Development of Drift-Flux Correlation and Flow Pattern Transition Criteria for Two-Phase Cross-Flow in Horizontal Tube Bundles

Keyou Mao, Purdue University

Abstract

In relation to void fraction and flow regime transition predictions of cross-flow in horizontal tube bundle of steam generator, a phenomenological drift-flux correlation and new flow regime transition criteria have been developed to meet the demand on the study of two-phase flow gas and liquid velocities, two-phase pressure drop, heat transfer, flow patterns and flow induced vibrations in the shell side of the U-bend section of the steam generator. The distribution parameter is obtained by assuming constant asymptotic values and taking into account the differences in channel geometry. The drift velocity is modeled depending on the non-dimensional viscosity number. Void fraction effects on drift-flux parameters are also considered for computation capabilities in higher void fraction regions. The new model agrees well with cross-flow experimental databases of air-water, R-11 and R-113 in parallel triangular, normal square and normal triangular arrays with a mean absolute error of 1.06% and a standard deviation of 4.47%. In comparison with other existing correlations, the developed correlation is superior to other studies due to improved accuracy. Prototypic analysis performed for typical steam generator along with common industry heat exchanger operating conditions demonstrates the scalability of the new drift-flux correlation due to plausible estimation trends opposed to other models. The current developed drift-flux correlation is able to calculate the void fraction of cross-flow over a full range with different sub-channel configurations in shell-tube heat-exchangers. A new approach for implementing the drift flux model to predict the void fraction over the entire steam generator region has been proposed. For the flow regime transition criteria, a new analysis approach has been proposed based on the analysis on the underlying physics of the cross-flow behavior. Based on the classical flow regime transition criteria by Mishima and Ishii (1940), the transitions from bubbly to cap bubbly, cap bubbly to churn and churn to annular have been modelled. The transition to finely dispersed bubbly flow has been modified based on the flow regime transition criterion for this regime developed by Taitel et al. (1980). The new phenomenological flow regime transition criteria include the fluid types, geometric effects and operating conditions, which can be applied to a wide range of engineering heat transfer systems. The newly developed flow regime map based on the developed flow regime transition criteria for the cross-flow have been validated with all the available data and existing flow regime maps. The new flow regime maps show reasonable trends against the other maps. In addition, sample flow regime maps using the newly developed criteria for typical steam generator and adiabatic heat exchanger systems working conditions have been plotted to provide a guide to predict the flow regime transition for upward cross-flow in a horizontal tube bundle system.

Degree

M.S.

Advisors

Hibiki, Purdue University.

Subject Area

Chemical engineering|Mechanical engineering|Nuclear engineering

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