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Experimental and Modeling Study of Forest Fire Effect on Soil thermal Conductivity

Pedosphere 2016年第4期26卷 462-473页

作者： Kathleen M.SMITS Elizabeth KIRBY William J.MASSMAN Larry Scott BAGGETT Center for the Experimental Study of Subsurface Environmental processes Department of Civil and Environmental EngineeringColorado School of Mines USDA Forest Service Rocky Mountain Research Station

An understanding of soil thermal conductivity after a wildfire or controlled burn is important to land management and post-fire recovery efforts. Although soil thermal conductivity has been well studied for non-fire heated soils, comprehensive data that evaluate the long-term effect of extreme heating from a fire on the soil thermal conductivity are limited. The purpose of this study was to evaluate the long-term impact of fire on the effective thermal conductivity of soils by directly comparing fire-heated and no-fire control soils through a series of laboratory studies. The thermal conductivity was measured for ten soil samples from two sites within the Manitou Experimental Forest, Colorado, USA, for a range of water contents from saturation to the residual degree of saturation. The thermal conductivity measured was compared with independent estimates made using three empirical models from literature, including the Campbell et al. （1994）, CSt~ and Konrad （2005）, and Massman et al. （2008） models. Results demonstrate that for the test soils studied, the thermal conductivity of the fire-heated soils was slightly lower than that of the control soils for all observed water contents. Modeling results show that the Campbell et al. （1994） model gave the best agreement over the full range of water contents when proper fitting parameters were employed. Further studies are needed to evaluate the significance of including the influence of fire burn on the thermal properties of soils in modeling studies.

关键词： controlled burn degree of saturation empirical model water content wildfire

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Improving IEC thermal model for oil natural air natural transformers using optimised parameters based on dynamic simulation

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High Voltage 2024年第1期9卷 217-229页

作者： Lijing Zhang Yingting Luo Gehao Sheng Zizhan Ni Xiuchen Jiang department of Electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina Electric Power Research Institute of Guangdong Power Grid Corporation GuangzhouChina

Accurate assessment of hot-spot temperature is essential for the safe operation of power *** dynamic thermal models cannot estimate hot-spot temperature accurately since some input parameters are roughly determined by transformer capacity and cooling mode while ignoring the effect of winding structure,tank dimensions,and material physical *** improve the accuracy of temperature assessment,empirical parameters of the IEC thermal model including thermal constants,winding and oil exponents are optimised with the help of numerical simulation in this *** on energy conservation and heat transfer theory,a computational fluid dynamic(CFD)model of a transformer in oil natural air natural(ONAN)cooling mode is *** CFD model simulates the entity's structure,sizes,and multi-stage heat dissipation processes realistically,so it can more precisely calculate the dynamic hot-spot *** to the simulated temperature curves at different operating conditions,the thermal constants and oil exponent are estimated using non-linear regression,and the winding exponent is optimised using linear regression.A case study is conducted on an ONAN *** shows the improved IEC model with optimised parameters can more accurately evaluate hot-spot temperature,and the absolute error is decreased by 2.4 K(38.7%)compared with traditional thermal models.

关键词： temperature properties. thermal

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Three-Dimensional Radiation in Absorbing-Emitting Scattering Medium Using the Discrete-OrdinatesApproximation

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Journal of thermal Science 1998年第4期7卷 255-263页

作者： Xiao-Lin Wei Tong-Mo Xu Shi-En Hui Institute of Mechanics Chinese Academy of Sciences Beijing China department of thermal Engineering Xi’an Jiaotong University China

The discrete-ordinates method is a simple, accurate and of little computational time solution to predict the radiative heat transfer in the combustion chambers. In this paperl three-dimension radiative problems for absorbing-emitting-scattering medium are modeled using this method in the rectangular enclosure. And in addition, new discrete-ordinates are developed to study the absorbing-emitting-scattering radiation processes for complex phase function. The reasonable results can be obtained through these new ordinates, yet the deviated results are only obtained through conventional Sn ordinates.

关键词： radiation discrete-ordinates method phase function

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Subduction and retreating of the western Pacific plate resulted in lithospheric mantle replacement and coupled basin-mountain respond in the North China Craton

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Science China Earth Sciences 2018年第4期61卷 406-424页

作者： Jianping ZHENG Hongkun DAI School of Earth Sciences State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhan

The North China Craton(NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods:(1) Late Paleozoic to Early Jurassic(~170 Ma);(2) Middle Jurassic to Early Cretaceous(160-140 Ma);(3) Early Cretaceous to Cenozoic(140 Ma to present). The last two stages saw the lithospheric mantle replacement and coupled basin-mountain response within the North China Craton due to subduction and retreating of the Paleo-Pacific plate, and is the emphasis in this paper. In the first period,the subduction and closure of the PaleoAsian Ocean triggered the back-arc extension, syn-collisional compression and then post-collisional extension accompanied by ubiquitous magmatism along the northern margin of the NCC. Similar processes happened in the southern margin of the craton as the subduction of the Paleo-Tethys ocean and collision with the South China Block. These processes had caused the chemical modification and mechanical destruction of the cratonic margins. The margins could serve as conduits for the asthenosphere upwelling and had the priority for magmatism and deformation. The second period saw the closure of the Mongol-Okhotsk ocean and the shear deformation and magmatism induced by the drifting of the Paleo-Pacific slab. The former led to two pulse of N-S trending compression(Episodes A and B of the Yanshan Movement) and thus the pre-existing continental marginal basins were disintegrated into sporadically basin and range pro vince by the Mesozoic magmatic plutons and NE-SW trending *** the anticlockwise rotation of the Paleo-Pacific moving direction, the subduction-related magmatism migrated into the inner part of the craton and the Tanlu fault became normal fault from a sinistral one. The NCC thus turned into a back-arc extension setting at the end of this period. In the third period, the refractory subcontinental lithospheric mantle(SCLM) was firstly remarkably eroded and thin

关键词： Paleo-Pacific slab Subduction and retreating Mantle replacement Mountain-basin coupling North China Craton Deep processes and shallow response Yanshan Movement

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Effects of Blending Long-Chain Alcohols with Jet Fuel on the Macroscopic Spray Characteristics

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China Petroleum Processing & Petrochemical Technology 2019年第4期21卷 49-57页

作者： Li Fengyu Liu Yanju Huang Qifu Fu Wei Shi Weidong Lin Qizhao department of thermal Science and Energy Engineering University of Science and Technology of ChinaHefei 230026 Beijing Mechanical Equipment Institute Beijing100854

Long-chain alcohols were considered to be promising alternative fuels and fuel additives. This study was aimed at figuring out the influences of blending long-chain alcohols with jet fuel on the macroscopic spray characteristic. n-Butanol and n-pentanol were chosen as tested alternative fuels. A common-rail injection system was used to create high-pressure injection conditions. The Schlieren imaging system was used to capture spray processes. Results showed that with the addition of long-chain alcohols, the spray tip penetration and the peak spray tip velocity increased, whereas the spray cone angle and the spray area decreased. Comparisons between those macroscopic spray characteristics of AKB blends and AKP blends were also conducted. Compared to AKB blends, AKP blends showed similar spray tip penetration, larger peak tip velocity, smaller spray cone angle, and smaller spray area.

关键词： macroscopic spray characteristics jet fuel n-butanol n-pentanol common-rail system

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Hierarchical crystalline-amorphous nanocomposites with high strength and large deformability enabled by elemental diffusion

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Journal of Materials Science & Technology 2024年第4期171卷 150-161页

作者： Liqiang Wang Heyi Wang Xin Zhou Huangliu Fu James Utama Surjadi Shuo Qu Xu Song Rong Fan Yang Lu department of Mechanical Engineering City University of Hong KongHong KongChina Nano-Manufacturing Laboratory(NML) Shenzhen Research Institute of City University of Hong KongShenzhen 518057China Chengdu Research Institute City University of Hong KongChengdu 610200China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China department of Mechanical and Automation Engineering The Chinese University of Hong KongHong KongChina department of Mechanical Engineering The University of Hong KongHong KongChina

Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch ***,we proposed a new strategy to develop a hierarchical and interconnected amorphous-crystalline nanocomposite arising from the nanoscale elemental interdiffusion and oxygen adsorption behavior dur-ing thermal treatment *** nanocomposite consisted of a three-dimensional(3D)hierarchical network structure where the crystalline phase(Cr-Co-Ni-Al)was embedded into the Al-O-based amor-phous phase network with critical feature sizes encompassing three orders of magnitude(from microm-eter to nanometer scale).It can achieve ultrahigh compression yield strength of-3.6 GPa with large homogeneous deformation of over 50%*** massive interstitial atoms induced lattice distortion and hierarchical amorphous phase boundary contributed to the strength *** situ Uniaxial compression inside a transmission electron microscope(TEM)revealed that the exceptional deformability of the nanocomposites resulted from the homogenous plastic flow of nano-sized amorphous phase and the plastic co-deformation behavior restricted by the nano-architected dual-phase *** proposed dual-phase synthesis approach can outperform conventional nanolaminates design strategies in terms of the mechanical properties achievable while providing a pathway to easily tune the microstructure of these nanolaminates.

关键词： Nanolaminates Dual-phase nanocomposites In situ transmission electron microscopy Multi-component alloy

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Optimal dynamic dispatch of surplus gas among buffer boilers in steel plant

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Journal of Central South University 2013年第9期20卷 2459-2465页

作者：孙文强蔡九菊 Institute of thermal and Environmental Engineering SEP Key Laboratory of Eco-industryNortheastern University

As valuable energy in iron-and steel-making process,by-product gas is widely used in heating and technical processes in steel *** being used according to the technical requirements,the surplus by-product gas is usually used for buffer boilers to produce *** the rapid development of energy conservation technology and energy consumption level,surplus gas in steel plant continues to get ***,it is significant to organize surplus gas among buffer boilers.A dynamic programming model of that issue was established in this work,considering the ramp rate constraint of boilers and the influences of setting *** a case study was *** is shown that dynamic programming dispatch gets more steam generation and less specific gas consumption compared with current proportionate dispatch depending on nominal capacities of *** ignored boiler ramp rate constraint was considered and its contribution to the result validity was pointed ***,the significance of setting gasholders was studied.

关键词： surplus gas dynamic programming buffer boiler steel plant

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Exergy Analysis of Charge and Discharge processes of thermal Energy Storage System with Various Phase Change Materials:A Comprehensive Comparison

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Journal of thermal Science 2024年第2期33卷 509-521页

作者： Mojtaba TAHERI Fathollah POURFAYAZ Roghayeh HABIBI Akbar MALEKI department of Renewable Energies and Environment Faculty of New Sciences and TechnologiesUniversity of TehranTehran***Iran Faculty of Mechanical Engineering Shahrood University of TechnologyShahrood***Iran

thermal energy storage(TES) is of great importance in solving the mismatch between energy production and *** this regard,choosing type of Phase Change Materials(PCMs) which are widely used to control heat in latent thermal energy storage systems,plays a vital role as a means of TES ***,this field suffers from lack of a comprehensive investigation on the impact of various PCMs in terms of *** address this issue,in this study,in addition to indicating the melting temperature and latent heat of various PCMs,the exergy destruction and exergy efficiency of each material are estimated and compared with each ***,in the present work the impact of PCMs mass and ambient temperature on the exergy efficiency is *** results proved that higher latent heat does not necessarily lead to higher exergy ***,to obtain a suitable exergy efficiency,the specific heat capacity and melting temperature of the PCMs must also be *** to the results,LiF-CaF_(2)(80.5%:19.5%,mass ratio) mixture led to better performance with satisfactory exergy efficiency(98.84%) and notably lower required mass compared to other ***,the highest and lowest exergy destruction are belonged to GR25 and LiF-CaF_(2)(80.5:19.5) mixture,respectively.

关键词： exergy analysis phase change materials thermal energy storage exergy efficiency

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Role of viscous heating in entransy analyses of convective heat transfer

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Science China(Technological Sciences) 2020年第10期63卷 2154-2162页

作者： CHENG XueTao WANG XiangYu LIANG XinGang department of Science and Technology of Anhui Province Hefei 230091China Key Laboratory for thermal Science and Power Engineering of Ministry of Education School of AerospaceTsinghua UniversityBeijing 100084China

The entransy theory is widely used and found to be effective in thermal analyses and *** researchers considered the entransy variation due to viscous heating as part of entransy dissipation and analyzed convective heat transfer based on the differential relationship between entropy and ***,it has been pointed out that the derivation of the differential relationship between entropy and entransy is *** this paper,the convective heat transfer processes with viscous heating is reconsidered and analyzed from the viewpoint of the energy conservation and the entransy balance *** is shown that the influence of the viscous heating is equivalent to that of an inner heat ***,the contribution of viscous heating to system entransy should not be treated as part of entransy dissipation,but entransy flow into the ***-stream parallel and counter flow heat exchangers with viscous heating and a thermal insulation transportation problem of heavy oil are taken as examples to verify the theoretical analyses *** the examples,the numerical results show that the entransy dissipation rates could be negative when the influence of the viscous heating on the system entransy is treated as part of the entransy *** is obviously ***,when the entransy contribution from the viscous heating to the system entransy is treated as entransy flow into the system,it is shown that the entransy dissipation rate is always positive,and the heat transfer processes can be well explained with the entransy theory.

关键词： entransy dissipation viscous heating convective heat transfer thermal analyses

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Multiphase fluid dynamics and transport processes of low capillary number cavitating flows

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Acta Mechanica Sinica 2009年第2期25卷 161-172页

作者： Xiangbin Li Guoyu Wang Zhiyi Yu Wei Shyy department of thermal Energy Engineering Beijing Institute of Technology 100081 Beijing China department of Nuclear Science and Engineering North China Electric Power University 102206 Beijing China department of Aerospace Engineering University of MichiganAnn Arbor MI 48109 USA

To better understand the multiphase fluid dynamics and associated transport processes of cavitating flows at the capillary number of 0.74 and 0.54, and to validate the numerical results, a combined computational and experimental investigation of flows around a hydrofoil is studied based on flow visualizations and time-resolved interface movement. The computational model is based on a modified RNG k-ε model as turbulence closure, along with a vapor-liquid mass transfer model for treating the cavitation process. Overall, favorable agreement between the numerical and experimental results is observed. It is shown that the cavi- tation structure depends on the interaction of the water-vapor mixture and the vapor among the whole cavitation stage, the interface between the vapor and the two-phase mixture exhibits substantial unsteadiness. And, the adverse motion of the interface relates to pressure and velocity fluctuations inside the cavity. In particular, the velocity in the vapor region is lower than that in the two-phase region.

关键词： Low capillary number cavitation Multiphasedynamics Flow visualization Turbulent cavitationmodeling

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