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Influence of heterogeneous temperature distribution along the premise height on the height of a plane of equal pressures during fire

Journal: Pozharovzryvobezopastnost/Fire and Explosion Safety (Vol.27, No. 7)

Publication Date:

Authors : ;

Page : 24-31

Keywords : ;

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Abstract

Introduction. Heat and mass transfer through open holes is influenced significantly by the temperature distribution over the height of the premise. In the first approximation in the integral model of calculating the dynamics of dangerous fire factors, the temperature along the height of the premise is assumed to be constant and equal to its average volume value. However, the temperature varies significantly along height, and the distribution of pressures along the height inside the premise is not linear. Therefore, it is necessary to conduct further experimental and theoretical studies of the influence of the inhomogeneity of the temperature field inside the premise on the parameters of heat and mass transfer through the openings. Goals and objectives. The purpose of the paper is to evaluate experimentally and theoretically the influence of the inhomogeneity of the temperature distribution along the height of the premise upon the height of the neutral plane. To achieve this, we used the formula for the temperature distribution along the altitude, which includes the empirical coefficient of the inhomogeneity of the temperature field. Experimental studies were carried out that made it possible to refine the above-mentioned coefficient and determine the position of the plane of equal pressures at the initial stage of the fire. Methods. A theoretical method for calculating the temperature distribution over the height of the premise and the height of the neutral plane is used, as well as an experimental method for studying heat and mass transfer in a small experimental installation. Results. Experimental dependences of the temperature distribution along the height of the experimental volume at different times and the height of the plane of equal pressures on time are obtained. A comparison is made between experimental data and the theoretical temperature distributions along the height obtained with and without allowance for temperature inhomogeneity. The existence of two planes of equal pressures at the initial stage of the fire is experimentally confirmed. It is shown that for a reliable justification of the response time of fire temperature detectors it is necessary to take into account the inhomogeneity of temperature along the height of the premise. Conclusion. The temperature distribution along the height of the premise, taking into account the inhomogeneity of the temperature field, is in satisfactory agreement with the experimental data. The above dependence allows us to justify the simultaneous existence of two planes of equal pressures, which has been experimentally confirmed for the initial stage of a fire in a pilot installation.

Last modified: 2018-10-16 23:12:42