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Enhance Flow Boiling in Microchannels by Regulating Two-Phase Transport Patterns
Başlık:
Enhance Flow Boiling in Microchannels by Regulating Two-Phase Transport Patterns
Yazar:
Li, Wenming, author.
ISBN:
9780438112261
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (187 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-11(E), Section: B.
Advisors: Chen Li Committee members: Jamil Khan; Guiren Wang; Guoan Wang.
Özet:
Flow boiling in microchannels is one of the most promising cooling techniques for microelectronics. Using latent heat by vaporization can significantly improve heat dissipation of high power density electronic devices. Most of the failure of electronic devices is induced by the occurrence of critical heat flux (CHF), which defines the maximum operating conditions. However, the vigorous rapid generation of vapor through phase change leads to chaotic two-phase flows in microchannels, resulting in flow instability in terms of severe flow, temperature and pressure drop fluctuations. Particularly, the very well-known bubble confinement exacerbates the two-phase flow instabilities and greatly deteriorates heat transfer performance in terms of CHF and heat transfer coefficient (HTC). On the other hand, the primary two-phase flow patterns, including bubbly flow, slug flow, and annular flow, are not in control in conventional microchannels. The regulation of two-phase transport is essential to improve flow boiling in microchannels.
In this dissertation, semi-theoretical and experimental studies are conducted to investigate the enhanced mechanism of microchannel flow boiling. Two novel methodologies were developed to radically solve the critical two-phase transport issues in microchannel flow boiling, including "two-phase oscillator " and "two-phase separation". Flow boiling performances are significantly enhanced by promoting nucleate boiling, convection and thin film evaporation through controlling two-phase transport based on the two methodologies. For example, multiple micronozzles are designed to efficiently remove confined bubble and extend mixing in microchannel by creating "two-phase oscillator" to generate high frequency jetting flows and high frequency two-phase oscillations. Furthermore, a better control of two-phase flow patterns is achieved, i.e., highly desirable annular flow. Novel micropin fin arrays have been developed to achieve " two-phase separation" through rectifying stochastic liquid/vapor interfaces into on-demand manner. Significant enhancements of flow boiling, and flow stabilities have been demonstrated. HTC model and CHF model have been developed to predict the HTC and CHF of flow boiling. HTC modeling provides insights into the enhanced HTC mechanisms.
Notlar:
School code: 0202
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(688928.1) | 688928-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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