Abstract
Effective heat transfer coefficients and mass transfer rates were determined at varying compositions of steam with 1.5% by weight volatile oils entrained in an air flow. The mixture of volatile oils is comprised of 50% menthol, 25% menthone, and other fractions of essential oils. The rate of transient mass transfer, relative partial pressures and the liquid phase resistances were used to evaluate recovery mechanisms for the volatile oils in the entrained aerosol. The size of the aerosol was (600 +/- 50) mu m. A stainless steel tube and shell condenser and a direct contact condenser were constructed in order to evaluate unsteady state models for mass transfer of the volatile oils, the unsteady state heat transfer, and the percent recovery of the aerosol. These data will be invaluable in the development of a collection and condensation system for the continuous microwave processing of mint hay. The Solvent Free Microwave System T vaporizes water and essential oils directly from cut hay. The coupled ionized interior of the microwave applicator seeds ions in the gas phase which provide a ready platform for aerosol nucleation of the steam in the air mixture. This aerosol must be recovered at an efficiency which rivals steam distillation. (C) 2011 Elsevier Ltd. All rights reserved.