Effect of lining thermal inertia on small-scale compartment fire

Abstract

The use of small scale facilities in experimental fire research studies is well estabhshed. This thesis concerns the use of small scale facilities to examine principally the influence of thermal inertia of the lining material on ventilated enclosure fire
The radiation error of the thermocouple reading was studied using radiation network models. Previous theoretical studies were implemented to provide improved models appropriate to the more complex arrangements considered here. Modeling was used to assess the radiation error of different sizes of thermocouple in the hot layer measuring position for post and pre flashover fires, and the models were compared with experiment.
The current range of thermal inertia values for building products is much wider than those used in the regression by which the classical theory of pre-flashover temperature was derived (McCaffery et al. 1981). The range considered here is greater then has previously been considered by systematic experimental testing whilst maintaining all other independent key variables constant.
Using of reasonable assumptions, the mass loss rates of non-flashover and flashover conditions were predicted by numerical calculation integrated with a zone model. Successful prediction was also made for published tests where sufficient information was available, and good agreement was found irrespective of flashover, scale or geometry. Two important and necessary assumptions used in the zone model, concerning specifically radiation heat transfer in the flashover condition are: that an average temperature of hot gas and flashover flame may be represented by a single thermocouple measurement; and that the massive increase in production of flanu-nable vapours from the fuel surface during flashover leads to a "cool core" partial scattering or blocking of the incident radiant heat from the flashover flame and hot gas.
A computer programme was developed to implement and test recent flashover theory (Graharn et al. 1995). A logarithinic relationship has here been suggested between the thermal inertia parameter ', 8' and thermal inertia value of lining material. That relationship matches the current experimental results and other published data. The occurrence of flashover and the value of hot gas peak or steady temperature can be predicted using the computer programme, based on the published theory.