مطالعه اثر لغزش بر عملکرد ریزمخلوط گرهای الکترواسموتیکی بر مبنای معیار انتروپی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی مکانیک، دانشگاه فردوسی مشهد، مشهد، ایران

2 دانشکده مهندسی مکانیک، دانشگاه رازی، کرمانشاه، ایران

چکیده

در این مقاله اختلاط الکتروکنتیکی درون ریزمجراهای ناهمگن مطالعه شده است و اثر ضریب لغزش، زتاپتانسیل، پارامتر دیبای هوکل و عدد رینولدز بر راندمان اختلاط بررسی شده است. ریزمجراهای مورد مطالعه دارای توزیع ناهمگن زتاپتانسیل روی دیواره هستند و سایر خواص سطحی آن یکنواخت است. برای بررسی اختلاط الکترواسموتیکی معادلات ناویر- استوکس، ارنست - پلانک، معادله پتانسیل الکتریکی و معادله غلظت به روش عددی حل شده اند. تایج نشان می دهد که رفتار ریزمخلوط گرهای الکترواسموتیکی به شدت وابسته به مقدار و توزیع زتاپتانسیل دیواره است و در اغلب موارد راندمان اختلاط با کاهش پارامترهای ضریب لغزش، دیبای- هوکل و عدد رینولدز، افزایش می یابد. مشاهده شد که ضریب لغزش نقش جدی بر راندمان اختلاط دارد به نحوی که در مقایسه با اختلاط کانال همگن می تواند در رینولدزهای کم باعث کاهش و در رینولدزهای بالا باعث افزایش راندمان اختلاط گردد. همچنین، دقت مدل تقریبی هلمهولتز - اسمولموکوفسکی نیز مورد بررسی قرار گرفت و معلوم شد که در مواردی که زتاپتانسیل دیواره زیاد باشد و یا مقدار پارامتر دیبای هوکل کم باشد، نتایج حاصل از این مدل دارای خطای قابل ملاحظه ای نسبت به مدل ارنست - پلانک خواهد بود. علاوه بر این نتیجه گردید که هرچه میزان عدم تقارن بار بیشتر باشد، عملکرد اختلاطی ریزمخلوط گر افزایش می یابد و لذا جهت رسیدن به میزان اختلاط مشخص، طول کمتری نیاز خواهد بود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Study of Slip Effect on Electro-osmotic Micromixer Performance Based on Entropy Index

نویسندگان [English]

  • A. R. Farahinia 1
  • J. Jamaati 2
  • H. Niazmand 1
1 Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
2 Department of Mechanical Engineering, Razi University, Kermanshah, Iran
چکیده [English]

In this article electrokinetic mixing through heterogeneous microchannels has been studied and
the effects of slip coefficient, zeta-potential, Debye-Huckel parameter and Reynolds number on mixing efficiency
have been investigated. The microchannels have homogenous surface properties except for zeta-potential. In order to
study the electro-osmotic mixing, the Navier-Stokes, Nernst–Planck, electric potential and concentration equations
have been solved numerically. In order to evaluate the mixing efficiency, entropy of concentration has been used as a
quantitative index. The results show that the behavior of electro-osmotic micromixers is highly depended to amount
and distribution of wall zeta-potential. Furthermore, mixing efficiency increases with reduction of slip coefficient and
Debye-Huckel and Reynolds number parameters in most cases. It is seen that slip coefficient can decrease or increase
mixing efficiency dependent on the Reynolds number. Furthermore the accuracy of Helmholtz-Smoluchowski
approximate model is also investigated and it is found that in high wall zeta-potential cases or low values of Debye-
Huckel parameter, results of this model have significant error compared to Nernst-Planck model. It is also found that
the mixing performance increases when as the charge pattern of micromixer is more asymmetric so that the certain
mixing value can be obtained in shorter length which is importance in micromixers design.

کلیدواژه‌ها [English]

  • Mixing
  • Heterogeneous zeta-potential
  • Mixing entropy
  • Electro-osmotic flow
  • Helmholtz-Smoluchowski model

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نشریه مهندسی مکانیک امیرکبیر
دوره 49، شماره 3
آبان 1396
صفحه 535-548

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