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Characteristics of temperature fluctuation in two-dimensional turbulent Rayleigh-Bénard convection

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Chinese Physics B 2022年第1期31卷 395-402页

作者： Ming-Wei Fang Jian-Chao He Zhan-Chao Hu Yun Bao School of Aeronautics and Astronautics Sun Yat-sen UniversityGuangzhou 510275China

We study the characteristics of temperature fluctuation in two-dimensional turbulent Rayleigh–Benard convection in´a square cavity by direct numerical *** Rayleigh number range is 1×10^(8)≤Ra≤1×10^(13),and the Prandtl number is selected as Pr=0.7 and Pr=*** is found that the temperature fluctuation profiles with respect to Ra exhibit two different distribution *** the thermal boundary layer,the normalized fluctuationθrms/θrms,max is independent of Ra and a power law relation is identified,i.e.,θrms/θrms,max∼(z/δ)0.99±0.01,where z/δis a dimensionless distance to the boundary(δis the thickness of thermal boundary layer).Out of the boundary layer,when Ra≤5×10^(9),the profiles ofθrms/θrms,max descend,then ascend,and finally drop dramatically as z/δ*** for Ra≥1×10^(10),the profiles continuously decrease and finally overlap with each *** two different characteristics of temperature fluctuations are closely related to the formation of stable large-scale circulations and corner ***,there is a critical value of Ra indicating the transition,beyond which the fluctuation hθrmsiV has a power law dependence on Ra,given by hθrmsiV∼Ra−0.14±0.01.

关键词： Rayleigh-Benard temperature fluctuation distribution patterns critical value

Effect of temperature fluctuation on hydrate-based CO_2 separation from fuel gas

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Journal of Natural Gas Chemistry 2011年第6期20卷 647-653页

作者： Xiaosen Li Chungang Xu Zhaoyang Chen Huijie Wu Jing Cai Key Laboratory of Renewable Energy and Gas Hydrate Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 510640 Guangdong China Guangzhou Center for Gas Hydrate Research Chinese Academy of Sciences Guangzhou 510640 Guangdong China Graduate University of Chinese Academy of Sciences Beijing 100083 China

A new method of temperature fluctuation is proposed to promote the process of hydrate-based CO2 separation from fuel gas in this work according to the dual nature of CO2 solubility in hydrate forming and non-hydrate forming regions [1].The temperature fluctuation operated in the process of hydrate formation improves the formation of gas hydrate *** amount of the gas consumed with temperature fluctuation is approximately 35% more than that without temperature *** is found that only the temperature fluctuation operated in the period of forming hydrate leads to a good effect on CO2 ***,with the proceeding of hydrate formation,the effect of temperature fluctuation on the gas hydrate gradually reduces,and little effect is left in the completion *** CO2 separation efficiencies in the separation processes with the effective temperature fluctuations are improved remarkably.

关键词： gas hydrate CO2 fuel gas temperature fluctuation

Influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2006年第3期7卷 180-185页

作者： WUMan-chang SUN Ke-wei ZHANG Yong School of Environmental Science and Engineering Kunming University of Science and Technology Kunming 650093 China National Engineering Research Center of Solid Waste Resource Recovery Kunming 650033 China

A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste （MOSW）. Heating failure was simulated by decreasing temperature suddenly from 55 ℃ to 20 ℃ suddenly, 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/（L·d） and 15 d respectively for MOSW load and retention time, following results were noted：（1） biogas production almost stopped and VFA （volatile fatty acid） accumulated rapidly, accompanied by pH decrease; （2） with low temperature （20 ℃） duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation, （3） the longer the low temperature interval lasted, the more the methanogenic bacteria would decay, hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation：（4） the thermophilic microorganisms were highly resilient to temperature fluctuation.

关键词： temperature fluctuation Low temperature duration Thermophilic anaerobic digestion Municipal organic solid waste

Study on Meniscus temperature fluctuation during Mold Oscillation in Continuous Casting by Modeling Experiments

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Journal of Shanghai University(English Edition) 2002年第3期6卷 236-237页

作者：雷作胜张邦文邓康任忠鸣 School of Materials Science and Engineering Shanghai University Shanghai China

The temperature of the meniscus in continuous casting was measured during mold oscillation by modeling experiments. It is found that the temperature of meniscus varied periodically along with mold oscillation. Based on the above phenomenon, the mechanism of some techniques, such as, hot top mold, high frequency and low amplitude mold oscillation, soft contact mold electromagnetic continuous casting and so on, which can improve the quality of continuous casting billets, was analyzed. The results show that the decrease of the temperature fluctuation of early solidification shell is their common mechanism.

关键词： continuous casting mold meniscus temperature fluctuation mold oscillation.

Experimental study on temperature fluctuations on plate surface induced by coaxial-jet flow

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Nuclear Science and Techniques 2024年第5期35卷 139-153页

作者： Xue-Yao Xiong Zun-Quan Liu Guo-Yan Zhou Xing Luo Shan-Tung Tu Key Laboratory of Pressure Systems and Safety(MOE) East China University of Science and TechnologyShanghai 200237China Institute of Thermodynamics Gottfried Wilhelm Leibniz University Hannover30823 GarbsenGermany

In nuclear reactors,temperature fluctuations of fluids may cause fatigue damage to adjacent structures;this is referred to as thermal *** on thermal striping in the upper plenum has mainly focused on fluid *** experimental studies have been reported on solid structures in a fluid field with a coaxial *** study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial *** temperature fluctuations of the fluid and plate surfaces located at different heights were *** cause of the temperature fluctuation was analyzed using a transient temperature *** results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial *** average surface temperatures tended to be *** the jet reaches the plate surface,the swing of the jet center,contraction and expansion of the cold jet,and changes in the jet shape result in temperature *** intensity of the temperature fluctuation was affected by the *** attention should be paid when the plate is located at a lower height,and between the hot and cold-fluid nozzles.

关键词： temperature fluctuation Thermal striping Coaxial jet Thermal mixing The upper plenum of nuclear reactor

Assessment of quality deviation of pork and salmon due to temperature fluctuations during superchilling

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2022年第7期23卷 578-586页

作者： Haoxin CUI Naymul KARIM Feng JIANG Haimei HU Wei CHEN Department of Food Science and Nutrition College of Biosystems Engineering and Food ScienceZhejiang UniversityHangzhou310058China Changhong Meiling Co.Ltd. Hefei230000China Ningbo Research Institute Zhejiang UniversityNingbo315100China

Superchilling is an emerging technology for meat preservation;however,the temperature changes during the process have been commonly ***,the effects of temperature fluctuations on meat quality during superchilling are yet to be *** our study,pork loins and salmon fillets were stored for several days(0,8,15,23,and 30 d)under different temperature fluctuations based on−3.5℃ as the target *** results showed that after 15 d of superchilling storage,the values of total volatile basic nitrogen,total viable count,and lipid oxidation were significantly(Pfluctuation group compared with the constant temperature *** the contrary,there was no significant difference in these parameters between the±1.0℃ fluctuation group and the constant temperature group after 30 d of *** addition,irregular temperature changes significantly accelerated the modulation of various *** brief,temperature fluctuations and irregular temperature changes accelerated the destruction of muscle structural integrity,increased the water loss,gradually widened the water loss channels,and thereby reduced the edibility by accelerating the spoilage of meat.

关键词： Pork Salmon Superchilling temperature fluctuation Meat quality

Partially-Premixed Combustion Characteristics and Thermal Performance of Micro Jet Array Burners with Different Nozzle Spacings

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Journal of Thermal Science 2021年第5期30卷 1718-1730页

作者： YANG Haolin WU Yong ZENG Xiaojun WANG Xiaohan ZHAO Daiqing Guangzhou Institute of Energy Conversion Chinese Academy of SciencesGuangzhou510640China Department of Energy and Mechanical Engineering Hunan University of HumanitiesScience and TechnologyLoudi417000China Key Laboratory of Renewable Energy Chinese Academy of SciencesGuangzhou510640China Guangdong Provincial Key Laboratory of New and Renewable Energy Research and Development Guangzhou510640China Guangdong Institute of Special Equipment Inspection and Research Shunde Branch Foshan528300China

In order to develop a burner with uniform temperature field,the combustion characteristics and thermal performance of partially premixed methane/air jet flames were experimentally studied by using micro jet array *** circular tubes of 1.0-mm inner diameter and 1.5-mm outer diameter were used as *** effects of nozzle spacing and equivalence ratio on flame phenomenology,temperature distribution and pollutant emissions were respectively investigated by camera photography,thermocouple measurement and sampling *** show that there are two clean flame patterns:clean merged-flame and clean non-merging *** flame patterns depend on the strength of flame interaction,the equivalence ratio of the mixture and the quantity of air entrainment through the gap between *** burners with small nozzle spacing such as 2 mm and 2.5 mm tend to produce fully merged flame with low equivalence ratio limit and the corresponding temperature fields are very uniform with fluctuations less than 0.3%,but a small increase in equivalence ratio will lead to rapid deterioration of combustion *** burner with a medium spacing of 3 mm can produce partially merged flame in a wide equivalence ratio range with low emissions,and the temperature fluctuation can be less than 0.5%(temperature fluctuation over 1%,while it can achieve clean combustion under high equivalence ratio due to large air *** analysis shows that the micro jet array burner with medium nozzle spacing of 3 mm has the best combustion characteristics and thermal performance.

关键词： micro jet array burner flame interaction methane/air flame temperature fluctuation thermal performance

Heat Transfer Characteristics of Dropwise Condensation of Steam on Vertical Polymer Coated Plates

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Chinese Journal of Chemical Engineering 2001年第1期9卷 17-21页

作者：马学虎陈嘉宾徐敦颀林纪方大连理工大学辽宁大连

The plasma polymerization method and dynamic ion-beam mixed implantation method were employed to coat ultra-thin polymer films on copper plates. Experiments indicated that steady dropwise condensation of steam at atmospheric pressure occurred. The condensation heat transfer coefficients increased by approximately 3 and 5－7 times for the polytrimethylvinylsilane film and polytetrafluoroethylene film respectively, compared with the value for film condensation under the same experimental conditions. The temperatures on the condensing surface and inside the test block were found to be rapidly and randomly fluctuated. The properties of the coated films and advantages of the methods used in this investigation were discussed briefly.

关键词： dropwise condensation heat transfer polymer film temperature fluctuation

Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1185-1200页

作者： Weicheng Zhang Andreas Eckert Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and TechnologyRollaMOUSA

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life *** MA can significantly compromise wellbore integrity by establishing enhanced fluid flow *** study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole *** emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening *** resulting state of stress during the life cycle of a typical injection well(***,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole *** results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding *** summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is *** results are different compared to laboratory studies without considering/simulating downhole *** kno

关键词： Micro-annulus Debonding Staged finite element analysis Cement hardening Poro-elastic bulk shrinkage Pore pressure temperature fluctuation