A VISUAL EXPERIMENT OF SINGLE BUBBLE GROWTH PROCESSES IN A VERTICAL RECTANGULAR CHANNEL

Single bubble growth processes under subcooled boiling condition in a vertical rectangular channel with a gap of 2.8 mm have been visually studied. A high-speed camera was used to observe and record the bubble growth processes at a rate of 6000 frames per second. Four kinds of bubbles with different equivalent radius change trends near the ONB (Onset of Nucleate Boiling) point were observed. The bubble equivalent radius change trends were fitted by traditional empirical formula R (t) = k . t(n) to and found that the value of empirical parameter n was in the range of 0.11 to 0.53 which was smaller than that in literatures, and the value of empirical parameter k had a positive correlation with Ja number. The bubbles generated at the same nucleation point under different heating powers, inlet fluid temperatures and mass flow rates were compared and found that within the experimental range the changes of heating power and inlet fluid temperature had a significant effect on bubble growth.