On the basis of the classification and definitions of two regions of pressure drop oscillation in our previous work

the transient and time-averaged heat transfer characteristics of steam-water two-phase flow during the second regional pressure drop oscillation were experimentally studied in a closed circulation system with a helical coiled tube boiling channel. New non-dimensional parameters and criterion for characterizing the effects of second regional pressure drop oscillation on transient and time-averaged heat transfer coefficient were proposed.