The flow structure under mixed convection in a uniformly heated vertical pipe

For decay heat removal systems in the conceptual Gas-cooled Fast Reactor (GFR) currently under development, passive emergency cooling using natural circulation of a gas at an elevated pressure is being considered. Since GFR cores have high power density and low thermal inertia, relative to the high temperature gas-cooled thermal reactor (HTGR), the decay heat removal (DHR) in depressurization accidents is a major challenge to be overcome. This is due to (1) a gas has inherently inferior heat transport capabilities compared to a liquid and (2) the high surface heat flux of the GFR strongly affects the gas flow under natural circulation. The high heat flux places the flow into a mixed convection regime, which is not yet fully understood. One of the issues of mixed convection is that the transition from laminar to turbulent flow is not clearly defined in the existing literature. Review of previous work on heat transfer mechanisms and flow characteristics of the mixed convection transitional regime shows that two transitional zones exist between laminar or laminar-like flow and fully turbulent flow for the upward heated case. Previous work has focused on liquids and thus is not applicable to gas mixed convection.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Lee, Jeongik

Advisor dc:contributor.advisor

• Mujid Kazimi.

• Nuclear Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34449

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34449