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Separations ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 6
Author(s):  
Yulong Zhang ◽  
Peikun Liu ◽  
Linjing Xiao ◽  
Long Chang ◽  
Fangping Yan ◽  
...  

In this study, a coal mine water flocculation system was established. A series of flocculation tests were carried out at different structural parameters (cylinder height, cone-plate insertion depth and cone-plate spacing) to better investigate the effect of the cone-plate clarifier on coal mine water treatment performance. Sixteen sampling points were set up in the system for data monitoring to generate the required data. The cone-plate clarifier was divided into five zones for flocculation analysis. The increased cylinder height facilitated the flocculation of particles in the micro flocculation zone and the settling of particles in the settlement zone. The chemicals used are polyaluminum chloride (PACl), Fe3O4 and polyacrylamide (PAM), corresponding to doses of 60 mg/L, 40 mg/L and 6 mg/L, respectively. Insufficient insertion depth of the cone-plate will cause the small flocs that have not been fully flocculated to enter the exit pipe zone directly through the cone-plate, while too much insertion depth will cause the large floc in the settlement zone to re-enter the exit pipe zone. The flocculation effect of small flocs increased as the cone-plate spacing decreased, which is consistent with the shallow pool theory. When the cone plate spacing was too narrow, the amount of fluid was reduced and the increase in fluid velocity reduced the flocculation effect. Curve fitting was conducted for Suspended solids(SS) and turbidity removal efficiency under each structural parameter to derive the variation of SS and turbidity removal efficiency under different structural parameters. The regression models of SS and turbidity removal efficiency on the cylinder height, cone-plate insertion depth and cone-plate spacing were established based on the curve fitting results, and the regression models were verified to be well fitted based on the comparison of experimental results. Finally, the optimal values of SS and turbidity removal efficiency were found based on the regression model. The flow rate of the cone-plate clarifier is 0.6 m3/h. The SS removal efficiency reached 96.82% when the cylinder height was 708 mm, the cone-plate insertion depth was 367 mm and the cone-plate spacing was 26 mm. The turbidity removal efficiency reached 86.75% when the cylinder height was 709 mm, the cone-plate insertion depth was 369 mm and the cone-plate spacing was 26 mm.


2021 ◽  
Author(s):  
Siwen Li ◽  
Yingzi Lin ◽  
SuiYi Zhu ◽  
Gen Liu

Abstract In this work, GAC@Ni/Fe particle electrodes were prepared and employed for the degradation of Sulfamethylthiadiazole (SMT) by three-dimensional electrocatalytic technology.The effects of particle electrode bi-metal loading ratio, cell voltage, particle electrode dosage, electrode plate spacing and SMT initial concentration on SMT removal were studied.In addition, GAC@Ni/Fe particle electrode was analyzed by the scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectrometer (FTIR) to characterize . which indicated that a significant amount of Iron-nickel oxide were formed on the surface of GAC@Ni/Fe particle electrode.The results indicated that when the nickel-iron loading ratio is 1:1, the SMT removal effect is the best, and the removal rate can reach 90.89% within 30 minutes,Compared with the granular activated carbon without bimetal, the removal efficiency is increased by 37.58%. The degradation of SMT in the GAC@Ni/Fe particle three-dimensional electrode reactor is the joint result of both direct oxidation and indirect oxidation. The contribution rates of direct oxidation of anode and particle electrode and indirect oxidation of ·OH in the degradation are 32%, 27% and 41%, respectively. Based on the intermediate detected by ultra high liquid chromatography and the calculation of bond energy of SMT molecule by Gauss software,the degradation pathway of SMT in the GAC@Ni/Fe three-dimensional electrode reactor is proposed. This research provides a green, healthy and effective method for removing sulfonamide micro-polluted wastewater.


2021 ◽  
Vol 2116 (1) ◽  
pp. 012028
Author(s):  
Georges Saliba ◽  
Vincent Raimbault ◽  
Stéphane Colin ◽  
Ahmad Batikh ◽  
Stéphane Orieux ◽  
...  

Abstract A growing portion of the thermal load on board airplanes is due to densely packed electronic systems. This increased thermal load along with constraints on weight and volume have made simple and reliable cooling solutions an urgent need in the aerospace industry. There is a wealth of cooling solutions available in order to meet these demands, the simplest and most adaptable of which is probably jet impingement cooling. In this study, fluidic oscillators capable of producing pulsating jets were used to cool a heated surface and were then compared to equivalent steady jets. Although pulsating jets can be produced using a number of devices, fluidic oscillators offer the advantage of not having any moving parts. These oscillators are sustained by a self-induced internal flow instability and can function at different scales. Although the major part of this work is based on prototypes that produce jets with sub-millimetric widths, designs at one tenth that scale, i.e. with an exit slot width of 50 µm, are also presented. Reynolds numbers ranging from ReD = 3500 to 5250 and jet-to-plate spacing from 1D to 10D were studied (where D is the initial width of the jet). The Nusselt number distribution is found for each case and a comparison is made between the performance of equivalent steady and pulsating jets based on the average Nusselt number.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1896
Author(s):  
Bolin Hu ◽  
Xiaoqiang Zhang ◽  
Zhaofeng Wang ◽  
Zixian Wang ◽  
Yuanfan Ji

This paper uses computational fluid dynamics (CFD) to simulate flow field distribution inside an electrochemical descaling reactor in three dimensions. First, the reactor flow field was obtained by steady-state simulation, and the grid independence was verified. Then, the steady state of the flow field was judged to ensure the accuracy of the simulation results. Transient simulations were performed on the basis of steady-state simulations, and residence time distribution (RTD) curves were obtained by a pulse-tracing method. The effects of plate height and plate spacing on reactor hydraulic characteristics (flow state and backmixing) were investigated using RTD curves, and the results showed that increasing the plate height and decreasing the plate spacing could make the flow more similar to the plug flow and reduce the degree of backmixing in the reactor. The flow field details provided by CFD were used to analyze the reactor flow field and were further verified to obtain the distribution patterns of dead and short circuit zones. Meanwhile, information regarding pressure drops was extracted for different working conditions (490, 560, and 630 mm for pole plate height and 172.6, 129.45, and 103.56 mm for pole plate spacing), and the results showed that increasing the pole plate height and decreasing the pole plate spacing led to an increased drop in pressure. In this case, a larger pressure drop means higher energy consumption. However, increasing the pole plate height had a smaller effect on energy consumption than decreasing the pole plate spacing.


2021 ◽  
Vol 21 (4) ◽  
pp. 253-260
Author(s):  
Ki-Chai Kim ◽  
Gyeong-Sik Park ◽  
Gyeong-Jun Min ◽  
Young-Ki Cho

This paper presents the transmission cross-section (TCS) of a dual plate with narrow small slots when a plane wave is incident from the left half-space. Numerical results show that the TCS depends mainly on the plate spacing for a specified frequency. The TCS fluctuates with the plate spacing; the fluctuation period is approximately 0.5λ. When the plate spacing is larger than 0.5λ, the TCS reduces to 90% in the single plate case, and TCS enhancement is extremely difficult. However, when the plate spacing is less than 0.5λ, the TCS decreases gradually to approximately 36% in the single plate case, and TCS enhancement can be realized using two parallel wires. The analysis results show that resonance transmission is effectively obtained by the wires connected on the slots for a plate spacing within 0.5λ. Experimental measurements are presented to validate the theory.


Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop

Abstract Nanoliquid impingement heat transfer with phase change material (PCM) installed radial system is considered. Study is performed by using finite element method for various values of Reynolds numbers (100 ≤ Re ≤ 300), height of PCM (0.25H ≤ hpcm = 0.7H ≤ 0.75H) and plate spacing (0.15H ≤ hpcm = 0.7H ≤ 0.40H). Different configurations with using water, nanoliquid and nanoliquid+PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM while best performance is achieved with nanoliquid and PCM installed configuration. At Re=100 and Re=300, heat transfer improvements of 26% and 25.5% are achieved with nanoliquid+PCM system as compared to water without PCM. Height of the PCM layer also influences the heat transfer dynamic behavior while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM height while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation.


2021 ◽  
Author(s):  
Tao Guo ◽  
Yun-Peng Ben ◽  
Yu-Chao Liu ◽  
Cun-Liang Liu ◽  
Hui-Ren Zhu

Abstract The paper proposes a technique of using advanced pin fins on a target plate to improve the impingement heat transfer performance in an array impingement cooling system. The initial shape of the advanced pin fin is a frustum of a cone. In order to enhance heat transfer and reduce flow resistance, the upper and lower sharp edges of the frustum of a cone are rounded. There are arrays of film holes on the target plate, and the influence of the crossflow is not considered. The flow and heat transfer characteristics of the array impingement flat plate and advanced pin fin plate were studied by numerical simulation. During the numerical simulation, the Reynolds number was varied from 2000 to 19500, the jet-to-plate spacing Z/d from 3 to 6 (d = 0.50mm) and the jet hole diameter d is 0.50 mm, 0.75 mm and 1.00 mm respectively. The results show that the averaged Nusselt number values for the advanced pin fin target plate showed an increase ranging from 15% to 20% over those for the flat target plate, It is generally considered that the enhancement of heat transfer is mainly due to the enhancement of fluid disturbance by the pin fins. However, by changing the size of the pin fins, it is found that the enhancement of heat transfer is mainly caused by the increase of heat transfer area, and the influence of enhancing the disturbance is not significant. The pressure loss is little higher than that of the flat plate. The averaged Nusselt number values for the advanced pin fin target plate decreases with the increase of the jet-to-plate spacing, and increases with the increase of Reynolds number. At the same mass flow rate, the averaged heat transfer performance of the pin fin target plate decreases with the increase of jet hole diameter, and the results show that the averaged heat transfer performance of 0.5mm jet hole diameter is the best.


Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 616
Author(s):  
Zhongqi He ◽  
Xu Zhou ◽  
Wenhui Wang ◽  
Wenbiao Jin ◽  
Wei Han ◽  
...  

The present study investigated the parameters and the mechanism of action of electrochemical cell lysis to reduce the return sludge from secondary settlers based on the theory of cell lysis-cryptic growth. The factors influencing the functioning of two electrodes (Ti/SnO2-Sb and Ti/RuO2-IrO2) were investigated to determine the optimal cell lysis parameters for each electrode, and the effects of the two electrodes on cell lysis were compared under these conditions. Finally, the Ti/SnO2-Sb electrode was selected for the subsequent experiments. The electrolysis reaction was performed using the following parameters: the initial sludge concentration was 7000 mg/L, the working voltage was 18 V, the plate spacing was 1 cm, the initial pH was 6.8 to 7.0, and the electrolysis duration was 90 min. The degree of disintegration of the sludge and the cell lysis rate reached 25.35% and 20.15%, respectively. In summary, electrochemical cell lysis has a good prospect for sludge reduction.


Author(s):  
Yinghao Zhang ◽  
Wenqiang Jiang ◽  
Hao Dong ◽  
Xuyang Hu ◽  
Baihui Fang ◽  
...  

In this study, a Ti/IrO2-Ta2O5 anode was prepared by a hydrothermal method, and the prepared electrode was characterized by techniques such as scanning electron microscopy, X-ray diffraction, and electron dispersive spectroscopy. At the same time, the anode characteristics before and after electrochemical experiments were analyzed. The electrode gradation mechanism of oxytetracycline is discussed. In the whole experimental process, the range of electrolysis conditions was determined by single factor experiment, and then the optimal removal condition of oxytetracycline was determined by orthogonal experiments. The removal rate of oxytetracycline reached 99.02% after 20 min of electrolysis under the following optimal conditions: a current of 0.500 A, plate spacing of 2 cm, Na2SO4 electrolyte concentration of 4 g/L, and solution pH of 3. Additionally, the mechanism of oxytetracycline removal was explored, free radical scavenging experiments were performed, and the degradation mechanism was inferred based on the changes in the ultraviolet absorption of the oxytetracycline solution before and after electrolysis. Then, based on the liquid chromatography–mass spectrometry data, seven possible compounds and five possible removal pathways were proposed.


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