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research-article

EXPERIMENTAL INVESTIGATION OF FLOW LAMINARIZATION IN A GRAPHITE FLOW CHANNEL AT HIGH PRESSURE AND HIGH TEMPERATURE

[+] Author and Article Information
Francisco Valentin

City College of New York, 160 Convent Ave, New York, NY 10031, USA
fiv@creare.com

Narbeh Artoun

City College of New York, 160 Convent Ave, New York, NY 10031, USA
narbeh.artoun@gmail.com

Masahiro Kawaji

City College of New York, The CUNY Energy Institute, 160 Convent Ave, New York, NY 10031, USA
mkawaji@ccny.cuny.edu

Donald McEligot

Idaho National Laboratory, 1955 N. Fremont Avenue, Idaho Falls, ID 83415-3560, USA
donald.mceligot@inl.gov

1Corresponding author.

ASME doi:10.1115/1.4039585 History: Received July 30, 2017; Revised January 10, 2018

Abstract

High pressure/high temperature forced and mixed convection experiments have been performed with helium and nitrogen at temperatures and pressures up to 893K and 64 bar, respectively. The test section had a 16.8-mm ID flow channel in a 108-mm OD graphite column. Flow regimes included turbulent, transitional and laminar flows with the inlet Reynolds numbers ranging from 1,500 to 15,000. Due to strong heating, the local Reynolds number decreased by up to 50% over the 2.7-m test section. In addition, heat transfer degradation and flow laminarization caused by intense heating led to Nusselt numbers 20~50% lower than the values given by the modified Dittus-Boelter and modified Gnielinski correlations. Flow laminarization criteria were considered based on a dimensionless acceleration parameter (Kv) and buoyancy parameter (Bo*). Upward turbulent flows displayed higher wall temperatures than downward flows, due to the impact of flow laminarization which is not expected to affect buoyancy-opposed flows. Laminar Reynolds number flows presented an opposite behavior due to the enhancement of heat transfer for buoyancy-aided flows. At low Reynolds numbers, downward flows displayed higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases. In the entrance region of downward flows, convection heat transfer was reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancy-induced mixing caused higher convection heat transfer and lower wall temperatures.

Copyright (c) 2018 by ASME
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