Mechanistic Multidimensional Modeling of Forced Convection Boiling Heat Transfer

Michael Z Podowski,Raf M Podowski

doi:10.1155/2009/387020

Abstract

Due to the importance of boiling heat transfer in general, and boiling crisis in particular, for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems, extensive efforts have been made in the past to develop a variety of methods and tools to evaluate the boiling heat transfer coefficient and to assess the onset of temperature excursion and critical heat flux (CHF) at various operating conditions of boiling channels. The objective of this paper is to present mathematical modeling concepts behind the development of mechanistic multidimensional models of low-quality forced convection boiling, including the mechanisms leading to temperature excursion and the onset of CHF.

Highlights

Because of the complexity of phenomenagoverning boiling heat transfer in general, and subcooled boiling inparticular, the predictions of critical heat flux (CHF) have traditionally been based on correlating data obtained from numerous experimental measurements
The objective of this paper is to discuss various physical and mathematical modeling concepts for local heat transfer phenomena in boiling systems, and to show that the proposed approach can be combined with mechanistic multidimensional models of two-phase flow and used to predict various parameters characterizing low-quality forcedconvection boiling, including the mechanisms leading to temperature excursion and the onset of CHF
The multifield modeling concept is based on coupling a complete mechanistic multidimensional model of two-phase flow with the models governing local heat transfer and phase change phenomena in heated channels

Summary

Introduction

Because of the complexity of phenomenagoverning boiling heat transfer in general, and subcooled boiling inparticular, the predictions of CHF have traditionally been based on correlating data obtained from numerous experimental measurements. Given the progress made in the computational fluid dynamics methods, the possibility of using complete multidimensional models to predict boiling heat transfer before, and up to, the onset of CHF becomes an attractive option complementing the traditional phenomenological approach used in the past. The objective of this paper is to discuss various physical and mathematical modeling concepts for local heat transfer phenomena in boiling systems, and to show that the proposed approach can be combined with mechanistic multidimensional models of two-phase flow and used to predict various parameters characterizing low-quality forcedconvection boiling, including the mechanisms leading to temperature excursion and the onset of CHF

Multidimensional Multifield Model of Forced-Convection Boiling

Near-Wall Heat Transfer in Nucleate Boiling

Bubble Ebullition Cycle

Model Testing and Validation

Findings

Conclusions