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Depth from defocus technique with convolutional neural networks for high particle concentrations

EXPERIMENTS IN FLUIDS 2025年第1期66卷 1-11页

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

Recent advantages in the depth from defocus technique for the size and location determination of particles in dispersed two-phase flows have enabled the technique to detect and analyze spherical particle images in flow systems with high number concentrations. In the present study, the use of convolutional neural networks for this task will be explored, with comparisons to the conventional analyses in terms of accuracy, tolerable concentration limits and computational speed. This approach requires a large teaching dataset of images, which is only practical and feasible if the dataset can be synthetically generated. Thus, the first development to be presented is an image generation procedure for out-of-focus neighboring spherical particles resulting in a known blurred image overlap. This image generation procedure is validated using laboratory images of known particle size distribution, position and image overlap, before creating a teaching dataset. The trained processing scheme is then applied to both synthetic datasets and to experimental data. The synthetic datasets allow limits of image overlap and tolerable volume concentration limits of the technique to be evaluated as a function of particle size distribution.(https://***/xu200911/Generate-overlapping-out-of-focus-particles)

关键词： Convolutional neural networks

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Experimental study of a rectangular microchannel printed circuit heat exchanger using supercritical carbon dioxide and water cooling

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APPLIED THERMAL engineering 2025年 262卷

作者： Ren, Yan Jiang, Ruowen Wang, Peidong Wu, Weidong Yang, Yingying Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Elect Power Generat Equipment Co Ltd Turb Shanghai 200240 Peoples R China

Printed circuit heat exchangers with rectangular microchannels (RM-PCHEs) have attracted interest in recent years owing to their excellent heat-transfer performance and efficient and convenient processing methods. However, experimental studies on RM-PCHE using supercritical carbon dioxide (SCO2) and cooling water as working fluids are still scarce. This study established an experimental system to investigate the flow and heattransfer characteristics of an RM-PCHE. The experiment considered inlet temperature ranges of 343.13-371.1 K for SCO2 and 283.13-293.13 K for the cooling water. The results showed that the SCO2 inlet temperature had the most significant effect on the heat-transfer performance. With a 1 % increase in the SCO2 inlet temperature, the test sample Qave increased by 2.18 %, and thermal performance decreased by 2.62 %. Decreasing the SCO2 inlet temperature or increasing the cooling-water inlet temperature improved the hot-side flow performance. The cold-side pressure drop and effectiveness were most significantly affected by the cooling-water mass flow rate and minimally affected by the cooling-water inlet temperature. The effectiveness increased to 96.9 % with an increase in the cooling-water mass flow rate to 1500 kg & sdot;h- 1. These results provide theoretical and data support for the structural design and performance optimization of SCO2 microchannel water coolers.

关键词： Printed circuit heat exchanger Supercritical carbon dioxide Cooling water flow and heat-transfer characteristics Rectangular microchannel

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Numerical study on the wake characteristics of a square cylinder in linearly stratified flow at a Reynolds number of 200

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PHYSICS OF FLUIDS 2025年第3期37卷

作者： Wei, Na Shi, Liuliu Chen, Eryun Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Jiao Tong Univ Key Lab Power Machinery Engn Minist Educ Shanghai 200240 Peoples R China

In this study, the flow structures and hydrodynamic forces acting on a square cylinder in a linearly stratified flow at a fixed Reynolds number of Re = 200 are analyzed using large eddy simulation across a Froude number range of 0.2 <= Fr <= infinity. This study examines the effects of stratification on flow structures and associated hydrodynamic coefficients, employing both qualitative and quantitative analysis. The findings indicate that the flow patterns can be categorized into two primary types: the V pattern and the W pattern. In the V pattern (2 <= Fr <= 10), the wake is characterized by large-scale vortices shed from the separated shear layers. In contrast, the W pattern (0.2 <= Fr <= 1) shows a complete absence of vortex shedding. In this case, internal waves are the primary factor influencing the flow field. A transition between these two patterns is observed at a Froude number of 1. Furthermore, as the strength of stratification increases, the size of the recirculation zone progressively diminishes, signifying a gradual suppression of vertical motion. The analysis of drag and lift coefficients, Strouhal number, and pressure coefficient reveals a dependence on the Froude number, with the transition at Fr = 1 serving to further validate the classification of the flow patterns.

关键词： Hydrodynamics

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Performance Analysis of Low GWP Refrigerants R1234yf and R448A in a Small High and Low-temperature Test Equipment

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Recent Patents on Mechanical engineering 2022年第3期15卷 277-284页

作者： Liqiang, Zhou Zhang, Hua Zilong, Wang Wenjing, Gao School of Energy and Power University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

Aim: The article presents an analysis of the feasibility of R1234yf and R448A, two new low GWP refrigerants, as alternatives to R404A in the refrigeration system of small high and low-temperature test equipment. Methods: The physical properties of R448A and R404A are similar. Compared with R404A, the GWP of R1234yf and R448A reduced by 99.9% and 67.7%, respectively. The analysis is based on an experimental comparison of R404A with R448A and R1234yf, comparing the compressor discharge tempera-ture, COP, cooling capacity, and the cooling rate of three refrigeration systems at different ambient temperatures. Results: The experimental results show that the cooling capacity of R448A is better than R404A at a higher condensing temperature. Conclusion: When the charging volume is 230g, and the ambient temperature is 25°C, the COP of the R448A system is increased by about 24.63% compared with the R404A system. © 2022 Bentham Science Publishers.

关键词： Refrigerants

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Fully coupled aero-hydrodynamic analysis of a biomimetic fractal semi-submersible floating offshore wind turbine under wind-wave excitation conditions

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RENEWABLE ENERGY 2023年第1期203卷 280-300页

作者： Huang, Haoda Liu, Qingsong Yue, Minnan Miao, Weipao Wang, Peilin Li, Chun Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

With wind energy utilization shifting to the deep sea, floating offshore wind turbines (FOWTs) have huge po-tential to improve the competitiveness of offshore wind energy generation. However, traditional FOWT systems are often in force imbalance due to the unique swaying characteristics caused by the unfixed foundation and high center of mass of the platform. Therefore, a novel bionic semi-submersible floating platform based on Victoria Amazonia (with random fractal structure) is proposed to increase the hydrodynamic stability of FOWT. A regular fractal structure with similar number of perforations and perforated area is also implemented to verify the effectiveness of the bionic FOWT. In this study, the unsteady computational fluid dynamic approach is adopted to simulate the aerodynamic and hydrodynamic response. More specifically, the dynamic fluid-body interaction module integrated in STAR-CCM+ is employed to establish a FOWT numerical model with rotating blades, tower, and mooring line system. Furthermore, the volume of fluid model in conjunction with the 6-DOF solver was used to efficiently solve the fluid-induced dynamic motion of FOWT in a multi-phase flow composed of air and water. Finally, the fully coupled calculation of the fractal structure FOWT was performed using the established reliable numerical model. The maximum average thrust and power of 736.43 kN and 5294.04 kW are obtained by random fractal FOWT in aerodynamic responses, while in hydrodynamic amplitude responses, the maximum decreases of 19.16% are obtained by both random fractal and regular fractal structures. As for amplitude re-sponses in heave and surge, the random fractal FOWT of 12.91% and 5.05% decreases performs relatively better than the regular one (11.48% and 4.09% decreases). In addition, the visualization of unsteady flow fields and vortices in fractal structures is investigated in detail. Compared with the regular fractal structure, vortices within random fractal structure interact

关键词： Floating offshore wind turbine Dynamic fluid body interaction Computational fluid dynamics Fractal structure Fully coupled aero-hydrodynamics

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Quantitative description of surface tension for nanodroplets containing ammonium sulfate and its application to the particle hygroscopicity prediction

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PHYSICS OF FLUIDS 2025年第1期37卷

作者： Zhang, Chao Lin, Haoyang Zhang, Zhichao Yang, Yang Pan, Jinxiong 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 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

Surface tension is critically important in the hygroscopicity prediction of nano-aerosols, but experimental measurements of suspended nanodroplet surface tension are currently unattainable. In this study, effect of size and solute concentration on the surface tension of aqueous ammonium sulfate (AS) droplet smaller than 10 nm is investigated based on molecular dynamics simulations. A surface tension formula is proposed and applied in the theoretical model for particle hygroscopicity, and the prediction is compared with models using traditional methods of surface tension description. Results show that with the increase in AS concentration, surface tension decreases first and then increases, and the correlation between surface tension and droplet size changes from positive to negative. Compared to the surface tension model considering only the AS concentration effect, the surface tension formula including both AS concentration and size corrections enables the particle hygroscopicity model to obtain a smaller hygroscopic growth factor, which is closer to the experimental results. The improvement effect of the new formula on the model accuracy increases with the decreasing particle size. Additionally, the new surface tension formula leads to an increase in the critical supersaturation for particles smaller than 5 nm but a decrease for larger particles. The present study highlights the importance of the molecular dynamics investigation for nanodroplets comprising of complex ingredients.

关键词： Surface tension

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Experimental Investigation on flow Pattern and Bubble Behavior during Subcooled flow Boiling of R1233zd(E)in Parallel Channels

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Journal of Thermal Science 2023年第6期32卷 2374-2385页

作者： FANG Yidong ZHANG Zhao XU Dan WANG Yuchen YANG Huinan HUANG Yuqi School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093China Key Laboratory of Clean Energy and Carbon Neutrality of Zhejiang Province Jiaxing Research InstituteZhejiang UniversityJiaxing314031China Key Laboratory of Smart Thermal Management Science&Technology for Vehicles of Zhejiang Province Taizhou317200China

In this study,the flow pattern and bubble behavior of R1233zd(E)during subcooled flow boiling in parallel channels are experimentally investigated with visualization and thermal *** test section is composed of 21 rectangular mini channels with the hydraulic diameter of 1.5 mm and the length of 140 *** flow,slug flow,churn flow and wavy-annular flow occur in sequence with the increase of vapor quality,while transient flow pattern transition process involving multiple flow patterns are also *** distribution of flow pattern is non-synchronized and axial-asymmetric,with earlier flow pattern transitions observed in peripheral channels away from the center *** initial nucleate site in each channel also show a random and axial-asymmetric distribution,while faster bubble growth can be noted in some channel under the comprehensive effects of liquid evaporation and bubble *** variation of heat transfer coefficient is correspondence to the flow pattern transition,showing different trends along the flow *** increase of mass flux can lead to delayed flow pattern transition and variation of heat transfer *** addition,higher heat transfer coefficient can be noted in channels away from the center axis.

关键词： flow boiling flow pattern bubble behavior parallel channel visualization

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Simple synthesis of AgInS2/ZnS core/shell quantum dots with wide tunable emission wavelength for white light-emitting diodes

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OPTICS COMMUNICATIONS 2025年 575卷

作者： Ma, Qing Yang, Bin Yan, Fengrui Sun, Yanzi Yuan, Jiandi Li, Qingping Huang, Lanting Zhang, Tingting Li, Qinghua Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Lingnan Normal Univ Sch Phys Sci & Technol Zhanjiang 524048 Peoples R China

Phosphor with efficient and broad range emission is necessary for lighting applications. I-III-VI group quantum dots (QDs) have the advantages of non-toxic composition and large adjustable spectrum range, and have potential applications in the field of lighting. However, the efficient luminescence of these QDs at shorter wavelengths still needs further study, which is crucial for the development of high color rendering index white light LED devices (WLEDs). In this work, wide visible range emitting AgInS2/ZnS QDs with broad band and high luminous efficiency were obtained by altering the Ag/In ratios and Zn2+ inter-diffusion with cation of AgInS2. Photo-luminescent (PL) wavelength range of the obtained core-shell structured AgInS2/ZnS extended from 703 nm to 524 nm with high PL quantum yield (QY) and stability. The champion device based on the optimized AgInS2/ZnS QDs exhibits warm white light (correlated color temperature = 3652 K) characteristics with high color rendering index (CRI Ra) of 92.85 while maintaining excellent color stability under different driving currents. These properties are far superior to those of WLEDs with YAG phosphor.

关键词： White light-emitting diodes AgInS2/ZnS Tunable emission Color rendering index

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Flame temperature and emissivity distribution measurement of solid propellant based on clustering analysis of multispectral radiation images

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OPTICS LETTERS 2024年第21期49卷 6161-6164页

作者： Ni, Hu Qiang, Kejie Wang, Wensong Yang, Bin Tao, Jinxin Yang, Yang Shi, Zhiquan Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Space Prop Technol Res Inst Shanghai 201109 Peoples R China

To measure the combustion parameters of a solid propellant, this Letter researches the fitting method for flame temperature and emissivity based on multispectral images and proposes the particle swarm optimization-K-means (PSO-K-means) clustering optimization algorithm of a flame multispectral image. Considering the difference in flame radiation characteristics in different regions, the flame multispectral image is clustered, and spectra in different regions are analyzed and selected in different fitting bands to inverse temperature and emissivity. On this basis, the method is applied to measure solid propellant combustion parameters with different formulations. The measurement shows that the flame temperature is between 1700 and 2100 K, and the emissivity is concentrated in 0.1-0.5. Compared with temperature measurements obtained from tungsten-rhenium thermocouples, the relative deviation of multispectral imaging thermometry is less than 5%. The distribution characteristics of solid propellant combustion parameters with different formulations were analyzed, which provided important data support for evaluating combustion conditions and optimizing solid propellant formulations. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Emissivity Image analysis Machine learning Multispectral imaging Spatial resolution Temperature sensors

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Thermodynamic and economic performance analysis of a liquid carbon dioxide energy storage system coupled with absorption refrigeration cycle

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ENERGY 2025年 319卷

作者： Wang, Yuhong Chen, Xi Xu, Jingxuan Lu, Yilin Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P 516 Jungong Rd Shanghai 200093 Peoples R China

Energy storage technology provides solutions for accommodating renewable energy and effectively managing power grid electricity. In recent years, liquid CO2 energy storage (LCES) has gained prominence among researchers due to considerable round-trip efficiency (RTE) and energy storage density (ESD) without geographical limitation. However, due to the high latent heat of vaporization at low temperature, the condensation of CO2 at the outlet of the turbine has emerged as a significant challenge that researchers are grappling with. Low-grade industrial waste heat (WH) is often neglected due to low power generation efficiency, but it can be employed as the driving heat source for the absorption refrigeration cycle (ARC). Therefore, this paper designs and investigates the liquid CO2 energy storage coupled with absorption refrigeration cycle (ARC-LCES), which is modeled in Aspen HYSYS and optimized by a multi-parameter genetic algorithm in Matlab. The ARC-LCES system demonstrates a high electrical round-trip efficiency (ERTE), ESD and exergy efficiency of 400.99 %, 10.78 kWh/m3 and 63.31 %, respectively. According to the economic analysis, Net present value (NPV) and levelized cost of electricity (LCOE) are 3.9703 million USD and 0.1008 USD/kWh. The results show that the proposed system may play an important role in managing power grid electricity and improving energy efficiency.

关键词： Carbon dioxide energy storage Exergy analysis Absorption refrigeration cycle Waste heat recovery Multi-parameter genetic algorithm optimization

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