scholarly journals Three Dimensional Imaging of Structure and Flow—Critical to Advances in Microfluidics

2007 ◽  
Vol 15 (6) ◽  
pp. 18-23
Author(s):  
Carlos Hidrovo ◽  
Terence Lundy
Keyword(s):  
Heat Transfer ◽  
Integrated Circuits ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Pem Fuel Cells ◽  
Industrial Applications ◽  
Two Phase ◽  
Microscale Heat Transfer ◽  
Flow Through ◽  
Micrometer Scale

Microfluidics, the study of fluid flow through structures with micrometer scale dimensions, is an increasingly important discipline within a number of commercial and industrial applications. One focus of active microfluidic research at the Stanford University Microscale Heat Transfer Laboratories (MHTL) is mass and heat transport in two-phase flows, which has applications in the cooling of integrated circuits and the management of water created in PEM fuel cells. At its core, two-phase microfluidics is the study of interactions between moving liquids and/or gases and/or solids (though not necessarily stationary) structures. Advanced confocal microscopy, with its ability to visualize and measure both flow and structure on a single instrumental platform, will certainly play a key role in the continuing development of microfluidic devices.

Thermal Characterization of Interlayer Microfluidic Cooling of Three-Dimensional Integrated Circuits With Nonuniform Heat Flux

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Young-Joon Lee ◽  
Sung-Kyu Lim
Keyword(s):  
Integrated Circuits ◽  
Mass Flow Rate ◽  
Thermal Management ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Phase ◽  
Hot Spot ◽  
Three Dimensional ◽  
Two Phase ◽  
Two Phase Cooling

It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ∼300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer.

Flowfield and Heat Transfer Numerical Analysis of a Stator Vane Endwall With High Freestream Turbulence

2015 ◽  
Author(s):  
A. Andreini ◽  
C. Bianchini ◽  
E. Burberi ◽  
B. Facchini ◽  
R. Abram ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Computational Methods ◽  
Gas Flow ◽  
Three Dimensional ◽  
Computational Procedure ◽  
Industrial Applications ◽  
Turbulence Modelling ◽  
Large Set ◽  
Present Contribution ◽  
Stator Vane

Among the different parts subjected to hot gas flow, endwall heat transfer evaluation is particularly challenging because the flow is strongly affected by secondary effects. Large three-dimensional flow structures introduce remarkable spatial variation of heat transfer, both along streamwise and spanwise directions, making the use of simplified modelling approaches questionable in terms of reliability, and at the same time increasing the challenge for high fidelity computational methods. The aim of the present contribution is to describe the work done in the assessment of computational methods for the estimate of high pressure vane endwall heat transfer for industrial applications. Efforts were first devoted to the development and validation of an accurate computational procedure against a large set of aerodynamic and heat transfer data, available from literature, for both airfoil and endwall of a low-pressure linear cascade with low and high inlet turbulence levels. The analysis, focused on steady state computations, is principally devoted to the turbulence modelling assessment, including non-linear turbulence closure as well as transition modelling. Obtained results showed that the aerodynamics of both passage and endwall are well captured independently of the turbulence modelling while a large impact on both pattern and averaged value is verified for the heat transfer.

Numerical simulation of nonlinear thermal radiation on the 3D flow of a couple stress Casson nanofluid due to a stretching sheet

2020 ◽  
pp. 1-28
Author(s):  
P. V. Satya Narayana ◽  
Tarakaramu Nainaru ◽  
G. Sarojamma ◽  
Isaac Lare Animasaun
Keyword(s):  
Heat Transfer ◽  
Couple Stress ◽  
Three Dimensional ◽  
Casson Fluid ◽  
Industrial Applications ◽  
Physical Parameters ◽  
Nonlinear Thermal Radiation ◽  
Scaling Analysis ◽  
Nonlinear Odes ◽  
Limiting Case

Abstract Little is known on the three-dimensional flow of couple stress Casson fluid conveying nanoparticles when the significance of Lorentz force, chaotic gesture of those minute particles and thermophoresis are significant. The intent of this investigation is to focus on the flow of such fluid along a horizontal surface due to dual stretching and internal heating. The dimensional nonlinear equations are reduced into a system of coupled nonlinear ODEs employing scaling analysis and later they are solved numerically. The results are discussed graphically for various emerged physical parameters through different plots. The results in the absence of stretching ratio factor indicate that the heat absorption parameter and Prandtl number accelerate the heat transfer rate. The temperature of the non- Newtonian couple stress fluid is found to be bigger than that of viscous case. It may be suggested that Casson couple stress nanofluid can be substituted for the corresponding viscous fluid in industrial applications for greater heat transfer. The outcomes are closely matched with the studies available in the literature as a limiting case.

Fluid Flow and Boiling Heat Transfer in Mini Channels

2010 ◽  
Author(s):  
M. Venkatesan ◽  
M. Aravinthan ◽  
Sarit K. Das ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Boiling Heat Transfer ◽  
Industrial Applications ◽  
Tube Diameter ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Mini Channels ◽  
Micro Propulsion

Two phase flows in mini channels occur in many industrial applications such as electronic cooling, compact heat exchangers, compact refrigeration systems and in micro propulsion devices. Due to its significance, research on two phase flow in mini channels has become attractive. However, in recent times a controversy exists whether flow in minichannel is different from macro flow because there are still substantial disagreements among various experimental results. In the present study an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1–3mm. The tubes were made of SS with water as the working fluid. The variation in friction factor and Nusselt number with decrease in tube diameter for single phase flow was systematically studied. The point of Onset of Nucelate Boiling (ONB) was identified based on wall temperature profile. The effect of heat flux and mass flux on two phase pressure drop with three different tube diameters during sub cooled boiling were investigated. The results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions.

Different Modes of Gas Entrainment Through Bottom Discharge Branch by Using Three Dimensional Particle Image Velocimetry System

2007 ◽  
Author(s):  
Wael Fairouz Saleh ◽  
Ibrahim Galal Hassan
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Structure ◽  
Particle Image ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Particle Image Velocimetry System ◽  
Three Dimension ◽  
Two Phase ◽  
Mean Velocity ◽  
Image Velocimetry

The discharge of two-phase flow from a stratified region through single or multiple branches is an important process in many industrial applications including the pumping of fluid from storage tanks, shell-and-tube heat exchangers, and the fluid flow through small breaks in cooling channels of nuclear reactors during loss-of-coolant accidents (LOCA). Knowledge of the flow phenomena involved along with the quality and mass flow rate of the discharging stream(s) is necessary to adequately predict the different phenomena associated with the process. Particle Image Velocimetry (PIV) in three dimension was used to provide detailed measurements of the flow patterns involving distributions of mean velocity, vorticity field, and flow structure. The experimental investigation was carried out to simulate two phase discharge from a stratified region through branches located on a semi-circular wall configuration during LOCA scenarios. The semi-circular test section is in close dimensional resemblance with that of a CANDU header-feeder system, with branches mounted at orientation angles of zero, 45 and 90 degrees from the horizontal. The experimental data for the phase development (mean velocity, flow structure, etc.) was done during single discharge through the bottom branch from an air/water stratified region over a three selected Froude numbers. These measurements were used to describe the effect of outlet flow conditions on phase redistribution in headers and understand the entrainment phenomena.

Numerical Simulation of Heat Transfer in a Closed Two-Phase Thermosiphon

2017 ◽  
Vol 743 ◽  
pp. 449-453
Author(s):  
Vladimir Arkhipov ◽  
Alexander Nee ◽  
Lily Valieva
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Phase Transitions ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Mathematical Modelling ◽  
Three Dimensional ◽  
Two Phase ◽  
One Dimensional ◽  
The Finite Difference Method

This paper presents the results of mathematical modelling of three–dimensional heat transfer in a closed two-phase thermosyphon taking into account phase transitions. Three-dimensional conduction equation was solved by means of the finite difference method (FDM). Locally one-dimensional scheme of Samarskiy was used to approximate the differential equations. The effect of the thermosyphon height and temperature of its bottom lid on the temperature difference in the vapor section was shown.

A VoF-Based Consistent Mass-Momentum Transport for Two-Phase Flow Simulations

2017 ◽  
Author(s):  
Annagrazia Orazzo ◽  
Isabelle Lagrange ◽  
Jean-Luc Estivalézes ◽  
Davide Zuzio
Keyword(s):  
Density Ratio ◽  
Three Dimensional ◽  
Industrial Applications ◽  
High Density ◽  
Momentum Transport ◽  
Two Phase ◽  
Mass Fluxes ◽  
Numerical Instabilities ◽  
Density Ratios ◽  
Control Volumes

The most part of two-phase flows relevant to industrial applications is characterized by high density ratios that make numerical simulations of such kind of flows still challenging in particular when the interface assumes complex shape and is distorded by high shear. In this paper a new strategy, to overcome the numerical instabilities induced by the large densities/shears at the interface, is described for staggered cartesian grids. It consists in a consistent mass-momentum advection algorithm where mass and momentum transport equations are solved in the same control volumes. The mass fluxes are evaluated through the Volume-of-Fluid color function and directly used to calculate momentum convective term. Two and three-dimensional high-density test cases (the density ratio goes from 103 to 109) are presented. The new algorithm shows signifcantly improvements compared to standard advection methods therefore suggesting the applicability to the complete atomization process simulations.

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