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Microchannel Flow (microchannel + flow)

Distribution by Scientific Domains
Life Sciences40%

Selected Abstracts

Estimation of Joule heating effect on temperature and pressure distribution in electrokinetic-driven microchannel flows

ELECTROPHORESIS, Issue 3 2006
Reiyu Chein Professor
Abstract In this study we present simple analytical models that predict the temperature and pressure variations in electrokinetic-driven microchannel flow under the Joule heating effect. For temperature prediction, a simple model shows that the temperature is related to the Joule heating parameter, autothermal Joule heating parameter, external cooling parameter, Peclet number, and the channel length to channel hydraulic diameter ratio. The simple model overpredicted the thermally developed temperature compared with the full numerical simulation, but in good agreement with the experimental measurements. The factors that affect the external cooling parameters, such as the heat transfer coefficient, channel configuration, and channel material are also examined based on this simple model. Based on the mass conservation, a simple model is developed that predicts the pressure variations, including the temperature effect. An adverse pressure gradient is required to satisfy the mass conservation requirement. The temperature effect on the pressure gradient is via the temperature-dependent fluid viscosity and electroosmotic velocity. [source]

Simulation and analysis of flow through microchannel

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
Madhusree Kundu
Abstract One-dimensional and two-dimensional models for microchannel flow with noncontinuum (slip flow) boundary conditions have been presented here. This study presents an efficient numerical procedure using pressure-correction-based iterative SIMPLE algorithm with QUICK scheme in convective terms to simulate a steady incompressible two-dimensional flow through a microchannel. In the present work, the slip flow of liquid through a microchannel has been modeled using a slip length assumption instead of using conventional Maxwell's slip flow model, which essentially utilizes the molecular mean free path concept. The models developed, following this approach, lend an insight into the physics of liquid flow through microchannels. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Kinetic Measurements of Protein Conformation in a Microchip

BIOTECHNOLOGY PROGRESS, Issue 5 2006
Matthew B. Kerby
This paper presents a microchip-based system for collecting kinetic time-based information on protein refolding and unfolding. Dynamic protein conformational change pathways were studied in microchannel flow using a microfluidic device. We present a protein-conserving approach for quantifying refolding by dynamically varying the concentration of the chemical denaturants, guanidine hydrochloride and urea. Short diffusion distances in the microchannel result in rapid equilibrium between protein and titrating solutions. Dilutions on the chip were tightly regulated using pressure controls rather than syringe-based flow, as verified with extensive on-chip tracer dye controls. To validate this protein assay method, folding transition experiments were performed using two well-characterized proteins, human serum albumin (HSA) and bovine carbonic anhydrase (BCA). Transition events were monitored through fluorescence intensity shifts of the protein dye 8-anilino-1-naphthalenesulfonic acid (ANS) during dilutions of protein from urea or guanidine hydrochloride solutions. The enzymatic activity of refolded BCA was measured by UV absorption through the conversion of p -nitrophenyl acetate (p-NPA). The microchip protein refolding transitions using ANS were well-correlated with conventional plate-based experiments. The microfluidic platform enables refolding studies to identify rapidly the optimal folding strategy for a protein using small quantities of material. [source]

Second-law analysis and optimization of microchannel flows subjected to different thermal boundary conditions

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2005
Kuan Chen
Abstract Entropy generation and transfer in microchannel flows were calculated and analyzed for different thermal boundary conditions. Due to the small flow cross-sectional area, fluid temperature variation in the lateral direction was neglected and a laterally lumped model was developed and used in the first- and second-law analyses. Since the Peclet numbers of microchannel flows are typically low, heat conduction in the flow direction was taken into consideration. Computed fluid temperature and entropy generation rate were cast into dimensionless forms, thus can be applied to different fluids and channels of different sizes and configurations. Local entropy generation rate was found to be only dependent upon the temperature gradient in the flow direction. The optimization results of microchannel flows exchanging heat with their surroundings indicate the optimal fluid temperature distribution is a linear one. Copyright © 2004 John Wiley & Sons, Ltd. [source]