Dryout and two-phase flow pressure drop in sodium heated helically coiled steam generator tubes at elevated pressures

Abstract

The dryout conditions were determined in three sodium-heated circular helically coiled steam generator tubes of 18 mm I.D. The heated straightened lengths of these coils were 40.13, 35.50 and 26.67 m and the coil diameters 0.7 and 1.5 m. The operating conditions of the tests were: pressure: 14.7–20.2 MN/m 2; mass velocity: 112–1829 kg/m 2 s; inlet subcooling: 35.6–156.8 K; dryout steam quality: 0.08–1; dryout heat flux = 41–731 kW/m 2. The 203 data obtained for the first and last detected dryouts, the 459 data taken in vertical, long and short electrically heated circular tubes for medium and high pressures and the 215 data taken in a 10 m long, vertical sodium-heated circular tube at high pressures were correlated to predict the dryout heat flux within 20 % accuracy for 98 % of the time. The RMS-error for all the 877 data was 0.01 %. In the above coils two-phase flow pressure drops were also measured for the following range of operating conditions: pressure: 14.9–20.1 MN/m 2; mass velocity: 296–1829 kg/m 2 s; steam quality at the termination of boiling: 0.15–1. The 70 data obtained and 299 data taken in a 10 m long, vertical, sodium-heated circular tube at high pressures were correlated within 20% accuracy for 98% of the time. The RMS error for all the 369 data was 9.87%.