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Enhanced Natural Convection for Accelerating Melting of Phase Change Material in Cellular Structure through Inserting Fin

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Journal of Thermal Science 2024年第2期33卷 548-563页

作者： KONG Dekui ZHANG Yongcun LIU Shutian State Key laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian116024China

The design of thermal conductivity enhancers(TCE) is quite critical to overcoming the disadvantage of the poor thermal conductivity of phase change materials(PCM).The main contribution of this study is firstly to discuss how to actively enhance natural convection of the melted PCM in cellular structure by the fin formed in the structure under the condition of the same metal mass,apart from simultaneously improving heat conduction,which can boost the heat transfer ***,a tailored hybrid fin-lattice structure(HFS) as TCE is designed and fabricated by additive manufacturing(AM).A two-equation numerical method is applied to study the heat transfer of the PCM,and its feasibility is validated with the experimental *** numerical results indicate that enhanced natural convection and improved heat conduction can be obtained simultaneously when a well-designed fin is embedded into a lattice *** enhanced natural convection results in the improved melting rate and the decreased wall temperature;e.g.,the complete melting time and the wall temperature are reduced by 11.6% and 19.7%,respectively,because of the fin for metal ***,the parameters of HFS including the porosity,pore density,and fin dimension have a great impact on the heat *** enhancement effect of the fin for HFS on the melting rate of the PCM increases as the thermal conductivity of the base material *** example,when the fin is introduced into the lattice structure,the complete melting time is reduced by 24.1% for metal *** summary,this study enables us to obtain a good understanding of the mechanism of the heat transfer and provides necessary experimental data for the structural design of HFS fabricated by AM.

关键词： natural convection heat transfer enhancement phase change material additive manufacturing hybrid fin-lattice structure

Kinematic-mapping-model-guided analysis and optimization of 2-PSS&1-RR circular-rail parallel mechanism for fully steerable phased array antennas

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Defence Technology 2024年第8期38卷 136-154页

作者： Guodong Tan Xiangfei Meng Xuechao Duan Lulu Cheng Dingchao Niu Shuai He Dan Zhang laboratory of Electromechanical Coupling in Electronic Equipment Xidian University Department of Mechanical Engineering The Hong Kong Polytechnic University

This paper presents a systematic methodology for analyzing and optimizing an innovative antenna mount designed for phased array antennas, implemented through a novel 2-PSS&1-RR circular-rail parallel mechanism. Initially, a comparative motion analysis between the 3D model of the mount and its full-scale prototype is conducted to validate effectiveness. Given the inherent complexity, a kinematic mapping model is established between the mount and the crank-slider linkage, providing a guiding framework for subsequent analysis and optimization. Guided by this model, feasible inverse and forward solutions are derived, enabling precise identification of stiffness singularities. The concept of singularity distance is thus introduced to reflect the structural stiffness of the mount. Subsequently, also guided by the mapping model, a heuristic algorithm incorporating two backtracking procedures is developed to reduce the mount's mass. Additionally, a parametric finite-element model is employed to explore the relation between singularity distance and structural stiffness. The results indicate a significant reduction(about 16%) in the antenna mount's mass through the developed algorithm, while highlighting the singularity distance as an effective stiffness indicator for this type of antenna mount.

关键词： Backtracking Circular rail Crank-slider linkage Innovative antenna mount Kinematic mapping model Stiffness singularity

A novel insight of degradation ibuprofen in aqueous by catalytic ozonation with supported catalyst:Supports effect on ozone mass transfer

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Journal of Environmental Sciences 2024年第11期145卷 216-231页

作者： Zizheng Huangfu Wei Ju Yunhan Jia Ruijun Ren Zhenbei Wang Chen Li Xiaomeng Shang Yujie Li Hongnan Liu YuWang Hao Zheng Fei Qi Amir Ikhlaq Jolanta Kumirska Ewa Maria Siedlecka Beijing Key laboratory for Source Control Technology of Water Pollution College of Environmental Science and EngineeringBeijing Forestry UniversityBeijing 100083China Beijing Forestry University Science Co. Ltd.Beijing 100083China Institute of Environment Engineering and Research University of Engineering and TechnologyLahore 54890Pakistan Department of Environmental Analysis Faculty of ChemistryUniversity of GdanskWita Stwosza 6380-308Poland

Catalytic ozonation is an effective wastewater purification ***,the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency(OUE),poor organic degradation performance,and high energy ***,there is an urgent need to develop efficient supported catalysts that can enhancemass transfer and ***,the reaction mechanism of the support on ozone mass transfer remains unclear,which hinders the development of catalytic ozonation *** this study,lava rocks(LR)-supported catalysts,specifically CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR,were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity,stability,and high *** of CuMn_(2)O_(4)@LR or MnO_(2)–Co_(3)O_(4)@LR increased IBP removal efficiency from 85%to 91%or 88%,and reduced energy consumption from 2.86 to 2.14 kWh/m^(3)or 2.60 kWh/m^(3),*** improvement was attributed to LRsupported catalysts enhancing mass transfer and promoting O3 decomposition to generate•OH and•O_(2)^(−),leading to IBP ***,this study investigated the effects of ozone dose,supporter sizes,and catalyst components on ozone-liquid mass *** results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass ***-sized LR(kLa=0.172 min^(−1))exhibited better mass transfer compared to smaller-sized *** on these findings,it was concluded that both CuMn_(2)O_(4)@LR and MnO_(2)–Co_(3)O_(4)@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater,and LR showed good credibility as a catalyst *** the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.

关键词： Catalytic ozonation Lava rocks Overall volumetric mass transfer coefficient Supported catalyst

Regulation of isobutane/1-butene adsorption behaviors on the acidic ionic liquids-functionalized MCM-22 zeolite

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Chinese Journal of Chemical Engineering 2018年第1期26卷 127-136页

作者： Keting Jin Tao Zhang Shaojun Yuan Shengwei Tang Multi-phase mass transfer and Reaction Engineering Lab College of Chemical EngineeringSichuan UniversityChengdu 610065China

The adsorption ratio of isobutane/1-butene on the catalyst surface is one of the most important factors for the C4 alkylation process. Regulation of isobutane/1-butene adsorption ratio on the zeolite-supported acid catalyst is a big challenge for catalyst preparation. To regulate the isobutane/1-butene adsorption ratio, four types of ionic liquid （i.e., IL） with different alkyl chain lengths and different acid group numbers were synthesized and were subsequently immobilized onto the MCM-22 zeolite. The as-synthesized IL-immobilized MCM-22 （i.e., MCM-22-IL） was characterized by FT1R, TGA, BET, XPS and XRD, and their adsorption capacities and adsorption molar ratios of isobutane to l-butene （I/O） were investigated to correlate with surface features of MCM-22-IL Results showed that the immobilization of ILs led to a decrease of specific surface area and pore volume. But the surface density of acid groups was increased and the adsorption molar ratio of isobutane/1-butene （I/O） was significantly im- proved by the immobilization of ionic liquids. The adsorption molar ratio of I/O is substantially improved from 0.75 to above 0.9 at 300 kPa upon immobilizing ILs. Although the alkyl chain length oflLs was found to have little effect on the adsorption molar ratio of I/O, the increase of acid group numbers led to a dramatic decrease in the adsorption I/O ratio. The results illustrated that immobilizing ionic liquids is an effective way to modify the textural, chemical and morphological properties of MCM-22. Accordingly, the immobilization of ionic liquids provides a novel and a feasible way to regulate the adsorption I/O ratio on an adsorbent or a solid catalyst.

关键词： Adsorption Catalyst Ionic liquids lsobutane 1-Butene

Numerical Investigation of heat and mass transfer in Nanofluid-Filled Porous Medium

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Advances in Nanoparticles 2024年第3期13卷 29-44页

作者： Dalel Helel Noureddine Boukadida ISSATS University of Sousse Souuse Tunisia laboratory of Metrology and Energy Systems ENIM University of Monastir Monastir Tunisia ESSTHS University of Sousse Sousse Tunisia

In this work, we numerically study the laminar mixed convection of fluid flow in a vertical channel filled with porous media during the drying process. The porous medium, modeled as a vertical wall, consists of solid and nanofluid phase (Water-Al2O3 or Water-Cu), as well as a gas phase. The established model is developed based on Whitaker’s theory and resolved by our numerical code using Fortran. Results principally show the influence of various physical parameters, such as nanoparticle volume fraction, ambient temperature, and saturation on heat and mass transfer on the drying process. This study brings the effect of the presence of nanofluids in porous media. It contributes not only to our fundamental understanding of drying processes but also provides practical insights that can guide the development of more efficient and sustainable drying technologies. .

关键词： Mixed Convection heat transfer Nanofluid Drying Porous Media

Covalent organic frameworks doped with manganese-metal organic framework for peroxymonosulfate activation

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Chinese Chemical Letters 2024年第4期35卷 199-203页

作者： Yinyin Xu Yuanyuan Li Jingbo Feng Chen Wang Yan Zhang Yukun Wang Xiuwen Cheng Key laboratory for Environmental Pollution Prediction and Control College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China Key laboratory of Pollutant Chemistry and Environmental Treatment College of Chemistry and Environmental ScienceYili Normal UniversityYining 835000China

A novel N, O modified Mn_(3)O_(4)@porous carbon catalyst(NOC-Mn_(3)O_(4)) was prepared by direct carbonization using the manganese-metal organic framework(Mn-MOF) and covalent organic framework(COF) as precursors to activate peroxymonosulfate(PMS) for the degradation of bisphenol A(BPA) and rhodamine B(Rh B). Benefiting from the N and O co-doping of COF, larger specific surface area, faster electron transfer and Mn cycling, the optimum 1NOC-Mn_(3)O_(4)could significantly improve the degradation performance of BPA and Rh B(92.1% and 96.9% within 30 min) as compared to C-Mn_(3)O_(4)without COF doping. In addition, 1NOC-Mn_(3)O_(4) showed good reusability and strong anti-interference ability. Radical quenching experiments, X-ray photoelectron spectroscopy(XPS), Electron paramagnetic resonance spectrometer(EPR) and electrochemical tests showed that the 1NOC-Mn_(3)O_(4)/PMS system degraded BPA and Rh B by both radical and non-radical pathways. Moreover, the possible degradation pathways of BPA and Rh B were proposed by liquid chromatography-mass spectrometry(LC-MS). Except for that, the toxicity of BPA, Rh B and their intermediates were evaluated. This study opens up a new prospect for the design of COF-doped PMS catalysts.

关键词： Peroxymonosulfate Covalent organic framework Mn-metal organic framework Organic pollutant Degradation

Nanoconfinement-induced water molecules and hydrogen molecules transport behaviors in ball-in-ball structure photocatalysts to improve hydrogen evolution

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Nano Research 2024年第5期17卷 3752-3760页

作者： Ben Chong Baorong Xu He Li Honghui Ou Guidong Yang XJTU-Oxford Joint International Research laboratory of Catalysis School of Chemical Engineering and TechnologyXi’an Jiaotong UniversityXi’an 710049China

The diffusion,adsorption/desorption behaviors of water molecules and hydrogen molecules are of great importance in heterogeneous photocatalytic hydrogen *** the study of structure-property-performance relationships,nanoconfined space provides an ideal platform to promote mass diffusion and transfer due to their extraordinary properties that are different from the bulk ***,we designed and prepared a nanoconfined CdS@SiO_(2)-NH_(2) nanoreactor,whose shell is composed of amino-functionalized silica nanochannels,and encapsulates spherical CdS as a photocatalyst *** and simulated results reveal that the amino-functionalized nanochannels promote water molecules’and hydrogen molecules’directional diffusion and *** molecules are enriched in the nanocavity between the core and the shell,and promote the interfacial photocatalytic *** a result,the maximized water enrichment and minimized hydrogen-occupied active sites enable photocatalyst with optimized mass transfer kinetics and localization electron distribution on the CdS surface,leading to superior hydrogen production performance with activity as high as 37.1 mmol·g^(-1)·h^(-1).

关键词： nanochannels photocatalytic hydrogen evolution mass transfer amino-functionalized CdS

Performance Analysis of a Multistage Centrifugal Pump Used in an Organic Rankine Cycle(ORC) System under Various Condensation Conditions

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Journal of Thermal Science 2019年第4期28卷 621-634页

作者： YANG Yuxin ZHANG Hongguang TIAN Guohong XU Yonghong WANG Chongyao GAO Jianbing College of Environmental and Energy Engineering MOE (Ministry of Education) Key Laboratory of Enhanced Heat Transfer and Energy ConservationBeijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100124China Department of Mechanical Engineering Sciences University of SurreyGuildford GUI 2LJUK School of Electrical and Mechanical Engineering Beijing Information Science and Technology UniversityBeijing 100192China

In an organic Rankine cycle(ORC)system,the working fluid pump plays an important role in the system *** paper focused on the operating characteristics of a multistage centrifugal pump at various speeds and condensation *** experimental investigation was carried out to assess the influence of the performance of the pump by the ORC system with special attention to actual net power output,thermal efficiency as well as back work ratio(BWR).The results showed that an increase in the pump speed led to an increase in the mass flow rate and expand in the operating range of the outlet *** mass flow rate decreased nonlinearly with the increase of the outlet pressure from 0.22 to 2.41 MPa;the electric power consumption changed between 151.54 and 2409.34 W and the mechanical efficiency of the pump changed from 7.90%to 61.88%when the pump speed varied from 1160 to 2900 r/***,at lower pump specific speed the ORC system achieved higher thermal efficiency,which suggested that an ultra-low specific speed pump was a promising candidate for an ORC *** results also suggested that the effects of condensation conditions on the pump performance decreased with the pump speed increasing and BWR was relatively sensitive to the condensation conditions,especially at low pump speed.

关键词： waste heat recovery organic Rankine cycle multistage centrifugal pump operating characteristics various condensation conditions back work ratio(BWR)

Carbon dioxide reforming of methane over bimetallic catalysts of Pt-Ru/γ-Al_2O_3 for thermochemical energy storage

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Journal of Central South University 2013年第5期20卷 1307-1313页

作者：杜娟杨晓西丁静魏小兰杨建平王维龙杨敏林 Key laboratory of Enhanced heat transfer and Energy Conservation of the Ministry of Education(South China University of Technology) Key laboratory of Distributed Energy Systems of Guangdong Province Dongguan University of Technology School of Engineering Sun Yat-sen University

The reaction of CO2 reforming of CH4 has been investigated with y-A1203-supported platinum and ruthenium bimetallic catalysts, with the specific purpose of thermochemical energy storage. The catalysts were prepared by using the wetness impregnation method. The prepared catalysts were characterized by a series of physico-chemical characterization techniques such as BET surface area, thermo-gravimetric （TG）, transmission electron microscope （TEM） and X-ray photoelectron spectroscopy （XPS）. In addition, the amount of carbon deposits on the surface of the catalysts and the type of the carbonaceous species were discussed by TG. It was found that the bimetallic Pt-Ru/7-A1203 catalysts exhibit both superior catalytic activity and remarkable stability by comparison of monometallic catalysts. During the 500 h stability test, the bimetallic catalyst showed a good performance at 800 ~C in CO2 reforming of CH4, exhibiting an excellent anti-carbon performance with the mass loss of less than 8.5%. The results also indicate that CO2 and CH4 have quite stable conversions of 96.0 % and 94.0 %, respectively. Also, the selectivity of the catalysts is excellent with the products ratio of CO/H2 maintaining at 1.02. Furthermore, it was found in TEM images that the active carbonaceous species were formed during the catalytic reaction, and well-distributed dot-shaped metallic particles with a relatively uniform size of about 3 nm as well as amorphous carbon structures were observed. Combined with BET, TG, TEM tests, it is concluded that the selected bimetallic catalysts can work continuously in a stable state at the high temperature, which has a potential to be utilized for the closed-loop cycle of the solar thermochemical energy storage in future industry applications.

关键词： carbon dioxide reforming of methane Pt-Ru/7-A1203 catalysts long-term stability thermochemical energy storage