Based on acoustic emission technique

the acoustic signals during pool boiling of water were measured and the relationship between boiling modes and acoustic signal characteristics was investigated by time-domain and frequency-domain analysis.The results showed that the values of acoustic energy

standard deviation(STD)and average absolute deviation(AAD)indicated extreme points when the boiling mode changed from natural convection to nucleate boiling at an excess temperature of 5℃.After transition boiling began at excess temperature of 30℃

the values of acoustic energy

STD and AAD changed irregularly.As excess temperature increased

the dominant frequency of acoustic signals showed two step decreases

at which excess temperatures were the turning points from natural convection to nucleate boiling and from nucleate boiling to transition boiling

respectively.Therefore

the step change of dominant frequency could be used as a criterion to identify the emergences of nucleate boiling and transition boiling.In comparison with the work published before

this work investigated transition boiling as well as natural convection and nucleate boiling.The criterion to determine boiling mode transition is proposed. Compared with conventional methods

this method was relatively fast

sensitive

accurate

non-intrusive and real-time online.