Comparative Research on Steam-Water Two-Phase Flow Instabilities between Internally Ribbed Tubes and Smooth Tubes

This paper compared the effects of two types of tubes, the internally ribbed tubes and the smooth tubes, on the two-phase flow instabilities in parallel inclined tubes based on the experimental investi- gation in high pressure test loops. Experimental results showed that the system parameters had important ef- fects on the two-phase flow instabilities both in the two types of tubes. The thresholds of heat flux of pressure drop oscillation in smooth tubes are smaller than that in the internally ribbed tubes; otherwise, the thresholds of density wave oscillation in internally ribbed tubes are smaller than that in the smooth tubes. Non-dimensional correlations of thresholds of heat flux both in the internally ribbed and the smooth tubes had been provided through the regression calculation of test data.