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numerical analysis of the return flow solar air heater(RF-SAH)with assimilation of V-type artificial roughness

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Energy and Built Environment 2024年第2期5卷 185-193页

作者： Prashant Raturi Hemlata Deolal Sanjeev Kimothi Department of Mechanical Engineering Swami Rama Himalayan University Dehradun248140India Department of Mechanical Engineering DIT UniversityDehradun248001India Division of Research&Innovation Dept.of PhysicsUttaranchal University248007India

A novel design of Return Flow Solar Air Heater(RFSAH)with different arrangements of baffles especially V-Type Artificial roughness is simulated and numerically analyzed with energy balance *** enhance the effectiveness of baffles,numerous studies have been *** performance of the RFSAH is studied in terms of thermal efficiency,thermo-hydraulic efficiency,and optimization of baffle *** Thermal efficiency and thermo-hydraulic efficiency are found in RFSAH with baffle on both sides of the absorber plate and mass flow rate above 0.2kg/*** analysis of the influencing parameters is carried out and reported the best performance of the system on selective geometrical parameters(ψ=0.7,β=20%,e/H=1,p/e=0.8,α=60°).The results obtained from the present model are validated with the published experimental results and have been found in quite reasonable agreement with an average error of 16.45%.Thermal and Thermohydraulic efficiency of RFSAH with a baffle on both sides of the absorber plate is maximum among baffles below,above,and on both sides of the absorber *** is observed that the thermal efficiency of RFSAH is greater than *** proposed optimum baffles roughness is suggested to increase the air upholding time period for more efficient output.

关键词： numerical analysis Energy Balance Equations Thermal Efficiency Return flow solar air heater V-baffles

numerical analysis of Steady Smoldering of Biomass Rods

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燃烧科学与技术 2024年第5期30卷 507-519页

作者： Zhao Wentao Yu Guangxin Zhang Yi Wang Youtang Zhou Dan He Fang School of Transportation and Vehicle Engineering Shandong University of TechnologyZibo 255049China

Understanding the steady mechanism of biomass smoldering plays a great role in the utilization of smoldering *** this study numerical analysis of steady smoldering of biomass rods was performed.A two-dimensional(2D)steady model taking into account both char oxidation and pyrolysis was developed on the basis of a calculated propagation velocity according to empirical *** model was validated against the smoldering experiment of biomass rods under natural conditions,and the maximum error was smaller than 31%.Parameter sensitivity analysis found that propagation velocity decreases significantly while oxidation area and pyrolysis zone increase significantly with the increasing diameter of rod fuel.

关键词： steady smoldering biomass rod numerical analysis 2D steady model sensitivity analysis

EXPERIMENTAL AND numerical analysis OF LAMINAR AND LOW TURBULENT FLOW DISTRIBUTIONS IN INLET DIVIDING HEADER OF SHELL AND TUBE HEAT EXCHANGER

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Journal of Hydrodynamics 2010年第4期22卷 494-502页

作者： KANNAN K. RUDRAMOORTHY R. Department of Production Engineering PSG College of Technology

Flow distribution headers play a major role in heat *** selection of header diameter,branch pipe diameter,branch pipe spacing *** based on the designer＇s experience and general guide *** proper selection of the header dimensions will yield uniform flow distribution in heat exchangers,which in turn will enhance the heat exchanger *** this work,the flow distribution in branch pipes and the pressure variation across the branch pipes in laminar and low turbulence region is studied with two models of the inlet dividing *** the numerical analysis has been applied,its inability to predict the no flow condition through the branch pipes is *** results are presented in the form of flow rate ratio through branch pipes and nondimensional coefficients across branch pipes which are useful to apply the existing mathematical models for the present experimental setup.

关键词： shell and tube heat exchanger inlet dividing header uniform flow distribution experimental setups numerical analysis

Shaking table test and numerical analysis of a 1:12 scale model of a special concentrically braced steel frame with pinned connections

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Earthquake Engineering and Engineering Vibration 2010年第1期9卷 51-63页

作者： Yu Haifeng Zhang Wenyuan Zhang Yaochun Sun Yusong School of Civil Engineering Harbin Institute of Technology Harbin 150090 China Northeast Electric Power Design Institute Changchun 130021 China

This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.

关键词： concentrically braced steel frame pinned connections shaking table test numerical analysis seismic performance

A numerical analysis OF THE VENTILATION PERFORMANCE FOR DIFFERENT VENTILATION STRATEGIES IN A SUBWAY TUNNEL

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Journal of Hydrodynamics 2012年第2期24卷 193-201页

作者： HUANG Yuan-dong LI Chan KIM Chang Nyung School of Environment and Architecture University of Shanghai for Science and Technology China College of Engineering Kyung Hee University Yongin 449-701 Korea Graduate School Kyung Hee University Yongin 449-701 Korea Industrial Liaison Research Institute Kyung Hee University Yongin 449-701 Korea

An unsteady three-dimensional analysis of the ventilation performance is carried out for different ventilation strategies to find out a ventilation method with a high performance in a subway *** natural ventilation performance associated with a train-induced air flow in a subway tunnel is *** dynamic layering method is used to consider the moving boundary of a train in the current CFD *** geometries of the modeled tunnel and the subway train are partially based on those of the Seoul *** effects of the structure of the ventilation duct and the geometry of the partitions on the ventilation performance are *** results show that the combined ventilation ducts （to be designed）,and the partitioning blocks installed along the middle of tunnel （already in existences） are helpful for air *** study can provide some guidance for the design of ventilation ducts in a subway system.

关键词： ventilation performance subway tunnel train-induced air flow natural ventilation duct numerical analysis

numerical analysis for the matching of the core driven compression system in a double bypass engine

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航空动力学报 2011年第5期26卷 1066-1076页

作者： ZHANG Xin LIU Bao-jie National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics School of Jet Propulsion Beijing University of Aeronautics and Astronautics Beijing 100191 China

The numerical analysis for the matching of the core driven compression system in a double bypass variable cycle engine was presented in this *** system consists of a one-stage-core driven fan stage(CDFS),an inner bypass duct and a five-stage high pressure compressor(HPC),providing two basic operating modes: the single bypass mode and the double bypass *** vanes are necessary to realize the mode switch of the *** correct matching in the double bypass mode requires a proper combination of the mass flow,total pressure ratio and blade *** work capacity of the system decreases in the double bypass mode and the pressure ratio tends to decrease more for the CDFS and the front stages of the *** overall system efficiency is higher in the double bypass *** radial distributions of aerodynamic parameters are similar in different *** notable redistribution of mass flow downstream the CDFS in the single bypass mode leads to strong radial flows and additional mixing *** absolute flow angles into the inner bypass increase for the inner span and decrease for the outer span when the system is switched from the single bypass mode to the double bypass mode.

关键词： numerical analysis aerodynamic double bypass variable cycle engine core driven compression system core driven fan stage operating mode

numerical analysis of a Spiral-groove Dry-gas Seal Considering Micro-scale Effects

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Chinese Journal of Mechanical Engineering 2011年第1期24卷 146-153页

作者： WANG Bing ZHANG Huiqiang School of Aerospace Tsinghua University Beijing 100064 China Beijing 3E Enemy Key Laboratory Tsinghua University Beijing 100084 China

A dry-gas seal system is a non-contact seal technology that is widely used in different industrial ***-groove dry-gas seal utilizes fluid dynamic pressure effects to realize the seal and lubrication processes,while forming a high pressure gas film between two sealing faces due to the deceleration of the gas pumped in or *** is little research into the effects and the influence on seal performance,if the grooves and the gas film are at the *** paper investigates the micro-scale effects on spiral-groove dry-gas seal performance in a numerical solution of a corrected Reynolds *** Reynolds equation is discretized by means of the finite difference method with the second order scheme and solved by the successive-over-relaxation（SOR） iterative *** Knudsen number of the flow in the sealing gas film is changed from 0.005 to 0.120 with a variation of film depth and sealing *** numerical results show that the average pressure in the gas film and the sealed gas leakage increase due to micro-scale *** open force is enlarged,while the gas film stiffness is significantly decreased due to micro-scale *** friction torque and power consumption remain constant,even in low sealing pressure and spin speed *** this paper,the seal performance at different rotor face spin speeds is also *** proposed research clarifies the micro-scale effects in a spiral-groove dry-gas seal and their influence on seal performance,which is expected to be useful for the improvement of the design of dry-gas seal systems operating in the slip flow regime.

关键词： micro-scale effect spiral-groove dry-gas seal numerical analysis Reynolds equation

numerical analysis of the self-heating effect in SGOI with a double step buried oxide

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Journal of Semiconductors 2011年第3期32卷 42-48页

作者：李斌刘红侠李劲袁博曹磊 Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education School of MicroelectronicsXidian University

To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator（SGOI） n-type metal-oxide-semiconductor field-effect transistors（nMOSFETs）,this paper proposes a novel device called double step buried oxide（BOX） SGOI,investigates its electrical and thermal characteristics,and analyzes the effect of self-heating on its electrical *** the simulation of the device,a low field mobility model for strained Si MOSFETs is established and reduced thermal conductivity resulting from phonon boundary scattering is considered.A comparative study of SGOI nMOSFETs with different BOX thicknesses under channel and different channel strains has been *** reducing moderately the BOX thickness under the channel,the channel temperature caused by the self-heating effect can be effectively ***,mobility degradation,off state current and a short-channel effect such as drain induced barrier lowering can be well ***,SGOI MOSFETs with a thinner BOX under the channel can improve the overall performance and long-term reliability efficiently.

关键词： self-heating effect step BOX SGOI mobility model numerical analysis

numerical analysis of matrix swelling and its effect on microstructure of digital coal and its associated permeability during CO_(2)-ECBM process based on X-ray CT data

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Petroleum Science 2023年第1期20卷 87-101页

作者： Hui-Huang Fang Zhang-Fei Wang Shu-Xun Sang Yan-Hui Huang School of Earth and Environment Anhui University of Science and TechnologyHuainanAnhui232001China Institute of Energy Hefei Comprehensive National Science CenterHefeiAnhui230000China Low Carbon Energy Institute China University of Mining and TechnologyXuzhouJiangsu221008China School of Resources and Geosciences China University of Mining and TechnologyXuzhouJiangsu221116China Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization China University of Mining and TechnologyXuzhouJiangsu221008China State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China

Matrix swelling effect will cause the change of microstructure of coal reservoir and its permeability,which is the key factor affecting the engineering effect of CO_(2)-ECBM *** Sihe and Yuwu collieries are taken as research ***,visualization reconstruction of coal reservoir is ***,the evolution of the pore/fracture structures under different swelling contents is ***,the influence of matrix phase with different swelling contents on permeability is ***,the mechanism of swelling effect during the CO_(2)-ECBM process is further *** results show that the intra-matrix pores and matrix-edge fractures are the focus of this study,and the contacting area between matrix and pore/fracture is the core area of matrix *** number of matrix particles decreases with the increase of size,and the distribution of which is isolated with small size and interconnected with large *** swelling effect of matrix particles with larger size has a great influence on the pore/fracture *** number of connected pores/fractures is limited and only interconnected in a certain *** the increase of matrix swelling content,the number,porosity,width,fractal dimension,surface area and volume of pores/fractures decrease,and their negative contribution to absolute permeability increases from 0.368% to 0.633% and 0.868%-1.404%,*** the increase of swelling content,the number of intra-matrix pores gradually decreases and the pore radius becomes shorter during the CO_(2)-ECBM *** matrix continuously expands to the connected fractures,and the width of connected fractures gradually *** the influence of matrix swelling,the bending degree of fluid flow increases gradually,so the resistance of fluid migration increases and the permeability gradually *** study shows that the matrix swelling effect is the key factor affecting CBM recovery,and the application of this effec

关键词： Matrix swelling CO_(2)-ECBM Absolutely permeability numerical analysis X-ray CT Qinshui Basin