VELLA WORLD

THERMAL HYDRAULICS

 

Thermal-hydraulic modelling and testing
Due to the specific properties of the heavy liquid metals, previous research on liquid metal cooled fast breeders, which used light alkali metals, can only be partially used to describe adequately the thermal-hydraulic behaviour in HLM. Moreover, the currently available computational fluid dynamics codes are not in such a state that they can reliably predict the thermal-hydraulics, because of the lack of adequate models, as the EUROPEAN ASCHLIM program has shown in FP 5.
Therefore, thermal-hydraulics experiments are carried out worldwide to develop physical models and validate numerical tools, useful both for the design and the safety analyses.
Forced convective heat transfer experiment of highly heat loaded surfaces, by means of LBE as e.g. at fuel claddings, beam windows or heat exchangers are foreseen.
Great attention will be devoted to the characterization of the thermal-hydraulics of the windowless target and to the modelling of the free surface.
The NACIE loop at the ENEA Brasimone research centre, will permit to carry out experimental tests of natural circulation and collect data on the heat transfer coefficient (HTC) for heavy liquid metal flowing through rod bundles.
A natural circulation experiment is carried out at the TALL facility of KTH. The experimental campaign envisaged will focus on three main issues: a.) the establishment of natural circulation as a dynamic process. b.) the determination of influencing parameters on the performance of natural circulation. c.) the study of transient flow and heat transfer under loss of coolant transients. Additionally the experiments will be accompanied by numerical analyses.

Pb/LBE-water interaction studies
Efforts are devoted to the LBE/Pb-water interaction studies in a SGTR scenario, devoted o assess the physical effects and the possible consequences related with this kind of interaction. Experimental campaigns in parallel to modelling activities are envisaged.

Measurement tecchniques
An assessment of the technologies that could be easily extrapolated from the knowledge on LBE to Pb is going on, expecially for what concerns new instruments for flow and level measurements, velocity and pressure meters.
Ultrasound Doppler Velocimetry (UDV) for a single phase flow measurement, ultrasonic and contactless electromagnetic flowmeters for an integral flow rate measurement are under development and testing up to a temperature of 400°C. Measurement techniques for scalar quantities (EMFM-v, Karman Vortex, Obstacle), pressure transducers with high resolution time for direct contact with HLM are investigated. For the vector quantities Pitot- and Prandtl-tubes and UDV is going to be developed and tested. The free surface monitoring techniques based on the LIDAR technology are under study.
New types of electromagnetic flow rate sensors will be tested.