Abstract
Short-, medium-, and long-wave infrared emitters have different effects on the temperature-rise and drying-rate characteristics in infrared radiation heating of water containing flat material. Accordingly they also significantly affect thermal efficiency. The heating characteristics also depend on the thickness of the heated material. It is known that absorbed radiation flux changes to heat within the heated substance, the absorption depends to a large extent on the amount of water in the substance, and the Lambert absorption coefficient of water varies significantly between the three wave-length regions. The coefficient is higher in the long-wave region, moderate in the medium one, and much lower in the short one. We assumed that the infrared emitter used was a black or perfectly grey body and that the heated substance acted as free water, and calculated the irradiance and generated heating-power distributions within the substance. The thickness in millimeters of the substance needed to absorb about 90% of the incident radiation flux is indicated by D's in the Figure and Table. The heating-power generated at the irradiated surface when heated by a long-wave emitter was noticeably higher. The high drying-rate, which is characteristic of long-wave emitter heating, is attributed to the concentrated heating-power at the irradiated surface. This high heating-power provides large latent heat for evaporation. The obtained results of Figures and Tables give basic and useful Informations for choice in advance of the emitter kind between the three ones in infrared heating of a water contained substance with a given thickness.
