کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7054030 | 1458015 | 2018 | 14 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Experimental comparison and visualization of in-tube continuous and pulsating flow boiling
ترجمه فارسی عنوان
مقایسه تجربی و تجسم جریان جوش جریان مستقیم و پالسی در لوله
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کلمات کلیدی
جریان جوش، ضربان جریان افزایش انتقال حرارت، تجسم، رژیم جریان،
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
چکیده انگلیسی
This experimental study investigated the application of fluid flow pulsations for in-tube flow boiling heat transfer enhancement in an 8â¯mm smooth round tube made of copper. The fluid flow pulsations were introduced by a flow modulating expansion device and were compared with continuous flow generated by a stepper-motor expansion valve in terms of the time-averaged heat transfer coefficient. The cycle time ranged from 1â¯s to 7â¯s for the pulsations, the time-averaged refrigerant mass flux ranged from 50â¯kgâ¯mâ2â¯sâ1 to 194â¯kgâ¯mâ2â¯sâ1 and the time-averaged heat flux ranged from 1.1â¯kWâ¯mâ2 to 30.6â¯kWâ¯mâ2. The time-averaged heat transfer coefficients were reduced from transient measurements immediately downstream of the expansion valves with 2â¯K and 20â¯K subcooling upstream, resulting in inlet vapor qualities at 0.05 and 0.18, respectively, and covered the saturated flow boiling range up to the dry-out inception. Averaged results of the considered range of vapor qualities, refrigerant mass flux and heat flux showed that the pulsations at low cycle time (1â¯s) improved the time-averaged heat transfer coefficients by 5.6% and 2.2% for the low and high subcooling, respectively. However, the pulsations at high cycle time (7â¯s) reduced the time-averaged heat transfer coefficients by 1.8% and 2.3% for the low and high subcooling, respectively, due to significant dry-out when the flow-modulating expansion valve was closed. Furthermore, the flow pulsations were visualized by high-speed camera to assist in understanding the time-periodic flow regimes and the effect they had on the heat transfer performance.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Heat and Mass Transfer - Volume 125, October 2018, Pages 229-242
Journal: International Journal of Heat and Mass Transfer - Volume 125, October 2018, Pages 229-242
نویسندگان
Martin Ryhl Kærn, Wiebke Brix Markussen, Knud Erik Meyer, Brian Elmegaard, Björn Palm,