کد مقاله کد نشریه سال انتشار مقاله انگلیسی ترجمه فارسی نسخه تمام متن
667080 1458603 2006 20 صفحه PDF سفارش دهید دانلود رایگان
عنوان انگلیسی مقاله ISI
Characterization of diabatic two-phase flows in microchannels: Flow parameter results for R-134a in a 0.5 mm channel
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موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی جریان سیال و فرایندهای انتقال
پیش نمایش صفحه اول مقاله
Characterization of diabatic two-phase flows in microchannels: Flow parameter results for R-134a in a 0.5 mm channel
چکیده انگلیسی
An optical measurement method for two-phase flow pattern characterization in microtubes has been utilized to determine the frequency of bubbles generated in a microevaporator, the coalescence rates of these bubbles and their length distribution as well as their mean velocity. The tests were run in a 0.5 mm glass channel using saturated R-134a at 30 °C (7.7 bar). The optical technique uses two laser diodes and photodiodes to measure these parameters and to also identify the flow regimes and their transitions. Four flow patterns (bubbly flow, slug flow, semi-annular flow and annular flow) with their transitions were detected and observed also by high speed video. It was also possible to characterize bubble coalescence rates, which were observed here to be an important phenomena controlling the flow pattern transition in microchannels. Two types of coalescence occurred depending on the presence of small bubbles or not. The two-phase flow pattern transitions observed did not compare well to a leading macroscale flow map for refrigerants nor to a microscale map for air-water flows. Time averaged cross-sectional void fractions were also calculated indirectly from the mean two-phase vapor velocities and compared reasonably well to homogeneous values.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Multiphase Flow - Volume 32, Issue 7, July 2006, Pages 755-774
نویسندگان
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