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双光路纹影仪观察气液传质界面湍动现象  [PDF]
陈杰,曾爱武,袁希钢
化工学报 , 2012, DOI: 10.3969/j.issn.0438-1157.2012.10.005
Abstract: 建立了双光路纹影仪实验系统,并利用双光路纹影仪,同时从垂直和平行于界面两个方向对氯苯吸收、解吸CO2的传质对流结构进行了观察,发现在氯苯吸收CO2时,没有明显的对流结构,只是在垂直界面的纹影图像中观察到逐渐变粗的暗条纹。在氯苯解吸CO2时,在垂直和平行于界面两个方向都观察到了明显的对流结构,在垂直界面的纹影图像中开始时出现分层现象,随着解吸的进行,对流加剧,分层现象被破坏;平行界面方向的对流结构发展较快,优先在平行界面的纹影图像中观察到明显的对流结构。由于传质的热效应,两个方向的对流结构都有向中心运动的趋势。实验表明,双光路纹影仪实验系统能观察界面传质对流过程的三维变化,可深化对界面传质对流过程的认识。
Experimental Study of Rayleigh-Benard Convection Destabilized by Heated Side Wall
M. Zeroual,P. Cerisier,M. Zereg
Journal of Engineering and Applied Sciences , 2012,
Abstract: A study of the influence, in addition to the effect of the vertical and horizontal heat gradient, of higher and lower walls, on the natural convection in a cavity was made. We studied the behavior of the induced roll (rI) in contact of the heating side wall, as well as Benard rolls (rB) number and the evolution of the convective structure according to the heating side. This study concerns two different values of the horizontal walls conductivity (polycarbonate and glass). The vessel is a parallelepipedic cavity filled with silicone oil (Pr 880 at 25°C) and which comprises three walls subjected to different temperatures (higher and lower walls as well as small with dimensions side). According to the small side wall temperature the observed structure is a network of transverse rolls (Rayleigh-Benard convection), in case of the side heating absence and network of transverse rolls with induced roll (rI). The dilation of the (rI) as well as the process of rB destruction are a function of the heat flow on the level of the side wall.
Second Law Analysis of Forced Convective Cooling in a Channel with a Heated Wall Mounted Obstacle  [PDF]
Z. Kheirandish, S. A. Gandjalikhan Nassab, M. Vakilian
Journal of Electronics Cooling and Thermal Control (JECTC) , 2013, DOI: 10.4236/jectc.2013.33012
Abstract:

The present work details a numerical simulation of forced convective laminar flow in a channel with a heated obstacle attached to one wall. The second law analysis is employed to investigate the distribution of entropy generation in the flow domain to demonstrate the rate of irreversibilities in thermal system. The conjugate problem including the convection heat transfer in the fluid flow and conduction one inside the obstacle is solved numerically to obtain the velocity and temperature fields in both gas and solid phases. To reach this goal, the set of governing equations including momentum and energy equations for the gas phase and conduction equation for the obstacle are solved by CFD technique to determine the hydrodynamic and thermal behaviors of the fluid flow around the obstacle and the temperature distribution in the solid element. An attempt is made to detail the local Nusselt number distribution and mean Nusselt number and also the local entropy generation distribution for the individual exposed obstacle faces. A good consistency is found between the present numerical results with experiment.

Bubble Dynamics of a Single Condensing Vapor Bubble from Vertically Heated Wall in Subcooled Pool Boiling System: Experimental Measurements and CFD Simulations  [PDF]
Arijit A. Ganguli,Aniruddha B. Pandit,Jyeshtharaj B. Joshi
International Journal of Chemical Engineering , 2012, DOI: 10.1155/2012/712986
Abstract: Bubble dynamics of a single condensing vapor bubble in a subcooled pool boiling system with a centrally heated cylindrical tank has been studied in the Rayleigh number range 7 . 9 × 1 0 1 2 < R a < 1 . 8 8 × 1 0 1 3 . The heat source in the system is steam condensing inside a vertical tube. The tube was placed in the center of the tank (300?mm i.d., 300?mm height) which is well filled with water. Experimental investigation has been carried out with High Speed Camera while Computational Fluid Dynamics (CFD) investigation has been performed using Volume of Fluid (VOF) method. The heat source has been modeled using simple heat balance. The rise behavior of condensing bubbles (change in size during rise and path tracking) was studied and the CFD model was validated both quantitatively and qualitatively. 1. Introduction Pool boiling is a complex nonlinear dynamic process. The microscopic aspects of boiling process, for example, embryo nucleation and surface roughness determine its nature largely. The microscopic effects eventually exhibit in a macroscopic behavior. Further, boiling is a highly stochastic process and the precise prediction of the location and time of the generation, collapse, coalescence is difficult with the present status of knowledge. The condensation of bubbles in subcooled boiling systems is extremely important for studying the hydrodynamics during subcooled pool boiling. The simple reason for this is that condensation changes the shape and size of the bubbles. When a bubble is formed at the interstitial site in the case of nucleate boiling the bubble grows to a certain diameter and then departs from the interstitial site. As the bubble departs from the nucleation site, it tends to slide along the hot surface and detaches from the surface. The bubble then does not necessarily follow a straight path but moves near or away from the wall. In addition to experimental investigations, Computational Fluid Dynamics (CFD) is useful to obtain better understanding of bubble dynamics. Experimental investigations on dynamics of single vapor bubbles condensing in a subcooled boiling liquid have been carried out by Voloshko and Vurgaft [1] and an analytical model was developed. The authors found the relation between the dynamics of vapor bubble during condensation and intensity of heat exchange at vapor bubble interface. Bubble dynamics of vapor bubbles in subcooled liquids have been investigated (both experimentally and numerically) by researchers [2–9]. Numerical investigations using volume of fluid (VOF) method have been recently carried out by
有机物水溶液解吸的界面湍动现象的观察与分析  [PDF]
金雾,曾爱武,杨宁,赵嵩
化工学报 , 2014, DOI: 10.3969/j.issn.0438-1157.2014.12.040
Abstract: 通过纹影光路,捕捉到低表面张力溶质从水中解吸导致的气液界面失稳过程及后续的对流结构图像.乙醇、异丙醇和丙酮水溶液中的现象相似:传质开始进行时,界面出现一个迅速变大的湍动区,湍动区扩张的同时,其边缘区域产生很多圆形的小胞,这些小胞逐渐演化成多边形,短暂的界面失稳过程之后,界面对流结构逐步发展为环形;但在乙酸乙酯体系中,界面对流结构一直都是团状的,而且湍动强度更为剧烈.结果表明,界面对流结构特点和剧烈程度取决于实验条件和体系的物理性质.
热线风洞湍谱仪  [PDF]
马振骅?,李惠云?,刘贤万?
气象学报 , 1965, DOI: 10.11676/qxxb1965.050
Abstract: 根据脉动气流的谱分析原理,制作了直接测量风洞气流脉动能谱密度的热线湍谱仪。本文介绍了该仪器的原理、详细结构和主要参数,并给出了一些测量结果。
加热对自然转捩湍斑产生影响的实验研究  [PDF]
杨立,蒋小勤,周福国,杜先之
工程热物理学报 , 1997,
Abstract: 本文利用流动显示和高速摄像技术,在湍流度为1%的水洞中,对加热的细长旅成体鱼雷模型表面的流动转捩过程进行了实验研究。实验发现,加热对自然转捩过程中湍流斑的猝发有明显影响,加热减小了湍斑产生的频率,增加了湍斑间的展向间距,使转捩过程中层流转变为完全湍流的过渡区延长.加热对瑞斑产生的纵向位置无明显影响。本文的实验结果正好解释在较高湍流庭环境中的加热减阻机理.
响叶杨(populusadenopoda)种子的形成及其寿命  [PDF]
吴琼美,樊汝汶
南京林业大学学报(自然科学版) , 1984, DOI: 10.3969/j.jssn.1000-2006.1984.01.014
Abstract: <正>用显微技术及软x射线摄影,定位观察响叶杨种子发育过程中的形态变化与胚胎发育的对应关系。根据观察、试验的结果,讨论了环境条件与种子寿命的关系;还测定了响叶杨种子寿命的变化规律及其影响因素,探索延长这种子寿命的方法。
响蜜Lie科的新记录
杨岚
动物学研究 , 1995,
Abstract: 1994年10月15日马中翼等人在云南省泸水县的老窝捕获到1只雄鸟,经中国科学院昆明动物研究所鉴定为黄腰响蜜lie,为我国鸟类科的新记录。标本保存在中国科学院昆明动物研究所鸟类标本室。科的特征体形较小。嘴形似雀,短而粗实,上嘴稍弯曲;尾羽12枚;翅形长而尖,仅具9枚初级飞羽;脚呈对趾型,第2、3趾向前,第1、4趾向后,似啄木鸟。
响蜜lie科的新记录  [PDF]
动物学研究 , 1995,
Abstract: 1994年10月15日马中翼等人在云南省泸水县的老窝捕获到1只雄鸟,经中国科学院昆明动物研究所鉴定为黄腰响蜜lie,为我国鸟类科的新记录。标本保存在中国科学院昆明动物研究所鸟类标本室。科的特征体形较小。嘴形似雀,短而粗实,上嘴稍弯曲;尾羽12枚;翅形长而尖,仅具9枚初级飞羽;脚呈对趾型,第2、3趾向前,第1、4趾向后,似啄木鸟。
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