Drying Of Sliced Materials Under The Influence Of Ultrasonic And Infrared Radiations
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Date
2011-07
Authors
Low, Hua Chin
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Convective drying has been commonly used in preservation of the agricultural products. The respective drying rates generally depend on the effective diffusion coefficients of moisture within the materials. Increase in ultrasonic power and frequency as well as infrared power have been found to enhance the convective drying process rates. The main aim of this work is to study the influence of the ultrasonic frequency and infrared power on the effective diffusion coefficients of moisture within the materials. For this purpose, experiments were carried out for banana, cassava and pumpkin based on the Design of Experiment (DOE) in the ranges of three air temperatures (85oC, 90oC and 95oC) with ultrasonic frequencies (0 kHz, 20 kHz and 50 kHz) and with infrared power (0 W/m2, 757.50 W/m2 and 1515 W/m2). The data collected from experiments were employed to determine the effective diffusion coefficients. The effective diffusion coefficients were statistically analyzed by Analysis of Variance (ANOVA) with parameters ultrasonic frequencies and infrared power for each slice thickness. The effective diffusion coefficients were observed to increase with increasing of ultrasonic frequencies and infrared power.
The effective diffusion coefficients were also observed strongly dependent on slice thickness. The dependence of the effective diffusion coefficients on the slice thickness was studied thereafter. A theoretical model was developed in order to correlate effective diffusion coefficient of moisture within the materials with slice
thickness as well as axial and radial diffusion coefficients. The model was found to describe the variation of effective diffusion coefficient with slice thickness very satisfactorily and it was validated with the experimental data with correlation coefficient of 0.948 to 0.999 for selected materials. The values of axial diffusion coefficients were found to be higher than radial diffusion coefficients due to anisotropic behaviour of the materials. The axial and radial diffusion coefficients were analyzed with the statistical analysis (ANOVA) with air temperatures, ultrasonic frequency and infrared power. The axial and radial diffusion coefficients too were observed to increase with increasing of air temperatures, ultrasonic frequencies and infrared power.
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Keywords
Influence of the ultrasonic frequency and infrared power , effective diffusion coefficients of moisture within the materials