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Potential changes of the cross section for rectangular microchannel with different aspect ratios

KOREAN JOURNAL OF CHEMICAL ENGINEERING 2007年第1期24卷 186-190页

作者： Lee, Hyo Song Kim, Ki Ho Yu, Jae Keun Noh, Soon Young Choi, Jae Ho Yoon, Soo Kyung Lee, Chang-Soo Hwang, Taek-Sung Rhee, Young Woo Chungnam Natl Univ Dept Biol & Chem Engn Taejon 305764 South Korea Accreditat Board Engn Educ Korea Seoul 135513 South Korea

In this study, we investigated the potential changes of a rectangular cross section having different aspect ratio and area. A 2D Poisson-Boltzmann equation was used to model the electric double layer field of the cross section. The potential change of the cross section was studied numerically with FEMLAB 3.0 to understand the geometry effects of the rectangular microchannel used for electroosmotic flow. According to the result, the cross-section geometry shows significant influences on the potential field. The potential distribution shows same tendency with various cross-section areas in the same aspect ratio. The potential gradient increases with the increase of the cross section area.

关键词： electroosmosis rectangular microchannel potential cross section

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EXPERIMENTAL STUDY OF GAS-LIQUID MASS TRANSFER IN A rectangular microchannel BY DIGITAL IMAGE ANALYSIS METHOD

EXPERIMENTAL STUDY OF GAS-LIQUID MASS TRANSFER IN A RECTANGU...

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ASME International Mechanical Engineering Congress and Exposition (IMECE)

作者： Yang, Shuo Kong, Gaopan Wu, Zan Lund Univ Lund Sweden

ISBN: (纸本)9780791885666

Study of mass transfer in microchannels is indispensable for the design of microreactors. Gas-phase volume monitoring method has been widely used to study the mass transfer process. When using this method, bubble length was measured in most studies to calculate the bubble volume by assuming a symmetrical bubble shape. Therefore, this method is not suitable for asymmetric bubbles. The present study focuses on the mass transfer of CO2 bubbles in a flat rectangular microchannel by using the method of digital image analysis (DIA), especially for deformed bubbles. The dynamics of gas-liquid flow at different volumetric flow rates were observed by a high-speed recording system. Flow patterns were mapped and scaling laws were given for bubble size and bubble velocity. The results showed that the bubble volume increases as gas flow rate increases, while decreases as liquid flow rate increases. It can be explained by the bubble breakup mechanism Besides, the bubble velocity increases as gas and liquid flow rates increase. The mass transfer of CO2 from bubbles to liquid slugs was quantitatively characterized by volumetric mass transfer coefficient k(L)a. The results showed that k(L)a and k(L), increase with increasing of superficial gas and liquid velocities. The same tendencies can be found in the literature. Finally, new mass transfer correlations were proposed. Predictions from the correlations showed a good agreement with the experimental data.

关键词： rectangular microchannel mass transfer digital image analysis gas-liquid scaling law

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AN EXPERIMENTAL INVESTIGATION ON CHARACTERISTICS OF LIQUID FILM THICKNESS OF GAS-LIQUID TAYLOR FLOW IN rectangular microchannel 7

AN EXPERIMENTAL INVESTIGATION ON CHARACTERISTICS OF LIQUID F...

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7th ASME International Conference on Micro/Nanoscale Heat and Mass Transfer (MNHMT)

作者： Fu, Dengwei Hong, Sihui Sun Yat Sen Univ Ctr Space Technol Sch Phys & Astron Zhuhai Peoples R China

ISBN: (纸本)9780791888155

Liquid film thickness is one of the most important parameters for understanding two-phase flow in micro-scales. In the present work, experiments were conducted to investigate the variation of liquid film thickness in square tubes with hydraulic diameter D-h = 0.3, 0.5, 0.7, 1.0 mm, and rectangular tubes with a depth of 0.5mm and widths of 0.3, 0.5, 0.7, 1.0 mm. The liquid film thicknesses were measured using a laser focus displacement meter, and visualization images were captured by a high-speed camera. The experiments revealed that at low capillary numbers, surface tension determines the lower limit of the liquid film thickness in either square or rectangular microchannels. At medium capillary numbers, viscous force becomes prominent, and increase the thickness of the liquid film. At high capillary numbers, inertia forces determine the upper limit of the liquid film thickness. The non-uniform distribution of the liquid film thickness in rectangular channels intensifies with the increase in the aspect ratio of channel width to depth.

关键词： Liquid film thickness Gas-liquid two-phase flow Square microchannel rectangular microchannel Precision measurement

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Research on heat dissipation of a new rectangular microchannel structure based on thermal bimetal 19

Research on heat dissipation of a new rectangular microchann...

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19th International Conference on Electronic Packaging Technology (ICEPT)

作者： Wan, Weikang Li, Haihua Wang, Qidong Liang, Xiaoxin Chinese Acad Sci Natl Ctr Adv Packaging NCAP China Inst Microelect Beijing Peoples R China Univ Chinese Acad Sci Chinese Acad Sci Inst Microelect Beijing Peoples R China

ISBN: (纸本)9781538663868

With the shrinkage of package size and the increasement of the integration, the heat dissipation in the electronics package deteriorates. microchannel technology therefore becomes one of the most active areas of research in thermal management. This paper investigated the impact of local deformation structure in a rectangular microchannel on heat dissipation performance, and a solution was proposed by introducing thermal bimetal to the rectangular microchannel. The thermal bimetal was designed to contact with the heat source through thermal columns, and the deformation of thermal bimetal regulates the flow velocity of local cooling fluid in microchannel to achieve self-adapted heat dissipation management. The results indicated that the concave thermal bimetal rectangular microchannel outperformed than the ordinary microchannel due to its lower average temperature and lower temperature difference, therefore kept the heat source chip (e.g. PA) at a lower temperature. These efforts could be helpful for the design and optimization in microchannel cooling system for high power chip packaging.

关键词： rectangular microchannel Thermal bimetal Heat dissipation Deformation High power chip packaging

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Analysis and experiment of transient filling flow into a rectangular microchannel on a rotating disk

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MICROFLUIDICS AND NANOFLUIDICS 2016年第4期20卷 52-52页

作者： Shen, Teng Huang, Liu Wang, Jiong Nanjing Univ Sci & Technol Sch Mech & Engn Nanjing Jiangsu Peoples R China

In order to predict the time-dependent behaviors of the moving front in lab-on-a-CD systems or centrifugal pumping, an analytical expression and experimental methods of centrifugal-force-driven transient filling flow into a rectangular microchannel in centrifugal microfluidics are presented in this paper. Considering the effect of surface tension, and neglecting the effect of Coriolis force, the velocity profile, flow rate, the moving front displacement and the pressure distribution along the microchannel are characterized. Experiments are carried out using the image-capturing unit to measure the shift of the flow in rectangular microchannels. The flow characteristics in rectangular microchannels with different cross-sectional dimensions (200, 300 and 400 mu m in width and 140, 240 and 300 mu m in depth) and length (18 and 25 mm) under different rotational speed are investigated. According to the experimental data, the model can be more reasonable to predict the flow displacement with time, and the errors between theoretical and the experimental will decrease with increasing the cross-section size of the microchannel.

关键词： Transient flow rectangular microchannel Centrifugal microfluidics Time-dependent behaviors

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Mechanistic model of combined pressure drop and heat transfer for the entire growth stage of an elongated bubble in a rectangular microchannel

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2022年 197卷

作者： Patra, Chinmaya Kumar Bhattacharya, Anandaroop Das, Prasanta Kumar IIT Kharagpur Dept Mech Engn Kharagpur 721302 West Bengal India

A one-dimensional flow-boiling model for the slug-flow regime is formulated to describe the pressure drop and heat transfer mechanism in a microchannel of rectangular cross-section. The pressure drop model considers three stages of bubble growth namely: (i) partial confinement, (ii) full confinement and (iii) vapour venting. The heat transfer coefficient at any particular location is obtained by assuming the periodic passage of four zones: (i) liquid slug zone, (ii) elongated bubble zone, (iii) partially dryout zone, and (iv) fully dryout zone. The model is evaluated using constant fluid properties, to study the paramet-ric variation of channel pressure drop and heat transfer coefficient. The effects of variation in channel dimension, flow velocity, heat flux and properties of working fluid on pressure drop and heat transfer coefficient have been studied using the model. The model is capable of simulating all the transport pro-cesses for a single bubble from its inception till it leaves the microchannel and thereby it can estimate the pressure drop in the channel along with the heat transfer coefficient i.e. spatially averaged over the channel length and at any location from channel upstream to the downstream end.(c) 2022 Elsevier Ltd. All rights reserved.

关键词： Flow boiling Pressure drop Heat transfer rectangular microchannel

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Bidirectional inward migration of particles lagging behind a Poiseuille flow in a rectangular microchannel for 3D particle focusing

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JOURNAL OF MICROMECHANICS AND MICROENGINEERING 2015年第2期25卷 027002-027002页

作者： Kim, Young Won Yoo, Jung Yul Korea Inst Ind Technol Honam Reg Div Kwangju 500480 South Korea Seoul Natl Univ Sch Mech & Aerosp Engn Seoul 151744 South Korea

Electrophoretic mobility of particles dispersed in an electrolyte solution induces the particles to lag behind a Poiseuille flow in a rectangular microchannel, which causes bidirectional inward migration of particles to the central axis of the channel. As a result, in the present theoretical and experimental study, three-dimensional (3D) particle focusing is clearly realized in such a manner that the particles are aligned in a single file along the axis of the channel as they are transported downstream. Theoretical prediction on the particle migration time provides an excellent assessment of the experimental results. The method proposed in the present study has potential for development of low-cost rapid manufacturing process of sheathless monolayer microchips for 3D particle focusing.

关键词： bidirectional inward migration 3D focusing rectangular microchannel electrophoresis Poiseuille flow

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Experimental test of rectangular microchannel printed circuit heat exchanger using supercritical carbon dioxide as working fluid

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JOURNAL OF SUPERCRITICAL FLUIDS 2023年第1期200卷

作者： Zhong, Shao-geng Ren, Yan Wang, Pei-dong Wu, Wei-dong Yang, Ying-ying Yang, Qi-guo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

This study proposed a new type of printed circuit heat exchanger with rectangular microchannels and established a test platform with supercritical carbon dioxide as working fluid. The heat transfer and pressure drop of the test sample were tested, and the experiments considered inlet temperature ranges of 335.0-338.9 K and 316.1-339.1 K for the hot and cold sides, respectively. The results revealed that hot-side inlet temperature had the most significant effect on the heat transfer rate and thermal performance. With a 10.3% increase in the hot-side inlet temperature, the heat transfer rate increased by 89.0%, and the thermal performance decreased by 17.7%. The test sample effectiveness was most significantly affected by the cold-side inlet temperature, and it increased by 23.3% as the cold-side inlet temperature increased by 5.9%. The effectiveness increased to 0.96 with an increase in the cold-side inlet temperature to 339.1 K.

关键词： Supercritical carbon dioxide Printed circuit heat exchanger rectangular microchannel Flow and heat transfer Effectiveness

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Research on heat dissipation of a new rectangular microchannel structure based on thermal bimetal

Research on heat dissipation of a new rectangular microchann...

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第十九届国际电子封装技术会议(ICEPT 2018)

作者： Weikang Wan Qidong Wang Haihua Li Xiaoxin Liang Institute of Microelectronics of Chinese Academy of Sciences National Center for Advanced Packaging( Institute of Microelectronics of Chinese Academy of Sciences University of Chinese Academy of Scienc

With the shrinkage of package size and the increasement of the integration,the heat dissipation in the electronics package *** technology therefore becomes one of the most active areas of research in thermal *** paper investigated the impact of local deformation structure in a rectangular microchannel on heat dissipation performance,and a solution was proposed by introducing thermal bimetal to the rectangular *** thermal bimetal was designed to contact with the heat source through thermal columns,and the deformation of thermal bimetal regulates the flow velocity of local cooling fluid in microchannel to achieve self-adapted heat dissipation *** results indicated that the concave thermal bimetal rectangular microchannel outperformed than the ordinary microchannel due to its lower average temperature and lower temperature difference,therefore kept the heat source chip(***)at a lower *** efforts could be helpful for the design and optimization in microchannel cooling system for high power chip packaging.

关键词： rectangular microchannel Thermal bimetal Heat dissipation Deformation High power chip packaging

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COMPARATIVE STUDY OF FLUID FLOW AND HEAT TRANSFER IN rectangular AND WAVY microchannel

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COMPUTATIONAL THERMAL SCIENCES 2017年第6期9卷 549-565页

作者： Dewangan, Satish Kumar Sinha, Shobha Lata Gupta, Prateek Kumar Natl Inst Technol Raipur Dept Mech Engn GE Rd Raipur 492010 Chhattisgarh India

A comparative study of steady, laminar, single-phase flow of nanofluid through a rectangular microchannel and wavy microchannel heat exchanger of equal dimensions has been carried out. The effect on three important variables (i.e., heat transfer coefficient, pumping power, and friction factor) have been analyzed by considering the effect of four parameters (i.e., effect of flow rate, effect of nanofluid concentration, effect of amplitude of wavy surface, and effect of wave length of wavy surfaces). Numerical simulation has been validated with the experimental work of Lee and Mudawar (Lee, J. and Mudawar, I., Assessment of the effectiveness of nanofluids for single and multiphase heat transfer in micro channel, Int. J. Heat Mass Transfer, vol. 50, pp. 452-463, 2007). It is concluded that, with an increase in the amplitude of a wavy surface, the heat transfer coefficient increases. Results show that the wavy channel performed better than the plane rectangular microchannel in terms of the rise in heat transfer coefficient but is costly due to the pump power requirement.

关键词： nanofluid rectangular microchannel wavy microchannel computational heat transfer

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