Abstract
The article presents a computer model of the fire extinguishing process using mist nozzles. A previously developed hybrid fire model was used for this purpose. Assumptions and relationships were given to represent a mathematical model of extinguishing process, which comprises a unique approach to the determination of sprinkling area in an elementary cell of field fire model. A description of simulation tests of the model was given for several different input data, differing by mean diameters of droplets. This enabled a study of their effects on such output parameters as received heat flux, temperature and rate of its growth. For one selected computational cell located on the axis of the nozzle at floor level having the coordinates [10, 10, 1], the obtained results were presented in the form of heat flux and temperature. To simplify the analysis, characteristic parameters of particular curves were listed in the table. Conclusions formulated on the basis of results obtained during tests were specified at the end of work. They confirmed the expected regularity assuming that the extinguishing process was more effective in the case of droplets of a smaller diameter and greater sprinkling intensity. This allows assessing the degree, to which these stream parameters affect the extinguishing effectiveness.
Highlights
Water is characterized by high specific heat (4.19 kJ/), high vaporization heat (2260 kJ/kg) and low boiling temperature
The objective of the study was to investigate the impact of the average sprinkling intensity and droplet diameter on the extinguishing effectiveness using computer simulation methods
A special program written by the first author was applied for modelling the extinguishing process using the spray generated by mist nozzles
Summary
Water is characterized by high specific heat (4.19 kJ/ (kgK)), high vaporization heat (2260 kJ/kg) and low boiling temperature (ca. 100 °C). When applied directly to the source of fire, it can absorb heat from gases, flames and fuel, as well as from the surface adjacent to the fire The cooling of these areas changes depending on the diameter of water drops. One of them is the assumption that the amount of water applied to the fire is sufficient to cause a decline in the rate of heat release and that the sprinkling intensity is constant It did not take into account the effect of the second sprinkler. The main objective of this study was to carry out simulation tests, on the basis of which it would be possible to determine the impact of the selected parameters, such as sprinkling intensity, and the average diameter of the water drops on the effectiveness of fire extinguishing using mist nozzles. The last chapter provides a summary and conclusions formulated on the basis of computer simulation results
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