The present work is concerned with the modeling of buoyancy-modified mixed convection flows, such flows being representative of low-flow-rate flows in the cores of Gas-cooled Reactors. Three different eddy viscosity models (EVMs) are examined using the in-house code, “CONVERT.” All fluid properties are assumed to be constant, and buoyancy is accounted for within the Boussinesq approximation. Comparison is made against experimental measurements and the direct numerical simulations (DNS). The effects of three physical parameters including the heat loading, Reynolds number, and pipe length on heat transfer have been examined. It is found that by increasing the heat loading, three thermal-hydraulic regimes of “early onset of mixed convection,” “laminarization,” and “recovery” were present. At different Reynolds numbers, the three thermal-hydraulic regimes are also evident. The k-ε model of Launder and Sharma was found to be in the closest agreement with consistently normalized DNS results for the ratio of mixed-to-forced convection Nusselt number (Nu/Nu0). It was also shown that for the “laminarization” case, the pipe length should be at least “500× diameter” in order to reach a fully developed solution. In addition, the effects of two numerical parameters namely buoyancy production and Yap length-scale correction terms have also been investigated and their effects were found to be negligible on heat transfer and friction coefficient in ascending flows.
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e-mail: a.keshmiri@manchester.ac.uk
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September 2011
This article was originally published in
Journal of Heat Transfer
Research Papers
Effects of Various Physical and Numerical Parameters on Heat Transfer in Vertical Passages at Relatively Low Heat Loading
Amir Keshmiri
Amir Keshmiri
School of Mechanical, Aerospace and Civil Engineering (MACE),
e-mail: a.keshmiri@manchester.ac.uk
The University of Manchester
, Manchester, M13 9PL, UK; Advanced Design Group AECOM, 1 New York St., Manchester, M1 4HD, UK
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Amir Keshmiri
School of Mechanical, Aerospace and Civil Engineering (MACE),
The University of Manchester
, Manchester, M13 9PL, UK; Advanced Design Group AECOM, 1 New York St., Manchester, M1 4HD, UK
e-mail: a.keshmiri@manchester.ac.uk
J. Heat Transfer. Sep 2011, 133(9): 092502 (8 pages)
Published Online: August 1, 2011
Article history
Received:
September 24, 2010
Revised:
March 19, 2011
Accepted:
April 4, 2011
Online:
August 1, 2011
Published:
August 1, 2011
Citation
Keshmiri, A. (August 1, 2011). "Effects of Various Physical and Numerical Parameters on Heat Transfer in Vertical Passages at Relatively Low Heat Loading." ASME. J. Heat Transfer. September 2011; 133(9): 092502. https://doi.org/10.1115/1.4003925
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