CHF in Vertical Round Tubes With Uniform Heat Flux

Abstract

In recent years it is well known that models based on the local condition hypothesis give significant correlations for the prediction of CHF (Critical Heat Flux), using only few local variables. In this work, a study was carried out to develop a generalized CHF correlation in vertical round tubes with uniform heat flux. For this analysis, a CHF database that composed of over 10,000 CHF data points, which were collected from 12 different sources, was used. The actual data used in the development of this correlation, after the elimination of some questionable data, consisted of 8,951 data points with the following parameter ranges: 0.101 ≤ P (pressure) ≤ 20.679 MPa, 9.92 ≤ G (mass flux) ≤ 18,619.39 kg/m2s, 0.00102 ≤ D (diameter) ≤ 0.04468 m, 0.03 ≤ L (length) ≤ 4.97 m, 0.11 ≤ qc (CHF) ≤ 21.42 MW/m2, and −0.87 ≤ Xe (exit qualities) ≤ 1.58. The result of this work showed that regardless of various flow patterns and regimes that exist in the wide flow conditions, the prediction of CHF can be made accurately with few major local variables: the system pressure (P), tube diameter (D), mass flux of water (G), and true mass flux of vapor (GXt). The new correlation was compared with 5 well-known CHF correlations published in world literature. The new correlation can predict CHF within the root mean square error of 13.44% using the heat balance method with average error of −1.34%.