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This work is focused on some properties of dried apple (Red Chief) and carrot (Misky). Water sorption isotherms of carrot and apple were investigated at three temperatures: 30, 40 and 60°C, corresponding to drying temperatures, by the static method consisting of the use of different sulphuric acid solutions. Guggenheim-Anderson-de Boer (G.A.B) model is found to describe the experimental curves better than Henderson, Hasley and Oswin models with a correlation coefficient superior to 0.97 for both products. The hysteresis phenomenon was clearly observed in the case of apple isotherms. The experimental data were also used to determine the isosteric enthalpy of desorption of apple and carrot. The isosteric enthalpy of desorption decreased with increase in moisture content and the trend became asymptotic.

Processing in vibrated beds is characterized by the versatility and the easy controlability through parameters of vibration (amplitude, frequency and intensity). The main task of the control of processing is the synchronization of the residence time of particles in the processing area with the duration of drying. The drying time depends on the physical properties of the processed material, on the thermal parameters of the bed and on the operational parameters. The residence time depends on the mechanical properties of the particles, on the intensity of transport and on the eometrical parameters of the equipment. Since most of the parameters of the vibrational processing depend on the intensity of vibration, synchronization of the drying time with the residence time of particles, optimization of the process and optimal design of the vibrational equipment in general must be performed by the control of this operational parameter. Therefore a sophisticated algorithm and software for optimal control and design of vibrational processing equipment is needed. Such an algorithm based on the "Classification Scheme of Vibrated Systems" is described in this paper. The design algorithm has been tested using experimental data measured in a laboratory scale aerovibrofluidized bed dryer.

The kinetics of combined convective and micro-wave drying presents universally more than the two habitual drying phases. Superimposed to a general heating of the product, a brutal and short acceleration of the drying rate raises all flux densities at a very important level. This is particularly evident with the class of product we used in this study : non porous polymeric gels.Moreover, an unusual correlation between the kinetics and the surface temperature around the micro-wave specific phase might appear : unexpectedly, the evaporation flux density decreases when the surface temperature increases noticeably.In order to elucidate this apparent complexity and understand the underlying physical phenomena, we analysed term by term all fluxes according to their origin. The splitting was achieved through mathematical modelling and partially validated by the recording of temperatures and mass fluxes.Usually with convective drying, all rate changes are governed by the state o f the product : hygroscopicity and porosity development. Here in the case of combined micro-wave drying, all accidents on the drying curves are determined by the heat generation and the heat transfer situation. The constant rate period is also governed by the balance of heat fluxes. The accelerated period corresponds to a heat wave arriving to the surface. Most of the time, the product gives out heat to the surrounding air : this heat is lost for the drying but this cooling effect may he used for the protection of the sample.