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This paper applies electromagnetic wave theory for the study of the internal radiant absorption field of a small spherical particle, particularly to determine the optimum combination of size-to-wavelength parameter and complex refractive index for maximum local peak absorption. A map is devised to illustrate the general pattern of the internal field, which can be divided into three main regimes: uniform, front-concentrated, and back-concentrated absorption. In addition, the current study employs geometrical optics to investigate the internal field of radiant absorption. A comparison between the results from the geometrical optics approach to those from electromagnetic wave theory shows that the error involved in the geometrical optics approach increases sharply with the real part of the complex refractive index. A criterion is established to define the region of the applicability of geometrical optics.

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The objective of the present work is to analyze rigorously the transient heat transfer of an irradiated particle by treating the radiant absorption on a local basis. A new conduction-to-radiation parameter is introduced to characterize the relative importance of heat transfer by conduction as compared with that by radiation. The study on the transient temperature field as a function of conduction-to-radiation parameter establishes a criterion identifying the circumstances where heat transfer by radiation is so predominant that conduction is negligible. The current effort is also directed at developing a convenient method for predicting the transient local maximum temperature and explosion time delay of an intensely irradiated liquid droplet.

Interesl in using sulfur hexafluoride (SF6J as a gas-fiJIin multipane windows has raised questions concerning the calculation of heal lransfer rates through such windows. The infrared absorption characteristics of this gas make the heat transfer analysis much more complicated. In order to account for the absorption effect, we measured the spectral absorptivity of several infrared-active bands of sulfur hexafluoride allow resolution and a temperature of 298 K. We correlated the spectral absorption data with the Edwards exponential wide-band model and with the Elsasser narrow-band model, and incorporated the wide-band model into a one-dimensional, finite-element heal transfer model. Thefiniteelement heal transfer model considered combined conduction and radU1JWn effects in a double-pane window, and was used to evaluate the overall heal transfer coefficients of double-pane windowsjilled with SF6> CO 2 , or air. Thenumerical results show good agreement with the experimental results.