Modelling and thermodynamic analysis of a fire resistance test furnace

Nowadays, technological developments swiftly accelerating not only to improve living conditions and comfort, but also to improve the security of life. The earth gets crowded every day and the ratio of people living in urban areas is increasing which causes an increase in the number of buildings such as malls, skyscrapers etc. The crowded condition of living spaces increases security of life issues. Fire is one of the most important security of life issue in crowded life spaces. The higher risks in fire are resulted with increased security of life and safety measures. These studies are not only conducted for firefighting conditions but also for decreasing security of life issues during fire conditions by increasing the fire resistance of the living spaces and materials such as furniture's, in the living spaces. The target of increasing fire resistance of living spaces and living space materials, fire resistance of the construction materials are questioned. Fire resistance of construction materials are defined in various standards. In order to determine whether the construction materials provide the necessities in the standard, conditions during a fire incident should be simulated and materials need to be tested in this simulated environment. Just as fire resistance of construction materials are defined with various standards, fire resistance testing also defined by standards. Fire resistance test furnaces which can simulate the environment and conditions during a fire incident are used to determine whether the construction materials provide the necessities in the standard or not. In this study, according to the general rules for fire resistance experiments defined in TS EN 1363-1 standard, a fire resistance test furnace is designed three dimensionally with SolidWorks three dimensional design program, thermodynamic calculations are made to determine the gas mass flow rates of the fire resistance test furnace and computational fluid dynamics analysis of the fire test furnace is done with ANSYS Fluent computational fluid dynamics analysis program in order to evaluate and determine the temperature, gas mass flow rate, pressure etc. distribution inside the furnace. One of the most important criteria in TS EN 1363-1 is time dependent temperature of the fire resistance test furnace. Since this modeling study includes combustion reactions, it is determined that even with using workstations that has E type processers; analyses would consume too much time. For this reason, the number of nods in the computational fluid dynamic analysis which is a result of discretization should be as low as it can. Because of this time problem, dimensions of the fire resistance test furnace which thermodynamic and computational fluid dynamics analyses are planned to be conducted, determined as 1 meter width, 1 meter height and 1 meter length. The designed fire resistance test furnace has a cubic shape with 1 cubic meter total volume. Before computational fluid dynamics analysis, a thermodynamic analysis is done for the fire test furnace. It is targeted to obtain the time dependent temperature curve which is given in TS EN 1363-1 and named as ISO 834 curve with these thermodynamic calculations. As a result of these thermodynamic calculations which are targeted to obtain the time dependent temperature curve which is given in TS EN 1363-1 and named as ISO 834 curve, mass flow rates of the propane which is the fuel and air which is the oxidant are determined. Along with the assumptions, initial and boundary conditions for computational fluid dynamics analysis are determined. After the thermodynamic analysis, studies are directed to computational fluid dynamics analysis. Placement of the burners and exhaust on the fire test furnace is determined with conducted computational fluid dynamics analyses. Inlet sections of the burners, that transport propane and air to fire resistance test furnace, are optimized according the velocities of air and propane on the inlet section. According to the computational fluid dynamics analyses, four burners which transport propane and air to fire resistance test furnace, are placed as cross symmetrically on the cubic fire resistance test furnace. Transport of air and propane to the fire resistance test furnace is provided by two concentric square sections. Propane and air entrances are provided by 10mm x 10mm and 30mm x 30 mm square sections. Time dependent propane and air mass flow rates which are entering fire resistance test furnace and determined in the thermodynamic analysis, is identified to ANSYS Fluent computational fluid dynamics program with user defined codes. Computational fluid dynamics analyses of fire resistance test furnace are conducted with the assumptions that were made in the thermodynamic analysis, 0,01 second time step, 10 mm distance between nodes considerations. According to the computational fluid dynamics analyses, temperature inside the fire resistance test furnace found higher than ISO 834 curve. This means more heat is transferred to fire resistance test furnace than needed. When this increase in the fire resistance test furnace temperature was investigated, it was found that exhaust temperatures were much lower than expected for the first 21 seconds. It was figured out that the lower value of exhaust gas temperature then expected caused the increase of the fire resistance test furnace temperature in the previous computational fluid dynamics analyses. The reason of the decreased exhaust gas temperature is found to be related with the nonuniformity of temperature distribution inside the fire resistance test furnace during the first 21 second of the computational fluid dynamics analyses. Error analysis studies showed that after the temperature distribution inside the fire resistance test furnace became uniform, % error rate of the average exhaust gas temperature according to ISO 834 curve stayed constant. With the fixed value of exhaust gas temperature error rate, % error rate of the average fire resistance test furnace temperature according to ISO 834 curve started to decrease. As a result of the fixed value of exhaust gas temperature error rate and the decrease of the % error rate of the average fire resistance test furnace temperature according to ISO 834 curve, the computational fluid dynamics analyses was ended on the 60th second. I took 15 days to conduct a fire resistance test furnace computational fluid dynamics analysis for 60 seconds. It was concluded that the higher values of mean temperature of the fire resistance test furnace which were obtained with the computational fluid dynamics analyses, then ISO 834 curve resulted because of the nonuniformity of temperature distribution inside the fire resistance test furnace during the first 21 second.