Unsteady Heat Transfer in an Optically Thick Semitransparent Liquid Layer Heated by a Radiant Heat Source

Abstract

The unsteady characteristics of heat transfer in an optically thick semitransparent liquid layer is deduced theoretically and demonstrated experimentally for the case in which the liquid layer is heated stepwise from the upper side by a radiant heat source.
The basic differential equation controlling the temperature field in the liquid layer is introduced and solved by using two models : Multiband model and Planck mean model. The theoretical results calculated from both the Multiband model (calc. I) and those from the Planck mean model (calc. II) for the time-change of liquid temperature distribution within the layer are in fairly good agreement with experimental data obtained by using an infrared lamp bundle as the radiant heat source and diethylphthalate as the liquid sample. Comparing “calc. I” with “calc. II”, however, “calc. I” shows a better coincidence with the experimental data than does “calc. II”.