Effect of Bubble Contact Diameter on Bubble Departure Size in Flow Boiling

Abstract

The growth and departure of bubbles on a vertical heated wall of an annular channel in flow boiling were observed by a high-speed camera, and the bubble contact diameter and bubble departure diameter were measured. It was found that bubble departure diameters were different among different nucleation sites in the same boiling area (same test condition, same surface roughness). Force balance on a single bubble attached to the heated surface was also analyzed to explain this phenomenon. The theoretical research results show that bubble contact diameter has a significant influence on bubble departure diameter, and the corresponding departure diameter is larger as the bubble contact diameter is larger. This agrees with the visual experimental results.

Keywords::

• flow boiling
• vertical heated surface
• force analysis
• bubble contact diameter
• bubble departure diameter

Funding

The authors are grateful for the support of the Natural Science Foundation of China (no. 51176008) and the Fundamental Research Funds for the Central Universities (no. 2011YJS055). The authors thank the National Natural Science Foundation of China (no. 11172026 and no. 11427802).