Effect of cross section and ventilation on heat release rates in tunnel fires

• Effect of tunnel cross section and velocity on heat release rate is investigated.
• For well ventilated pool fires, tunnel width nearly has no influence on HRR.
• For well ventilated solid fires, HRR increases by 25% relative to a free burn test.
• For well ventilated solid fires, HRR is not sensitive to width, height or velocity.

Model scale fire tests were performed in tunnels with varying tunnel widths and heights in order to study the effect of tunnel cross-section and ventilation velocity on the heat release rate (HRR) for both liquid pool fires and solid fuel fires. The results showed that for well ventilated heptane pool fires, the tunnel width nearly has no influence on the HRR whilst a lower tunnel height clearly increases the HRR. For well ventilated solid fuel fires, the HRR increases by approximately 25% relative to a free burn test but the HRR is not sensitive to either tunnel width, tunnel height or ventilation velocity. For solid fuel fires that were not well ventilated, the HRRs could be less than those in free burn laboratory tests. In the case of ventilation controlled fires the HRRs approximately lie at the same level as for cases with natural ventilation.

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