Experimental study on temperature property along a tunnel axis with flat ceiling in natural ventilation

In this study, detailed measurements of the temperature in a horizontal tunnel with a rectangular cross section were conducted. The temperature decrease along the tunnel axis, the thermal thickness, and the temperature distribution of a steady fire-driven ceiling jet were compared with those for an unconfined smooth-ceiling jet flow. Results of this study showed that the temperature decrease along the tunnel axis was gradual, with the thermal thickness in the tunnel being about two times than that of a ceiling jet under an unconfined ceiling. The temperature distribution in the tunnel exhibits a more bulging shape. Empirical formulae defining the temperature decrease along the tunnel axis, the thermal thickness, and the temperature distribution are also presented.