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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

EXPERIMENTAL STUDY OF FORCED CONVECTION HEAT TRANSFER DURING UPWARD AND DOWNWARD FLOW OF HELIUM AT HIGH PRESSURE AND HIGH TEMPERATURE

DOI: 10.1615/TFESC1.fnd.012797
pages 981-984

Francisco I. Valentin
City College of New York, 160 Convent Ave, New York, NY 10031, USA

Narbeh Artoun
City College of New York, 160 Convent Ave, New York, NY 10031, USA

Masahiro Kawaji
Department of Mechanical Engineering, City College of New York, New York, USA; The CUNY Energy Institute, City University of New York, New York, USA; Dept. of Chemical Engineering & Applied Chemistry, University of Toronto, Canada

Donald M. McEligot
Aerospace and Mechanical Engineering Department, University of Arizona,Tucson, AZ 85721; Idaho National Laboratory (INL), Idaho Falls, ID 83415-3885, USA; and Institut für Kernenergetik und Energiesysteme, Universitat Stuttgart, Stuttgart, Germany


KEY WORDS: forced convection, heat transfer, helium, VHTR, high temperature gas reactor, buoyancy effect, high pressure

Abstract

Fundamental high pressure/high temperature forced convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments utilize a high temperature/high pressure flow test facility constructed for forced convection and natural circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer for helium at high pressures up to 70 bar and high temperatures up to 873 °K. Wall temperatures have been compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancy-induced mixing causes higher convection heat transfer and lower wall temperatures. However, their influences are reduced as the Reynolds number increases. This experimental study is of specific interest to VHTR design and validation of safety analysis codes.

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