Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: 13.3.2 - Liquid Films and Droplet Deposition in a Fuel Rod Bundle Geometry under Adiabatic Conditions
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Title: 13.3.2 - Liquid Films and Droplet Deposition in a Fuel Rod Bundle Geometry under Adiabatic Conditions Experimental Methods for Multiphase Flows
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Damsohn, M.
Prasser, H.-M.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
Subject: annular flow
droplet deposition
CFD validation
high-speed liquid film sensor
Abstract: In the upper part of boiling water reactors the flow regime is dominated by a steam-water droplet flow with liquid films on the nuclear fuel rod, the so called annular flow regime. The film thickness distribution over the circumference of the fuel rod and the process of entrainment and deposition of droplets from and to the liquid film play an important role especially in regard to dryout, which is the main phenomenon limiting the thermal power of a fuel assembly. To delay dryout so called functional spacers are introduced into the fuel assembly. CFD is increasingly becoming a tool to predict the flow behaviour and with it the location of dryout in the proximity of functional spacers. To keep computational cost bearable, simplified models are used that need to be validated with high resolved experimental data. In this work adiabatic experiments in the annular flow regime are conducted in a setup in which gas and water are circulated through a vertical test section, resembling two neighboring subchannels of a fuel assembly. The gas is helium, air or octofluorcyclobutane (C4F8) to study the effect of gas density on the flow. In a first set of experiments the dynamic liquid film thickness is measured with high time and spatial resolution around the resembled fuel rod. In a second set droplet deposition from the gas core unto the liquid film is measured spatially resolved. By inserting spacers of different geometries, the influence of these spacers on the liquid film and droplet deposition can be measured. For both experimental sets, a sensor is used which measures non-intrusively the electrical conductance between electrodes flush to the wall. The sensor consists of 64 x 16 measuring points with a lateral pitch of 2 x 2 mm2 and operates at a measuring frequency of 10’000 frames per second (Damsohn, 2009). The film thickness is measured by the change of conductance caused by film thickness variations, while the droplet deposition is measured by the increase of conductivity in the liquid film when a droplet with a salt tracer deposits. CFD simulations are conducted with STAR-CCM+. The simulations are based on Reynolds-Avaeraged-Navier-Stokes equations with standard turbulence models. The droplet velocity field is calculated in a Lagrangian way with one-way coupling. The liquid film is modeled with a numerical scheme proposed by Kishore (2004). In the results experimental time-resolved and time-averaged film thickness distributions are shown and compared with the simulations. Experiments and simulations are in good qualitative but poor quantitative agreement. The comparison shows that with increasing wall shear the film becomes thinner even in non equilibrium conditions. Experimental data of the droplet deposition distribution in the spacer proximity is shown for a selected case with Spacer 1 and compared with the results of the simulation. A sensitivity analysis of the simulation with different parameters shows the main effects of enhanced droplet deposition in the spacer proximity. Droplet deposition seems to be enhanced mainly by the interaction of droplets with the spacer.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
 Record Information
Bibliographic ID: UF00102023
Volume ID: VID00324
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: 1332-Damsohn-ICMF2010.pdf

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