Temperature distribution within a ceiling jet propagating in an inclined flat-ceilinged tunnel with natural ventilation

•A new correlation for representing the temperature distribution was proposed.•Temperature distribution in a horizontal tunnel showed a greater bulge shape.•Temperature distribution varied with an increase in the tunnel inclination angle.

In this study, we conducted detailed measurements of the temperature distribution within a steady fire-driven ceiling jet, formed in a tunnel with a rectangular cross-section. We then compared the measured temperature distributions with those for an unconfined smooth-ceiling jet flow, and estimated the relative errors between them. The results showed that the temperature distribution in a horizontal tunnel exhibits a greater bulge than that of a ceiling jet under an unconfined ceiling and varied from a bulging shape to an exponential shape as the tunnel inclination increased. We propose a new correlation for representing the temperature distribution, which takes the tunnel inclination into account, and which consists of an exponential function and a cubic function with a coordinated transformation.