Heat transfer and boiling during forced convection of sodium in an induction-heated tube

Abstract

On the sodium boiling loop (NSK) a series of forced convection boiling and heat transfer experiments has been performed. The test section was an HF-induction heated Ni-tube of 9 mm inner diameter and 168 mm heated length. The results of the preliminary liquid-phase heat transfer measurements at heat fluxes up to 720 W/cm2 can be correlated by the equation Nu = 5.3 + 0.018 · Pe0.85. The boiling experiments have been performed under the following conditions: 1. heat flux: 170-600 W/cm2 2. presure: 0.3-1 ata 3. mass flow: 0.06-0.12 kg/sec 4. inlet subcooling: 85-170°C. The incipient boiling wall superheat was between 40 and 125°C. It increased with increasing heat flux and decreased with increasing sodium velocity. In the whole range of parameters the phenomenon observed was violently pulsating boiling with partial discharge and subsequent refilling of the test section and strong oscillations of wall temperature. The course of the boiling process was mainly determined by the liquid phase pressure drop before the test section and the heat flux. At low pressure drops dryout of the test section occurred at heat fluxes of about 250 W/cm2. At high pressure drop generated by throttling no dryout could be observed at heat fluxes up to 400 W/cm2. © 1970.