The influence of non-condensible gas on two-phase critical flow

The present paper deals with a two-phase steam-water critical flow experiment in long tubes, in which known air flow rates are injected into the stagnation region. The aim of the experiment is to detect the influence of non-condensible gas on the two-phase critical mass flux as well as to establish the limit, in terms of air concentration, beyond which the critical flow is affected by the presence of the gas. The test section is a vertical, circular channel with i.d. 4.6 mm and a length of 1500 mm (L/D = 325). Results of experiments with initially subcooled liquid (together with some data from saturated liquid discharges), up to pressures of 1.5 MPa are reported together with the analysis of the effects of the non-condensibles under the different stagnation conditions.