Pool-boiling/bubbling void fraction in an annular flow channel

Abstract Void fractions were measured in narrow-gap annular flow channels under pool-bubbling/boiling conditions. The experiments were conducted in an air-water system with a test section of an outer tube with an inner diameter of 22 mm and an inner rod with a diameter of 12 mm, and in a 3 MPa steam-water system with a test section of an outer tube with an inner diameter of 22 mm and a heated inner rod with a diameter of 12.27 mm. Griffith's void fraction correlation compared well with void fraction data obtained from the air-water and steam-water experiments while other correlations examined could not consistently predict both sets of experimental results. The RELAP5/MOD2 code for thermal-hydraulic analyses of a light water reactor overpredicted the void fractions. The interfacial drag calculation model of the code was modified with Griffith's void fraction correlation. The modified code gave satisfactory results.