Distinguishing evaporation-like and boiling-like modes of pseudo-boiling in supercritical pressures

•Pseudo-boiling of supercritical fluid is investigated using Pt wire and NiCr wire.•Bubble-like interface is tracked by the grey extracting method based on image files.•Evaporation-like mode occurs for Pt wire, both evaporation-like and boiling-like modes occur for NiCr wire.•Intermittent boiling-like heat transfer is caused by the piston motion of the wire.•Continuous boiling-like heat transfer is caused by the temporal-spatial temperature variations of the wire.