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Mass Transport Analysis of Non-Newtonian Fluids under Combined Electroosmotically and Pressure Driven Flow in Rectangular Microreactors

Yousefian, Zakie | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45360 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saidi, Mohammad Hassan
  7. Abstract:
  8. In recent two decades, with developments in micro and nano scale fabricating techniques, use of microfluidic systems is increasing in different fields. How to drive fluid is a hard question because of high pressure drop in micro scale. Different methods has been suggested to solve this problem, among which, electroosmotic pump is preferred because of its advantages. One of the main applications of microsystems is in biomechanical devices like microreactors which are usually working with non-Newtonian fluids. The cross section of these devices are most often close to rectangular shape.Therefor, in this study,Hydrodynamic charactristics and mass transport of non-Newtonian fluids under combined electroosmotically and pressure driven flow in rectangular microreactors is analysed. The governing equations are first made dimensionless and then transformed into new ones based on the computational parameters which provide mesh clustering near the wall and after that are solved numerically thorough a finite difference procedure.
    The results reveal that in the case of favorable pressure gradient velocity is increasing function of channel aspect ratio and decreasing function of flow behavior index, while the opposite trend is seen in the case of adverse pressure gradient. It is also found that, increasing the dimensionless Debye-Hückel parameter and the zeta potential will increase velocity. Furthermore, rate of decrease of mean concentration through microreactor length reduces speed by increasing peclet, and Debye-Hückel parameter and by decreasing Damkohler number. In all mentioned cases, favorable pressure gradient slows the rate of decrease of mean concentration and adverse pressure gradient does the opposite. Also, in presense of favorable pressure gradient, the rate of decrease of mean concentration for shear-thining fluids is the slowest of all. For Newtonian and shear-thickening fluids, mean concentration decrease faster, respectively, while the opposite trend is seen in the case of adverse pressure gradient. Increasing aspect ratio will make mean concentration decrease more sloly
  9. Keywords:
  10. Electroosmotic Flow ; Power-Low Fluid ; Mass Transfer ; Microfluidic System ; Microreactor

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