Cryogenic two-phase flow characteristics of Helium 1 in vertical tubes

Experimental and analytical studies are carried out on the two-phase flow phenomena of Helium 1 flowing in the upward direction in smooth tubes. Pressure drops are measured at both adiabatic and diabatic conditions with exit vapor qualities ranging from 0 to 100 percent. The void fraction at the exit of the test section is measured with a capacitance probe connected to a sensitive circuit designed to detect small density changes. Tests are carried out on three 1000 mm long test sections of sizes 6.35, 2.7 and 2.1 mm ID. Data for pressure drop and exit void fraction is obtained at different pressures ranging from 1 to 2 atm, liquid helium flow rates of 5 to 35 l/hr and temperatures of 4.2-5.2 K. An empirical threshold criterion for the inception of the observed density wave oscillations is developed from similarity analysis.