COMBINED SUPERHEATED STEAM AND MICROWAVE DRYING OF SINTERED GLASS BEADS

摘要

A new drying method of combined superheated steam and microwave drying isrnbeing proposed. The drying rates of sintered glass beads in combined superheated steamrnand microwave drying are experimentally and theoretically investigated. Dryingrnexperiments have been carried out in a waveguide where a standing wave is formed tornuniformly heat a small sample. Concerning drying rate curves in combined superheatedrnsteam and microwave drying, a distinct constant rate period has been observed. For thernfalling rate period, high drying rates have been observed. For both periods, the dryingrnrates in combined superheated steam and microwave drying are higher than those inrnsuperheated steam alone. Also, in comparison with the results of combined nitrogen andrnmicrowave drying, the normalized drying rates in combined superheated steam andrnmicrowave drying are higher than those at less than the critical moisture content inrncombined nitrogen and microwave drying. Moreover, theoretical drying rates for thernfalling rate period (predicted by a modified receding evaporation front model) inrncombined superheated steam and microwave drying, are in good agreement with thernobserved drying rates. The combined superheated steam and microwave drying methodrncan attain higher drying rates under mild external conditions.