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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

Creare, 16 Great Hollow Rd, Hanover, NH 03755
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

1Corresponding author.

ASME doi:10.1115/1.4040786 History: Received January 18, 2018; Revised June 09, 2018

Abstract

Hot wire anemometer (HWA) measurements of turbulent gas flow have been performed in upward forced convection experiments at pressures ranging from 0.6 MPa to 6.3 MPa and fluid temperatures ranging from 293 K to 673 K. The results are relevant to deteriorated turbulent heat transfer (DTHT) and flow laminarization in strongly heated gas flows which could occur in gas ­cooled Very High Temperature Reactors. The HWA signals were analyzed to directly confirm the occurrence of flow laminarization phenomenon due to strong heating. An X­-probe was used to collect radial and axial velocity fluctuation data for pressurized air and pure nitrogen flowing through a circular 16.8 mm diameter flow channel in a 2.7 m long graphite test section for local Reynolds numbers varying from 500 to 22,000. Analyses of the Reynolds stresses and turbulence frequency spectra were carried out and used as indicators of laminar, transition or fully turbulent flow conditions. Low Reynolds stresses indicated the existence of laminar or transitional flow until the local Reynolds number reached a large value, ~11,000 to 16,000, much higher than the conventional Re = 4,000­ ~ 5,000 for transition to fully turbulent flow encountered in pipe flows. The critical Reynolds number indicating the completion of transition approximately doubled as the pressure was increased from 0.6 MPa to 2.8 MPa.

Copyright (c) 2018 by ASME
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