Experimental Investigation on the Characteristics of Bubble Departure Frequency of Subcooled Flow Boiling in Narrow Rectangular Channel

Subcooled flow boiling in narrow rectangular channel is a very effective heat transfer method and is very important to nuclear reactor design and thermal hydraulic safety. The departure frequency of bubbles in subcooled boiling flow has direct influence on heat transfer. Subcooled flow boiling experiment is carried out to investigate the effect of different working conditions on the bubble departure frequency in the narrow rectangular channel. Because the test section is composed of quartz glass and Sapphire crystal Glass, it can be observed from four different directions to obtain high quality images. The experiment is conducted with mass fluxes of 400 to 1500 kg/(m2s) and heat flow density between 50∼300 (KW/m2). Besides, the system pressure is 100 kPa to 700kpa and inlet subcooled is 10 to 60 °C. Two types of nucleation sites can be detected from the experimental results: sliding growth and condensation. The bubble departure frequency of sliding is significantly higher than that of condensation. Besides, the effect of different working conditions on the bubble departure frequency in narrow rectangular channels was investigated. Finally, the departure frequency is analyzed and compared with previous models. The results show that the model proposed by Cole is in good agreement with the experimental results.