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Entropy Generation of R513A Condensation flow Inside the Horizontal Microfin Tubes

JOURNAL OF THERMAL SCIENCE AND engineering APPLICATIONS 2024年第7期16卷 071002-071002页

作者： Zhang, Suhan Tao, Leren Huang, Lihao Jin, Cheng 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

It is widely acknowledged that the pressure drop increases with enhanced heat transfer in heat exchanger tubes, and entropy generation analysis serves as an effective method to comprehensively evaluate heat transfer and pressure drops. This paper conducts experimental research on in-tube condensation heat transfer using refrigerants R513A and R134a in six test tubes, comprising both smooth and microfin tubes with outer diameters of 9.52 mm and 12.7 mm, respectively. The microfin tubes are available in two types, with 60 and 65 fins, respectively, and a helix angle of 18 deg. The experimental conditions included mass fluxes of 50-250 kg/m(2) s and condensation temperatures of 35 degrees C, 38 degrees C, and 40 degrees C. The findings indicate that replacing R134a with R513A is feasible. The 9.52 mm tube exhibits superior overall heat transfer performance compared to the 12.7 mm tube, and the 60-fin microfin tube outperforms the 65-fin tube in terms of heat transfer efficiency. This suggests that microfin tubes with smaller diameters and an optimal number of fins are more effective in enhancing condensation heat transfer performance. Graphical Abstract Figure

关键词： R513A and R134a microfin tube condensation heat transfer entropy generation minimization analysis thermophysical properties

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Experimental and numerical analysis of the multilayer distributed Joule-Thomson cooler with pillars

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2021年第4期45卷 6086-6103页

作者： Geng, Hui Cui, Xiaoyu She, Hailong Chang, Zhihao Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai Peoples R China

The conventional Joule-Thomson cooler is not compact in heat exchanger and insufficient in cooling capacity, which is limited in applying integrated electronics. However, microchannels with pillars are effective in increasing the area to volume ratio and enhancing heat transfer through the presence of vortex. Besides, multilayer microchannels are essential to enlarge the mass-flow rate in the cooler. In this study, a multilayer distributed J-T cooler with pillars is investigated. A new mathematical model of the cooler is developed and validated against the experimental data;the relative errors of the temperature and mass-flow rate are both within 5%. Furthermore, the distribution of temperature and pressure in the microchannel is analyzed by the model calculation. Numerical results show that the temperature of the high-pressure fluid decreased slightly under the influence of the heat exchange and distributed J-T effect. When the inlet pressures are 3.00, 4.00 and 5.40 MPa, the cold-end temperatures are 233.0, 185.8 and 161.2 K, respectively, with the cooling capacity reaching 2.25, 3.40 and 3.87 W, respectively. In addition, the influences of the axial heat conduction and heat leakage on the cooling performance are analyzed by using the models. The temperature rise of the cold end increases by 6.8 and 6.2 K at 5.40 MPa, respectively, considering the above two factors. The simulation model provides a useful tool for the J-T cooler.

关键词： cooling capacity heat transfer J‐ T cooler microchannel pressure drop

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Study of Unforced Unsteadiness in Centrifugal Pump at Partial flow Rates

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Journal of Thermal Science 2021年第1期30卷 88-99页

作者： YANG Jun XIE Tian LIU Xiaohua SI Qiaorui LIU Jun School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Fluid and Power Machinery(Xihua University) Ministry of EducationChengdu 610039China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China Research Center of Fluid Machinery Engineering and Technology Jiangsu UniversityZhenjiang 212013China

In order to explore the unforced unsteadiness of centrifugal pumps,a 2-D frequency domain imaging display technology was used to study the development of these unsteady flow structures at partial flow *** results showed that,the unsteady flow field was not only affected by rotor and stator interaction,but also appeared an unforced unsteadiness with fundamental frequency of St≈0.23 around the impeller throat ***,as the flow rates decreased,this unsteady flow structure gradually weakened and *** the flow rate was reduced to 0.6 times of design flow rate,another two unforced unsteady flow structures with characteristic frequencies of St≈0.0714 and St≈0.12 began to appear in the same ***,with the operating condition smaller than design flow rate,the internal flow became more and more *** addition to the forced unsteadiness,the unforced unsteadiness which is not connected with the blade passage frequency became more and more obvious.

关键词： centrifugal pumps partial flow conditions pressure pulsations unforced unsteadiness 2-D frequency domain visualization method

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Temperature dependence photoluminescence properties of ZnSe-based core-shell quantum dots

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Optics Express 2025年第11期33卷 22588-22597页

作者： Zhang, Tingting Ma, Qing Li, Qingping Huang, Lanting Feng, Yuqiong Duan, Hongwei Chen, Xinlei Li, Qinghua Jin, Xiao Bai, Jinke Xu, Bing Key Laboratory of Environmentally Friendly Functional Materials and Devices School of Physics Science and Technology Lingnan Normal University Guangdong Zhanjiang524048 China School of Energy and Power Engineering Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Department of Materials and Chemical Engineering Taiyuan University Taiyuan030032 China

Heavy metal-free ZnSe-based core-shell quantum dots (QDs) are promising emitting material for achieving violet-blue luminescence. Investigating the temperature-dependent variations in the photoluminescence (PL) properties of ZnSe-based QDs will enhance our understanding of the intrinsic factors that influence their diverse luminescence characteristics. Here we select the optimally synthesized ZnSe core QDs with three diameters (4.1, 5.2, and 8.3 nm) and ZnSe/ZnS core-shell QDs to study their temperature-dependent photoluminescence properties. As the sample temperature is increased, the PL intensity decreases, the emission energy redshifts, and the spectral become broader. We observe a reduction in the exciton-longitudinal optical (LO)-phonon coupling constant from 21.7 meV to 16.1 meV as the diameter of ZnSe core QDs increased from 4.1 nm to 8.3 nm. This decrease is associated with a narrower homogeneous broadening of the emission spectrum. Besides, the epitaxial growth of a ZnS wide bandgap shells onto the ZnSe core QDs can effectively isolate the photogenerated excitons away from the inorganic-organic interface, thus reducing the PL peak width and increasing the exciton binding energy of the QDs. Our research provides a valuable addition to the existing studies on the photoluminescence properties of ZnSe-based core-shell QDs. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Atomic emission spectroscopy

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An improved DSMC method for acoustic agglomeration of solid particles assisted by spray droplets

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INTERNATIONAL JOURNAL OF multiphase flow 2024年 176卷

作者： Zhao, Hao Fan, Fengxian Su, Junxu Hu, Xiaohong Su, Mingxu 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

The direct simulation Monte Carlo (DSMC) method was improved for describing the process of acoustic agglomeration assisted by spray droplets. The agglomeration and rebound as consequences of inter -particle collisions were modeled by considering all possible particle types, in particular, mixed -phase particles associated with the immersion and distribution mechanisms. Numerical predictions by the present method were validated by both analytical solutions and experimental data. The dynamic process of the acoustic agglomeration in terms of the size and type evolution as well as the evolution of number concentration of different particle types were examined. Results suggest that the strong interaction between the solid particles and the spray droplets causes the significant enhancement of acoustic agglomeration. Furthermore, the effect of frequency varying from audible to ultrasonic range on the acoustic agglomeration was evaluated. Overall, a better performance of acoustic agglomeration can be achieved at a lower frequency, regardless of addition of spray droplets. Agglomeration efficiency of 64.8 % can be achieve at acoustic frequency of 1000 Hz in case with spray droplets. This study provides not only a numerical model for describing the agglomeration of complex particles in particleladen gas flows, but also important insights into the acoustic agglomeration assisted by spray droplets.

关键词： Direct simulation Monte Carlo (DSMC) method Acoustic agglomeration Mixed-phase particle Particle-laden gas flow Numerical simulation Model validation

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Molecular dynamics investigation on structural and interfacial characteristics of aerosol particles containing mixed organic components

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ATMOSPHERIC ENVIRONMENT 2024年 319卷

作者： Zhang, Chao Zhang, Zhichao Xiong, Wei Yang, Yang Wang, Yueshe 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 Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Microscopic morphology plays a significant role in the description of aerosol particle evolution, but the knowledge on particles containing mixed organic matters is insufficient. In this study, molecular simulation (MD) method is employed to investigate the morphologies of particles containing two or three of malonic acid (MA), adipic acid (AA) and eicosane (C20). The key point is the effects of organic species and water content on structural and interfacial characteristics of particles. Results show that all dry particles exhibit the approximate core-shell structure with the shell composed of organic with longer hydrocarbon chain. With water content increasing from 100 to 1000, MA + AA + H2O particles present the core-shell structure with decreasing MA in the core, while particles containing C20 successively exhibit the core-shell structure and the ball-cap structure with three layers. These structural differences are caused by the surface propensity of organics, which is positively correlated with both the length of hydrocarbon chain and the water content. At the particle surface, hydrophobic groups of organic molecules direct towards the gas phase. MA (AA) located between water droplet and C20 cluster orient their hydrophobic groups toward C20. Furthermore, ratios of hydrophilic and hydrophobic atoms (K) at the surface of all studied particles increases with increasing water content, and at each water content the order is K(MA + AA) > K(MA + AA + C20) > K(AA + C20) > K(MA + C20). These findings provide microscopic information support for the development of theoretical model for the particle formation and growth.

关键词： Aerosol particles Microscopic structure Interface Molecular dynamics simulation

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Characterization of a distributed Joule-Thomson effect cooler with pillars

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2021年第9期45卷 13965-13977页

The application of general Joule-Thomson (J-T) coolers in the integrated electronic equipment is limited by its compactness in the heat exchanger and cooling power (a few milliwatts to hundreds of milliwatts). However, the microchannel with pillars has many advantages, such as compact structure, tiny axial thermal conductivity, and large heat transfer area. Besides, when the pressure variation of the fluid is large in the microchannel, the distributed Joule-Thomson effect is generated significantly. Therefore, this study proposed a throttling and heat exchange structure, where heat transfer and throttling coexisted, and fabricated a laminated microchannel distributed J-T cooler with pillars utilizing the processing technology of printed circuit heat exchanger. The refrigeration performance concerning the cold-end temperature, cooling power, and temperature distribution was then investigated through experiments with two refrigerants (argon and nitrogen). The study implies that the temperature difference and cooling power of the cooler both increase with the rise of the inlet pressure with argon, the no-load cold-end temperature is 166.1 K, and the gross cooling power is 3.83 W at 5.20 MPa. The temperature of the cooler increases with the rise of heat load, while the parasitic heat load decreases. The cold-end temperature is 186.0 K, then the parasitic heat load and the gross cooling power are respectively 3.17 W and 7.17 W at 5.20 MPa under the heat load's condition of 4 W. Comparing the refrigeration performance of nitrogen and argon, the cold-end temperature of nitrogen at 5.20 MPa is 235.7 K, which is close to that of argon at 2.98 MPa. Whereas the cooling time of nitrogen is slightly shorter than that of argon, and the cooling power is 3.10 W, higher than that of argon. In addition, this study provides new insight into increasing the cooling power and reducing the application cost of miniature coolers.

关键词： cooling power distributed Joule‐ Thomson effect microchannel PCHE pillars

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Depth from Defocus Technique for High Number Densities and Non-Spherical Particles

SSRN

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SSRN 2024年

作者： Xu, Rixin Huang, Zuojie Gong, Wenchao Zhou, Wu Tropea, Cameron School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering Shanghai China Institute for Fluid Mechanics and Aerodynamics Technical University of Darmstadt Darmstadt Germany

The Depth from Defocus (DFD) imaging technique for measuring the size and number concentration of particles in a dispersed two-phase flow has up to now been restricted to relatively sparse particle densities and to identifying only spherical particles. The present study examines two advancements to the technique, widening its range of application significantly. The first advancement introduces an image processing procedure which can identify and size particle images which are overlapping. This increases the tolerable number concentration of particles which can be identified and processed within the measurement volume. The second advancement explores the possibility of determining the size and position of non-spherical particles within an observation volume. These enhancements are experimentally validated using a dedicated apparatus in which particles of known size, shape and degree of overlapping images can be systematically varied. This experimental setup provides benchmark data to quantify the accuracy and limitations of the processing algorithms. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

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Enhanced catalytic activity for simultaneous removal of PCDD/Fs and NO over carbon nanotubes modified MnO_(x)-CeO_(2)/TiO_(2)catalyst at low temperatu

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Waste Disposal and Sustainable Energy 2021年第1期3卷 63-71页

作者： Qiulin Wang Zhuping Jiang Jianjian Zhou Jin Jing School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Henan Diesel Engine Industry Co LtdLuoyang 471000China

Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO ***-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was *** comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen *** addition improves the catalytic activity for their simultaneous *** optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed *** results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO ***,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen *** the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simulta

关键词： o-DCBz catalytic oxidation Simultaneous removal MnO_(x)-CeO_(2)catalyst Composite carrier Carbon nanotube

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The proposal and calculation method of the annular domain weight function for the electromagnetic flowmeter under annular conductivity distribution

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flow MEASUREMENT AND INSTRUMENTATION 2024年 100卷

作者： Yang, Yang Yang, Biaohu Zhang, Chao Yang, Bin 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

Researching on the characteristic of weight function distribution under non-uniform conductivity distribution is of significant importance for expanding the engineering applications of electromagnetic flowmeter. In this paper, the characteristic of weight function distribution is firstly explored for annular conductivity distribution where the center and outer ring are both conductive. The research results indicate an important finding that the average value of the weight function within any small annular domain of the center or outer ring remains constant as the radial position changes. Therefore, the concept of 'annular domain weight function' is then innovatively proposed. Furthermore, the relationship is studied between the ratio of the annular domain weight function of the center and outer ring and the annular feature parameters. Ultimately, the correlations are obtained for calculating the annular domain weight functions of the center and outer ring.

关键词： Electromagnetic flowmeter Weight function Annular conductivity distribution Annular domain weight function

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