Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles

Abstract

Post-dryout heat transfer to high pressure water was investigated experimentally in vertical tubes and annuli containing various flow obstacles. The operational conditions during the experiments were as follows: mass flux from 500 to 1750kg/m2s, pressure from 5 to 9MPa, inlet subcooling from 10 to 40K and heat flux up to 1.5MW/m2. Five different test sections were used in experiments: three annular test sections with inner diameter 12.7mm and outer diameter 24.3mm, containing cylindrical and grid flow obstacles in the upper part, and two tubular test sections with inner diameter 24.3mm with and without pin flow obstacles. The heated length in all test sections was 3650mm. The wall temperature was measured with 88 thermocouples located along the inner rod and the outer tube surfaces. Due to the presence of flow obstacles, only developing post-dryout heat transfer was observed. Selected post-dryout heat transfer correlations were compared to the experimental data. It has been concluded that all tested correlations predict significantly higher wall temperatures than those obtained in the present experiment. A simple correction function to the Saha model has been suggested which significantly improves the agreement between the correlation and the present data.