The Differences in Drying Rate Curves of Sintered Glass Beads at Subatmospheric and Atmospheric Pressures and at Lower Pressures in Steam

Abstract

AbstractSteam drying of sintered glass beads under vacuum was investigated. The drying rates were predicted from an evaporation zone model for the constant rate period, and from a receding evaporation front model for the falling rate period in which the data of moisture contents in the pendular state were estimated from those in air under vacuum. The predicted, as well as observed, normalized drying rate curves including the critical moisture contents in steam under vacuum were different from those in steam at subatmospheric and atmospheric pressures. However, they were similar to those in air under vacuum in the corresponding pressure range. This was because the moisture content in the pendular state under vacuum was larger than that at subatmospheric and atmospheric pressures, and heat transfer was a rate‐controlling step both in steam and in air under vacuum.