Multi-dimensional investigation of ceiling jet temperature characteristics beneath curved ceiling produced by fire in the utility tunnel

Abstract

To study the temperature profile beneath the curved ceiling from a multi-dimensional perspective, an experimental investigation was conducted in utility tunnels with two different sizes, and a series of models were established to predict a two-dimensional longitudinal temperature profile and transverse temperature attenuation in this study. The prediction models for the two-dimensional longitudinal temperature profile were developed by modeling the vertical temperature distribution, thermal boundary layer thickness, Gaussian thermal layer thickness and maximum longitudinal temperature attenuation. Through the experimental validation on two sizes, it is found that the proposed prediction model can express the longitudinal temperature profile from a two-dimensional view within the relative error range of 20%. Besides, the prediction model for transverse temperature attenuation was established by the definition of characteristic tilt angle, and the three detailed expressions of this model were proposed according to different types of ceiling jets after impingement. The proposed prediction model for transverse temperature attenuation was also validated, and the verification results showed that the relative error of the transverse temperature attenuation prediction model can be controlled within a 25%. The developed prediction models in this study can be applied in the fire protection engineering of utility tunnels.