Abo Bibliothek: Guest
ICHMT DL Home Aktuelles Jahr Archive Vorstand International Centre for Heat and Mass Transfer

Simulation of Void Fraction Profile Evolution in Subcooled Nucleate Boiling in a Vertical Annulus with a Bubble-Tracking Model

Ivo Kljenak
Reactor Engineering Division, Jozef Stefan Institute, Jamova 39, Ljubljana, Slovenia

Borut Mavko
Reactor Engineering Division, "Jozef Stefan" Institute, Jamova 39, 1000 Ljubljana, SLOVENIA

Abstrakt

A three-dimensional bubble-tracking model of subcooled nucleate boiling flow in a vertical channel at low-pressure conditions is proposed, with specific application to the case of boiling in an annulus with a central heating rod. In the model, vapour is distributed in the liquid in the form of individually tracked bubbles. The overall behaviour of the liquid-vapour system results from motion, interaction, coalescence and boiling mechanisms prescribed mostly at the level of bubbles. The wall heat transfer coefficient and the wall temperature are calculated from one-dimensional correlations. The partitioning of the heat flux, which is consumed for bubble nucleation and heating of the liquid, varies along the flow and depends on bubble size as well as on local flow conditions. Bubbles are nucleated with constant frequencies at fixed nucleation sites randomly distributed over the heated surface. Liquid temperature profiles at different axial locations are determined from steady-state energy balances. The nucleation site density is determined from a balance between vapour generation rate, bubble departure sizes and nucleation frequencies. After nucleation, bubbles slide on the heated surface, detach and then gradually migrate into the low-temperature region away from the heated surface, where they eventually condense. Both bubble detachment and migration are modelled probabilistically. Bubble lateral migration is restricted by the lift force due to the liquid velocity gradient.
The proposed model was applied to experiments on subcooled boiling that were carried out at Purdue University (USA) by Bartel [1]. A good agreement between measured and calculated void fraction profiles at different axial locations was obtained.

ICHMT Digital Library

Bow shocks on a jet-like solid body shape. Thermal Sciences 2004, 2004. Pulsed, supersonic fuel jets - their characteristics and potential for improved diesel engine injection. PULSED, SUPERSONIC FUEL JETS - THEIR CHARACTERISTICS AND POTENTIAL FOR IMPROVED DIESEL ENGINE INJECTION
View of engine compartment components (left). Plots of temperature distributions in centreplane, forward of engine (right). CHT-04 - Advances in Computational Heat Transfer III, 2004. Devel... DEVELOPMENT AND CURRENT STATUS OF INDUSTRIAL THERMOFLUIDS CFD ANALYSIS
Pratt & Whitney's F-135 Joint Strike Fighter Engine under test in Florida is a 3600F class jet engine. TURBINE-09, 2009. Turbine airfoil leading edge stagnation aerodynamics and heat transfe... TURBINE AIRFOIL LEADING EDGE STAGNATION AERODYNAMICS AND HEAT TRANSFER - A REVIEW
Refractive index reconstructed field. (a) Second iteration. (b) Fourth iteration. Radiative Transfer - VI, 2010. Theoretical development for refractive index reconstruction from a radiative ... THEORETICAL DEVELOPMENT FOR REFRACTIVE INDEX RECONSTRUCTION FROM A RADIATIVE TRANSFER EQUATION-BASED ALGORITHM
Two inclusion test, four collimated sources. Radiative Transfer - VI, 2010. New developments in frequency domain optical tomography. Part II. Application with a L-BFGS associated to an inexa... NEW DEVELOPMENTS IN FREQUENCY DOMAIN OPTICAL TOMOGRAPHY. PART II. APPLICATION WITH A L-BFGS ASSOCIATED TO AN INEXACT LINE SEARCH