کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7054477 | 1458018 | 2018 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
On the thermal characteristic of a heating flat surface under low frequency ultrasonic waves
ترجمه فارسی عنوان
بر روی ویژگی حرارتی یک سطح تخت گرم تحت امواج اولتراسوند فرکانس پایین
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کلمات کلیدی
امواج التراسونیک، انتقال گرما، صفحه تخت، جریان آرام، کریستال مایع،
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
چکیده انگلیسی
This study investigates the heat transfer capability between the near-wall water and a heating flat surface under the low frequency ultrasonic waves. The experiment was conducted at the main stream velocities of 0.12, 0.14, and 0.17â¯m/s, corresponding with the local Reynolds number between 60,000 and 200,000. The ultrasound, having a frequency of 25, 33, and 40â¯kHz was released from a 60â¯W flat transducer in a downward direction to disturb a near-wall flow over the flat surface having a constant heat flux of 1875â¯W/m2. The temperature decrease due to the disturbance of ultrasound, detected by 7 thin-leaf thermocouples, led to the increase in the Nusselt number by up to 10%, 16.5%, and 20.8%, at the wave frequency of 25, 33, and 40â¯kHz, respectively. The use of the thermochromic liquid crystals on the heating surface, disturbed by the 40â¯kHz wave, revealed that the bound of the wave incident region was shaped like a spiky structure that alternately occurs following with time. This incident region moved further downstream when the mainstream velocity increased and caused a retardation of the near wall flow, leading to a worse heat transfer in the upstream region. Therefore, the inclination of the acoustic beam, occurring as a variation of mainstream velocity, must be considered in order to use the ultrasound to enhance the heat transfer. Finally, the predictive formulas for the local Nusselt number under the 25-40â¯kHz waves are also provided and the mechanism of heat transfer is discussed.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Heat and Mass Transfer - Volume 122, July 2018, Pages 1153-1161
Journal: International Journal of Heat and Mass Transfer - Volume 122, July 2018, Pages 1153-1161
نویسندگان
Nathat Inworn, Weerachai Chaiworapuek,