VISUALIZATION OF THERMOSIPHON BOILING TWO-PHASE FLOW OF LIQUID NITROGEN IN A VERTICAL LUNATE NARROW CHANNEL

摘要

The present study investigates two-phase flow patterns and thermosiphon boiling heat transfer of liquid nitrogen in a vertical luante narrow channel. A visualization experiment is conducted using high-speed photography technique and a 3CCD digital video camera. The experiment shows that bubbles first appear at the contact line of the lunate channel and are deformed into oblate ones. Five flow patterns are defined and the picture of each pattern is also provided. The thermosiphon two-phase flow of liquid nitrogen in the lunate narrow channel is an oscillation flow. The effects of heat transfer enhancement in the lunate narrow channel is remarkable compared to large diameter channel.