TWO-PHASE PRESSURE DROPS IN THE LOW FLOWRATE REGION.

Pressure drops of a water-nitrogen mixture flowing upward in two different tubular test sections were measured. The data were obtained in the low specific mass flowrate region for the whole gas weight function. In general, pressure drops turned out to decrease by increasing specific mass flowrate or gas weight fraction, which is just the opposite of what is normally found. Moreover, a steep pressure drop decrease in vicinity of pure gas conditions may be present. In terms of friction pressure drops this decrease is steeper and present also in vicinity of pure liquid conditions. The data analysis confirmed the validity of the CISE generalized pressure drop correlation, and suggested slight modifications both in the correlation structure and the relevant empirical constant values.