A new criterion for evaluating the extinction abilities of moving droplets: Applied for radiative thermal shielding

Abstract

In this study, the thermal shielding ability of sprays and the accompanying scientific problem of the optimal extinction diameter of moving droplets have been analyzed with the Lagrangian model and Mie theory under the overall consideration of dynamical and optical characteristics. A correction factor is introduced to eliminate the forward scattering effects of large droplets. Then, a new variable, named the thermal shielding index, has been presented as a criterion evaluating the extinction abilities of moving droplets, which analyzed the extinction performance during the whole lifetime of droplets. According to the evaluation method defined in this paper, the optimal extinction diameters obtained based on the thermal shielding index are far greater than those obtained based on the optical properties. In addition, if the initial droplet sizes were relatively large, the upward injection way will perform better than the downward injection way for a longer traveling distance and, of course, a longer lifetime.