CHF for Uniformly Heated Vertical Tube Under High Pressure Conditions

Abstract

In this study, a total of 2,870 high pressure (70 bar ≤ P ≤ 206 bar) data points of critical heat flux (CHF) in uniformly heated round vertical tube for water were collected from 5 different published sources. The data consisted of following parameter ranges: 28.07 ≤ G (mass flux) ≤ 10,565.03 kg/m2s, 1.91 ≤ D (diameter) ≤44.68 mm, 40 ≤L (length) ≤4966 mm, 0.14 ≤qc (CHF) ≤ 9.94 MW/m2, and −0.85 ≤X (exit qualities) ≤ 1.22. With these data a comparative analysis is made on available correlations, and a new correlation is presented. The new high pressure CHF correlation, as in the low and medium pressure cases of earlier studies, comprised of local variables, namely, “true” mass quality, mass flux, tube diameter, and two parameters as a function of pressure only. This study reaffirms our earlier findings that by incorporating “true” mass quality in the local condition hypothesis, the prediction of CHF under these conditions can be obtained quite accurately, overcoming the difficulties of flow instability and buoyancy effects that are inherent in the phenomena. The new correlation predicts the CHF data significantly better than those currently available correlations, with average error 0.12% and rms error 13.52% by the heat balance method.