Development of CFD models for wall boiling and development of high resolution ultrafast X-ray tomography fort the analysis of two-phase flow in heated rod bundles
Based on the experimental investigation of the local microscopic phenomena done by the partners of the project the existing model approaches for wall boiling are further developed and validated. The interfacial area is an essential parameter for the behaviour of the two phase flow. The coupling of the wall boiling model with the multiple bubble size group approach (MUSIG) and other approaches has to be validated in close cooperation with ANSYS Germany. For a realistic modelling of wall boiling the heat conduction in the heated wall has to be considered. In the next step the derivation of local criterions for film boiling is intended.
A 3 x 3 rod bundle test will be constructed and operated at HZDR at the thermal hydraulic test facility TOPFLOW. The fast X-ray tomography has to be adapted and applied for the visualization of steam distributions in bundle cross-sections. The complete new tomographic technique will enable the investigation of transient boiling processes in never reached spatial and time resolution.
University of Applied Sciences Zittau/Görlitz (HSZG)
Experimental investigation of boiling processes using optical methods and determination of parameters for CFD models
The intended measurement technique comprises (in addition to classic measurements like thermocouples):
- Optical methods like high speed and infra red cameras inclusive of digital image processing methods
- Micro-PIV (Particle Image Velocimetry) and optical coherence tomography (in close cooperation to Technical University of Dresden, Medical faculty)
Technische Universität Dresden, Faculty of Medicine Carl Gustav Carus
Investigation of boiling processes using PIV and optical Coherence Tomography
The working group “Clinical sensoring and monitoring” at the Technische Universität Dresden has long term experience on the application of optical coherence tomography in biomedical research. This measurement technique is further developed for industrial applications and applied to the investigation of boiling processes.
Technische Universität Dresden, Chair of Hydrogen and Nuclear Engineering
Experimental investigation of the influence of nuclear reactor typical chemical coolant additives on boiling phenomena
The effect of PWR-specific coolant additives on boiling phenomena at metallic heated surfaces is investigated experimentally and the results are processed for model development. For this purpose, a newly designed test facility enables the study into these effects in single rod and bundle geometries. Measurements are procured using optical methods and the wire mesh sensor technique developed at FZD.
Technische Universität München, Chair of Thermodynamics
Influence of turbulence and secondary flow on subcooled boiling in nuclear reactor typical configurations
Applying holographic measurement techniques at small scale test facilities boiling phenomena are observed. The facility is operated with a refrigerant, simulating the conditions typical for reactors. The whole range of phenomena from the onset of boiling up to critical conditions is observed. Both optical probes and holographic techniques are applied. The effect of turbulence and secondary flows shall be shown. The data are processed for model development.
Technische Universität Dresden, Institute of Fluid Mechanics
Turbulence and bubble dynamics
The suitability of RANS turbulence models for CFD describing the two phase flow phenomena in rod bundle geometries is investigated by comparing it to Large Eddy Simulations. In a second part of the project the application of Direct Numerical Simulations to single bubbles in a fluid is used to derive the necessary modifications of RANS models to describe two phase flow. Main topics are the exchange of momentum, heat and mass in boiling processes, the bubble dynamics and the bubble-bubble and the bubble-fluid interaction.
Karlsruhe Institute of Technology (KIT)
Validation of sub channel and CFD codes by means of rod bundle tests
The project is focussed on the CFD-simulation of two phase flows and the validation of models describing cross flow exchange and critical heat flux in rod bundle geometries. The hot channel models are to be improved. The validation is based on experimental data gained at the Forschungszentrum Karlsruhe. In the rod bundle tests the refrigerant R12 was used to investigate critical heat flux.
Ruhr-Universität Bochum, Chair of Energy Systems and Energy Economics, Reactor Simulation and Safety Group
Development of boiling models for application in Lumped Parameter codes to estimate external reactor pressure vessel cooling (ERVC)
A boiling model for a Lumped Parameter code like ATHLET-CD has to be developed and implemented, which enables the estimation of the efficiency of RPV cooling from outside. The possible transfer of CFD methods for this purpose has to be considered. Finally the models have to be validated by means of experimental data published in the literature.
CFD model development and validation of 3-D simulations of boiling flow in PWR rod bundles
The small scale tests of the project partners and the TOPFLOW integral tests are used to improve the CFD models of boiling processes in PWR rod bundles. Main topics are the coupling of the boiling model with the heat transfer in the adjacent wall (CHT), the coupling of the RPI-wall boiling models with bubble population balance models, the extension of the RPI-wall boiling model and the improvement simulating the interfacial area and the fluiddynamic forces between the phases for different flow regimes with increasing vapour volume fraction.