Lectures on Thermal-hydraulics, Master NE

THERMAL-HYDRAULICS, MASTER NE & OPTION ENERGIE

A SHORT INTRODUCTION TO TWO-PHASE FLOWS

Hervé Lemonnier, CEA/Grenoble, Wednesday, 25 January 2012

TEXT (in French)

SLIDES SETS

LECTURES

1. Industrial occurrence and flow regimes. Industrial applications where two-phase thermal-hydraulics are relevant, a few figures on REP’s, check the thermal balance, definitions of two-phase flow variables, flow pattern description (Gas-liquid two-phase flows), flow pattern map prediction, flooding and flow reversal.

PC software for plotting the Taitel and Dukler’s flow regime maps. Vertical upward flows (VertTD02.zip), horizontal or slightly inclined pipes (HoriTD03.zip).

2. Void fraction: experimental techniques and simple models. Definitions of the void fraction, experimental techniques for local void fraction, line-averaged, area-averaged and volume-averaged void fractions. Models for predicting void fraction: the homogeneous model, the Bankoff model, the Wallis model and the Zuber and Findlay model.

Suggested homework on void fraction. Void fraction calculation from experimental data. My solution to the homework.

3. Two-phase flows balance equations. Mathematical tools, first principles, local balance equations of continuum mechanics, the closure issue, local balances equations for two-phase flows and jump conditions, area-averaged balance equations, local time-averaged balance equations, composite averaging, the two-fluid model and the closure issue. More details on single-phase balance equations : Equations de bilan monophasiques et sources d’entropie.

4. 1D-Time averaged models. Mass, momentum and energy balances of the 1D-model, mixture equations, alternative secondary equations. The HEM, drift-flux and two-fluid models, Consequences of the topological relation on the consistency of the two-fluid model, the Kelvin-Helmholtz instability, pressure drop modelling.

Suggested homework on pressure drop modelling. Analyse du fonctionnement d’un réacteur bouillant. It is in French, I suggest those reading French help those who cannot… My solution.

5. Condensation and boiling heat transfer. Drop and film condensation on a flat vertical wall and on tubes, pool boiling, Nukiyama’s experiment, natural convection, onset of nucleate boiling, nucleate boiling mechanisms, critical heat flux and film boiling, Convective boiling, description of heat transfer mechanisms, the boiling surface, single-phase convection, onset of nucleate boiling and suppression, onset of significant void, Chen’s model for developed boiling, the critical heat flux issue. A summary of boiling and condensation heat transfer by J.-M. Delhaye.

6. Critical flow phenomenon. Industrial occurrence, experimental characterization in two-component and flashing flows, relation to propagation of waves and critical points, application to single-phase flow of gas and steam and water at thermal equilibrium, theoretical analysis with the two-fluid model, effect of non-equilibriums on the critical section location.

Exercices : 1D single-phase balance equations and entropy sources of the 1D model (1D Single-phase balance equations). Discharge of a a perfect gas through a nozzle (Problem and solution)

Project : Analysis of wall temperature evolution in boilng flow (Text). References : Manon (2000) and Winterton (1998).

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