Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

J. L. T. Azevedo
Instituto Superior Técnico, LASEF Technical University of Lisbon, Lisbon, Portugal

J. M. C. Pereira
Instituto Superior Técnico / Technical University of Lisbon, Department of Mechanical Engineering / LASEF, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

J. C. F. Pereira
Instituto Superior Técnico / Technical University of Lisbon, Department of Mechanical Engineering / LASEF, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

During a fire in a tunnel smoke and hot combustion products can spread against longitudinal ventilation, a phenomenon usually referred as “backayering”. This has a significant influence on evacuation and fire fighting. The minimum ventilated air velocity necessary to prevent backlayering is designated as “critical velocity”. This phenomenon has been recently observed in the large scale tests conducted in the Runehammar road tunnel (2003), where, during several heavy goods vehicle (HGV) fire simulations, backflow velocity oscillations and reversal where observed. The present work addresses this issue by the study of the influence of the fire heat release rate (HRR) curve slope on the smoke flow dynamics. Threedimensional simulations were carried out in a realistic tunnel model, with the ventilation fans represented as implicit momentum sources in the CFD calculations, and comparison with available experimental results showed good agreement. In addition, the results predict that a small variation of the HRR curve slope induces oscillations in the backlayer flow.

COM-18 pages DOI: 10.1615/IHTC13.p26.170 Download article

Article price - $35.00

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