Rates of High-Temperature Evaporation of Promising Fire-Extinguishing Liquid Droplets

Geniy Kuznetsov,Svetlana Kralinova,Ivan Voytkov,Anastasia Islamova

doi:10.3390/app9235190

Geniy Kuznetsov, Svetlana Kralinova + Show 2 more

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https://doi.org/10.3390/app9235190

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Abstract

Differences in the rates of heating and evaporation of droplets with the component composition are important parameters of heat transfer processes and phase transformations. This paper presents the values of high-temperature (up to 600 °C) evaporation rates of droplets of promising fire-extinguishing compositions (water, bentonite suspension, bischofite solution, EA-5 solution, and foaming agent emulsion) at convective (in the air stream), conductive (on a heated surface), and radiation (in a muffle furnace) heating. A high-speed video recording system and tracking software algorithms are used. At identical initial sizes of droplets of fire-extinguishing suspensions, known as emulsions and solutions, the times of their complete evaporation are shown to differ 3.7 times when heating on the substrate, 1.25 times in the air flow, and 1.9 times in the muffle furnace. A general approximation expression is formulated, and the empirical constants are calculated to predict the evaporation rate of the droplets of extinguishing agents in a wide range of temperatures (up to 600 °C) and heat fluxes (up to 100 kW/m2), which are characteristic of forest fires. With the use of the experimental data obtained, it is possible to predict the completeness of evaporation of promising extinguishing liquids at different schemes of heat supply.

Highlights

Technologies of large-scale fire extinguishing are being developed toward simultaneous intensification of different mechanisms of localization and suppression of combustion and thermal decomposition [1]
Similar to the experiments with water droplets in the study [12], we have found out the tendency to a pronounced time interval during which the droplet warms up intensively
Experimental studies have shown that the lifetime of droplets of Experimental studies have shown that the lifetime of droplets of promising extinguishing agents

Summary

Introduction

Technologies of large-scale fire extinguishing are being developed toward simultaneous intensification of different mechanisms of localization and suppression of combustion and thermal decomposition [1]. These are reducing the temperature in the combustion and pyrolysis zone, displacing the oxidant from the combustion zone, and blocking the mixing of pyrolysis and combustion products with the oxidant. Introducing liquid in large monolithic volumes to this zone is not sufficient In this case, the liquid volume variation has little effect on combustion characteristics of a fire bed

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