TOTAL THERMAL-RADIATION ABSORPTION BY A SINGLE SPHERICAL DROPLET

The total energy absorption distribution inside a liquid droplet irradiated by blackbody emission is determined by spectral and solid angle integrations of the spectral absorption distribution given by electromagnetic theory. Total absorptances are calculated from volume integration of the absorption distribution and from efficiency factor spectral integration. Results are presented for 1-100 mum radius n-decane and water droplets irradiated by a blackbody at 850-2000 K, in several axisymmetric configurations. Under spherically symmetric irradiation conditions the water absorption results are used to verify the applicability and accuracy of the geometrical-optics approximation through comparison with those results. The band characteristics of decane absorption are also analyzed. It is verified that the trapezoidal quadrature is usually a good approximation for spectral integration. The geometrical-optical approach leads to total absorptance values with errors larger than 10% for droplets smaller than 25 mum. Only the two principal bands of decane, including their wings, are needed to fairly well predict total absorption distribution in decane droplets.