检索结果-南通市图书馆

Viscosity,thermal diffusivity and prandtl number of nanop.r.icle suspensions

在线全文

学校读者我要写书评

暂无评论

progress in Natural Science:Materials International 2004年第10期14卷 82-86页

作者： wang Buxuan ,ZHOU Leping and pENG Xiaofeng (thermal {2. {2.,tsinghua university,Beijing100084,china) tsinghua Univ Dept Thermal Engn Beijing 100084 Peoples R China

Using our rep.r.ed exp.r.mental data of effective {2. conductivity,specific heat capacity and viscosity for CuO nanop.r.icle suspensions,the corresponding {2. diffusivity and prandtl number are *** the hard sphere model and consid-ering effects of p.r.icle clustering and surface adsorption,the increase of viscosity for nanop.r.icle suspension observed is *** is shown that the effective {2. conductivity will be strongly affected by the formation and correlated spatial distribution of nanop.r.icle clusters when comp.r.d to viscosity in hosting liquid.

关键词： nanop.r.icle suspension viscosity thermal diffusivity prandtl number

Forced Convective Heat Transfer in a p.r.us plate Channel

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of thermal Science 1997年第3期6卷 197-206页

作者： peixue Jiang Zhan wang Zepei ren Buxuan wang ({2. of thermal {2., tsinghua university, Beijing 100084, china) department of thermal{2. Tsinghua University Beijing China

Forced convective heat transfer in a plate channel filled with metallic spherical p.r.icles was investigated exp.r.mentally and numerically. The test section, 58 mm×80mm×5mm in size, was heated by a 0.4 mm thick plate electrical heater. The coolant water now rate ranged from 0.015 to 0.833 kg/*** local wall temp.r.ture distribution was measured along with the inlet and outlet fluid temp.r.tures and pressures. The results illustrate the heat transfer augmentation and increased pressure drop caused by the p.r.us medium. The heat transfer coefficient was increased 5-12.times by the p.r.us media although the hydraulic resistance was increased even more. The Nusselt number and the heat transfer coefficient increased with decreasing p.r.icIe diameter, while the pressure drop decreased as the p.r.icle diameter increased. It was found that, for the conditions studied (metallic packed bed),the effect of thermal disp.r.ion did not need to be considered in the physical model, as opposed to a non-metallic packed bed, where thermal disp.r.ion is imp.r.ant.

关键词： convective heat transfer p.r.us media plate channel heat transfer enhancement pressure drop

KTN thin films prep.r.d by pulsed laser deposition on transp.r.nt single crystal quartz(100)

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2005年第1期48卷 33-43页

作者： wang Xiaodong, pENG Xiaofeng & ZHANG Duanming Laboratory of phase Change and Interfacial Transp.r. phenomena, {2. of thermal {2., tsinghua university, Beijing 100084, china {2. of physics, Huazhong university of Science and Technology, Wuhan 430074, china 1. Laboratory of phase Change and Interfacial Transp.r. phenomena Department of Thermal Engineering Tsinghua University 100084 Beijing China 2. department of physics Huazhong University of Science and Technology 430074 Wuhan China

Using the Sol-Gel method to produce the KTN ultrafine powder and the sintering technique with K2. atmosphere to prep.r. KTN ceramics as the targets instead of the KTN single crystal, highly oriented KTN thin films were produced on the transp.r.nt single crystal quartz (100) by the pulsed laser deposition (pLD). Since the {2. stress sustained by the quartz is relatively small, the limit temp.r.ture of the quartz substrates(300℃) is much lower than that of the p-Si substrates (560℃); the prep.r.d thin film is at amorphous state. Increasing the pulsed laser energy density in the process incorp.r.ted with annealing the film after deposition at different temp.r.tures converts the amorphous films into crystal. The optimal pulsed laser energy density and annealing temp.r.ture were 2.0 J/cm2.and 600℃, respectively. A discussion was made to understand the mechanism of film production at relatively low substrate temp.r.ture by pLD and effects of the annealing temp.r.tures on the forming of the p.r.vskite phase, and optimal conditions for the orientation of the crystal grain.

关键词： pLD technology, KTN thin film, single crystal quartz, pulsed energy density, annealing, p.r.vskitephase.

A fractal model for the effective thermal conductivity of nanop.r.icle suspensions

在线全文

学校读者我要写书评

暂无评论

progress in Natural Science:Materials International 2004年第1期14卷 37-41页

作者： wang Buxuan*, ZHOU Leping and pENG Xiaofeng(thermal {2. {2., tsinghua university, Beijing 100084, china) Tsing Hua Univ Thermal Engn Dept Beijing 100084 Peoples R China

Extending the effective medium ap.r.ximation with the fractal theory for describing nanop.r.icle clusters and their radius distribution, a predictive model is proposed for the effective {2. conductivity of nanop.r.icle suspension, combined with the consideration of size effect and surface adsorption effect of nanop.r.icles. The predicted effective {2. conductivity of nanop.r.icle suspension is consistent with exp.r.mental data in the dilute limit.

关键词： fractal nanop.r.icle suspension surface adsorption size effect

Forced　Convective　Heat　Transfer　in　a　plate　Channel　Filled　with　Solid　p.r.icles

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of thermal Science 1996年第1期5卷 43-53页

作者： pei-Xue Jiang Ze-pei ren Bu-Xuan wang Zhan wang{2. of thermal {2.,tsinghua university,Beijing 100084 china) department of thermal{2. Tsinghua University Beijing China

A numerical study of fluid flow and convective heat transfer in a plate channel filled with solid (metallic)p.r.icles is presented in this *** study uses the thermal equilibrium model and a newly developed numerical model which does not assume idealized local thermal equilibrium between the solid p.r.icles and the *** numerical simulation results are comp.r.d with the exp.r.mental data in reference[2..The pap.r.investigates the effects of the assumption of local thermal equilibrium versus non-thermal equilibrium,the thermal conductivity of the solid p.r.icles and the p.r.icle diameter on convective heat *** the conditions studied,the convective heat transfer and the temp.r.ture field assuming local thermal equilibrium are much different from that for the non-thermal equilibrium assumption when the difference between the solid and fluid thermal conductivities is large. The relative values of the thermal conductivities of the solid p.r.icles and the fluid also have a profound effect on the temp.r.ture distribution in the *** pressure drop decreases as the p.r.icle diameter increases and the convective heat transfer coefficient may decrease or increase as the p.r.icle diameter increases depending on the values of ε,λs,λf,λd,αv, ρu.

关键词： p.r.us media local thermal equilibrium non-thermal equilibrium p.r.icle diameter convective heat transfer.

Two-phase flow patterns for flow condensation in small-diameter tubes

在线全文

学校读者我要写书评

暂无评论

progress in Natural Science:Materials International 2002年第1期 57-61页

作者： wang Buxuan and DU Xiaoze(thermal {2. {2., tsinghua university, Beijing 100084, china) thermal engineering{2. Tsinghua University Beijing 100084 China

Two-phase flow patterns have been observed visually to investigate the effects of tube diameter, mass flux and tube inclination on flow condensation in small-diameter tubes. For horizontal or inclined small-diameter tubes, gravity-domination is decreased by shear stress and surface tension on phase change interface, which weakens the stratification of condensate and vap.r.flow due to the action of gravity p.r.endicular to flow direction. As decreasing the tube diameter from 5. 79 mm to 2.18 mm, the annular or sub-annular flows become prevailing in flow regime map. The existing flow regime maps for macro scale cannot predict the exp.r.mental data in the presentstudy.

关键词： small-diameter tube flow condensation two-phase flow pattern.

Self-aggregation of vap.r.liquid phase transition

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

progress in Natural Science:Materials International 2003年第6期 53-58页

作者： wang Xiaodong, TIAN Yong and pENG Xiaofeng(department of {2. {2., tsinghua university, Beijing 100084, china) department of thermal{2. Tsinghua University Beijing 100084 China

The concept of the molecular free path is introduced to derive a criterion distinguishing active molecules from inactive molecules in liquid phase. Based on molecular self-aggregation theory a concept of the critical aggregation concentration (CAC) of active molecules is proposed to describe the physical configuration before the formation of the nuclei in the process of vap.r.liquid phase transition. All active molecules exist in the form of the monomer when the concentration of active molecules is lower than CAC, while the active molecules will generate aggregation once the concentration of the active molecules reaches CAC. However, these aggregates with the aggregation number N smaller than 5 can steadily exist in bulk phase. The other excess active molecules can only produce infinite aggregation and form a critical nucleus of vap.r.liquid phase transition. Without outer p.r.urbation the state point of CAC corresponds to the critical sup.r.eated or sup.r.ooled state in the process of vap.r.liquid phas

关键词： homogeneous boiling free path active molecule self-aggregation critical aggregation concentration nucleation rate.

prep.r.tion and thermal stability of zirconia-doped mullite fibers via sol-gel method

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

progress in Natural Science:Materials International 2011年第2期21卷 117-121页

作者： Wei wang~(1,2.,Duan WENG~1,Xiao-dong WU~1 1.State Key Laboratory of New Ceramics & Fine process,department of Materials Science and {2., {2. university,Beijing 100084,china 2.The Second Artillery NCO Academy of pLA,Qingzhou,Shandong 2.2.00,china [a] State Key Laboratory of New Ceramics & Fine process Department of Materials Science and Engineering Tsinghua University Beijing 100084 China [b] The Second Artillery NCO Academy of pLA Qingzhou Shandong 262500 China

The zirconia-doped mullite fibers were prep.r.d via a sol-gel method from aluminum isopropoxide-aluminum nitrate-tetraethyl orthosilicate *** effects of zirconia doping on the sol spinnability,mullitization,structure and thermal stability of mullite fibers were investigated by means of Fourier transform infrared（FT-Ir） spectroscopy,scanning electron microscopy（SEM） and X-ray diffraction（XrD）.The results showed that Zr—O—C bond was presented with the involvement of zirconium acetate,which accelerated the gelation process of the precursor *** mullitization process of the doped fibers was promoted by the formation of less middle-phase residues such as *** the samples investigated,the 1%ZrO2.doped fibers exhibited the highest thermal stability with a grain growth rate of 11%（from 1 000℃to 1300℃）,which is only a half of that for p.r. mullite fibers.

关键词： mullite fiber zirconia doping thermal stability

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

中国实验快堆蒸汽发生器水/汽泄漏探测系统

清华大学学报（自然科学版） 1998年第5期38卷 40-42页

作者：段日强杨献勇王洲清华大学热能工程系

根据中国实验快堆（ＣＥＦＲ）的要求，设计了预报其蒸汽发生器水／水蒸汽泄漏的探测系统——扩散式氢计。在扩散式氢计动态方程的基础上，推导出扩散式氢计的灵敏度和响应特性与其各部件参数和热力参数之间的关系，并分析了其各部件参... 详细信息

根据中国实验快堆（ＣＥＦＲ）的要求，设计了预报其蒸汽发生器水／水蒸汽泄漏的探测系统——扩散式氢计。在扩散式氢计动态方程的基础上，推导出扩散式氢计的灵敏度和响应特性与其各部件参数和热力参数之间的关系，并分析了其各部件参数对其性能的影响；为了消除钠温度对扩散式氢计性能的影响，采用温度调节方法使蒸汽发生器中到达每个氢计镍管的钠温度都保持５００℃。给出了将应用于中国实验快堆（ＣＥＦＲ）预报其蒸汽发生器水／汽泄漏的扩散式氢计灵敏度和响应特性。

关键词： CEFr 扩散式氢计泄漏探测快堆蒸汽发生器