Study on Natural Convection around a vertical heated rod using PIV/LIF technique

R. Szijártó, B. Yamaji, A. Aszódi,Budapest University of Technology and Economics, Hungary

20th Symposium of AER on VVER Reactor Physics and Reactor Safety (2010, Hanasaari, Espoo, Finland)
Nuclear applications of three-dimensional thermal hydraulics

Abstract

The Nuclear Training Reactor of the Institute of Nuclear Techniques (Budapest
University of Technology and Economics, Hungary) is a pool-type reactor with light water
moderator and with a maximum thermal power of 100 kW. The fuel elements are cooled by
natural convection. An experimental setup was built to analyse the nature of the natural
convection around a heated rod. The flow field was investigated using an electrically heated
rod, which models the geometry of a fuel pin in the training reactor. The electric power of the
model rod is variable between 0?500 W. The rod was placed in a square-based glass tank.
PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) measurement
techniques were used to study the velocity and temperature field in a two-dimensional area.
The thermal and the hydraulic boundary layers were detected near a rod in a lower
section of the aquarium. The laminar-turbulent transition of the flow regime was observed,
the maximum velocity of the up-flow was 0.025-0.05 m/s. From the temperature
measurements the local heat transfer coefficient was estimated.

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