Joule Heating Induced Heat Transfer and Its Effects on Electrokinetic Mixing in T-Shape Microfluidic Channels

2007 ◽  
Author(s):  
Gongyue Tang ◽  
Chun Yang ◽  
Yee Cheong Lam
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Numerical Simulations ◽  
Joule Heating ◽  
Solution Temperature ◽  
Microfluidic Channels ◽  
Governing Equations ◽  
Electrokinetic Flow ◽  
Layer Potential ◽  
Temperature Distributions

In this paper, we report numerical and experimental studies of the Joule heating-induced heat transfer in fabricated T-shape microfluidic channels. We have developed comprehensive 3D mathematical models describing the temperature development due to Joule heating and its effects on electrokinetic flow. The models consist of a set of governing equations including the Poisson-Boltzmann equation for the electric double layer potential profiles, the Laplace equation for the applied electric field, the modified Navier-Stokes equations for the electrokinetic flow field, and the energy equations for the Joule heating induced conjugated temperature distributions in both the liquid and the channel walls. Specifically, the Joule number is introduced to characterize Joule heating, to account for the effects of the electric field strength, electrolyte concentration, channel dimension, and heat transfer coefficient outside channel surface. As the thermophysical and electrical properties including the liquid dielectric constant, viscosity and electric conductivity are temperature-dependent, these governing equations are strongly coupled. We therefore have used the finite volume based CFD method to numerically solve the coupled governing equations. The numerical simulations show that the Joule heating effect is more significant for the microfluidic system with a larger Joule number and/or a lower thermal conductivity of substrates. It is found that the presence of Joule heating makes the electroosmotic flow deviate from its normal “plug-like” profiles, and cause different mixing characteristics. The T-shape microfluidic channels were fabricated using rapid prototyping techniques, including the Photolithography technique for the master fabrication and the Soft Lithography technique for the channel replication. A rhodamine B based thermometry technique, was used for direct “in-channel” measurements of liquid solution temperature distributions in microfluidic channels, fabricated by the PDMS/PDMS and Glass/PDMS substrates. The experimental results were compared with the numerical simulations, and reasonable agreement was found.

JOULE HEATING INDUCED HEAT TRANSFER IN ELECTROKINETIC FLOW THROUGH MICROFLUIDIC CHANNELS

Equipment ◽  
2006 ◽  
Author(s):  
C. Yang ◽  
G. Y. Tang ◽  
D. G. Yan ◽  
H. Q. Gong ◽  
John C. Chai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Joule Heating ◽  
Microfluidic Channels ◽  
Electrokinetic Flow ◽  
Flow Through

Heat Transfer and Electrokinetic Flow Analysis in Poly(Dimethylsiloxane) Microfluidic Systems

2003 ◽  
Author(s):  
David Erickson ◽  
David Sinton ◽  
Vesna Nikolic ◽  
Dongqing Li
Keyword(s):  
Heat Transfer ◽  
Joule Heating ◽  
Volume Flow Rate ◽  
Flow Analysis ◽  
Numerical Approach ◽  
Temperature Sensitive ◽  
Microfluidic Systems ◽  
Buffer Solution ◽  
Channel Network ◽  
Electrokinetic Flow

Electrokinetic pumping is commonly used as a mechanism for species transport in microfluidic systems. Joule heating, caused by current flow through the buffer solution during electroosmotic flow, can lead to significant increases in the system temperature which can be detrimental to electrophoretic separations and temperature sensitive chemical reactions. In this paper, a combined experimental and numerical approach was used to examine Joule heating and heat transfer at a T intersection for PDMS/PDMS and PDMS/Glass hybrid microfluidic systems. In general it was found the PDMS/Glass chips maintained a more uniform and lower buffer temperature than the PDMS/PDMS systems, since the internally generated heat could be transferred more efficiently (due to the higher thermal conductivity of the glass component) from the channel network to the room temperature reservoir. This increase in temperature was shown to significantly increase the current load and the volume flow rate through the PDMS/PDMS system.

scholarly journals Steady Flow over a Rotating Disk in Porous Medium with Heat Transfer

2009 ◽  
Vol 14 (1) ◽  
pp. 21-26 ◽  
Author(s):  
H. A. Attia
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Energy Transfer ◽  
Viscous Fluid ◽  
Steady Flow ◽  
Numerical Solutions ◽  
Rotating Disk ◽  
Incompressible Viscous Fluid ◽  
Governing Equations ◽  
Temperature Distributions

The steady flow of an incompressible viscous fluid above an infinite rotating disk in a porous medium is studied with heat transfer. Numerical solutions of the nonlinear governing equations which govern the hydrodynamics and energy transfer are obtained. The effect of the porosity of the medium on the velocity and temperature distributions is considered.

Numerical Simulations of Capillary Electrokinetic Pinched Injection Separation Flows in Microchannels

2004 ◽  
Author(s):  
Bakhtier Farouk ◽  
Fang Yan
Keyword(s):  
Electric Field ◽  
Numerical Simulations ◽  
Separation Performance ◽  
Species Concentration ◽  
Separation Channel ◽  
Electrokinetic Flow ◽  
Step Flow ◽  
Optimal Separation ◽  
Separation Flows ◽  
Separation Performances

Numerical simulations were performed to study the capillary electrokinetic flow in microchannels. A sample stream consisting of three different species is focused during the loading step and driven into a separation channel during the dispensing step. Flow fields and species distributions are simulated for both the loading and the dispensing steps in a two dimensional cross channel device. The evolution of each sample species concentration at the end of the separation channel is predicted. The separation resolution is defined from the sample species concentration band retention time and band width. Different separation performances can be obtained by manipulating the electric field strengths. A series of simulations for different electric field distributions and field magnitudes in the channel are presented. The goal of these simulations is to identify the parameters providing optimal separation performance. The effect of both loading and dispensing schemes on species concentration and separation resolution is presented.

Study of the Freezing Chuck for Non-Traditional Clamping Applications

2010 ◽  
Author(s):  
Rong-Yuan Jou
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Transient State ◽  
Experimental Measurements ◽  
Thermoelectric Coolers ◽  
Flow Rates ◽  
Temperature Distributions ◽  
Surface Temperatures ◽  
Convective Fluid ◽  
Heat Transfers

A freezing chuck with thermoelectric coolers and coolant channels is investigated. Measurement for freezing/thawing processes and analysis of heat transfer enhancements are conducted. Three channel configurations are designed and investigated by numerical simulations and experimental measurements, respectively, to compare the temperature distributions and heat transfer enhancements. Regarding to experiments, inlet temperatures and flow rates of coolants are altered, and transient and steady surface temperatures on the top-plate are measured for these three channel designs. In numerical analysis, convective fluid flows and heat transfers are solved to find temperature, velocity, and pressure fields inside the channel and surface temperatures of top-plate of the freezing chuck by a software package. Comparisons between experimental measurements and numerical simulations are made. Effects of flow rates, inlet coolant temperatures, and channel designs, upon the steady and transient state of temperature distributions and heat transfer enhancements are discussed and conclusions are addressed.

Heat Transfer Characteristics of Steady Electroosmotic Flows in Two-Dimensional Straight Microchannels

2003 ◽  
Author(s):  
Keisuke Horiuchi ◽  
Prashanta Dutta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Joule Heating ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Temperature Distributions ◽  
Electroosmotic Flows

Analytical solutions for the temperature distributions, heat transfer coefficients and Nusselt numbers of steady electroosmotic flows are obtained for two-dimensional straight micro-channels. This analysis is based on infinitesimal electric double layer (EDL) in which flow velocity becomes “plug-like” uniform except very close to the wall. Both constant surface temperature and constant surface heat flux conditions are considered in this study. Separation of variables techniques are applied to obtain analytical solutions of temperature distributions from the energy equation in which Joule heating is a significant contributor due to the applied electric field. The thermal analysis considers interaction among inertial, diffusive and joule heating terms in order to obtain the thermally developing behavior of electroosmotic flows. Heat transfer characteristics are presented for low Reynolds number microflows where the viscous and electric field terms are very dominant. For the parameter range studied here (Re ≤ 0.7), the Nusselt number is independent of the thermal Peclet number, except in the thermally developing region. In both isothermal and constant surface heat flux boundary conditions, the Nusselt number becomes constant in the fully developed region for a uniform volumetric heat generation. Analytical results for no Joule heating cases are also compared with the classical heat transfer results, and in the thermally fully developed region an excellent agreement is obtained between them.

scholarly journals An Exact Analysis of Heat and Mass Transfer Past a Vertical Plate with Newtonian Heating

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Abid Hussanan ◽  
Ilyas Khan ◽  
Sharidan Shafie
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Nusselt Number ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Vertical Plate ◽  
Newtonian Heating ◽  
Governing Equations ◽  
Exact Analysis ◽  
Temperature Distributions

An exact analysis of heat and mass transfer past an oscillating vertical plate with Newtonian heating is presented. Equations are modelled and solved for velocity, temperature, and concentration using Laplace transforms. The obtained solutions satisfy governing equations and conditions. Expressions of skin friction, Nusselt number, and Sherwood number are obtained and presented in tabular forms. The results show that increasing the Newtonian heating parameter leads to increase velocity and temperature distributions whereas skin friction decreases and rate of heat transfer increases.

Electrokinetic Microflow Instability With Conductivity Gradients

2003 ◽  
Author(s):  
Chuan-Hua Chen ◽  
Hao Lin ◽  
Sanjiva K. Lele ◽  
Juan G. Santiago
Keyword(s):  
Electric Field ◽  
Convective Instability ◽  
Flow Instability ◽  
Microfluidic Channels ◽  
Charge Accumulation ◽  
Electrokinetic Flow ◽  
Dc Electric Field ◽  
Bulk Charge ◽  
First Time ◽  
And Diffusion

We have experimentally identified and quantified an electrokinetic flow instability that occurs in DC-electric-field driven microfluidic channels with significant conductivity gradients. We have, for the first time, developed a physical model for this instability which captures the interactions between bulk charge accumulation, electromigration, convection, and diffusion. A linear stability analysis based on this model captures key physics of this convective instability with a threshold electric field. The model and experiments show conductivity gradients and their associated bulk charge accumulation are crucial for such instabilities.

scholarly journals MHD-Conjugate Free Convection from an Isothermal Horizontal Circular Cylinder with Joule Heating and Heat Generation

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
NHM. A. Azim ◽  
M. K. Chowdhury
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Skin Friction ◽  
Heat Generation ◽  
Joule Heating ◽  
Numerical Study ◽  
Internal Heat ◽  
Governing Equations ◽  
Generation Parameter ◽  
Horizontal Circular Cylinder

The present work is devoted to the numerical study of laminar magnetohydrodynamic (MHD) conjugate natural convection flow from a horizontal circular cylinder taking into account Joule heating and internal heat generation. The governing equations and the associated boundary conditions for this analysis are made nondimensional forms using a set of dimensionless variables. Thus, the nondimensional governing equations are solved numerically using finite difference method with Keller box scheme. Numerical outcomes are found for different values of the magnetic parameter, conjugate conduction parameter, Prandtl number, Joule heating parameter, and heat generation parameter for the velocity and the temperature within the boundary layer as well as the skin friction coefficients and the rate of heat transfer along the surface. It is found that the skin friction increases, and heat transfer rate decreases for escalating value of Joule heating parameter and heat generation parameter. Results are presented graphically with detailed discussion.

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