Antoni Koziol

Microwave Drying of Porous Materials

Abstract Experimental results on microwave drying of the porous particles exposed to air stream at 40°C are presented. The temperature and moisture distribution inside a particle were measured for gypsum spheres of 9, 18, 28, and 38 mm. The mass reduction was monitored during the drying process. The rate of drying and changes in temperature and moisture profiles for different drying conditions were analyzed and compared with the ones for convective drying. #Keynote lecture at PRES 2004, Session H4.

IR Technique for Studies of Microwave Assisted Drying

This article examines the idea of using an infrared technique in obtaining temperature profiles in solid particles heated with microwaves. The geometry of a cylinder and a regular prism made from thermally and structurally different materials (potato and gypsum) were tested. A suitability of the IR photography for visualization and quantification of temperature distribution in heated samples has been confirmed. Symmetrical temperature profiles were detected in cylinders in contrast to non-symmetrical ones in prisms.

Temperature Distribution in a Single Sphere Dried with Microwaves and Hot Air

This paper examines the temperature distribution within a spherical particle of the porous material dried with microwaves and hot air. Experimental results are compared with results obtained from a simple mathematical solution, where the problem of the internal electric field pattern was considered to be either uniform or non-uniform.

The Changes of Quality in Rapeseeds during Microwave Drying

The experimental analysis of the influence of microwave-assisted drying on rapeseed properties were explored in this study. The samples of rapeseeds were dried with microwaves on a laboratory scale. The influences of initial moisture content and microwave power levels on mechanical damage to the obtained products were tested. It appears that microwave-assisted drying at low power levels leads to a small amount of damaged seeds. The ability to sprout was also tested. Seeds that were dried with microwaves appeared to be totally sterilized and were unable to sprout. The final parameter tested was mutual seeds attenuating, which is important in cases of dense beds of granular materials. Higher microwave power levels gave surprisingly fewer damaged seeds than lower power levels. Seeds heated with microwaves were completely sterilized and unable to sprout. The number of damaged seeds heated with microwaves was lower than for seeds heated with hot air.

Microwave drying of rapeseeds on a semi-industrial scale with inner emission of microwaves.

The results of experimental studies on microwave drying of rapeseeds on a semi-technical scale are presented. An innovative mode of microwaves supplied to the drying material through an antenna placed in the geometrical center of a cylindrical drying chamber is proposed. It is shown that the emitted microwave energy is almost totally absorbed by the bed of a drying material and that the mechanical expression of liquid water due to the internal pressure gradient is a dominant driving force for moisture removal. Because only a fraction of water is removed through evaporation, this mode of microwave irradiation offers lower energy consumption than conventional microwave drying.

The temperature and moisture distribution of rapeseeds in a fixed bed during microwave-vacuum drying on a semi-technical scale

The temperature and moisture distribution of rapeseeds in a fixed bed during microwave-vacuum drying on a semi-technical scale A research into microwave vacuum drying of rapeseeds in a fixed bed on a semi-technical scale was done. The temperature and moisture distribution for a different value of microwave power and pressure were determined. The economic analysis of the drying processes, description of equipment and measurement methodology were presented, too.

Optimization of the quintic equation of the state based model for the calculations of different thermodynamic properties

Optimization of the quintic equation of the state based model for the calculations of different thermodynamic properties Different thermodynamic properties (the vapour density, the liquid density and the saturation pressure) were calculated by the model based on the Nakamura-Breedveld-Prausnitz equation of state (NBP EOS). Since the original form of the NBP EOS often generates inaccurate results for liquids, it was modified to describe this phase better. The calculations were realized in the subcritical region. So far, the temperature-dependent NBP EOS parameters have been obtained by special correlations. Their constants were fitted to a lot of experimental data. In this paper the equation of state temperature-dependent parameters were obtained by a new method which was based at piecewise cubic Hermite interpolating polynomials (PCHIPs). In the proposed method some experimental data (called the key ones) were used, thus reducing the experimental effort. Seven substances were chosen for the test calculations. Each of them is common in industry. The calculation results were compared with the experimental data. The new method has made an accurate description of vapour-liquid equilibrium for the considered pure substances over a wide temperature range possible.