Department News
POOL BOILING HEAT TRANSFER ON SMALL HEATERS:
Seminar Date
2001-08-31
Author
손문숙
Date
2001-08-31
Views
1308
1. 제 목 : POOL BOILING HEAT TRANSFER ON SMALL HEATERS:
EFFECTS OF GRAVITY AND SUBCOOLING LEVEL
2. 연 사 : Prof. Jungho Kim
University of Maryland College Park, MD 20742
3. 일 시 : 2001년 7월 9일 (월) 16:00 – 17:00
4. 장 소 : 301동 1512호
5. 내 용 : Measurements of pool boiling of FC-72 in a microgravity environment provided by the KC-135 at various levels of subcooling were performed. Use of a microscale heater array allowed the measurement of time and space resolved heat transfer. For all the test cases, the pressure in the chamber was held at nominally atmospheric pressure (about 57 °C) and the bulk temperature was varied from 23.0 °C to 49.6 °C. The wall temperature was stepped down from 101.7 °C to 63.1 °C in ~5 °C increments. The gravity level during the series of tests varied between 10-2 g (KC-135), 1 g (earth gravity), and high-g (1.6-1.8 g on the KC-135). Data from each of the heaters in the array along with high-speed digital video were obtained at 250 Hz. During the nucleate boiling, CHF, and transition boiling regimes, a large primary bubble was observed to form on the heater surface that acted as a "sink" for many smaller bubbles surrounding it. Dryout of the heater occurred under the primary bubble. For a given superheat, this primary bubble was observed to increase in size with bulk fluid temperature. At the highest bulk fluid temperature, a very large primary bubble was observed that was sensitive to g-jitter. Marangoni convection around the bubble was also observed to develop in microgravity, forming a "jet" of fluid into the bulk fluid. Boiling curves at various subcoolings and gravity levels are presented along with time and space resolved heat flux data.
6. 문 의 : 기계항공공학부 유 승 문 교수 (☏ 880-7110)
EFFECTS OF GRAVITY AND SUBCOOLING LEVEL
2. 연 사 : Prof. Jungho Kim
University of Maryland College Park, MD 20742
3. 일 시 : 2001년 7월 9일 (월) 16:00 – 17:00
4. 장 소 : 301동 1512호
5. 내 용 : Measurements of pool boiling of FC-72 in a microgravity environment provided by the KC-135 at various levels of subcooling were performed. Use of a microscale heater array allowed the measurement of time and space resolved heat transfer. For all the test cases, the pressure in the chamber was held at nominally atmospheric pressure (about 57 °C) and the bulk temperature was varied from 23.0 °C to 49.6 °C. The wall temperature was stepped down from 101.7 °C to 63.1 °C in ~5 °C increments. The gravity level during the series of tests varied between 10-2 g (KC-135), 1 g (earth gravity), and high-g (1.6-1.8 g on the KC-135). Data from each of the heaters in the array along with high-speed digital video were obtained at 250 Hz. During the nucleate boiling, CHF, and transition boiling regimes, a large primary bubble was observed to form on the heater surface that acted as a "sink" for many smaller bubbles surrounding it. Dryout of the heater occurred under the primary bubble. For a given superheat, this primary bubble was observed to increase in size with bulk fluid temperature. At the highest bulk fluid temperature, a very large primary bubble was observed that was sensitive to g-jitter. Marangoni convection around the bubble was also observed to develop in microgravity, forming a "jet" of fluid into the bulk fluid. Boiling curves at various subcoolings and gravity levels are presented along with time and space resolved heat flux data.
6. 문 의 : 기계항공공학부 유 승 문 교수 (☏ 880-7110)
