EFFECT OF INITIAL LIQUID LEVEL ON THE COUNTERCURRENT FLOW LIMITATION IN A HORIZONTAL PIPE CONNECTED TO AN INCLINED RISER

摘要

In an effort to carryout an in-depth study of the initial liquid level effect, in particular, on the air-water countercurrent flow limitation (CCFL) in a horizontal pipe connected to an inclined riser by a 35° bend, which simulates the geometry of a PWR hot leg, an extension of the previous work has been made. For various combination of test parameters, a total of 312 experimental data (including 118 data obtained previously) for the onset of CCFL and zero liquid penetration (299 for the onset of CCFL and 13 for the zero liquid penetration) have been obtained in a simulated PWR hot leg. Based on the present and the previous experimental results, the parametric effects of ① pipe diameter, ② horizontal pipe length, ③ horizontal pipe length-to-diamter ratio, and initial water level (or conversely, initial void fraction) on the onset of air-water CCFL have been analyzed. An empirical correlation for the onset of CCFL in a simulated PWR hot leg has also been develo[ed in terms water and air Wallis flooding parameters, initial void fraction, and horizontal pipe length-to-diameter particularly for the low inlet water flow rate region (0< j_L~(*0.5) <0.2). Comparisons of the present and existing empirical correlations with the air-water CCFL data of large pipe diamters show that the present correlation agrees more closely with the experimental data than the existing CCFL correlations.