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Depth from Defocus technique for irregular particle images

MEASUREMENT 2024年 238卷

作者： Xu, Rixin Huang, Zuojie Gong, Wenchao Zhou, Wu Tropea, Cameron Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Tech Univ Darmstadt Inst Fluid Mech & Aerodynam Darmstadt Germany

The Depth from Defocus (DFD) imaging technique for measuring the size and number concentration of particles in dispersed two-phase flows has up to now been restricted to the processing of spherical particle images. This study examines how this technique can be extended to process irregular particle images, arising either from neighboring spherical particles which lead to overlapping images, or from the imaging of non-spherical particles. In either case, the application scope of the DFD technique is significantly expanded. On the one hand the ability to identify and process overlapping images allows measurements to be performed at higher number/volume concentrations. On the other hand, especially solid particles are often non-spherical, thus making the DFD technique attractive for these applications. For both cases, the processing algorithms are experimentally benchmarked against ground truth using a dedicated apparatus in which particles of known size, shape and degree of overlapping images can be systematically varied.

关键词： Two-phase flow Dispersion Particle sizing Particle imaging Non-spherical particles

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Aerodynamic performance improvement analysis of Savonius Vertical Axis Wind Turbine utilizing plasma excitation flow control

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ENERGY 2022年第PartD期239卷 122133-122133页

作者： Xu, Wen Li, Cheng-cheng Huang, Sheng-xian Wang, Ying Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Sch Energy & Power Engn Shanghai 200093 Peoples R China

Drag type Savonius Vertical Axis Wind Turbine (VAWT) has the advantages of the low total cost, simple manufacture and maintenance. Although the efficiency is low, it is suitable for residential areas with low wind speed. This article intends to use flow control methods to improve the efficiency of Savonius VAWT. Plasma excitation flow control is a relatively new type of active flow control technology. Therefore, this article uses the User-Defined Function (UDF) in ANSYS Fluent to load the plasma excitation sources on the Savonius VAWT blades. This paper numerically studies the influence of plasma flow control on the aerodynamic performance of a two-blade Savonius VAWT. Firstly, the changes in wind turbine performance under different excitation parameters are analyzed. The research results show that adding plasma exciter at a reasonable position can effectively improve the performance of the wind turbine, and the electric field force distribution in different directions will effect its range of action. Meanwhile, the voltage excitation frequency is also an influencing factor. Secondly, the principle and process of plasma excitation on the Savonius VAWT are analyzed. Finally, the relationship between the power consumed by the plasma and the increased power to drive the wind turbine is analyzed. Besides, the influence of plasma excitation on the overall performance of the wind turbine is summarized. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Savonius Vertical axis wind turbine Plasma excitation flow control Numerical simulation Aerodynamic performance

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Direct Observation of HONO Emissions from Real-World Residential Natural Gas heating in China

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ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023年第12期57卷 4751-4762页

作者： Ding, Xiang Huang, Cheng Liu, Wenyang Ma, Dongxiang Lou, Shengrong Li, Qing Chen, Jun Yang, Huinan Xue, Chaoyang Cheng, Yafang Su, Hang Shanghai Acad Environm Sci State Environm Protect Key Lab Format & Prevent Ur Shanghai 200233 Peoples R China Fudan Univ Inst Atmospher Sci Dept Environm Sci & Engn Shanghai Key Lab Atmospher Particle Pollut & Preve Shanghai 200433 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Univ Orleans CNRS Lab Phys & Chim Environm & Espace LPC2E CNES F-245071 Orleans France Max Planck Inst Chem Minerva Res Grp D-55128 Mainz Germany Max Planck Inst Chem Multiphase Chem Dept D-55128 Mainz Germany

Atmospheric nitrous acid (HONO) is an important precursor of atmospheric hydroxyl radicals. Vehicle emissions and heterogeneous reactions have been identified as major sources of urban HONO. Here, we report on HONO emissions from residential natural gas (RNG) for water and space heating in urban areas based on in situ measurements. The observed HONO emission factors (EFs) of RNG heating vary between 6.03 and 608 mg center dot m-3 NG, which are highly dependent on the thermal load. The highest HONO EFs are observed at a high thermal load via the thermal NO homogeneous reaction. The average HONO EFs of RNG water heating in winter are 1.8 times higher than that in summer due to the increased thermal load caused by the lower inlet water temperatures in winter. The power-based HONO EFs of the traditional RNG heaters are 1085 times and 1.7 times higher than those of gasoline and diesel vehicles that meet the latest emission standards, respectively. It is estimated that the HONO emissions from RNG heaters in a typical Chinese city are gradually close to emissions from on-road vehicles when temperatures decline. These findings highlight that RNG heating is a non-negligible source of urban HONO emissions in China. With the continuous acceleration of coal-to-gas projects and the continuous tightening of NOx emission standards for vehicle exhaust, HONO emissions from RNG heaters will become more prominent in urban areas. Hence, it is urgently needed to upgrade traditional RNG heaters with efficient emission reduction technologies such as frequency-converted blowers, secondary condensers, and low-NOx combustors.

关键词： nitrous acid residential natural gas heater in situ measurements emission factors reactive nitrogen

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Improving water electrolysis assisted by anodic biochar oxidation for clean hydrogen production

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ENERGY 2022年第PartB期238卷 121793-121793页

作者： Ying, Zhi Geng, Zhen Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Biochar-assisted water electrolysis (BAWE) for hydrogen production is an effective way to integrate renewable electricity and biomass utilization. But it is limited by slow biochar oxidation reaction (BOR). Here we adopted the biochar derived from pyrolysis (PB) and hydrothermal carbonization (HB) of rice husk. Replacement of oxygen evolution reaction with BOR leaves a significantly reduced onset potential (E-onset) and an increased current density. Strongly related to carbonization temperature, the physicochemical properties of biochar markedly affected BOR. The abundant -OH groups in HB contributed to a low E-onset, while the well-developed pore structure and high specific surface area of PB enhanced its reactivity at higher potential. Exposure of functional groups on PB surface after pickling made an increase in current density, but the simultaneous elimination of easily oxidized solutes in HB dominated and caused current density decline. H2SO4 electrolyte of 1 mol/L was most appropriate for the uniform dispersion of biochar particles. The oxidation of PB derived at 800 degrees C with a slurry concentration of 10 g/L showed the lowest charge-transfer resistance and a favorable kinetics. Continuous BAWE indicated that PB was more superior than HB in increasing current density and H-2 production. This work provides favorable strategies for improving BAWE. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Biochar-assisted water electrolysis Biochar oxidation reaction (BOR) Biochar Structure Hydrogen

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Smog chamber study of secondary organic aerosol formation from gas- and particle-phase naphthalene ozonolysis

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ATMOSPHERIC ENVIRONMENT 2023年 294卷

作者： Liu, Jixing Zhu, Shuping Guo, Teng Jia, Bin Xu, Li Chen, Jun Cheng, Ping Shanghai Univ Sch Environm & Chem Engn Shanghai 200444 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Naphthalene (Nap), one of the most abundant PAHs in the atmosphere, has been shown to be an important secondary organic aerosol (SOA) precursor. In this study, the gas- and particle-phases (Suspended Nap-coated polystyrene latex spheres (PSLs) generated by vaporization condensation) Nap ozonolysis were investigated in a 1000 L volume cubic Teflon smog chamber. Gas-phase products and Nap-SOAs were observed from the gas- and particle-phase Nap ozonolysis via homogeneous and heterogeneous reactions, respectively. The time-dependent size distribution and mass concentration of Nap-SOAs were analyzed using a scanning mobility particle sizer and a laboratory-developed single-particle aerosol mass spectrometry (SPAMS) instrument. The chemical components of the homogeneous and heterogeneous reaction products were analyzed on-line by single photo ionization mass spectrometry (SPIMS), SPAMS, as well as by thermal desorption gas chromatograph-mass spectrometry. The results showed that the chemical components of the gas-and particle-phase Nap ozonolysis were essentially the same, with the dominant products being phthalaldehyde, phthalic anhydride, 2-carboxybenzaldehyde, and benzoic acid;Nap-SOA formation was attributed to the formation of new particles as well as the uptake of homogeneous and heterogeneous Nap oxidation products on the gas-phase or/and the particle surface. Based on the online measurement results, the reaction mechanism of Nap-ozonolysis also exhibits an initial carbon atom or double-bond attacks by O-3, and kinetic analysis of Nap-coated PSLs ozonolysis shows a heterogeneous reaction rate constant of 2.55E-4 s(-1) with R-2 = 0.984. This study provides a systematic approach to characterize the chemical and physical properties of the gas- and particle-phase Nap ozonolysis in real time, which will deepen our understanding of the migration and transformation of PAHs in the atmosphere.

关键词： Naphthalene Homogeneous and heterogeneous reaction Secondary organic aerosol Ozonolysis

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Quantitative description of self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose and citric acid solution based on molecular dynamics simulations

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PHYSICS OF FLUIDS 2025年第5期37卷

作者： Bao, Han Zhang, Chao Pan, Silin Zhang, Zhichao Yang, Yang Li, Shaopeng Wang, Yueshe Wiedensohler, Alfred Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Marine Diesel Engine Res Inst Shanghai 201100 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Leibniz Inst Tropospher Res D-04318 Leipzig Germany

The diffusion coefficient plays a crucial role in predicting the equilibration timescale of atmospheric aerosol particles, however current knowledge on the subject remains limited. In this study, the self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose (SC) and citric acid (CA) solution are investigated using the molecular dynamics (MD) method. key aspects include comparisons with experimental and theoretical models, as well as the effects of temperature and solute concentration on diffusion coefficients. The results demonstrate that MD results align well with experimental data. Additionally, the McCarty-Mason equation and the Darken equation generally underpredict the self- and Maxwell-Stefan diffusion coefficients, respectively. The self-, Maxwell-Stefan, and Fick diffusion coefficients in SC and CA solutions exhibit a positive correlation with temperature and a negative correlation with solute mass fraction. Furthermore, the intensity of these influences varies: the impact of solute mass fraction on diffusion coefficients decreases with increasing temperature, while the effect of temperature diminishes with higher solute concentrations. Moreover, based on the MD simulation results, fitting formulas for the diffusion coefficients are also developed. This study underscores the value of the MD simulation method in accurately describing diffusion coefficients in solutions containing complex components.

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Numerical Study of Multi-Factor Coupling Effects on Energy Conversion Performance of Nanofluidic Reverse Electrodialysis

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Frontiers in heat and Mass transfer 2025年第2期23卷 507-528页

作者： Hao Li Cunlu Zhao Jinhui Zhou Jun Zhang Hui Wang Yanmei Jiao Yugang Zhao School of Physical and Mathematical Sciences Nanjing Tech UniversityNanjing211816China MOE Key Laboratory of Thermo-Fluid Science and Engineering Xi’an Jiaotong UniversityXi’an710049China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing210016China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai200093China Key Laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development CenterMianyang621000China

Based on the rapid advancements in nanomaterials and nanotechnology,the Nanofluidic Reverse Electrodialysis(NRED)has attracted significant attention as an innovative and promising energy conversion strategy for extracting sustainable and clean energy fromthe salinity gradient ***,the scarcity of research investigating the intricate multi-factor coupling effects on the energy conversion performance,especially the trade-offs between ion selectivity and mass transfer in nanochannels,of NRED poses a great challenge to achieving breakthroughs in energy conversion *** numerical study innovatively investigates the multi-factor coupling effect of three critical operational factors,including the nanochannel configuration,the temperature field,and the concentration difference,on the energy conversion processes of *** this work,a dimensionless amplitude parameter s is introduced to emulate the randomly varied wall configuration of nanochannels that inherently occur in practical applications,thereby enhancing the realism and applicability of our *** results reveal that the application of a temperature gradient,which is oriented in opposition to the concentration gradient,enhances the ion transportation and selectivity simultaneously,leading to an enhancement in both output power and energy conversion ***,the increased fluctuation of the nanochannel wall from s=0 to s=0.08 improves ion selectivity yet raises ion transport resistance,resulting in an enhancement in output power and energy conversion efficiency but a slight reduction in ***,with increasing the concentration ratio cH/cL from 10 to 1000,either within a fixed temperature field or at a constant dimensionless amplitude,the maximumpower consistently attains its optimal value at a concentration ratio of 100 but the cation transfer number experiences amonotonic decrease across this entire range of concentration ***,uponmodifying the ope

关键词： Salinity gradient energy nanofluidic reverse electrodialysis energy conversion nanochannel configuration multi-factor coupling effect

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Thermodynamic evaluation and comparison of direct geothermal power systems and their expanders

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ENERGY REPORTS 2021年 7卷 1319-1335页

作者： Tian, Yafen Geng, Yanting Zhao, Zhaorui Xing, Ziwen Zhang, Hua Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Peoples R China

Direct geothermal power system is an effective method to utilize medium-high temperature geothermal resources employing geothermal steam as working fluid. The most widely applied technology are single flash and double flash system. Recently, full flow system has been introduced into geothermal fields and developed to work with two-phase expansion in several geothermal fields in China. To theoretically understand the thermodynamic characteristics of these three direct geothermal power systems and their expanders, a comparative study and thermodynamic evaluation were performed in this paper. A thermodynamic model, taking into account the power consumption of cooling water pump and fan, was developed to simulate the performance of direct geothermal power systems and their expansion equipment. The effects of operating parameters were discussed and analyzed, including inlet dryness, inlet temperature and outlet temperature. Results showed that full flow system has larger output power and thermal efficiency than flashing systems, especially at lower inlet dryness. When inlet dryness is 0.1, the thermal efficiency of full flow system is 38% higher than that of single flash system. Moreover, the output power increases with inlet dryness under constant mass flowrate, but shows opposite variation trend under constant volume flowrate. Higher inlet temperature and lower outlet temperature lead to higher output power and thermal efficiency, however it is limited by the expansion ratio and volume flowrate of expanders. The full flow system is more competitive than flash systems when the isentropic efficiency of full flow expander can reach 50%-70%. (C) 2021 The Author(s). Published by Elsevier Ltd.

关键词： Geothermal power system Screw expander Steam turbine Full flow Efficiency

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Bionic Packings Enhance the Absorption of SO2 in a Bubble Column

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ENERGY & FUELS 2023年第18期37卷 14074-14085页

作者： Cai, Yuyang Wang, Zhen Liu, Dunyu Chen, Jun Jin, Jing Shi, Huancong Cheng, Qian Li, Wei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shanghai Marine Diesel Engine Res Inst Shanghai 200237 Peoples R China Dongfang Turbine Co Ltd Deyang 618099 Peoples R China Huzhou Inst Zhejiang Univ Huzhou 313000 Zhejiang Peoples R China Univ Regina Clean Energy Technol Res & Innovat Ctr Regina SK S4S 0A2 Canada

The development of compact reactors has attracted wide interest from chemical engineering society. Inspired by the special shape of "sea urchin", we propose that bionic packings with this type of shape are superior in breaking bubbles in a bubble column, and therefore, the mass transfer rate of gases in liquids may be greatly enhanced. In this study, different structures and quantities of bionic packings were added to a bubble column to enhance SO2 absorption into water. The absorption rates of SO2 into water with different bionic packings were compared with these systems with commercial packings of Pall rings and Dixon rings. The mass transfer coefficients and gas-liquid specific interfacial areas of different packings with the same volume of packings' addition were measured. Based on the comparison of SO2 removal efficiency for systems with different packings, the system with the addition of 24 "3.5 mm + 5 mm" packings presented the optimum promotion effect. The liquid volumetric mass transfer coefficient (k(L)a) of adding 24 "3.5 mm + 5 mm" packings was 1.5 times of the baseline, indicating that the process was mainly controlled by liquid-phase mass transfer. The increase of the liquid volumetric mass transfer coefficient (k(L)a) was the combined effect of the increased liquid-phase mass transfer coefficient (k(L)) and the specific interfacial area (a).

关键词： Absorption Bubbles Liquids Mass transfer Oxidation

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Heterogeneity of nanoparticle deposition micro-structure and modeling deposition layer thickness variation underneath periodically growing single boiling bubbles in nanofluids

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AIP ADVANCES 2023年第12期13卷 125319-125319页

作者： Wang, Dongmin Lin, Gaoshuai Dong, Wuhan Gao, Min Shang, Lixing Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Yanjie Environm Equipment Co Ltd Shanghai 201413 Peoples R China

Nanoparticle deposition in nanofluid boiling can significantly impact heat transfer efficiency. However, there is still much to be uncovered regarding the heterogeneity of micro-structures in nanoparticle deposition and how to quantitatively model variations in deposition layer thickness. To gain a deeper understanding, we conducted experiments where single boiling bubbles were grown from an artificial micro-cavity in SiO2 nanofluids with varying concentrations and durations under a constant heat flux. Our results reveal that the nanoparticle deposition region increases with concentration and boiling duration. Notably, while the deposition morphology is irregular near the bubble nucleation site, it becomes more uniform further away from the bubble nucleation site. We believe that the heterogeneity in the micro-structure of the deposition layer is due to differences in the evaporation time of the liquid microlayer at different positions, variations in its thickness beneath a single boiling bubble, and dependency of nanoparticles Brownian motion on temperature. Additionally, the thickness of the deposition layer decreases as the distance from the nucleation site increases. To accurately describe this variation in thickness, we have proposed a semi-empirical correlation based on the liquid microlayer evaporation theory and the conservation of mass of nanoparticles beneath a single boiling bubble. The thickness of the nanoparticle deposition layer is determined by the number of growing bubbles, liquid density, initial thickness of the liquid microlayer, local nanoparticle concentration, and local nanoparticle stacking density. This study provides valuable insights into optimizing micro-structures or thickness of the deposition layer, leading to improved nanofluid boiling heat transfer.

关键词： Nanoparticles

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