Mercury boiling with forced convection at low pressures in vertical tubes

The boiling behavior of pure mercury in a vertical steel tube at low exit pressures was investigated. In the upward flow stable and unstable boiling modes were found. At the tube exit maximum mass flow rate was always established. For the stable boiling system the pressure drop and the axial distribution of heat transfer rates were determined. Visualization of the boiling zone and the two phase flow was obtained by X-ray photography. Any similarity to wellknown flow patterns was not found. An attempt was made to determine the dynamics and the frequency of the unstable, periodic boiling mode.