Subcooled pool boiling on thin wire in microgravity
- Paper number
IAC-06-A2.3.07
- Author
Prof. Jian-Fu Zhao, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Mr. Shi-Xin Wan, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Mr. Gang Liu, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Ms. Na Yan, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Dr. Wen Rui Hu, Institute of Mechanics, Chinese Academy of Sciences, China
- Year
2006
- Abstract
The present paper reports a new set of experimental data of subcooled pool boiling on a thin wire in microgravity aboard the 22nd Chinese recoverable satellite using the temperature-controlled pool boiling (TCPB) device, which was developed to perform pool boiling heat transfer studies in both normal gravity and microgravity. The results of the experiments in normal gravity before and after the flight experiment were also presented in the present paper, which were compared with those in microgravity.
In all cases, the bulk fluid was R113 at 0.1 MPa and subcooled by 24 ∘C nominally. A thin platinum wire of 60 µm in diameter and 30 mm in length was simultaneously used as heaters and thermometers. The heater resistance, and thus the heater temperature, was kept constant by a feedback circuit. 16 adjustable states of average wire temperature were switched automatically with the order of increase-decrease-increase. The first heat transfer mode is single phase convection in normal gravity, while single phase conduction in microgravity. Excellent agreements between the experimental data and the predictions of the model of Churchill and Chu (1975) in both normal and microgravity conditions showed that the experimental facility and data acquisition system are reliable.
According to the designed procedure, boiling is initialized in all cases with two-mode transitional boiling, in which nucleate and film boiling co-exist along the wire steadily. Due to the focus of the present study is the nucleate boiling, most data were obtained about the nucleate boiling. Three group of vapor bubble were observed with different size in microgravity. The biggest bubble of the order of 10 mm, which was yielded during the two-mode transition boiling, was still staying on the wire till the CHF. The smallest bubbles were of the order of 10 −1mm. They departed from the wire, and assembled around the wire. There existed some bubble with about several millimeters in diameter, staying on the wire. A qualitative model about bubble departure regime was also presented to reveal this phenomenon. Based on this model, due to the thermocapillary effect, there exist 3 characteristic bubble departure radius, namely R1, R2, and R3 in increasing order. If the bubble radius is between R1 and R2 or is greater than R3, the bubble will depart from the heat surface. If the bubble radius is less than R1 or is between R2 and R3, the bubble will stay on the heat surface.
New data of CHF on a thin wire in different gravity levels were also presented and discussed. It’s found that the correlation of Lienhard and Dhir (1973) can predict the present data with good agreement, although the range of the dimensionless radius R’ is extended by three or more decades above the originally set limit. This is consistent with Straub (2001), but contradict with Di Marco and Grassi (1999).
- Abstract document
- Manuscript document
IAC-06-A2.3.07.pdf (🔒 authorized access only).
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