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Transient Cooling Performance of R134a Flash-Evaporation Spray Enhanced by Cold Air Jet: A Novel Heat Transfer Enhancement Method in Laser Dermatology

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SSRN 2022年

作者： Li, Bufa Wang, Junfeng Tian, Jiameng Chen, Bin Xu, Haojie School of Energy and Power Engineering Jiangsu University Zhenjiang212013 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Nevus of Ota is a dermal hyperplastic pigmented disease with a morbidity rate of 0.1%–0.6% in the Asian population. Laser surgery with the assistance of cryogen spray cooling (CSC) is a potential clinical treatment for nevus of Ota. However, for Asians with high melanin content, it is necessary to enhance cooling capability without the increment of refrigerant amount. In this study, a R134a flash-evaporation cryogen spray cooling coupled with cold air jet (CSC-CAJ) was developed to improve the cooling capacity. Epoxy resin was employed as a skin phantom to investigate the heat transfer characteristics of CSC-CAJ with different air jet parameters. Air jet parameters of CSC-CAJ are recommended to be T a = -7 °C, V a = 3 m 3 /h Z a = 10 mm and Φ a = 30°. Compared to CSC, CSC-CAJ could reduce the minimum surface temperature from -39 °C to -42.1 °C, and the average value of convection heat transfer coefficient ( h ) of CSC-CAJ could increase from 8 W/(m 2 ·k) to 12.9 W/(m 2 ·k) or 61.3% for the recommended parameters. The liquid film residence time ( τ ) decreases from 301 ms to 234 ms or 23.3%. In addition, based on the visualization observation and surface heat transfer measurement, the frost formation phenomenon on the surface and the heat transfer enhancement mechanisms are well understood. Four modes, including Leidonfrost mode, no runoff mode, runoff mode and evaporation mode, are proposed to describe the four stages of CSC-CAJ. A non-dimensional correlation of normalized Nusselt number ( Nu *) and time ( t *) is summarized. The primary heat transfer enhancement mechanism of CSC-CAJ is found to be the increase in cryogen evaporation rate and the ratio of heat removal from the phantom surface to phase change latent heat. © 2022, The Authors. All rights reserved.

关键词： Evaporation

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Dynamic simulation of coal-fired power plant integrated with trough solar collector operating in parallel with high pressure heaters

Dynamic simulation of coal-fired power plant integrated with...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Yan, Hui Li, Xin Liu, Ming Chong, Daotong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (纸本)9780791883747

Solar-aided coal-fired power plant (SACFPP) is a costeffective approach to overcome solar energy intermittency. SACFPPs frequently operate in dynamic processes due to power load and solar energy fluctuations. This study investigated the dynamic characteristics of SACFPPs;such characteristics are important for flexibility evaluation and control system design. The SACFPP used in this study was based on a 660 MW coalfired power plant, and a trough collector system (TCS) operates in parallel with high pressure (HP) heaters. After model development and validation, the dynamic performance of the SACFPP was analyzed under four load ratios of power plant, with disturbances of two parameters: direct normal irradiance (DNI) and mass flowrate ratio to TCS. The performance was also compared with three parallel TCS connection modes. Results showed that the magnitude and response time for power variation under DNI disturbance increased with load ratio. With 500 W/m2 DNI step increments, power increased by approximately 18.4, 21.2, 24.7, and 29.8 MW in 2200, 2330, 2550 and 2620 s at 70%, 80%, 90%, and 100% load ratios, respectively, when all the HP heaters were replaced. The serial number and the number of HP heaters replaced also increased the power variation and response time. Under mass flowrate ratio to TCS increase disturbance, the power rapidly changed to its maximum and then slowly decreased, but the variation value depended on the load ratio. Copyright © 2020 ASME.

关键词： Coal fired power plant

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Conducting Polymers Meet Lithium-Sulfur Batteries:Progress,Challenges,and Perspectives

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Energy & Environmental Materials 2023年第5期6卷 159-182页

作者： Xin Chen Chengcheng Zhao Kai Yang Shiyi Sun Jinxin Bi Ningrui Zhu Qiong Cai Jianan Wang Wei Yan Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'an 710049China Xi'an Key Laboratory of Solid Waste Recycling and Resource Recovery Department of Environmental EngineeringXi'an Jiaotong UniversityXi'an 710049China Advanced Technology Institute University of SurreyGuildfordSurrey GU27XHUK College of Arts College of Landscape Architecture Fujian Agriculture and Forestry UniversityFuzhou 350108China Department of Chemical&Process Engineering Faculty of Engineering and Physical Sciences University of SurreyGuildford GU27XHUK

Lithium-sulfur(Li-S)batteries have attracted increased interest because of the high theoretical energy density,low cost,and environmental *** polymers(CPs),as one of the most promising materials used in Li-S batteries,can not only facilitate electron transfer and buffer the large volumetric change of sulfur benefiting from their porous structure and excellent flexibility,but also enable stronger physical/chemical adsorption capacity toward polysulfides(LiPSs)when doped with abundant heteroatoms to promote the sulfur redox kinetics and achieve the high sulfur *** review firstly introduces the properties of various CPs including structural CPs(polypyrrole(PPy),polyaniline(PANi),polyethylene dioxothiophene[PEDOT])and compound CPs(polyethylene oxide(PEO),polyvinyl alcohol(PVA)and poly(acrylic acid)[PAA]),and their application potential in Li-S ***,the research progress of various CPs in different components(cathode,separator,and interlayer)of Li-S batteries is systematically ***,the application perspective of the CPs in Li-S batteries as a potential guidance is comprehensively discussed.

关键词： conducting polymers Li-S batteries modified materials polysulfides

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Characteristics of Bubble Dynamic Behavior on the Surface of Photoelectrode Under the Influence of a Vertical Magnetic Field

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SSRN 2023年

作者： Feng, Yuyang Wang, Yechun Zhang, Bo Cao, Zhenshan Liu, Miaomiao Zhen, Canghao Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xinjin Weihua Institute of Clean Energy Research Nanhai District Guangdong Province Foshan City China

The magnetohydrodynamic (MHD) flow around the bubble induced by the Lorentz force owing to the applied magnetic field significantly affects the behavioral characteristics of the bubble on the electrode surface. However, the mechanism of the impact of a magnetic field perpendicular to the electrode on the dynamic behavior of bubbles remains unclear. In this study, the evolution law of a single oxygen bubble on the surface of a TiO2 photoelectrode under the influence of a vertical magnetic field with different magnetic induction intensities was investigated. The vertical magnetic field effectively promoted the rapid detachment of bubbles from the electrode surface, and greatly improved the gas evolution efficiency. The mass transfer was dominated by single-phase free convection during bubble evolution. Under the influence of the vertical magnetic field, the mass transfer coefficient near the electrode was enhanced, and the adverse effects of bubbles on mass transfer were counteracted when they entered the reaction-controlled growth phase. The further multiphysics simulation found that the MHD convection decreased the local supersaturation of reaction product oxygen molecules near the electrode, thereby reducing concentration overpotential and increasing the reaction rate. This study provides an experimental and theoretical basis for promoting the bubble detachment and the reaction rate on the gas evolving electrode surface during photoelectrochemical water splitting. © 2023, The Authors. All rights reserved.

关键词： Efficiency

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X-ray computed tomography (XCT) study of jetting in a fluidized bed: Effects of two-component fluidization

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Particuology 2025年 102卷 264-274页

作者： Xiang, Zhong Chen, Xi Liu, Shuguang Heindel, Theodore J. School of Energy and Environment Southeast University Nanjing210096 China State Key Laboratory of Low-carbon Smart Coal-fired Power Generation and Ultra-clean Emission Southeast University Nanjing210096 China Center for Multiphase Flow Research and Education and Department of Mechanical Engineering Iowa State University AmesIA50011 United States

Fluidization of non-spherical particles is commonly found in the biomass and solid waste processing industry, and the jetting characteristic above the aeration plate is critical to the fluidization performance of these particles. In this study, cylindrical particles are used as typical non-spherical particles and co-fluidized with small bed material particles. X-ray computed tomography (XCT) is used to reconstruct the 3D structure of the aeration plate region, allowing for the identification of individual aeration jets. The effects of jet velocity (Uj), cylindrical particle mass fraction (ω), cylindrical particle density (ρi), and the cylindrical particle sphericity () on jet shape and volume are investigated. The experimental results indicate that decreasing the cylindrical particle mass fraction (ω) and particle density (ρi) increases the jet length (L), maximum jet diameter (D), and maximum jet volume (V), but have little effect on the jet half angle (θ). The cylindrical particle density (ρi) is the most sensitive factor for jet shape, while the effect of cylinder particle sphericity () on jet shape is insignificant. A correlation of jet length (L) in a two-component fluidized bed with cylindrical particles and bed material is proposed based on all the experimental results. © 2025 Chinese Society of Particuology and Institute of Process engineering, Chinese Academy of Sciences

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Experimental Study on the Performance Difference of Pulsating Heat Pipe Using R170 and R134a as Working Fluids

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SSRN 2023年

作者： Song, Yuxin Chen, Xi Zhan, Jingru Zhang, Hua School of Energy and Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China

The pulsating heat pipe (PHP), as a type of heat pipes, is a flexible heat transport device with highly efficient conduction, which is widely used in many fields including aerospace, waste heat recovery, cryogenic refrigerator and so on. The working fluids have an important effect on the thermal performance of PHPs. This study experimentally compares a PHP with R170 and R134a as the working fluids, respectively, examining temperature fluctuations, thermal resistance, and temperature differentials. Findings indicate that R170 PHP exhibits sensitivity to heat input (HI), with temperature fluctuations stagnating at 70 W. Increasing the filling ratio (FR) from 30% to 60% results in a steady rise in R170 PHP thermal resistance. While R170 PHP thermal resistance increases with higher inclination angles (IAs), it does so to a lesser extent compared to R134a PHPs. In the temperature region of -20 ℃ to 0 ℃, both R170 and R134a perform similarly. However, as the working temperature (WT) decreases, R170 PHP outperforms R134a PHP. Overall, the thermal performance of R170 PHP is superior to R134a PHP. This study provides reference value for the future research of PHPs in the temperature region of -60 ℃ to 0 ℃. © 2023, The Authors. All rights reserved.

关键词： Heat resistance

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Experimental Study on Stable Jet Impact Process Under Simulated Pipeline Rupture

Experimental Study on Stable Jet Impact Process Under Simula...

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Student Conference on Research and Development (SCOReD)

作者： Zhang Tao Bi Qincheng Zhao Jinle Wang Teng Chen Jingrong Feng Fan State Key Lab Multiphase Flow Power Engn Xi’an Jiaotong University Xi’an Shaanxi China School of Energy Power and Mechanical Engineering North China Electric Power University Bao’ding Hebei China

ISBN: (数字)9798350318821

ISBN: (纸本)9798350318838

In this study, an advanced experimental system was utilized that incorporated heating, jetting, recycling, and cooling capabilities to ensure the successful execution of stable jet impact experiment that simulating a pipeline complete rupture. High-temperature resistant tempered glass was employed in the experimental system to realize the visibility. During the experiment, 8mm pipes/nozzles of varying lengths were employed as the test sections, and jetting phenomena when the import status is single-phase cold water or two-phase mixture at 0-2MPa were obtained by high-resolution photos. Additionally, the shape of the jet cone and the impact force exerted on the target plate were meticulously analyzed after the working fluid under different state parameters jetting into an atmospheric pressure environment through pipes/nozzles. The research also focused on the variation trend in the magnitude of the jet-impact force, as a function of inlet pressure and temperature, target plate distances, and length-to-diameter ratios. The research findings revealed that cold water(below 100°C), sub-cooled water(above 100°C but not reaching saturation temperature), and two-phase steam-water mixture exhibited distinct jet cone shapes during the jetting process, resulting in varying distributions of the jet force. Furthermore, the distance from the spout to the target plate and the length-to-diameter ratio significantly influenced the magnitude of the jet impact force.

关键词： Resistance Visualization Temperature distribution Fluids Shape Force Pipelines

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Unveiling micro- and nanoscale bubble dynamics for enhanced electrochemical water splitting

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Advances in Colloid and Interface Science 2025年 343卷 103544页

作者： Lu, Xinlong Yadav, Devendra He, Baichuan Zhou, Yu Zhou, Liwu Zeng, Zilong Ma, Lijing Jing, Dengwei International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China Department of Chemical Engineering Technion - Israel Institute of Technology Haifa3200003 Israel College of Mechanical Engineering Xi'an Shiyou University Shaanxi Xi'an710065 China

Bubbles generated during electrochemical and photoelectrochemical water splitting critically influence efficiency through complex factors, including chemical reactions, species transport, mass transfer at the three-phase interface, and bubble coverage. A detailed understanding of the nucleation, growth, coalescence, and detachment of micro- and nanoscale bubbles is vital for advancing water splitting technologies. Surface-attached bubbles significantly reduce the electrocatalytically active area of electrodes, leading to increased surface overpotential at a given current density. Consequently, their effective removal is pivotal for optimizing the electrolysis process. However, the intricate interplay among single bubble evolution, mass transport, bubble coverage, and overpotential remain inadequately understood. This review explores the fundamental mechanisms underpinning bubble evolution, with an emphasis on the Marangoni effect and its influence on bubble dynamics. Furthermore, recent advancements in understanding individual bubbles on micro and nano-electrodes are highlighted, offering valuable insights into scale-dependent bubble behavior. These findings enrich our knowledge of gas-liquid interfacial phenomena and underscore their industrial significance, presenting opportunities to enhance water splitting performance through optimized bubble dynamics. © 2025

关键词： Electrolysis

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Development, Validation and Application of Sub-Channel Thermal-Hydraulic Analysis Code for Liquid Metal Cooled Reactor

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SSRN 2024年

作者： Wang, Jinshun Chen, Ronghua Liang, Yu Gui, Minyang Zhu, Xinyang Tian, Wenxi Qiu, Suizheng Su, Guanghui School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China College of Nuclear Science and Technology Harbin Engineering University Harbin150001 China

The liquid metal reactor, specifically the lead-based fast reactor and the sodium-cooled fast reactor, are generally recognized as the most significant representatives of the Gen IV reactors due to their sustainability, economy, security and reliability. In order to conduct thermal-hydraulic safety analysis for liquid metal cooled fast reactors, adaptive improvements are made to the model and solution algorithms based on the sub-channel analysis method, and a Sub-channel Analysis Code Of Safety for Liquid Metal cooled Reactor (SACOS-LMR) is developed. The validation of SACOS-LMR is conducted using classic experimental data of liquid metal. The results show that the dimensionless temperature deviations of ORNL 19-pin test and Toshiba 37-pin test are within 10%, and the relative temperature deviations of KIT-KALLA 19-pin test are within 25%. These findings confirm the accuracy and reliability of SACOS-LMR in predicting the temperature distribution of liquid metal reactors. Ultimately, calculations conducted on the ALFRED lead-cooled fast reactor demonstrated the practical utility of the code and have certain guiding significance for its subsequent design and development. © 2024, The Authors. All rights reserved.

关键词： Liquid metals

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General analytical equation of state for nanoconfined gases derived from statistical physics

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Physical Review E 2025年第2期111卷 025413-025413页

作者： Chengzhen Sun Haoxuan Li Zhixiang Zhao Mehdi Neek-Amal Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China School of Urban Planning and Municipal Engineering Xi'an Polytechnic University Xi'an Shaanxi 710048 China Department of Physics Faculty of Sciences Shahid Rajaee Teacher Training University 16875-163 Lavizan Tehran Islamic Republic of Iran Department of Physics University of Antwerp Groenenborgerlaan 171 2020 Antwerp Belgium

The pressure prediction of nanoconfined gases is crucial for various industrial applications, yet existing equations of state (EOS) often compromise between accuracy and usability. This study derives a theoretical EOS in analytical form, combining precision and practicality through statistical physics. It begins by examining the pressure drop mechanism due to adsorbed molecules and refines molecular pairing and potential energy interactions. The resulting EOS accurately predicts the pressure of gases in nanoconfined spaces, especially with an average prediction error of about 5% for strongly adsorbing gases like nitrogen, oxygen, and argon. Additionally, it aligns with the Van der Waals EOS under macroscopic conditions, offering a unified framework across scales. This model enhances both engineering applications and the understanding of nanoconfined EOS.

关键词： Van der Waals forces

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