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thermal stratification in Lake Zige Tangco, Central Tibetan Plateau

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Wuhan University Journal of Natural Sciences 2005年第4期10卷 689-693页

作者： LIWan-chun YANGXiang-dong YINYu JIJiang LIShi-jie PUPei-min NanjingInstituteofGeographyandLimnology ChineseAcademyofSciencesNanjing210008JiangsuChina

Lake Zige Tangco is an endorheic saline lake in central Tibetan *** of 1998 and 1999 revealed that is was a typical stratified lake. The characteristicsof thermal stratification of the lake have been extensively discussed from 4 aspects, i. ***, hydrochemistry and dissolved oxygen, stable isotope oxygen, and stability. Thethermocline coupled with chemocline was further analyzed.

关键词： thermal stratification Tibetan Plateau Lake Zige Tangco

Diurnal and Seasonal Variations of thermal stratification and Vertical Mixing in a Shallow Fresh Water Lake

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Journal of Meteorological Research 2018年第2期32卷 219-232页

作者： Yichen YANG Yongwei WANG Zhen ZHANG Wei WANG Xia REN Yaqi GAO Shoudong LIU Xuhui LEE Yale–NUIST Center on Atmospheric Environment Nanjing University of Information Science & Technology School of Environmental Science and Engineering Nanjing University of Information Science & Technology School of Atmospheric Physics Nanjing University of Information Science & Technology School of Applied Meteorology Nanjing University of Information Science & Technology School of Forestry and Environmental Studies Yale University

Among several influential factors, the geographical position and depth of a lake determine its thermal structure. In temperate zones, shallow lakes show significant differences in thermal stratification compared to deep lakes. Here,the variation in thermal stratification in Lake Taihu, a shallow fresh water lake, is studied systematically. Lake Taihu is a warm polymictic lake whose thermal stratification varies in short cycles of one day to a few days. The thermal stratification in Lake Taihu has shallow depths in the upper region and a large amplitude in the temperature gradient,the maximum of which exceeds 5°C m–1. The water temperature in the entire layer changes in a relatively consistent manner. Therefore, compared to a deep lake at similar latitude, the thermal stratification in Lake Taihu exhibits small seasonal differences, but the wide variation in the short term becomes important. Shallow polymictic lakes share the characteristic of diurnal mixing. Prominent differences on the duration and frequency of long-lasting thermal stratification are found in these lakes, which may result from the differences of local climate, lake depth, and fetch. A prominent response of thermal stratification to weather conditions is found, being controlled by the stratifying effect of solar radiation and the mixing effect of wind disturbance. Other than the diurnal stratification and convection, the representative responses of thermal stratification to these two factors with contrary effects are also discussed. When solar radiation increases, stronger wind is required to prevent the lake from becoming stratified. A daily average wind speed greater than 6 m s–1 can maintain the mixed state in Lake Taihu. Moreover, wind-induced convection is detected during thermal stratification. Due to lack of solar radiation, convection occurs more easily in nighttime than in daytime. Convection occurs frequently in fall and winter, whereas long-lasting and stable stratification causes less co

关键词： Lake Taihu thermal stratification solar radiation wind speed convection

Transient Behaviors of Thermo-Hydraulic and thermal stratification in the Pressurizer Surgeline for the Nuclear Power Plant

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Journal of thermal Science 2022年第2期31卷 344-358页

作者： YU Huajie LI Lu TANG Qionghui PENG Yue LI Yinshi State Key Laboratory of Nuclear Power Safety Monitoring Technology and Equipment Shenzhen 518172China Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001China

In pressurized water reactor(PWR)system,the surgeline plays an important role in bonding the pressurizer and the primary *** considerable problems,including the thermo-hydraulics,the thermal stratification and the accompanying thermal stress under transient conditions,pose risks to the surgeline ***,a fully-coupled flow-heat-thermo-elasticity model was developed to investigate the transient behavior of thermo-hydraulic parameters and the thermal stratification phenomenon in *** evaluate the nonuniformity of the stratified flow,a stratification degree indicatorζis *** is found that during the outsurge flow,the increase of temperature variation will enlarge the temperature gradient on the wall,corresponding to a more serious *** the cases of positive temperature variation,the higher temperature variation causes higher stratification degreeζ,and vice *** mass flow rate m and the stratification degree are in negative *** local deformation can reach 1.802 cm under a 50 K temperature variation,while its location varies from case to *** attention should be paid to the regulation between the highest deformation location and the surgeline thermo-hydraulic parameters.

关键词： pressurized water reactor surgeline transient thermo-hydraulic thermal stratification thermal stress-strain

Assessment of thermal stratification, stability and characteristics of deep water zone of the southern Caspian Sea

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Journal of Ocean Engineering and Science 2017年第3期2卷 203-216页

作者： Siamak Jamshidi Iranian National Institute for Oceanography and Atmospheric Science(INIOAS) No.3Etemadzadeh St.Fatemi Ave.Tehran ***Iran

Variations of seawater properties and stratification of water column in the southern deep water zone(470 m depth)of the Caspian Sea were evaluated based on field measured *** of physical characteristics(temperature,salinity,density and sound speed)of seawater mainly were limited to the upper 100 m *** this layer,seasonal changes of seawater parameters were *** structure of temperature in the southern Caspian Sea waters was characterized by a significant seasonal thermocline approximately between 20 and 50 m depths in summer with a vertical gradient of around 16℃.Destruction of the thermocline occurred with the general cooling of the sea surface water and deepening of the mixed layer during late of autumn and *** of stability in water column often across the upper layers(surface mixed and thermocline)was more than deeper *** of salinity were around 12.4 PSU in the time of *** of thermocline and pycnocline were characterized by a significant homogeneity especially in offshore stations during the *** to high agreement between density and temperature in the Caspian Seawater,a strong seasonal pycnocline was observed in the position of the ***,structure of sound speed variations followed vertical variations of seawater *** of chemical characteristics(dissolved oxygen and pH)of seawater mainly were continued from sea surface to near the sea bed in deep water zone.

关键词： Caspian Sea Seawater properties thermal stratification Water masses,Stability

Analyzing thermal stratification and Nanoparticle Shapes Influence on an EMHD Ternary Nanofluid Flow amidst Two Spinning Disks

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Journal of Applied Mathematics and Physics 2024年第8期12卷 3017-3025页

作者： Muhammad Ramzan Saima Riasat Department of Computer Science Bahria University Islamabad Pakistan Department of Mathematical Science Fatima Jinnah Women University Rawalpindi Pakistan

The present study examines the thermal distribution of ternary nanofluid flow amid two spinning disks influenced by electric and magnetic fields. Keeping in view the shape of the particles, the electrically conducting ternary nanofluid is analyzed with variable thermophysical features. Three types of nanoparticles namely Copper, Aluminum Oxide, and Graphene with spherical, cylindrical, and platelet shapes are taken respectively and are immersed in a (50-50)% ratio of water and ethylene glycol mixture which acts as a base fluid. The anticipated problem is addressed by employing a reliable and user-friendly numerical bvp4c built-in collocation scheme. This solution is then showcased through illustrations and tables. Strengthening the radiation results in an enhanced heat transfer rate. Radial and azimuthal velocities once rotation of disks is enhanced. The key findings provide a strong theoretical background in photovoltaic cells, solar collectors, radiators, solar water heaters, and many other applications.

关键词： Trihybrid Nanofluid Flow thermal stratification Particle Shapes Spin-ning Disks

Varying water column stability controls the denitrification process in a subtropical reservoir,Southwest China

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Journal of Environmental Sciences 2022年第1期34卷 208-219页

作者： Gaoyang Cui Xiao-Dong Li Siqi Li Shiyuan Ding Qinkai Li Mengdi Yang Hong Lv Yiyao Wang Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions Ministry of EducationCollege of Environment and PlanningHenan UniversityKaifeng 475004China Institute of Surface-Earth System Science School of Earth System ScienceTianjin UniversityTianjin 300072China Tianjin Key Laboratory of Earth’s Critical Zone Science and Sustainable Development in Bohai Rim Tianjin UniversityTianjin 300072China

Reservoirs are regarded as hotspots of nitrogen transformation and potential sources of nitrous oxide(N_(2)O).However,it remains unclear how the hydrological conditions due to dam construction control the processes of nitrogen transformation in reservoir *** address this issue,we examined the spatial-temporal characteristics of nitrate concentrations,δ^(15)N-NO_(3)^(-),δ^(18)O-NO_(3)^(-),δ^(18)O-H_(2)O,relative water column stability(RWCS),and related environmental factors in a subtropical eutrophic reservoir(Hongfeng Reservoir,HFR),Southwest *** found that denitrification was the most important nitrogen transformation process in the HFR and that higher denitrification intensity was associated with increased RWCS in summer,which suggested hydrological control of the denitrification *** contrast,low RWCS conditions favored the nitrification process in the HFR in ***,dissolved oxygen(DO;pstratification and the coupling/decoupling of nitrification-denitrification at the local and global *** study would advances our knowledge of the impacts of RWCS and thermal stratification on nitrogen transformation processes in reservoirs.

关键词： thermal stratification RWCS Denitrification Nitrogen transformation Reservoir

Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

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Building Simulation 2021年第3期14卷 579-599页

作者： Yakai Bai Ming Yang Jianhua Fan Xiaoxia Li Longfei Chen Guofeng Yuan Zhifeng Wang Key Laboratory of Solar thermal Energy and Photovoltaic Systems Chinese Academy of SciencesBeijing 700190China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering Technical University of DenmarkBrovej 1182800 Kgs.LyngbyDenmark Joint Laboratory Institute of Electrical EngineeringChinese Academy of Sciences and Guangdong Five Star Solar Energy Co.Ltd.Beijing 100190China Lanzhou University of Technology Gansu 730050China

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating.A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in *** thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive *** takes four to six years for the water pit to reach steady-state *** operation data from the tenth year was selected to evaluate the thermal performance of each *** results show that because of the thermal insulation on top of the water pit,the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than *** annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall *** is an almost linear increase in the thermal stratification number of a water pit with *** an increase in the height,thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower *** findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

关键词： water pit seasonal heat storage truncated cone storage capacity thermal stratification coordinate transformation

Destratification and oxygenation efficiency of a water-lifting aerator system in a deep reservoir:Implications for optimal operation

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Journal of Environmental Sciences 2018年第11期30卷 9-19页

作者： Yang Li Tinglin Huang Xinlin Tan Zizhen Zhou Weixing Ma Key Laboratory of Northwest Water Resource Environment and EcologyMOEXi'an University of Architecture and Technology Shaanxi Key Laboratory of Environmental Engineering Xi'an University of Architecture and Technology

thermal stratification is a common phenomenon in lakes and reservoirs and has a significant influence on water quality dynamics. Heihe Reservoir is a canyon-shaped reservoir in Shaanxi Province with strong thermal stratification. Therefore, eight water-lifting aerators （WLAs） were installed in this reservoir, which could overcome thermal stratification and increase oxygenation with gas flows between 20 and 50 m3/hr, and oxygenate the hypolimnion with gas flows less than 20 m3/hr. To examine the destratification efficiency of the WLA system, we used a three- dimensional hydrodynamic module based on MIKE 3 to simulate the thermal structure of Heihe Reservoir and compared the simulations with measured data. Results showed that operation of the WLA system promoted water mixing and effectively oxygenated the hypolimnion. Through the established energy utilization assessment method, the energy utilization efficiency of the WLA system was between 5.36% and 7.30%, indicating the capability of the technique for destratification in such a large reservoir. When the surface water temperature dropped to the theoretical mixed water temperature calculated by the energy utilization assessment method, reducing gas flow could save energy. This would prevent anaerobic conditions from occurring in the bottom water and maintain good water quality in Heihe Reservoir.

关键词： Reservoir thermal stratification Numerical simulation Water-lifting aerator Mixing Oxygenation

Development and application of a multi-physics and multi-scale coupling program for lead-cooled fast reactor

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Nuclear Science and Techniques 2022年第2期33卷 40-52页

作者： Xiao Luo Chi Wang Ze-Ren Zou Lian-Kai Cao Shuai Wang Zhao Chen Hong-Li Chen School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China China Nuclear Power Technology Research Institute Co.Ltd Shenzhen 518000China

In this study,a multi-physics and multi-scale coupling program,Fluent/KMC-sub/NDK,was developed based on the user-defined functions(UDF)of Fluent,in which the KMC-sub-code is a sub-channel thermal-hydraulic code and the NDK code is a neutron diffusion *** coupling program framework adopts the"master-slave"mode,in which Fluent is the master program while NDK and KMC-sub are coupled internally and compiled into the dynamic link library(DLL)as slave *** domain decomposition method was adopted,in which the reactor core was simulated by NDK and KMC-sub,while the rest of the primary loop was simulated using Fluent.A simulation of the reactor shutdown process of M2LFR-1000 was carried out using the coupling program,and the code-to-code verification was performed with ATHLET,demonstrating a good agreement,with absolute deviation was smaller than 0.2%.The results show an obvious thermal stratification phenomenon during the shutdown process,which occurs 10 s after shutdown,and the change in thermal stratification phenomena is also captured by the coupling *** the same time,the change in the neutron flux density distribution of the reactor was also obtained.

关键词： Multi-physics and multi-scale coupling method User-defined functions Dynamic link library thermal stratification Lead-cooled fast reactor