Continuous Boiling Phenomena of Sodium under Forced Convection by Direct Heating

Abstract

The results of an experimental study on the continuous boiling behavior of sodium with upward forced convection loop are reported. The sodium was passed through a vertical tube of 14.9mm I. D., where it was heated by d. c. power (∼4V, ∼5, 000A) directly applied through the flowing sodium, The experiments were carried out in the following range of conditions:Input power: 6∼12kwPressure at the condenser: 0.9∼1.1kg/cm2Flow rate: 1.0∼3.0l/minInlet temperature: 750°∼830°C.Under certain conditions, steady boiling occurred, but boiling generally had a tendency to become unstable, and flow patterns representing violently pulsating boiling were observed. These latter flow patterns were either of single bubble ejection type with expulsion and subsequent re-filling of sections of the tube mainly by liquid sodium falling back from above, or else of slug type with periodical expulsions, without fall-back of liquid. For these patterns of pulsating boiling, the frequencies of oscillation ranged from 0.5 to 1.0Hz. The film thickness remaining on the channel wall was also measured.