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A theoretical critical heat flux (CHF) model based on microlayer dryout and Helmholtz instability for subcooled tube flow under pressurized water reactor operation conditions is first extended to t...

The performance of five critical heat flux (CHF) correlations with the COBRA IIIC/MIT-1 code was evaluated. These correlations were evaluated against a data group comprised of 2943 axial nonuniform...

Based on the Helmholtz instability at the microlayer/vapor interface as a trigger condition for microlayer dryout, Lee and Mudawwar developed a mechanistic critical heat flux (CHF) model for subcoo...

A new technique of identifying the flow regimes of air/water two-phase flow in a vertical pipe is proposed. This technique is based on analyzing the statistical characteristics of the static and differential pressure signals by an optimum modeling method. The major concept of the optimum modeling method is to fit the two-phase flow pressure noise by autoregressive moving average (ARMA) models with an optimization technique. The results show that it is possible to identify the flow patterns from a set of “flow regime indices,” such as dynamic signature, order of dominant dynamics mode, and order of ARMA model. A computer code based on these indices has been built on an IBM-PC/XT microcomputer to perform two-phase flow pattern identification. The success probability of this code is ∼85% on the data base collected from our experimental work. The experimental data points are also indicated in a Taitel flow map and excellent matching has been shown, except for some points around the flow regime transition boun...

A wide range of combinations of gas and liquid flow rates that form various flow patterns are investigated. By analyzing the signal spectra detected by a single sensor using light techniques, the criteria for identifying two-phase flow patterns are proposed. By applying these criteria with only one parameter, the high-frequency contribution fraction (HFCF), the reasonable identifying performance is 76% when churn flow is counted and 88% when churn flow is not counted. When ..cap alpha..-bar is added as an auxiliary to HFCF, the identifying performance can be increased to 83 and 96%, depending on whether churn flow is counted. Both parameters can be acquired by signals from a single void fraction sensor. The criteria are expected to apply to other void fraction measurable systems for identifying two-phase flow patterns.