Seminar: New Development in Two-Phase Flow Heat Transfer CFD (or CMFD) Applied to Thermal-hydraulics Problems

When: November 10, 2009, 12:00 PM
Where: Clarice Chalmers Conference Room (MC 331), Mechanical Engineering Building, 5 King’s College Road

Dr. Djamel Lakehal
ASCOMP GmbH & ETH Zurich, Switzerland
lakehal@ascomp.ch

ABSTRACT
In practical thermal-hydraulics applications, multi-phase heat transfer flow involves phenomena acting at different time/length scales. At each level of the scale cascade, the flow physics is amenable to numerical prediction by scale-specific strategies; an example of which is interfacial heat & mass transfer.

To respond to the growing needs of reactor design of the new generations, new computational tools and methods are required to address both the microscopic and component scales segment of the problem; to complement or couple -where needed- with the ‘mature’ system scale treated so far with 1D system codes. The approach followed thus-far is based on interface tracking methods (ITM) which have been until now used for simple ‘academic’ test cases. We will show in this talk that these methods can indeed be employed for more complex practical problems. The techniques could be coupled with heat transfer (conjugate, with phase change, with buoyancy), and used under turbulent conditions as well, using RANS and LES. The complexity of the geometries could be alleviated by using the Immersed Surfaces Technology (IST), treating solid boundaries like in interface tracking context, fluid-solid surfaces instead of fluid-fluid interfaces. Various fundamental microscopic flow problems will be discussed, including thin-film boiling, predicted using ITM’s. Other component scale thermal-hydraulics problems will be discussed as well, namely the ECC injection in the cold leg, the two-phase flow and heat transfer in a reduced fuel bundle, the stratified condensing two-phase flow, highlighting the advantages of the IST in treating conjugate heat transfer. The IST merits will be emphasized through other single-phase flow examples, e.g. the simplified PWR reactor core (ROCOM) involving Boron mixing.