Experimental investigation on maximum ceiling jet temperature generated by a vertically spreading cable fire

Abstract

Maximum ceiling jet temperature (MCJT) is an important parameter for evaluating fire risk. An important characteristic of vertical cable tray fire is the upward spreading of the cable flame along the cable tray, which leads to a decrease in the distance between the fire source and compartment ceiling during such a fire. Thus, full-scale fire experiments using vertical cable trays were conducted in a confined compartment to investigate the MCJT. The upward spreading of the cable flame leads to transition of the MCJT dominated by the plume region to intermittent region of the flame. In particular, it is observed that the MCJT suddenly increases from ~200 °C to more than 600 °C at this transition point. Taking the upward spreading cable flame along the vertical cable tray as a point fire source moving with constant velocity, a modified model is proposed to estimate the MCJT. Prediction using the proposed modified model yields promising results. The local prediction error for the modified model is less than 12%, and the global prediction error is between 23.6% and 38.6%. These errors are significantly lower than those for other models that assume a fixed fire source.