Configuration of Micro-Layer in Nucleate Boiling

The objective of the study is to clarify the configuration of micro-layer formed between growing bubble and the heat transfer surface in nucleate pool boiling of region of isolated bubble. Micro-layer thickness was measured by specially devised measuring system applying the laser extinction method. The thin optic fiber of 94 μm in diameter arranged in a thin stainless tube was inserted in the liquid pool with the gas blowing both for preventing the getting wet of fiber made of fluorinated glass and removing the pool water in the path of laser light. The precision of the measurement was improved by using the two high speed cameras to decide the distance from bubble incipient site. It was elucidated that the thickness of the initially formed micro-layer was decided uniquely. The thickness was between 1 μm and 8 μm and was increased with the increase of distance between incipient bubble site and measuring position independently upon heat flux in this experiment.