Heat and mass transport in microwave drying of porous materials in a spouted bed

A heat- and mass-transfer model was developed to simulate microwave and spo uted-bed combined (MWSB) drying of diced apples a hygroscopic porous materi al. A total gas-pressure equation was introduced to take into account inter nal vapor generation during microwave drying The governing equations for he at and mass transfer were simplified using a scaling technique and numerica lly solved with the finite difference method. The physical, thermodynamic, thermal, transport and dielectric properties used in the simulation were ei ther from our measurements or from the literature. Model predictions agreed well with experimental results. The pressure-driven moisture migra tion du ring MWSB drying resulted in a high drying rate. The numerical analysis pre dicted a temperature-leveling effect that was confirmed by experimental res ults. The unique temperature leveling in MWSB drying helps to control produ ct temperature and improves product qualify as compared to microwave-assist ed fired-bed hot-air drying methods.