Absorption of infrared radiation and the radiation transfer mechanism in paper. Part II: Application to infrared dryers.

A comparison of the absorption in paper of radiation from different IR sources has been made based on a theoretical model. As a first approach, blackbody spectra at 1300 K and 2500 K were compared. The radiation from the body at 1300 K is more readily absorbed by the paper There is, however only a small difference in the in-depth absorption when the intensities are adjusted to give the same amount of absorbed energy. Measurements of the spectral distribution from a gas-fired heater were used for a more careful comparison between gas-fired and electrical IR dryers. For electrical dryers, no such measurements have been found in the literature and therefore a mathematical model was developed. The absorption of radiation in the thickness direction was compared for a wet paper a board with a wet core and for a coated paper The radiation from the gas-fired dryer is more readily absorbed by the paper For all these cases, the electrically generated radiation is absorbed somewhat more evenly in the thickness direction than the radiation from the gas-fired heater.