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Particuology 2024年第7期90卷 404-411页

作者： Hanqiao Che Yuanhe Yue Zhaohua Jiang Duan Li School of Mechanical Engineering Guangxi UniversityNanningGuangxi530004China School of Chemical Engineering University of BirminghamBirminghamB152TTUK Hebei Engineering Research Center of Advanced Energy Storage Technology and Equipment School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China Hebei Key Laboratory of Thermal Science and Energy Clean Utilization School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China School of Mechatronics and Vehicle Engineering Chongqing Jiaotong UniversityChongqing400074China School of Instrumentation and Opto-Electronic Engineering Beihang UniversityBeijing 100191China

The transient heat transfer behaviours in a packed bed have been studied using coupled computational fluid dynamics(CFD)and discrete element method(DEM).Intra-particle thermal diffusion,which is a crucial but rarely explored issue,is considered by introducing a one-dimensional diffusion equation in the DEM solver.To achieve a sufficiently long physical time of simulations,we further reduce the computational cost by applying periodic boundary condition to a small segment of the packed bed.Our study demonstrates a shifting peak heat flow rate from the bottom to the top of the packed bed during the initial warming phase.We affirm that the influence of thermal diffusion within a particle is noteworthy only for particles exhibiting a high Biot number(e.g.,Bi=1.2).This insight enriches our understanding of heat transfer mechanisms in packed beds and their practical engineering applications.

关键词： packed bed Intra-particle heat transfer CFD–DEM

Ray tracing particle image velocimetry-Challenges in the application to a packed bed

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Particuology 2024年第1期84卷 194-208页

作者： Christin Velten Mirko Ebert Christian Lessig Katharina Zahringer Lehrstuhl für Strömungsmechanik und Strömungstechnik Otto-von-Guericke-Universität Magdeburg39106MagdeburgGermany Institut für Simulation und Graphik Otto-von-Guericke-Universität Magdeburg39106MagdeburgGermany

Ray tracing Particle Image Velocimetry(RT-PIV)is an optical technique for high resolution velocity measurements in challenging optical systems,such as transparent packed beds,that uses ray tracing to correct for distortions introduced by transparent geometries in the light paths.The ray tracing based correction is a post processing step applied to the raw PIV particle images before classical PIV evaluation.In this study,RT-PIV is performed in the top layer of a body centred cubic(bcc)sphere packing with gaseous flow,where optical access is obtained by the use of transparent N-BK7 glass balls with a diameter of d=40 mm.RT-PIV introduces new experimental and numerical challenges,for example a limited field of view,illumination difficulties,a very large required depth of field and high sensitivity to geometric parameters used in the ray tracing correction.These challenges and their implications are the main scope and discussed in the present work.Further,the validation of the ray tracing reconstruction step is presented and examples for the obtained corrected vector fields in a packed bed are given.The results show the strength of the method in reconstructing velocity fields behind transparent spheres that would not have been accessible by optical measurement techniques without the ray tracing correction.

关键词： Ray tracing particle image velocimetry(RT-PIV) Transparent spherical particles packed bed Distortion correction Gas flow

Investigating the inflow into a granular bed using a locally resolved method

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Particuology 2024年第2期85卷 89-101页

作者： Maximilian Brommer Maik Scharnowski Enric Illana Mahiques Siegmar Wirtz Viktor Scherer Ruhr University Bochum Institute of Energy Plant TechnologyUniversitätsstraβe 15044780BochumGermany

Discrete Element Method-Computational Fluid Dynamics(DEM/CFD)simulations of industrial-scale granular systems employ spatial averaging(porous media approach)for the fluid-particle interaction in the whole domain,which can lead to poor accuracy,for instance at flow inlets,as local particle bulk morphology is not resolved.This paper presents an approach where the interstitial flow in crucial areas with large gradients can be resolved locally in an otherwise unresolved domain,so that a mixed resolved-unresolved method is realized.As a generic example to show the feasibility and performance of the new approach,the inflow of ambient air into a flat-bottom hopper through a narrow orifice is investigated.In an experimental setup,the vertical profile of the pressure decay through the inlet and across the packing is chosen for com-parison with respective simulations.Results obtained with the conventional porous media method and the locally resolved approach are compared to these experiments for varying volume flow rates and for two different particle shapes.Spheres of different size as well as dodecahedrons are examined.It is found that although averaging methods already provide good approximations,the locally resolved method can improve the result especially when conventional drag laws are not applicable due to wall effects or if large velocity gradients exist.

关键词： DEM/CFD packed bed Pressure drop

packed bed Thermocline Thermal Energy Storage for Medium-Temperature Concentrating Solar Systems: Numerical and Experimental Study

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Journal of Power and Energy Engineering 2023年第5期11卷 1-23页

作者： Nikolaos Stathopoulos Nikolaos Papadimitriou Vassilis Belessiotis Elias Papanicolaou Solar and Other Energy Systems Laboratory Demokritos National Center for Scientific Research Attiki Athens Greece

Thermal Energy Storage is becoming a necessary component of sustainable energy production systems as it helps alleviate intrinsic limitations of Renewable Energy Sources, such as intermittent use and mismatch between power demand and supply. This paper discusses a packed bed thermocline tank as a thermal energy storage solution. Firstly, this paper presents the development of a numerical model calculating heat transfers within the tank, based on a discretization over several nodes and the nodal formulation of the heat balance equation. The model considers a filler material and a heat transferring fluid and uses the finite difference method to calculate the temperature evolution of the two media across the tank. The model was validated with two different packed bed systems from the literature during a discharging process, presenting a good fit with the experimental results. Secondly, the experimental packed bed is presented and characterized for a charging cycle from ambient temperature to approximately 180?C. The charging experiment was accurately reproduced with the numerical model requiring minimal computational time. Two additional charging modes were simulated with different inlet HTF conditions: constant temperature and varying temperature following the profile produced by a thermal solar collector field. The temperature profiles obtained from the three charging modes were analysed and compared to each other. The proposed numerical and experimental tools will be used in future studies for a better understanding of the design and operating conditions of packed bed thermal energy storage systems.

关键词： Thermal Energy Storage packed bed Numerical Model Experimental

Thermal performance of a single-layer packed metal pebble-bed exposed to high energy fluxes

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Frontiers in Energy 2021年第2期15卷 513-528页

作者： Shengchun ZHANG Zhifeng WANG Hui BIAN Pingrui HUANG Key Laboratory of Solar Thermal Energy and Photovoltaic System Chinese Academy of SciencesBeijing 100190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100190China Beijing Engineering Research Center of Solar Thermal Power Beijing 100190China 2.Lanzhou University of TechnologyLanzhou 730050China

It is difficult to accurately measure the temperature of the falling particle receiver since thermocouples may directly be exposed to the solar flux.This study analyzes the thermal performance of a packed bed receiver using large metal spheres to minimize the measurement error of particle temperature with the sphere temperature reaching more than 700°C in experiments in a solar furnace and a solar simulator.The numerical models of a single sphere and multiple spheres are verified by the experiments.The multiple spheres model includes calculations of the external incidence,view factors,and heat transfer.The effects of parameters on the temperature variations of the spheres,the transient thermal efficiency,and the temperature uniformity are investigated,such as the ambient temperature,particle thermal conductivity,energy flux,sphere diameter,and sphere emissivity.When the convection is not considered,the results show that the sphere emissivity has a significant influence on the transient thermal efficiency and that the temperature uniformity is strongly affected by the energy flux,sphere diameter,and sphere emissivity.As the emissivity increases from 0.5 to 0.9,the transient thermal efficiency and the average temperature variance increase from 53.5%to 75.7%and from 14.3%to 27.1%at 3.9 min,respectively.The average temperature variance decreases from 29.7%to 9.3%at 2.2 min with the sphere diameter increasing from 28.57 mm to 50 mm.As the dimensionless energy flux increases from 0.8 to 1.2,the average temperature variance increases from 13.4%to 26.6%at 3.4 min.

关键词： packed bed solar thermal power plants high heat fluxes radiative heat transfer

Thermal Performance Analysis of PCM Capsules packed-bed System with Biomimetic Leaf Hierarchical Porous Structure

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Journal of Thermal Science 2021年第5期30卷 1559-1571页

作者： DONG Yan WANG Fuqiang YANG Luwei SHI Xuhang ZHANG Guoliang SHUAI Yong School of New Energy Harbin Institute of Technology at WeihaiWeihai 264209China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

As an efficient natural selection nutrient transport system,biomimetic leaf hierarchical porous structure has unique advantages in material transportation and energy transfer.Biomimetic leaf hierarchical porous structure has been widely used in solar thermochemical reactions,photocatalysis,and energy storage.To improve the thermal efficiency and reduce the power consumption,the authors introduce the idea of bionic leaf hierarchical porous structure packed-bed latent heat thermal energy storage(LHTES)system.Under the same porosity,the diameter of the PCM capsules is designed to change along the flow direction to optimize the thermal performance.The effects of velocity on temperature distribution,pressure drop,liquid fraction,and thermal storage capacity of the conventional uniform model and bionic leaf hierarchical porous model are analyzed.The results show that the bionic leaf hierarchical porous structure can thin the thickness of the thermocline,reduce the pressure drop,increase the heat transfer area,and improve the thermal response of the packed-bed compared with the conventional uniform model.The maximum increases of liquid fraction and completion rate are 36.6%and 20.3%with pressure drop reduction of 25 Pa,respectively.The maximum decrease of the above-melting point(MP)thermocline is 51.7%as well.These results provide suggestions to optimize the packed-bed LHTES system and improve its thermal performance under practical conditions.

关键词： solar energy thermal energy storage packed bed biomimetic phase change hierarchical porous structure

Numerical study on the thermal performance of packed-bed latent heat thermal energy storage system with biomimetic alveoli structure capsule

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Science China(Technological Sciences) 2021年第7期64卷 1544-1554页

作者： WANG FuQiang DONG Yan LI Yang XU Jie ZHANG GuoLiang School of Physics Harbin Institute of TechnologyHarbin150001China School of New Energy Harbin Institute of TechnologyWeihai264209China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China College of Petroleum Engineering Liaoning Shihua UniversityFushun113001China

Bionics provides a positive and beneficial impact on the development of various materials and systems, which has been widely used in energy storage, heat transfer enhancement, and solar thermochemical reactions. In this paper, the idea of heat storage unit with biomimetic alveoli structure is proposed and introduced to increase the heat transfer area and improve the thermal performance of the packed-bed latent heat thermal energy storage(LHTES) system. The effects of heat storage unit structure on temperature distribution, liquid fraction, thermal storage capacity, and other performance indexes of the conventional model and biomimetic model are analyzed. The numerical results indicate that the biomimetic alveoli structure can improve the thermal response of heat storage unit, increase the specific surface area, and achieve a faster heat storage process of the packed-bed compared with the conventional structure. Among various existing models, the double-cell model has a significant improvement.Compared with the conventional model, the maximum increase of liquid fraction and charging efficiency are 9.8% and 6.4%,respectively. This study can provide references to optimize packed-bed LHTES and improve its thermal performance under practical conditions.

关键词： solar energy thermal energy storage packed bed biomimetic alveoli phase change material

A New Mathematical Model for Description of the Liquid Discrete Flow Within a packed bed

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Journal of Iron and Steel Research(International) 2008年第6期15卷 16-23页

作者： WANG Cheng-shan MU Xiao-jing ZHENG Shao-bo JIANG Guo-chang XIAO Xing-guo College of Materials Science and Engineering Chongqing University Chongqing 400044 China College of Chemistry and Chemical Engineering Chongqing University Chongqing 400044 China State Enhance Laboratory of Ferro Metallurgy Shanghai University Shanghai 200072 China School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China

The molten liquid discrete flow inside a packed bed is a typical transport phenomenon in the blast furnace. As for the reported mathematical models presenting the liquid discrete flow within the packed bed, there are some barriers for their application to an engineering scale-up, or some imperfections in model descriptions. To overcome these deficiencies, the effects of the packed bed on the liquid discrete flow have been divided into resistance action and dispersal action, and appropriate descriptions have been given for the two aetions, respectively. Consequently, a new mathematical model has been built to present the liquid discrete flow inside a coke bed in the blast furnace. The mathematical model can predict the distribution of liquid flux and the liquid flowing range inside the packed bed at any time. The prediction of this model accords well with the experimental data. The model will be much better for the simulation of the ironmaking process, compared with the existent model.

关键词： mathematical model liquid discrete flow packed bed blast furnace ironmaking process

NO_x Formation from Several Chinese Coals during Combustion in packed bed

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International Journal of Minerals,Metallurgy and Materials 1998年第2期12卷 65-69页

作者： Shengli Wu Chunbao Xu Qiushuang Shou Daqiang Cang Metallurgy School, UST Beijing, Beijing 100083, China Metallurgy School UST Beijing Beijing 100083 China

The formation characteristics of NO_x during combustion of four typical Chinese coals have been studied in a packed bed combustor. The studies included the effects of chemical composition of coals and volatile matters, and combustion conditions, i.e. preheating temperatures of combustion gas, on conversion of NO_x during combustion. In term of the combustion experiments, there is a close relation between coal composition and conversions of NO_x. Coals with a higher nitrogen content give a lower F_(NO_x)~0, and coals with a higher volatile content give a lower F_(NO_x)~0. The further devolatilization experiments showed that volatile matters in the coal have an important effect on reducing conversion of coal-nitrogen to NO_x. It was interpreted as that the release of volatile matters during combustion caused a fuel-rich circumstance in the vicinity of coal particles which may restrain the formation of NO_x. Preheating temperatures of combustion gas has significant effects on conversions of NO_x and there exist a critical preheating temperature. At such temperature, lower F_(NO_x)~0 can be reached.

关键词： coal combustion packed bed NO_x formation

Highly reactive and reusable heterogeneous activated carbons-based palladium catalysts for Suzuki-Miyaura reaction

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中国化学工程学报:英文版 2023年第8期60卷 165-172页

作者： Yifan Jiang Bingqi Xie Jisong Zhang State Key Lab of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China

Suzuki-Miyaura reaction of aryl halides with phenylboronic acid using a heterogeneous palladium catalyst based on activated carbons(AC) was systematically investigated in this work. Two different reaction modes(batch procedure and continuous-flow procedure) were used to study the variations of reaction processing. The heterogeneous catalysts presented excellent reactivity and recyclability for iodobenzene and bromobenzene substrates in batch mode, which can be attributed to stabilization of Pd nanoparticles by the thiol and amino groups on the AC supports. However, significant dehalogenation in the reaction mixture and Pd leaching from the heterogeneous catalysts were observed in continuous-flow mode.This unique phenomenon in continuous-flow mode resulted in a dramatic decline in reaction selectivity and durability of heterogeneous catalysts comparing with that of batch mode. In addition, the heterogeneous Pd catalysts with thiol-and amino-modified AC supports exhibited different reactivity and durability in batch and continuous-flow mode owing to the difference of interaction between Pd species and AC supports.

关键词： Suzuki-Miyaura reaction Heterogeneous palladium catalysts Activated carbon Thiol-and amino-functionalization Catalyst support packed bed