Incipient Boiling Phenomena of Sodium under Forced Convection by Direct Heating

The results of an experimental study on incipient sodium boiling with upward forced convection loop are reported. Forced convection sodium in a vertical tube of 14.9mm I.D. was directly heated by direct current (–4V, –5,000A). The experiments were carried out under the following conditions: Input power: 6–12kW, Pressure at the condenser: 0.9–1.1 atm Flow rate: 1.0–3.0l/min, Inlet temperature: 7,500°–830°C The incipient boiling phenomena observed were either violent single bubble ejection or else slow vapor formation depending on the conditions. It was indicated from observations of the position of boiling inception that the boiling did not always occur at the position of maximum temperature.