Thermal Radiation Transport in a Cloud of Dry Water Particles

This paper reports a numerical study on the thermal radiative transport in a cloud of dry water particles. Dry water is a water-in-air inverse foam which consists of micrometer-sized water droplets encapsulated by hydrophobic fumed-silica nanoparticles. The radiative properties of this novel material were estimated using the Mie theory for coated spheres. The radiative transport equation (RTE) was solved for a one-dimensional geometry using the discrete ordinates method. The effects of silica particle and water droplet size as well as the volume fraction of dry water particles on reducing radiative heat transfer were studied numerically. The results were compared with respect to two limiting cases: (i) system with no particles and (ii) silica particles with no water. The results showed that dry water reduced the local radiative heat flux as much as 20% more than that by silica particles alone. Additionally, reduction of the diameter of dry water particles from 75 to 25 μm reduced the radiative heat flux by 17%. Finally, parametric analysis showed that increasing the volume fraction of dry water by 10 times decreased the radiative heat flux by about 30% at the receiver end.