Pre-drying Textile Fabrics with Infrared Radiation

Abstract

A number of different fabrics were pre-dried in a pilot-scale electric infrared oven, using tubular radiant heaters placed evenly above and below the web. For most of the fabrics, the degree of drying, for given conditions using both medium- and short-wave sources, was independent of the nature of the fibers and the material construction. The textile simply served as an inert support for a sheet of water. This was true provided the wet fabric was thick enough to avoid any significant transmission of the radiation incident on it, and its final water content was not much below the critical value cor responding to the end of the constant rate drying period. At the optimum fabric width, the energetic efficiency for pre-drying using this particular oven was 73% for medium- wave quartz tubes and 56% for short-wave T-3 tubes. The lower efficiency of the short- wave sources was a consequence of decreased absorption of radiation by the wet web at wavelengths below 1.5-2.0 μm. The effects of source-web distance and fabric width were determined with the aid of view factor calculations based on the specific geometry of the dryer. The drying rate was not greatly influenced by variations in the rate of air flow. There was a contribution from convective heat transfer between the warm air and the textile, but this was difficult to assess.