Transient Simulation of the Electrolyte Flow in a Closed Device for Precise Electrochemical Machining - new
M. Hackert-Oschätzchen, M. Penzel, M. Kowalick, G. Meichsner, A. Schubert[1,2]
Professorship Micromanufacturing Technology, Technische Universität Chemnitz, Chemnitz, Germany
Fraunhofer Institute for Machine Tools and Forming Technology, Chemnitz, Germany
Precise electrochemical machining (PEM) is an innovative machining technology which results from further development of the electrochemical sinking. PEM works with pulsed low frequency direct current and oscillation of the tool electrode. As part of the project ‘Electrochemical machining of internal precision and micro-geometries with high aspect ratios by process-state-dependent electrolyte ...
赵旭山 , 郝雷 , 蒋利军 , 米菁 , 杨海龄 ,
随着能源紧张、油价攀升，环境污染严重，利用可再生绿色能源又成为不懈努力的方向。槽式太阳能热发电技术具有兼容性强、对电网冲击小、性价比高、发电成本低、可存储可调度等特点，近年来得到了迅猛发展，其核心部件为高温太阳能真空集热管，如图1所示。本研究利用 COMSOL Multiphysics® 针对真空集热管真实工况下的动态过程开展研究，并在此基础上开展集热管结构的优化设计。 由图1可知：集热管在电站中服役工况下，槽面会聚的太阳光主要集中于集热管下半面，上半面接收的会聚太阳光较少；导热工质自吸收管一端进入，接收会聚太阳光辐照能量，从吸收管另一端流出，流入→流出过程中，导热工质被加热；集热管外表面与外部环境通过热辐射和对流两种方式换热；吸收管与玻璃罩管间形成的环形密闭高真空区域各内表面通过热辐射换热，不考虑对流；集热管两端支撑固定于聚光器上，由于本身自重和热应力 ...
P. Lin, C. Chang, H. Huang, and B. Zheng
Mechanical and Aerospace Eng., Rutgers, The State University of New Jersey, Piscataway, NJ
FTR Systems (Shanghai) Inc., Shanghai, China
PolarOnyx, Inc., San Jose, CA
School of Mechatronics Eng., University of Electronic Science and Technology of China, Chengdu, China
The heat sink designs using impinging liquid jets, which form stagnation flows, feature uniform heat transfer coefficients, and provide thin thermal boundary layers, are studied to reduce the heat from GPUs. Three different designs using central, micro, and uniform-cross-section (UCS) central jets are studied and simulated in COMSOL. The efficiency factors, defined as the ratio of total ...
D. C. Raharja , R. E. Hincapie , M. Be , C. L. Gaol , L. Ganzer ,
 Clausthal University of Technology, Clausthal-Zellerfeld, Germany
Aqueous polymers used for enhanced oil recovery (EOR) application is considered a complex fluid. It can exhibit Newtonian and Non-Newtonian behavior depending on the velocity or the stresses that it is submitted during the flooding process. Therefore, the polymer flooding project requires a detailed understanding of chemical and physical process occurred in the porous subsurface reservoir, ...
Control the Poly-Dispersed Droplet Breakup Mode in a Droplet-based Microfluidic Device by External Electric Field
Y. Li , K. Nandakumar , M. Jain ,
 Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, USA
Droplet–based microfluidics has received special research attentions in last two decades due to its superior control over fluid flow as well as other unique advantages. By introducing two immiscible fluids into microfluidic systems, the reagent fluid is encapsulated inside discrete droplets or slugs of nanoliter volume . Interestingly, two breakup modes, termed as “mono-dispersed” and ...
K. Lund, S. Lord
Kurt Lund Consulting, San Diego, CA, USA
SML Associates, Encinitas, CA, USA
It is frequently necessary to electrically heat gases; a convenient geometry is the familiar tube-in-shell heat exchanger, where the tube side is modified for electrical heater-rods, and the baffled shell side contains the flowing gas, as indicated in Fig. 1. However, this modification changes the essence of the thermal boundary conditions near the baffles from being temperature-limited to ...
E. Luz, D. M. P. Cunha, V. H. C. Lemos
Universidade Federal do Pará - UFPA, Belém, PA, Brasil; Centro de Instrução Almirante Braz de Aguiar - CIABA, Belém, PA, Brasil
Centro de Instrução Almirante Braz de Aguiar - CIABA, Belém, PA, Brasil
The phenomenon of cavitation can severely affect the working of valves used to control liquid flow. Cavitation occurs when the pressure is reduced and the water evaporates, forming bubbles. When bubbles pass into an area of higher pressure, they condense and collapse, releasing a large amount of energy able to removing the surface layers of the material. In this work, we model the effects of ...
基于 Level-Set 界面跟踪方法建立了激光熔覆过程的三维瞬态数值模型，研究了瞬态熔化和凝固过程中传热传质的演化规律。该模型使用 Level-Set 方法跟踪熔池气/液界面，采用焓－多孔度（enthalpy-porosity）方法得到了固/液界面之间的糊状区，并考虑了质量添加、材料熔化/凝固、热毛细效应（Marangoni效应）、浮力效应、活性元素质量传输等对熔池流动和界面的影响。通过该模型，具体分析了质量添加、力和界面平衡条件对熔池气/液界面的影响，以及由熔池温度/浓度分布引起的热毛细效应、金属材料的熔/凝过程和熔池流动形式对熔池固/液界面的影响。结果表明：熔池的气/液界面主要由力平衡条件决定，截面近似为圆弧型，其尺寸与单位时间的质量添加量相关。熔池的固/液形态由于熔池的表面温度梯度和表面活性元素含量共同引起的熔池流动方向和速度的变化，出现三种不同的类型，分别为下凹型（熔池内流） ...
P. A. Haris, T. Ramesh
National Institute of Technology Tiruchirappalli, Tiruchirappalli, Tamil Nadu, India
Design and manufacture of thrusters for producing very low thrust force in the range of milli or micro newtons using micronozzles has been actively developed in the last decade. The nature of propellant flow in such micronozzles differs from that of macro nozzles. In micronozzles, viscous effect dominates; hence the flow is always in laminar regime with high viscous losses. Objective of this ...
I .F. Melikhov , A. S. Amosov , S. A. Chivilikhin ,
 Corning Scientific Center, Saint Petersburg, Russia
 ITMO University, Saint Petersburg, Russia
Ultrasonic levitation is a novel technology for contactless handing of various objects. It is already used in various manufacturing processes where it is important to keep untouched surface. In this paper we introduce a model of so-called near-field ultrasonic levitation which allows flying heights of the hundred-micron order. Our model computes air flow in the gap between a vibration source and ...