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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Numerical Investigation of the Flow and Temperature Uniformity in the Reactor Core of a Pebble Bed HTGR Using Porous Media Method

Get access (open in a dialog) DOI: 10.1615/IHTC15.pmd.008665
pages 6813-6825

Résumé

The safety of a pebble bed modular HTGR has been proved to be excellent. The porosity in the reactor core is not uniform due to the random packing of the fuel pebbles and the wall effect. Understanding the influences of wall channeling effect and random porosity on the temperature non-uniformity in the reactor core will give deeper into the safety of a pebble bed HTGR. The probability distribution of the random porosity was determined by re-analyzing the experimental measurements of Auwerda et al. (2010), a new formula was proposed for describing it. A correlation based on previous investigation and experiments was also proposed for describing the near wall porosity variation. Based on the porosity characteristics, the flow and temperature fields in the reactor core with wall channeling effect and random porosity were numerically simulated using porous media method. Commercial software Fluent was used for solving the governing equations. The wall channeling effect has very little influences on the overall reactor core temperature. The bypass flow rate caused by wall channeling effect is below 0.6 percent of the total flow rate. Maximum or minimum porosity in certain regions only causes minor changes in local temperature. The coolant velocity and temperature fluctuations caused by random porosity are very little. The wall channeling, extreme porosity and random porosity effects on the temperature variations in the pebble bed reactor core were summarized. They have little influence on the overall temperature distribution in the reactor core.