the cavitation number were controlled and systematically varied for both single and tandem Venturis. Moreover, a specified amount of H2O2 was injected into the flow as required. The effects of operating pressure and the cavitation number on cavitating flow characteristics for single and tandem Venturis were experimentally observed and the results were compared. In addition, the performance of the tandem-Venturi reactor for degradation of non-VOC contaminants (2-chlorophenol) was studied. Its performance was compared with the performance of a conventional Venturi reactor. Two different categories were conducted for the experiments. In the first category, the effect of the net cavitating flow on degradation of non-VOC for the single and tandem Venturis was compared. In the second category, the effect of H2O2 injection into the cavitating flow on degradation of non-VOC (“cavitation-oxidation” process) was studied. The performance of the single and tandem Venturis for the cavitation-oxidation process was compared. Further investigation was performed to assess the advantage of utilizing the tandem Venturi from the viewpoint of efficiency of the oxidation process. The results of the energy efficiency were compared with the corresponding efficiency of the single Venturi. Finally, the relationship between the main parameters of cavitation reaction flow with the chemical performance was discussed.

Unsteady Cavitating Flow Around an Inclined Rectangular Cylinder

Volume 3 ◽  
2004 ◽  
Author(s):  
Terukazu Ota ◽  
Isao Tsubura ◽  
Hiroyuki Yoshikawa
Keyword(s):  
Separation Bubble ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Low Frequency ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Dynamic Force ◽  
Unstable Flow ◽  
Rectangular Cylinder ◽  
Cavity Configuration

Unsteady characteristics of cavitating flow around an inclined rectangular cylinder with a width to height ratio of 8.0 were experimentally investigated for various angles of attack and cavitation numbers. Measurements of fluid dynamic force and surface pressure were made and the cavity configuration was observed with a camera. Especially considered are the self-oscillating unstable flow characteristics along with the time variation of cavity configuration. It is found that a severe vibration occurs at some cavitation number, in which the attached cavity is formed in the separation bubble. As the cavitation number further decreases, the low frequency fluctuation of flow occurs.

scholarly journals Cavitating Flow through a Micro-Orifice

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 191 ◽  
Author(s):  
Zhi-jiang Jin ◽  
Zhi-xin Gao ◽  
Xiao-juan Li ◽  
Jin-yuan Qian
Keyword(s):  
Pressure Difference ◽  
Rapid Development ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Hydrodynamic Cavitation ◽  
Apparent Difference ◽  
Microfluidic Systems ◽  
Vapor Cavity ◽  
Exit Pressure ◽  
Flow Through

Microfluidic systems have witnessed rapid development in recent years. As one of the most common structures, the micro-orifice is always included inside microfluidic systems. Hydrodynamic cavitation in the micro-orifice has been experimentally discovered and is harmful to microfluidic systems. This paper investigates cavitating flow through a micro-orifice. A rectangular micro-orifice with a l/d ratio varying from 0.25 to 4 was selected and the pressure difference between the inlet and outlet varied from 50 to 300 kPa. Results show that cavitation intensity increased with an increase in pressure difference. Decreasing exit pressure led to a decrease in cavitation number and cavitation could be prevented by increasing the exit pressure. In addition, the vapor cavity also increased with an increase in pressure difference and l/d ratio. Results also show the pressure ratio at cavitation inception was 1.8 when l/d was above 0.5 and the cavitation number almost remained constant when l/d was larger than 2. Moreover, there was an apparent difference in cavitation number depending on whether l/d was larger than 1.

scholarly journals PIV Analysis of Cavitating Flow Behind Square Multi-Orifice Plates

10.29007/fhdg ◽  
2018 ◽  
Author(s):  
Zhiyong Dong ◽  
Wenqian Zhao
Keyword(s):  
Conventional Technique ◽  
Disinfection Byproducts ◽  
Cavitating Flow ◽  
Water Disinfection ◽  
Hydrodynamic Cavitation ◽  
Pathogenic Microorganisms ◽  
Turbulence Structures ◽  
Image Velocimetry ◽  
Piv Analysis ◽  
Mutagenic Effects

Currently, in water supply engineering, the conventional technique of disinfection by chlorination is used to kill pathogenic microorganisms in raw water. However, chlorine reacts with organic compounds in water and generates disinfection byproducts (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) etc. These byproducts are of carcinogenic, teratogenic and mutagenic effects, which seriously threaten human health. Hydrodynamic cavitation is a novel technique of drinking water disinfection without DBPs. Turbulence structures of cavitating flow were observed by the Particle Image Velocimetry (PIV) technique in a self-developed hydrodynamic cavitation device due to square multi- orifice plates, including effects of orifice number and orifice layout on velocity distribution, turbulence intensity and Reynolds stress, which aimed at uncovering mechanism of killing pathogenic microorganisms by hydrodynamic cavitation.

scholarly journals A novel process of dye wastewater treatment by linking advanced chemical oxidation with biological oxidation

2015 ◽  
Vol 41 (4) ◽  
pp. 33-39 ◽  
Author(s):  
Haiming Zou ◽  
Wanzheng Ma ◽  
Yan Wang
Keyword(s):  
Oxidation Process ◽  
Chemical Oxidation ◽  
Chinese Government ◽  
Biological Oxidation ◽  
Dye Wastewater ◽  
Organic Substances ◽  
Combination Process ◽  
Fenton’S Oxidation ◽  
New Process ◽  
Fenton's Oxidation

Abstract Dye wastewater is one of typically non-biodegradable industrial effluents. A new process linking Fenton’s oxidation with biological oxidation proposed in this study was investigated to degrade the organic substances from real dye wastewater. During the combination process, the Fenton’s oxidation process can reduce the organic load and enhance biodegradability of dye wastewater, which is followed by biological aerated filter (BAF) system to further remove organic substances in terms of discharge requirement. The results showed that 97.6% of chemical oxygen demand (COD) removal by the combination process was achieved at the optimum process parameters: pH of 3.5, H2O2 of 2.0 mL/L, Fe(II) of 500 mg/L, 2.0 h treatment time in the Fenton’s oxidation process and hydraulic retention time (HRT) of 5 h in the BAF system. Under these conditions, COD concentration of effluent was 72.6 mg/L whereas 3020 mg/L in the influent, thus meeting the requirement of treated dye wastewater discharge performed by Chinese government (less than 100 mg/L). These results obtained here suggest that the new process combining Fenton’s oxidation with biological oxidation may provide an economical and effective alternative for treatment of non-biodegradable industrial wastewater.

scholarly journals One-step Oxidation of Total Organic Carbon, Total Nitrogen, and Total Phosphorous using Wet Chemical Oxidation

2020 ◽  
Vol 42 (12) ◽  
pp. 603-609
Author(s):  
Jeong-Hwan Choi ◽  
Dong-Hun Shin ◽  
Hye-Bin Kim ◽  
Jong-Gook Kim ◽  
Kitae Baek
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Total Nitrogen ◽  
Uv Irradiation ◽  
Oxidation Process ◽  
Irradiation Time ◽  
Suitable Condition ◽  
Chemical Oxidation ◽  
Total Phosphorous ◽  
Wet Chemical

Objective:This study proposed the simultaneous multi-oxidation of total organic carbon, total nitrogen, and total phosphorous using modified wet chemical oxidation method.Methods:The multi oxidation process was based on the dual radical system with sulfate and hydroxyl radicals. The sodium persulfate (Na2S2O8) and sodium hydroxide (NaOH) were activated at 40℃ and UV irradiation with 254 nm to generate the sulfate radical and hydroxyl radical. The organic matters were oxidized by the dual radicals, and TOC, TN, and TP values were compared with the control group.Results and Discussion:The dual radical system oxidized organic carbon to carbon dioxide effectively, and the TOC values were similar to the value obtained from the high-temperature combustion technique. However, the residual persulfate after oxidation process interfered the absorbance for TN and inhibit the complexation in TP measurement. The residual persulfate was effectively converted to sulfate by longer heating and UV irradiation, and the interferences were more sensitive to reaction temperature than UV irradiation time. As a result, a higher temperature condition was more effective and enhanced the applicability of multi-oxidation.Conclusions:The multi oxidation of TOC, TN, and TP was demonstrated by wet chemical oxidation, and the proposed method is expected to secure the sample and reduce the analytic time. However, the more suitable condition to enhance the accuracy of TOC, TN, and TP in the multi-oxidation system should be studied further.

Numerical Simulation of Cavitating Flow Over 2D Hydrofoil Using OpenFOAM Adapted for Debian Operating System With LXDE Based in Kernel GNU/Linux

2014 ◽  
Author(s):  
Victor Hugo Hidalgo Diaz ◽  
XianWu Luo ◽  
RenFang Huang ◽  
Edgar Cando
Keyword(s):  
Operating System ◽  
Open Source ◽  
Open Source Software ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Cavitating Flows ◽  
Ansys Fluent ◽  
Flow Features ◽  
Free Open Source

Though commercial CFD codes are widely used in flow analysis, but there are free/open source programs which have been applying for computational fluid dynamics. An open source software makes it possible to customize the solver according to the flow features. In the present paper, cavitating flows over 2D NACA66 hydrofoil were simulated based on open source software, where SALOME is used for mesh generation, OpenFOAM for flow solution under Debian GNU/Linux operating system. The results show the simulated cavitating flow characteristics such as cavity revolution, vortex shedding, cavitation induced pressure vibrations, etc. are validated by experiments and results obtained from proprietary software as Ansys Fluent. Thus, the proposed numerical methods based on open source platform are suitable for flow simulations, even for depicting the complicated physics of cavitation.

Synthesis, characterization, and application of polyanisidines as efficient photostabilizers for poly(vinyl chloride) films

2019 ◽  
Vol 52 (6) ◽  
pp. 537-547
Author(s):  
Magdy W. Sabaa ◽  
Mohamed A Sanad ◽  
Mahmoud A Abd El-Ghaffar ◽  
Nourelhoda A Abdelwahab ◽  
Soha MA Sayed ◽  
...  
Keyword(s):  
Vinyl Chloride ◽  
Uv Irradiation ◽  
Oxidation Process ◽  
Irradiation Time ◽  
Chemical Oxidation ◽  
Polymeric Chain ◽  
Conductivity Measurements ◽  
Uv Absorber ◽  
Poly Vinyl Chloride ◽  
Pvc Film

Conducting polymers have great attention due to their electrical activity in π-electrons conjugation over backbone of the polymeric chain. These properties make them attractive for enormous applications. On that account, we prepared polyanisidines (PAs) derivatives ( ortho, meta, and para) by chemical oxidation process using ammonium peroxydisulfate as an initiator. The prepared PAs were characterized using various techniques. Moreover, conductivity measurements of PA derivatives showed that the ortho-derivative gave the highest value. The prepared PAs were investigated as photostabilizers for poly(vinyl chloride) (PVC) films. Different PVC films were prepared in the absence and the presence of PA derivatives and they were exposed to ultraviolet (UV) irradiation for 30 days. The gel weight % for irradiated PVC films was followed as a function of irradiation time. The results revealed that the blank PVC film (free PA derivatives) was completely degraded reaching 100% gel content. PVC films contain PA derivatives showed higher photostability than PVC blank film. A comparison between the investigated PA derivatives as UV stabilizers and Chimassorb commercial UV absorber was also investigated. PA derivatives showed better efficiency as UV stabilizers than the commercial one till 288 h of UV irradiation.

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