Experimental and theoretical studies on the smoke temperature distribution along the tunnel ceiling with natural ventilation by the board-coupled shafts

Abstract Experiments were conducted in a 1/20 scale model tunnel to explore the gas temperature distribution along the tunnel ceiling by the natural ventilation, both the traditional shaft and the board-coupled shaft (BCS) were included. The influence of the shaft type and the board location on the gas temperature distribution along the tunnel ceiling was investigated. The results indicate that the variation trends of excess gas temperature distribution in the near fire region and the far fire region are consistent with the exponential attenuation, whether it is a traditional shaft or a BCS shaft. The relational function of the reference temperature between the far fire region and the near fire region was developed. Beyond that, the correlation function between the smoke layer thickness in the near fire region and the far fire region was developed. Furthermore, the mechanisms of the main heat transfer in the near fire region and the far fire region were discussed. And based on the premise that the radiative heat transfer dominates the heat transfer to the tunnel walls in the near fire region and the convective heat transfer dominates the heat transfer in the far fire region, empirical models for predicting the ceiling excess gas temperature distribution in the near fire region and the far fire region were developed. These studies may contribute positive significance for promoting the application of natural ventilation with vertical shafts.