An Improved Solution for Shielding of Thermal Radiation From Fires Using Mist Curtains of Pure Water or Seawater

Abstract

An improved theoretical model for shielding of thermal radiation from large-scale fires using pure water or seawater mists is presented. It is a continuation of a recent study and takes into account both the reabsorption of radiation in the absorption bands of gases and the variations of the radiative flux along the flame. The combined heat transfer problem consists of the radiative transfer, droplet evaporation kinetics, and convective heat transfer along the curtain. Previously suggested spectral models for the optical properties of water droplets and salt particles are used in the calculations. Radiative heat losses to the nozzle head and the floor below the curtain, as well as a decrease in the downward velocity near the floor, are taken into account for the first time. It is shown that these heat losses are insignificant even for thick curtains. The use of smaller droplets in the second layer of the mist curtain has been confirmed to reduce the required total water supply flow rate. It is also shown that the protection provided by a seawater curtain is almost the same as that obtained with pure water. Seawater is even preferable for better protection against fire radiation in the lower part of the curtain, where pure water droplets evaporate completely, whereas hollow sea salt particles remain in the lower part of the seawater mist curtain. The study confirms that seawater can be used in coastal areas, offshore platforms, and maritime transportation ships.

Fire Dynamics Simulator Analysis of Smoke Confinement and Radiation Shielding using Water Mist Curtains

“…in a double layer to improve the thermal-radiation shielding effect and derived a 2D-analytical model that reflected the optical thickness of the water curtain, the absorption rate, and the scattering rate based on the velocity and size of the droplets to predict the attenuation of thermal radiation [7]. Their model required less time and computational overhead compared to 3D computational fluid dynamics (CFD) simulations, making it applicable to real-time analysis of full-scale fires.…”