Heat release rate (HRR) is most important factor in the tunnel fire. Therefore, an accurate understanding of the relationship between tunnel fire and HRR is required. The HRR of a pool fire is related to the heat feedback mechanism. Heat feedback is mainly affected by the flow around the fire source. However, considering the flow characteristics that depend on the tunnel slope is insufficient. Therefore, in this study, the effect of flow with respect to the tunnel slope on the heat feedback was analyzed with an experimental method. The experiment was conducted with a reduced-scale shallow underground tunnel. The slope of the tunnel was limited to 0° to 7°, which corresponds to the construction standard. The ceiling jet and entrained-air flow were affected by the pool diameter and tunnel slope. Owing to the effect of the air entrainment, the ratio of the re-radiation heat flux incident on the fuel surface decreased linearly with increasing tunnel slope. Moreover, the re-radiation and re-convection ratios of the tunnel slope and pool pan size showed linear trends. Based on the analysis of the heat feedback mechanism, the empirical correlation for the effect of the tunnel slope on the HRR can be presented in terms of the re-radiation/re-convection fraction.

放热率（HRR）是隧道火灾中最重要的因素。因此，需要对隧道火灾和HRR之间关系的准确理解。池火的HRR与热反馈机制有关。热反馈主要受火源周围流动的影响。然而，仅考虑依赖于隧道坡度的流动特性是不够的。因此，在这项研究中，采用实验方法分析了流量相对于隧道坡度对热反馈的影响。该实验是在缩小规模的浅层地下隧道中进行的。隧道的坡度限制在0°至7°之间，这符合施工标准。天花板射流和夹带气流受到池直径和隧道坡度的影响。由于空气夹带的影响，随着通道斜率的增加，入射在燃料表面的再辐射热通量的比例呈线性下降。此外，隧道边坡的再辐射和对流比和水池的底盘尺寸呈线性趋势。基于对热反馈机制的分析，可以根据再辐射/对流分数来表示隧道坡度对HRR影响的经验相关性。