Temperature Uniformity in Water Films and Wet Paper Through Spectrally Selective Infrared Heating

Abstract

Experimentally-derived radiant emissions from a near-greybody source, as well as a source with a narrow-band emission centered at 1.5 µm (both gas radiant burners), were used to calculate temperature distributions along the depth of water and wet paper (fiber–water suspensions) films. A grey emitter resulted in a wide temperature gradient through the film depth due to significant overlap of regions of high spectral emission with regions of high spectral absorption. The narrow-band emitting source succeeded in the goal of reducing the temperature gradient though the water film, though a significant percentage of radiant energy transmitted through the entirety of the film. Using numerical optimization, narrow-band spectral emission sources were calculated from Gaussian functions (3.8 µm for water and 1 µm for paper with 80% water) which improved temperature uniformity without high transmission radiation losses.