Рассматриваются процессы, происходящие у борта резервуара во время тушения горючей жидкости пеной после того, как бóльшая часть зеркала жидкости покроется огнетушащим слоем пены. Приведен анализ двух случаев, необходимых для тушения оставшихся очагов горения у борта резервуара: охлаждения свободного борта резервуара до температуры, при которой нагретый пламенем борт перестает служить источником зажигания паров топлива, и понижения температуры горючей жидкости до температуры, при которой уже не происходит воспламенения горючей смеси. Для первого случая разработана математическая модель, описывающая изменение температуры при охлаждении борта резервуара в зависимости от времени, и получены с определенными допущениями аналитические решения. Предложено выражение, определяющее время тушения горючей жидкости, по которому с учетом имеющихся экспериментальных данных представлены расчетные значения коэффициента теплоотдачи. Для второго случая получено уравнение изменения температуры борта резервуара при охлаждении во время тушения горючей жидкости пеной.
When fire extinguishing foam is applied for fire suppression of flammable liquid in the tank, after the most part of the liquid mirror is already covered by a fire extinguishing foam layer, the fuel continues to burn at the side of the tank. This rather complex case is often implemented in practice, but it wasn’t fully described in the existing theoretical literature. Extinguishing of these last fire sources occur in the following two cases: § cooling of a free side of the tank to a temperature at which the side heated by flame ceases to serve as a source of ignition of fuel vapors; § lowering of the temperature of the combustible fluid located at the side surface of the reservoir to a temperature at which the ignition of the combustible mixture formed by mixing of the fuel vapor with air can not occur. The article presents the analysis of the two cases needed to extinguish remaining pockets of burning at the side of the tank. For the first case (cooling of a free side of the tank to a temperature at which the side heated by flame ceases to serve as a source of ignition of fuel vapors), the mathematical model describing the temperature change during the cooling of the sides of the reservoir was developed. Analytical solutions with certain assumptions were obtained. The expression that defines the time of extinguishing of flammable liquid was also obtained. The values of heat transfer coefficient calculated with the usage of the resulting equation together with the available experimental data obtained in the burning tank, are presented in the paper. The values of the heat transfer coefficient are 0.34¸0.51 W·m-2·K-1. For the second case (lowering of the temperature of the combustible fluid to a temperature at which the ignition of the combustible mixture can not occur), the resulting expression describes changes in temperature of the side of the tank during cooling by fire extinguishing foam. The expression was derived from the heat equation with a number of assumptions and the usage of integrating methods of research of physical processes involving integral relations derived from the analysis of differential equations. The obtained equation of temperature change of the side of the tank while cooling by fire suppression foam during extinguishing of flammable liquid, can be later used in the modeling of processes of extinguishing of tanks and in calculating of the flow rate of the foam.
The authors declare that there are no conflicts of interest present.