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Experimental Study of Pool Boiling Heat Transfer on Hydrophilic and Hydrophobic Surface Coupled Micro-Pin-Finned

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SSRN 2023年

作者： Song, Gege Ma, Xiang Xu, Pengzhuo Zhang, Yonghai Weia, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Xi’an Navigation Technology Research Institute Shannxi Xi’an710068 China Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The pool boiling heat transfer properties of uniform micro-pin-finned surface, hydrophilic and hydrophobic surface were evaluated by employing FC-72 as the working medium. Three hydrophilic and hydrophobic coupled rectangular copper column surfaces (HH4, HH9, and HH16) were invented in order to investigate their boiling heat transfer characteristics further. The effect of several subcoolings (0K, 15K, and 25K) on the critical heat flux was explored by connecting the micro-pin-finned surface (PF) and the smooth surface (SS). A high-speed camera was set up to study the bubbles' behaviors. The results reveal that the hydrophilic and hydrophobic coupled micro-pin-finned copper surface can achieve a higher critical heat flux (CHF) than the rectangular micro-pin-finned surface, but heat transfer performance (HTC) drops slightly (both saturated boiling and subcooling boiling). Visual monitoring demonstrates that the hydrophilic and hydrophobic coupled rectangular micro-pin-finned copper surface may successfully avoid bubble coalescence, especially during subcooled boiling. Furthermore, the hydrophilic and hydrophobic coupled rectangular micro-pin-finned copper column surface described in this paper might serve as an ideal replenishment route to avoid drying and delay the emergence of a boiling crisis. The factors responsible for the impact of the Lattice width coefficient and the Vapor column spacing coefficient on CHF were analyzed. Fluid replenishment and bubble formation behavior were applied to clarify the strengthened heat transfer and triggering mechanism of CHF on the surface of the hydrophilic and hydrophobic coupled rectangular micro-pin-finned copper column surface. © 2023, The Authors. All rights reserved.

关键词： Heat flux

Pool Boiling Heat Transfer Enhancement on the Hybrid Surfaces Coupling Capillary Wick and Minichannels

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SSRN 2022年

作者： Zhang, Yonghai Ma, Xiang Wang, Jinyu Liu, Wanbo Wei, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Pool boiling heat transfer can fully utilize the latent heat of the vaporization, to meet the heat dissipation needs of high-power electronic components. In this study, several enhanced hybrid surfaces were designed and processed by sintering spherical copper powder on the minichannels in different ways. The coupled effects of various parameters of capillary wick and minichannels were considered to enhance the pool boiling heat transfer performance of these hybrid surfaces using HFE-7100 as the working fluid. The bubble dynamic behaviors were captured and analyzed by the high-speed camera. The results indicate that the ring groove around the minichannels and the capillary wick have a significant impact on the boiling heat transfer of these hybrid surfaces. This is because the capillary wick provide a large number of nucleation sites and large specific surface area, which can greatly reduce the contact thermal resistance between the capillary wick and the minichannels. At ΔTsub = 30 K, the critical heat flux (CHF) of hybrid surfaces coupling capillary wick and minichannels is up to 147.4 W/cm2, and its maximum heat transfer coefficient (HTC) is 2.69 W/(cm2·K). Compared with minichannels without capillary wick covered, the CHF and HTC are increase by 86.8% and 192.0%, respectively. Furthermore, a correlation for predicting CHF on these hybrid surfaces covered capillary-wick is proposed. Dimensionless parameters such as the subcooled Jakob coefficient (Jasub), the outer surface area enhancement ratio (AER), the particle distribution coefficient (PDC) and the ratio of inner to outer surface area of capillary wick (IOR) are defined to estimate the effect of different factors on the CHF. © 2022, The Authors. All rights reserved.

关键词： Heat flux

Design and Optimal Thermal Efficiency Contrastive Analysis on Closed Brayton Cycle Systems with Different Fluids of Fluoride-Salt-Cooled High-Temperature Advanced Reactor

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SSRN 2022年

作者： Li, Xinyu Zhang, Dalin Yun, Shichang Zhou, Xingguang Jiang, Dianqiang Lv, Xindi Feng, Zhenyu Wu, Wenqiang Tian, Wenxi Qiu, Suizheng Su, Guanghui Zhao, Quanbin Liu, Xiuting State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China

To match the advantages of Fluoride-Salt-cooled high-Temperature Advanced Reactor, the closed Brayton cycle system was selected as the energy conversion system, and the thermodynamic analysis, conjugate gradient optimization, and exergy analysis were performed. The pinch point constraint method based on simultaneous equations was proposed to improve the calculation efficiency and ensure the unity of comparison standards, and the exergy analysis was used to quantify and optimize the exergy losses for the equipment. For the simple regenerative cycle configuration, the thermal efficiency and mass flow rate of the cycle system with various fluids (far-critical fluids: air, nitrogen, helium, and argon, near-critical fluids: carbon dioxide, sulfur hexafluoride, propane, and xenon) were analyzed. The results of the thermodynamic analysis show that the thermal efficiency of the sulfur hexafluoride cycle is the highest and reaching 46.6% with the simple regenerative cycle configuration. The thermal efficiency of the far-critical fluid cycle is more sensitive to turbine efficiency. The results of the exergy analysis show the CO2 cycle has the highest potential to improve thermal efficiency, which has the highest improvement from 43.48% to 49.31% with the recompression process. The method and conclusion of this paper can provide references for the design and optimization of the Brayton power cycle system © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

The Role of Particle-Vortex Interaction in Hydraulic Performance and Erosion Behavior of Semi-Open Centrifugal Pump: Effect of Particle Size

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SSRN 2023年

作者： Wang, Kai Liu, Hanyu Wang, Like Guo, Pengcheng Wang, Yueshe Yang, Junfeng State Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi’an University of Technology No.5 Jinhua South Road Xi’an710048 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University No.28 Xianning West Road Xi’an710049 China Shaanxi Provincial Dongzhuang Water Conservancy Engineering Co. Ltd Xi’an713200 China

The interaction between the particle migration and vortex evolution aggravates the complexity of erosion on the flow components. In this work, the liquid-solid two-phase flow of semi-open centrifugal pump under different particle sizes is simulated based on the four-way coupling Euler-Lagrange method, in which the fluid-particle interaction and particle-particle interaction are taken into account. The interrelationship among vortex structure, particle migration and surface erosion behavior is revealed. The results show that the erosion area is mainly distributed in the blade leading edge, the pressure surface inlet edge and the hub. When the particle size is 0.1 mm and 0.3 mm, due to the good following characteristic of particles and the inhibition effect on tip leakage vortex, the particles are easy to impact the outlet edge of blade suction surface and the hub, which induce severe erosion. As the particle size decreases, the number of particles flowing into the tip clearance layer increases. Therefore, the frequent impact of particles on the tip leakage vortex leads to the breakup, separation and refusion of the vortex, which aggravates the flow instability. This paper provides a new insight into the hydraulic performance and erosion characteristics of semi-open centrifugal pump in terms of particle-vortex interaction. © 2023, The Authors. All rights reserved.

关键词： Particle size

Design and Optimal Thermal Efficiency Analysis on Closed Brayton Cycle System of Fluoride-Salt-Cooled High-Temperature Advanced Reactor (Fustar)

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SSRN 2022年

作者： Li, Xinyu Zhang, Dalin Yun, Shichang Zhou, Xingguang Jiang, Dianqiang Lv, Xindi Feng, Zhenyu Wu, Wenqiang Tian, Wenxi Qiu, Suizheng Su, G.H. Zhao, Quanbin Liu, Xiuting State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology Nuclear Power Institute of China Chengdu610213 China

To match the advantages of Fluoride-Salt-cooled high-Temperature Advanced Reactor (FuSTAR): the high temperature, inherent safety, compact structure, and modularization, the closed Brayton cycle system was selected as the energy conversion system, and the enthalpy analysis, conjugate gradient optimization, and exergy analysis were performed. The pinch point constraint method based on simultaneous equations was proposed to improve the calculation efficiency and ensure the unity of comparison standards, and the exergy analysis was used to quantify and optimize the exergy losses for the equipment. For the simple regenerative cycle configuration, the thermal efficiency and mass flow rate of the cycle system with various fluids (far-critical fluids: air, nitrogen, helium, and argon, near-critical fluids: carbon dioxide, sulfur hexafluoride, propane, and xenon) were analyzed, at the highest thermal efficiencies. The results of enthalpy analysis show that the thermal efficiency of the sulfur hexafluoride cycle is the highest with the simple regenerative cycle configuration. The thermal efficiency of the far-critical fluid cycle is more sensitive to turbine efficiency. The exergy analysis shows the CO2 cycle has the highest potential to improve thermal efficiency. The method and conclusion of this paper can provide references for the design and optimization of the Brayton power cycle system. © 2022, The Authors. All rights reserved.

关键词： Enthalpy

Solar-Wind Energy Complementary Coupling Realizes Magnetic-Field Assisted Efficient Photocatalytic Co2 Reduction

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SSRN 2023年

作者： Kong, Biao Ren, Yuqi Liu, Maochang Zhou, Jiancheng Wang, Ke Wang, Nan Li, Naixu School of Chemistry and Chemical Engineering Southeast University No.2 Dongnandaxue Road Jiangsu Nanjing211189 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Shaanxi Xi'An710049 China

We report the synthesis of a Z-scheme monolithic photocatalyst in the form of copper foam supported TiO2 combining Cu2O and Ag nanoparticles (CF@TiO2/Cu2O-Ag). The designed catalysts with efficient charge separation show superior photocatalytic activity toward CO2 reduction, with a maximum CO yielding rate of 25.58 μmol‧g-1‧h-1. More importantly, we develop a solar-wind energy complementary device, which enables the strong coupling of the magnetic field into the photocatalytic reaction. Specifically, the in-situ space electric field generated from the wind-driven induced electromotive force further enhances the separation and transportation of photogenerated charge carriers in the Z-scheme system. The productivity of CO in the proof-of-concept device based on the use of CF@TiO2/Cu2O-Ag catalyst reaches 71.66 μmol‧g-1‧h-1. This study provides an ideal approach for reinforcing photocatalytic CO2 reduction through muti-field coupling and highlights the prospect of solar-wind energy coupled photocatalysis. © 2023, The Authors. All rights reserved.

关键词： Titanium dioxide

Multi-parameter optimization to improve the erosion resistance of coating by FE simulation

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Multi-parameter optimization to improve the erosion resistan...

ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, GT 2021

作者： Li, Fang Wang, Shunsen Cai, Liuxi Feng, Zhenping State Key Laboratory of Multiphase Flow in Power Engineering Institute of Turbomachinery Xi'an Jiaotong University No. 28 Xianning West Road Xi'an710049 China School of Chemical Engineering and Technology Xi'an Jiaotong University No. 28 Xianning West Road Xi'an710049 China

ISBN: (纸本)9780791885000

Finite element method (FEM) was used to study the stress peak of stress S11 (Radial stress component in X-axis) on the steam turbine blade surface of four typical erosion-resistant coatings (Fe2B, CrN, Cr3C2-NiCr and Al2O3-13%TiO2). The effect of four parameters, such as impact velocity, coating thickness, Young's modulus and Poisson's ratio on the stress peak of stress S11 were analyzed. Results show that: the position of tensile stress peak and compressive stress peak of stress S11 are far away from the impact center point with the increase of impact velocity. When coating thickness is equal to or greater than 10μm, the magnitude of tensile stress peak of stress S11 on the four coating surfaces does not change with the coating thickness at different impact velocities. When coating thickness is equal to or greater than 2μm, the magnitude of tensile stress peak of stress S11 of four coatings show a trend of increasing first and then decreasing with the increase of Young's modulus. Meanwhile, the larger the Poisson's ratio, the smaller the tensile stress peak of stress S11. After optimization, When coating thickness is 2μm, Poisson's ratio is 0.35 and Young's modulus is 800 GPa, the Fe2B coating has the strongest erosion resistance under the same impact conditions, followed by Cr3C2-NiCr, CrN, and the Al2O3-13%TiO2 coating, Al2O3-13%TiO2 coating has the worst erosion resistance. Copyright © 2021 by ASME.

关键词： Finite element method

Effects of Hydrothermal and Hydrothermal Oxidation Pretreatments on Physicochemical Properties of High Value-Added Biochar Fuel Pellets and Activated Carbon Materials

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SSRN 2023年

作者： Lang, Sen Zhang, Shouyu Yang, Jifan Zhou, Yi Liu, Simeng Xu, Zihang Han, Xiuyuan Huang, Jiantian School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China Huazhan Aerospace Electric Appliance Co. LTD Aerospace Science and Industry Corporation Suzhou215129 China

In this paper, cotton stalk (CS) and Chinese fir sawdust (FS) were treated for hydrothermal pretreatment with or without H2O2, and then respectively pyrolyzed and activated to prepare biochar pellets and activated carbon materials. The results show that compared with hydrothermal pretreatment (HT), hydrothermal oxidation (HTO) pretreatment has stronger degradation ability of hemicellulose and cellulose. With the increase of pretreatment temperature, some decomposed substances repolymerize to form lignin-like substances. In the 160-260oC temperature range, the physical properties of biochar pellets prepared under HT 230oC and HTO 200oC are the best, and crystalline cellulose plays a key role in it. The calorific value and energy density of the biochar pellets obtained after pretreatment were consistent with the variation trend of their physical properties. The combustion characteristics of treated CS/FS biochar pellets gradually decreased with the increase of temperature. Compared with CS, FS biochar have better energy density and physical properties due to high cellulose content. The CS-HTO200-A has the highest specific surface area and pore volume, which is 118.1% and 111.7% higher than that of raw materials, and mainly consists of micropores. Cellulose is beneficial to increase the specific surface area of activated carbon, while lignin has the opposite effect. © 2023, The Authors. All rights reserved.

关键词： Physicochemical properties

Experimental and Kinetic Modeling Study on the Oxidation and Laminar Combustion Characteristics of Natural Gas

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SSRN 2023年

作者： Chen, Xiaoxiao Zeng, Wen Zheng, Weilin Hu, Erjiang Ma, Hongyu Liaoning Key Lab of Advanced Test Technology for Aerospace Propulsion System Shenyang Aerospace University Liaoning Shenyang110136 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shanxi Xi'An710049 China AECC Shenyang Engine Research Institute Shenyang110015 China

The oxidation process in the flow tube reactor at the conditions of P=0.1 MPa, T=500-1850 K, f=0.5, 1.0, 3.5, and the laminar combustion process in the constant volume combustion bomb at the conditions of P=0.1, 0.2, 0.3 MPa, T=300, 350, 400 K, f= 0.7-1.4, the O2 contents of 15%, 18% and 21%, the CO2 and H2O contents of 0%, 10%, and 20% of natural gas (0.9 methane/0.07 ethane/0.03 propane, mole fraction) were experimental tested. In the oxidation process of natural gas, with the equivalence ratio increasing, the starting and ending temperatures for oxidation reaction of natural gas are increased, the reaction temperatures corresponding to CO generation and consumption are higher, and the amount of NO production is decreased. In the the laminar combustion process of natural gas, at the conditions of higher pressure, equivalence ratio, CO2 and H2O contents, the flame front is not smooth as a large number of cracks and cell structures appear, and the flame is unstable. Moreover, with the initial temperature and oxygen content increasing or the initial pressure, CO2 and H2O contents decreasing, the laminar flame speed is increased. Furthermore, combined the path sensitivity analysis, rate of production analysis, reaction path analysis and the decoupling method, a reduced reaction mechanism (including 40 species and 189 reactions) of natural gas was developed. Through comparing with the calculated results by the Aramco 2.0 mechanism and the corresponding test data, the reduced reaction mechanism can well predict the oxidation, ignition delay and laminar combustion characteristics of natural gas under various conditions. © 2023, The Authors. All rights reserved.

关键词： Sensitivity analysis