Novi metod za određivanje bezbednog rastojanja ljudi od požara kao izvora toplotnog zračenja

Abstract

The aim of this paper is to, on the basis of current knowledge about the fire dynamics and by using the Fire Dynamics Simulator (FDS) and CST Studio Suite, display and analyze the basic parameters of fire, temperature, combustion rate, the amount of heat release and especially radiant heat flux which is one of the most significant values of heat transfer in a developed stage of fire. Based on the obtained results, an anatomical model of man and especially human skin model was developed in order to determine a safe distance from the fire. For this purpose, a new algorithmic procedure for determining safe distance of humans from the fire as a source of thermal radiation has been created. It comprises of the following steps: determining the value of the radiant heat flux on human skin and surface temperature of the body; calculating the energy contribution of all ranges of thermal radiation; calculating the intensity of the electric field for the selected scope of thermal radiation; forming an anatomical skin model; calculating penetrated components of the electromagnetic field in the skin tissue and analyzing the depth of these components; developing a new heat source whose dimension is the same as the penetration depth of surface skin layer and calculating the power of this source; the formation of a new skin anatomy model by adding another layer to the previous layer, defining a secondary heat source and calculating the components of the electromagnetic field, the absorbed energy density and the temperature distribution in the model; the analysis of the results and making decisions whether the pain of colour has been exceeded at any point, and consequently, determining the safe distance. The subject matter of this study has been presented in the following chapters: • Introduction; • The transfer of heat radiation and the influence on matter; • Maxwell's theory of electromagnetic wave propagation; • The effects of thermal radiation of fire and biological materials; • Numerical methods of calculation thermal radiation; • A new method for determining the safe distance from fire; • Conclusion. In the introduction, the problem and the initial solution have been presented. The first chapter gives an overview of the basic laws of heat transfer by fire radiation and its effects on matter. Special attention was paid to the content and the purpose of the study, in order to provide the reference to the issues that follow. In the second chapter, Maxwell's theory of electromagnetic radiation was explained in details, as well as the basic parameters of electric and magnetic fields, the theory of electromagnetic wave propagation and penetration and absorption of heat radiation. The third chapter contains the information on the skin as a biological material, the structure, the function, as well as the theoretical predictions and experimental knowledge about the relationship between thermal radiation and tissue damage. The literature data and references used for comparative analysis are the results of various experiments. The fourth chapter provides a description of the numerical methods used in the software packages for simulation of thermal radiation (FDS, PiroSym and CST Studio Suite). The fifth chapter outlines the steps of the new method for determining the safe distance from the fire, the simulation results and their comparative analysis with the data from the third chapter. The conclusion points out the proper correspondence between the simulation results obtained in the literature and published experimental results. The importance of the obtained results is reflected in the fact that the results and the proposed model can be widely used in fire prevention and protection.