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Experimental Investigation on flow and Heat Transfer Characteristics of Helium in Rectangular Narrow Slit Channel

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SSRN 2024年

作者： Li, Changzhong Wang, Chenglong Sun, Yanyu Chen, Ronghua Tian, Wenxi Su, Guanghui Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering China Department of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China China Nuclear Power Engineering Co. Ltd. Beijing100840 China

Helium is utilized as coolant in high temperature gas cooled reactors. Rectangular narrow slit channels are commonly present in the core. The flow and heat transfer properties of helium significantly affect the core temperature and flow distribution. This paper experimentally investigates the flow and heat transfer properties of high temperature helium in rectangular narrow slit channel. The Reynolds numbers ranged from 468 to 5327, the temperature ratio of wall to bulk from 0.91.to 1.22, the helium outlet temperature up to 944 K, and the maximum heat flux density up to 0.1.1.MW/m². In the experiment, the total and local convective heat transfer coefficients, along with the friction factors, are measured. Correlation equations for the Nusselt number and friction factor with respect to Reynolds number are derived. The primary findings are as below: the friction factors of helium in rectangular narrow slit channels are significantly larger than those calculated by current empirical correlations. In the turbulent zone, the measured local Nusselt numbers are in excellent accordance with the Gnielinski correlation;however, a significant discrepancy exists in the laminar zone. New flow heat transfer correlation equations are proposed on the bases of experimental data. Upon comparison, the total Nusselt numbers fall in the error of 1.%, and almost all local Nusselt numbers and the friction factors fall in the error of 20%. © 2024, The Authors. All rights reserved.

关键词： Helium

Investigation of Macro-fin Structure on Heat Transfer Performance of Close-Loop R41.A Flashing Spray Cooling 15

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Investigation of Macro-fin Structure on Heat Transfer Perfor...

1.th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Zhou, Zhifu Ji, Renjie Chen, Bin Thrassos, Panidis State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Laboratory of Applied Thermodynamics Mechanical Engineering Aeronautics Department University of Patras Rio Patras26504 Greece

The rapid development in performance, integration and miniaturization of electronics and other high power devices cause huge heat flux values. However, transitional cooling methods can hardly meet the requirement of dissipating effectively the high heat flux at the normal working temperature (usually smaller than 75 oC). The refrigerants flash evaporation spray cooling with phase change has been considered as one of the most promising technologies of heat dissipation for electronic devices and other high power devices due to its high heat removal capability at relatively low surface temperature, cooling uniformity, non-corrosivity. This study presents an experimental study on the heat transfer performance of the close-loop R41.A flashing spray cooling, mainly focusing on the influence of macro-fin structure of cooling surface. The flat, square fin, pyramid fin surfaces and a newly designed tetrahedral fin surface are systematically examined. The results indicate that the newly designed tetrahedral fin surface has superior cooling performance than other fin surfaces. © 2021.ICLASS 2021.- 1.th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Electronic cooling

Regulating Surface Terminals and Interlayer Structure of Ti3c2tx for Superior Nh3 Sensing

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SSRN 2024年

作者： Li, Jiazheng Li, Yanqiong Zeng, Wen Bai, Bofeng Ren, Shan College of Materials Science and Engineering Chongqing University Chongqing400030 China School of Electronic information & Electrical Engineering Chongqing University of Arts and Sciences Chongqing400030 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

MXene materials have exhibited potential in electrochemistry, particularly in gas sensing, due to their excellent conductivity, large specific surface area of layered materials, and unique functional groups. However, the gas sensing performance of intrinsic 2D MXene materials is often limited by their fluorine-containing terminals and interfacial structure. In this study, based on intrinsic Ti3C2Tx, we employed alkali treatment and annealing to prepare oxygen-rich Ti3C2(OH)x/Ti3C2Ox with expanded interlayer spacing, achieving enhanced gas sensing performance for NH3. By utilizing the intercalation effect of layered materials and the synergistic effect of regulating MXene unique surface terminations, the sensing materials prepared have achieved optimization of surface chemistry and structural. Compared to intrinsic Ti3C2Tx, the interlayer spacing of oxygen-rich Ti3C2(OH)x/Ti3C2Ox increased from 9.1.Å to 1..1.Å. The surface terminations of oxygen-rich Ti3C2(OH)x/Ti3C2Ox have been defluorinated and oxygenated. The maximum response value of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3 was 35.66, approximately twice that of the original Ti3C2Tx at an NH3 concentration of 200 ppm. DFT (Density functional theory) calculations and DRIFT (In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy) tests explained the interaction between the surface terminals and NH3, indicating good selectivity and sensitivity of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3. The results of this study demonstrate that the synergistic effects of surface chemistry and structural engineering are crucial for MXene to optimize the electrochemical performance, particularly the gas sensing performance. This provides a feasible approach for the performance optimization of intrinsic MXene materials. © 2024, The Authors. All rights reserved.

关键词： Oxygen

Influence of Bi3+ Doping on the Electrochemical Properties of Ti/Sb-Sno2/Pbo2 Electrode for Zinc Electrowinning

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SSRN 2024年

作者： Wu, Jia Kang, Xuanqi Xu, Shuangwen Wei, Zhen Xu, Shangyuan Liu, Kang Feng, Qing Jia, Bo Wang, Yunhai Xían Taijin New Energy & Materials Sci-Tech CO. Ltd Xi’an710016 China Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiao tong University Xi’an710049 China

Bi3+ doped Ti/Sb-SnO2/PbO2 electrode materials were fabricated by electrodeposition to improve its electrochemical performance in zinc electrowinning. The surface morphology, chemical composition and hydrophilicity of the as-prepared electrodes are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and contact angle. The electrochemical measurement and the accelerate lifetime experiment are also conduct to investigate the electrocatalytic performance and stability of the electrodes. The results showed that Bi3+ modification electrode has an important effect on the coating morphology, crystal structure, surface hydrophilicity, electrocatalytic activity and stability. The electrode prepared from the solution containing 2 mmol·L-1.Bi(NO3)3 (marked as the Ti/Sb-SnO2/2Bi-PbO2 electrode) exhibits the best hydrophilicity performance (θ=21.6°) and the longest service life (1.96 h). During the electrochemical characterization analysis, the Ti/Sb-SnO2/2Bi-PbO2 electrode showed the highest oxygen evolution activity, which can be attributed to the highest electroactive surface (qT*=21.20 C·cm-2) and the best charge transfer efficiency. DFT calculation demonstrate that the doping of Bi lead to the decrease in the OER reaction barrier and increase the DOS of the electrode, which further enhanced the catalytic activity and conductivity of the electrode. Moreover, the simulated zinc electrowinning experiment demonstrate that the Ti/Sb-SnO2/2Bi-PbO2 electrode consume less energy than other electrodes. Therefore, it is expected that the Bi modified electrodes may become a very promising electrode material for zinc electrowinning in the future. © 2024, The Authors. All rights reserved.

关键词： Hydrophilicity

Pani Grafted Onto Waste Poros Polyurethane for Co-Adsorption of Multiple Pollutants in Industrial Wastewater

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SSRN 2023年

作者： Wang, Ning Guo, Yirui Song, Yi Yan, Wei Gong, Xuesong Li, Yunfeng Mu, Ruihua Liu, Yonghong Zhang, Luohong School of Environmental and Chemical Engineering Xi'an Polytechnic University Xi'An710048 China Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China

Up-taking the pollutants simultaneously from industrial wastewater is an urgent in the advanced treatment. In this work, the polyaniline (PANI)-based efficient adsorbent supported by the waste polyurethane(PU) was designed for synchronous adsorption of pollutants (acid red G (ARG), methylene blue (MB), hexavalent chromium Cr(VI), phosphorus (TP), NH4+-N (ammonia nitrogen), NO3-N (nitrate nitrogen) and COD (chemical oxygen demand)). The results showed that the synchronous removal efficiency of ARG, MB, Cr(VI), TP, NH4+-N, NO3-N and COD in simulated wastewater reached 88%, 40%, 90%, 58%, 42%, 30% and 63%, respectively. The adsorption lasted for 1.00 min (1.4 columns) before saturation, and no significant decrease was observed after 5 cycles of regeneration. Combined with the XPS (X-ray photoelectron spectroscopy) and EEM (excitation-emission matrix spectroscopy) analysis, ARG, Cr(VI), NO3-N and TP competed for the same adsorption sites, and the adsorption affinity order was ARG>Cr(Ⅵ)>TP>NO3-. During the adsorption process, Cr(VI) and =N- in PANI chain underwent redox reaction to form Cr(III) and -NH+-, which further promoted the adsorption of anionic pollutants, like H2PO4-. Redox reactions also occurred between Cr(VI) and MB before adsorption forming Cr(III) and small organic fragments. These conclusions prove the feasibility and effectiveness of PU-P/T as a potential engineering adsorbent for co-adsorption of a variety of pollutants. © 2023, The Authors. All rights reserved.

关键词： Adsorption

Efficient Water Recovery and power Generation System Based on Air-Cooled Fuel Cell with Semi-Closed Cathode Circulation Mode

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SSRN 2024年

作者： Yang, Yuchen Wu, Zhen Yao, Jing Wang, Bofei Yang, Fusheng Zhang, Zaoxiao Ren, Jianwei School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering Science University of Johannesburg Johannesburg2092 South Africa

Air-cooled proton exchange membrane hydrogen fuel cell with on-line hydrogen production by hydrolysis has potential for portable applications due to its high volumetric power density and self-humidification. However, plenty of reserve water significantly reduces the power density of fuel cell system. Moreover, water recovery from fuel cell tail gas is difficult, because the tail gas humidity is very low due to excess cathode air as coolant. In this work, the dead-ended anode and semi-closed cathode proton exchange membrane fuel cell is proposed to achieve efficient water recovery and energy conversion via semi-closed cathode circulation mode. In this mode, cathode O2-poor tail gas is recycled as coolant instead of fresh air, which helps to enlarge the tail gas humidity by reducing the stoichiometric ratio of cathode to anode gas. The system lumped model with detailed component description is developed for optimization. More than 96% water production can be recycled under atmosphere temperature. The demand of fresh air is greatly reduced from 56 to 2 times of the consumption. Besides, the multi-objective optimization between water recovery and electrochemical performance shows high-efficiency water recovery of 94.70% and high energy conversion efficiency of 54.82%. © 2024, The Authors. All rights reserved.

关键词： Cathodes

Optimization of Heliostat Fields Using Advanced Particle Swarm Optimization (APSO) 4

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Optimization of Heliostat Fields Using Advanced Particle Swa...

4th IEEE International Conference on Renewable Energy and power {1., REPE 2021

作者： Rizvi, Arslan A. Yang, Dong Khan, Talha Ali Xi'An Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China University of Europe for Applied Sciences Department of Data Science Potsdam Germany

ISBN: (纸本)9781665443715

Optical losses account for 40% of all the losses in a central receiver system. These optical losses occur due to factors like shading, blocking, atmospheric attenuation, spillage, cosine loss, and mirror reflectivity. These factors are collectively represented using a single factor known as optical efficiency. There exists a tradeoff among these factors. The unavoidable optical loss can be minimized by optimizing the positions of heliostats in a strategic manner. An advanced particle swarm algorithm is used to optimize the position of heliostats around a dense radial staggered field. An efficiency map of the heliostat field is generated. Using instantaneous optical efficiency as an objective function, a single objective optimization is performed using 30 particles and 2 dimensions (each dimension representing an optimization variable). The results highlight the areas in the heliostat field with the highest losses associated with different components of optical efficiency and their solution. The instantaneous efficiency increases by 1.5% after optimization. © 2021.IEEE.

关键词： Particle swarm optimization (PSO)

Rate-limiting factors in thin-film evaporative heat transfer processes

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arXiv

arXiv 2024年

作者： Zhao, H. Poole, R. Zhou, Z. Wolfson School of Mechanical Electrical and Manufacturing Engineering Loughborough University Loughborough LeicestershireLE11 3TU United Kingdom State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

In this paper, we present a theoretical study aimed at investigating the rate-limiting factors in thin-film evaporative heat transfer processes, considering the finite-rate evaporation kinetics. The problems of evaporation of a flat thin-film in either pure vapours or vapour-inert-gas mixtures are analysed based on the non-dimensionalised macroscopic transport equations for continuum fluids, coupled with out-of-equilibrium kinetic boundary conditions. Both the full numerical solutions and asymptotic analytical solutions at slow evaporation limit are provided and applied to analyse thin water film evaporation. Existing solutions, assuming negligible heat transfer in the gas domain, or negligible temperature jump across the non-equilibrium kinetic layer, or more boldly a thermodynamically equilibrial interface (i.e. its temperature is at the saturation temperature), can be fully recovered from the more general solutions presented here. Our results show that while these assumptions hold in special cases, they can lead to significant errors in many conditions, especially when the film thickness δ is reduced to a few micrometers or thinner. We show that the conventional views that the rate-limiting factors in thin-film evaporative heat transfer is either the heat diffusion through the liquid film or the mass transfer in the gas domain only apply to thick film (i.e. δ λ where λ is the mean free path in the vapour phase). As δ decreases to a few micrometer or smaller (more precisely when the Knudsen number Kn increases beyond O(1. in an pure vapour environment or when the kinetic Peclet number Pe is reduced below O(1. in inert gases), the interfacial thermal resistance due to the evaporation kinetics can be on the same orders of magnitude as the thermal resistance in the liquid film. The analysis also allow us to compare the heat transfer processes during the evaporation of a thin-film in pure vapours to those in inert gases, providing deeper insight into the effectiveness

关键词： Thin films

Rotor Dynamic Analysis of Supercritical Carbon Dioxide Bryton Cycle Coaxial Integrated Unit

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Rotor Dynamic Analysis of Supercritical Carbon Dioxide Bryto...

Prognostics and System Health Management Conference (PHM-Qingdao)

作者： Xiaokang Xu Yi Yang Jiangfeng Wang Juwei Lou Liangqi Chen State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an China Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and Technology National University of Defense Technology Changsha China

The rotor system plays a very important role in supercritical carbon dioxide Brayton cycle system, and its dynamic problem will directly affect the motion stability and safety of the whole unit. In this paper, the rotor dynamic model of supercritical CO 2 coaxial unit is established by finite element method, and the critical speed, modal shape and unbalance response of the rotor are studied. The first seven critical speed of the rotor and the first seven natural frequency of the rotor at the working speed are calculated. The bending modal of the rotor and the position where the rotor amplitude is the largest are analyzed, which can provide reference for the optimization design of the rotor stability. The influences of mass unbalances at the operational speed of rotor are analyzed. The research can provide some suggestions for the optimal design and actual operation of the supercritical CO 2 coaxial integrated unit.

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