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Scaling effect of breakthrough character in porous media

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Chinese Science Bulletin 2001年第10期46卷 878-880页

作者： Xuejiao Hu Jianhua Du Xiang Liu buxuan wang Tsing Hua Univ Dept Thermal Engn Beijing 100084 Peoples R China

Breakthrough phenomenon during fluids percolating through wet saturated porous layer is widely met in the study of heat and mass transfer in porous media. Breakthrough pressure (BP) is a characteristic pressure that indicates the intrinsic properties of seepage within porous media. Measuring results of BP for saturated narrow-sieved sand are reported here. The curve of BP varying with the height of porous layer was obtained. Experiment and analysis indicate that BP is independent of the height of particle packed layer if thick enough; however, when the height is less than a certain critical value, BP diminishes with the decrease of the height according to a universal scaling law.

关键词： breakthrough pressure porous media percolation boiling enhanced porous surface scaling law.

Infrared experiment on the wall temperature distribution for a particle packed channel with constant heat flux

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Chinese Science Bulletin 2001年第18期46卷 1566-1568页

作者： Jianhua Du Xuejiao Hu Bin Ma Wei Wu buxuan wang Tsing Hua Univ Dept Thermal Engn Beijing 100084 Peoples R China

With constant heat flux, wall temperature distribution for a particle filled channel was measured using infrared thermal vision technology. It was found that non-uniform relative high-temperature regions were randomly distributed on the heating wall, possibly due to the lower flow velocity, or even due to the blocked flow near the points where particles contact with the heating wall directly. Not only porosity but also the size and shape of the pores are changed in the wall region of particle-packed structures, because of the limitation of the wall, and the changes affect largely the fluid flow and heat transfer. The transition of the flow pattern in pores can be inferred according to the variation of Nu with Re, where the area weighted wall temperature is adopted to calculate the Nu.

关键词： porous media heat transfer enhancement infrared thermograph.

Viscosity,thermal diffusivity and Prandtl number of nanoparticle suspensions

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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 Engineering Department,Tsinghua University,Beijing100084,China) Thermal Eng. Dept. Tsinghua Univ. Beijing 100084 China

Using our reported experimental data of effective thermal conductivity,specific heat capacity and viscosity for CuO nanoparticle suspensions,the corresponding thermal diffusivity and Prandtl number are *** the hard sphere model and consid-ering effects of particle clustering and surface adsorption,the increase of viscosity for nanoparticle suspension observed is *** is shown that the effective thermal conductivity will be strongly affected by the formation and correlated spatial distribution of nanoparticle clusters when compared to viscosity in hosting liquid.

关键词： nanoparticle suspension viscosity thermal diffusivity Prandtl number

ADSORPTION OF NANO-PARTICLES ON BUBBLE SURFACE IN NANO-PARTICLE SUSPENSION

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China Particuology 2005年第4期3卷 208-212页

作者： buxuan wang Chunhui Li Xiaofeng Peng Laboratory of Phase-Change and Interfacial Transport Phenomena Department of Thermal Engineering Tsinghua UniversityBeijing 100084 P. R. China

The adsorption of nano-particles on bubble surface is discussed for saturated boiling on thin wire of nano-particle suspensions. Owing to the decrease of surface tension for suspensions, the nano-particles tend to adsorb on the bubble surface to decrease the Gibbs free energy for stability, and meanwhile the velocity of nano-particles would be smaller than that of bubble growth. The long-range van der Waals force existing between “water particles” and nano-particles is considered the attractive force between the nano-particles and the bubble surface. Thus, the nano-particles would attach on the bubble surface if the particle-surface distance is smaller than its critical value. The distribution of nano-particles on the bubble surface and in the adjacent region is also investigated.

关键词： nano-particle suspension attachment critical distance

Forced Convective Heat Transfer in a Porous Plate Channel

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

作者： Peixue Jiang Zhan wang Zepei Ren buxuan wang (Department of Thermal Engineering, Tsinghua University, Beijing 100084, China) Department of Thermal Engineering Tsinghua University Beijing China

Forced convective heat transfer in a plate channel filled with metallic spherical particles was investigated experimentally 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 temperature distribution was measured along with the inlet and outlet fluid temperatures and pressures. The results illustrate the heat transfer augmentation and increased pressure drop caused by the porous medium. The heat transfer coefficient was increased 5-12 times by the porous media although the hydraulic resistance was increased even more. The Nusselt number and the heat transfer coefficient increased with decreasing particIe diameter, while the pressure drop decreased as the particle diameter increased. It was found that, for the conditions studied (metallic packed bed),the effect of thermal dispersion did not need to be considered in the physical model, as opposed to a non-metallic packed bed, where thermal dispersion is important.

关键词： convective heat transfer porous media plate channel heat transfer enhancement pressure drop

颗粒团聚对低浓度纳米流体热性质和热过程的影响

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机械工程学报 2009年第3期45卷 1-4页

作者：王补宣清华大学热能工程系北京100084

添加纳米颗粒的悬浮液正在成为迅速开发应用中的新型功能流体,并被命名为"纳米流体"。颗粒在液体中的随机布朗运动和颗粒表面的吸附促成了颗粒团聚成簇,改变了悬浮液的均匀性,引起悬浮液物性的变异,影响了热过程的特性。提出以纳米颗粒... 详细信息

添加纳米颗粒的悬浮液正在成为迅速开发应用中的新型功能流体,并被命名为"纳米流体"。颗粒在液体中的随机布朗运动和颗粒表面的吸附促成了颗粒团聚成簇,改变了悬浮液的均匀性,引起悬浮液物性的变异,影响了热过程的特性。提出以纳米颗粒团聚统计平均尺度的团簇表观特征量的解析计算方法,计算简易,物理含义清晰易懂。将悬浮液视作悬浮的开放型多孔结构,成功地按有效介质理论预测团簇分布不均匀的特性影响,这对有意识地筛选纳米流体的匹配具有实际指导意义。

关键词：纳米流体颗粒团聚团簇的宏观统计特征量纳米流体热物性的预测

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微通道气液柱塞流头部流场三维实验研究

西南交通大学学报 2013年第2期48卷 223-235,242页

作者：王凌罗锐王补宣冀北电力有限公司物资供应分公司北京100075 清华大学热能工程系北京100084

为研究微通道气液柱塞流三维流场特性,采用三维Micro PIV技术对微通道气液柱塞流进行实验研究,通过处理分析柱塞流图像,获得气泡前部区域的示踪颗粒分布图和三维速度分布图.研究结果表明:在气泡前部区域存在两个对称的方向相反的漩涡;... 详细信息

为研究微通道气液柱塞流三维流场特性,采用三维Micro PIV技术对微通道气液柱塞流进行实验研究,通过处理分析柱塞流图像,获得气泡前部区域的示踪颗粒分布图和三维速度分布图.研究结果表明:在气泡前部区域存在两个对称的方向相反的漩涡;在气柱头部附近区域,流体以较大速度沿着气柱表面流动;在远离气柱头部的区域,与单相流有类似的抛物线速度分布;在气液界面和壁面之间的流体运动复杂,有可能流向气液界面,也有可能流向壁面,气液界面近似为刚性.

关键词：微通道柱塞流三维流场 Micro—PIV

A fractal model for the effective thermal conductivity of nanoparticle suspensions

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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 Engineering Department, Tsinghua University, Beijing 100084, China) Tsing Hua Univ Thermal Engn Dept Beijing 100084 Peoples R China

Extending the effective medium approximation with the fractal theory for describing nanoparticle clusters and their radius distribution, a predictive model is proposed for the effective thermal conductivity of nanoparticle suspension, combined with the consideration of size effect and surface adsorption effect of nanoparticles. The predicted effective thermal conductivity of nanoparticle suspension is consistent with experimental data in the dilute limit.

关键词： fractal nanoparticle suspension surface adsorption size effect

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细圆管内流动凝结换热的实验研究

工程热物理学报 2000年第3期21卷 324-328页

作者：王补宣杜小泽清华大学热能工程系北京100084

通过实验，分析细圆管的倾斜角度和管径对管内蒸气流动凝结换热的影响。利用实测的管壁温度变化。估计凝结液沿周向的分布。探讨不同倾角和管径条件下；重力作用影响凝结换热的机制。研究表明，在小尺度下，重力的影响受蒸气剪切力和表... 详细信息

通过实验，分析细圆管的倾斜角度和管径对管内蒸气流动凝结换热的影响。利用实测的管壁温度变化。估计凝结液沿周向的分布。探讨不同倾角和管径条件下；重力作用影响凝结换热的机制。研究表明，在小尺度下，重力的影响受蒸气剪切力和表面张力作用而削弱，现有通行的关联式不适用于细圆管内的凝结换热。

关键词：细圆管流动凝结实验研究换热