EFFECT OF RADIATIVE HEAT TRANSFER ON FIRE DYNAMICS

Abstract

Computer programs developed to predict the effect of radiative heat transfer on fire dynamics. Which is an important tool when working with fire safety. This study is performed on fire in cables those made of polyvinyl chloride insulation material. In this context different Computational Fluid Dynamics models, so called CFD models, where the domain of interest is divided into thousands of small control volumes, is widely used. An important task when developing fire models are validation against experiments. This involves recreating the experimental setup in the CFD models and comparisons of the results from the simulation with the experimental results. Initially, in the work with this thesis, literature from previous cable fire experiments was collected and organized through a literature search. The experimental data compared with results of CFD model FDS (Fire Dynamics Simulator). The simulation is performed on 4rnx4mx4m computational domain to investigate the characteristics of fire in cables. Two steel trays are used on which cables are kept. A cable tray has Im length and 30 cm width. A burner with different-different capacity used to ignite the fire in cables. The simulation is performed for 20 minutes. There are several parameter those measured in simulation. The heat release rate, flame temperature, cable temperature, temperature near ceiling, radiative heat flux, convective heat flux and concentration of carbon dioxide are measured in simulation. With comparison of some of the parameter with experiments, there is some disagreement have seen. This disagreement caused by several reason like the environment in which experiment perform, setup condition of experiments, and complexity in chemistry which difficult to explain exactly to CFD model FDS. The simulation is also performed with and without consideration of radiation to measure the effect of it on fire behaviour. It has seen that without radiation the flame temperature is high because no loss of heat due to radiation by the flame. This change the several other parameters also. It has seen that as the temperature is high the radiation is more effective than convection in fire scenarios because radiative heat transfer vary with the fourth power of temperature.