تحقيق و مدل سازي فرايند خشك كردن ورقه هاي موز به شيوه الكتروهيدروديناميك

چكيده انگليسي :

Study and Modeling of Electrohydrodynamic Drying of Banana Slices Kianoosh Pirnazari K pirnazari@ag iut ac ir February13 2012 Department of Agricultural Machinery Isfahan University of Technology Isfahan 84156 83111 Iran Language FarsiDegree M Sc Supervisors Ali Esehaghbeygi esehaghbeygi@cc iut ac ir Morteza Sadeghi sadeghimor@cc iut ac ir AbstractDrying is the most common method of food preservation which extends the food self life and minimiziespackaging storage and transportation costs Electrohydrodynamic EHD drying is the least well known of allthe drying methods perhaps because of its relative novelty and recent development In this method high electricfield is used for drying of fruits and vegetables The principle mechanism of electrohydrodynamic drying isconvective without the involvement of heat so is useful in drying heat sensitive materials The high electric fieldgenerates electric wind that is the main driving force for the accelerated drying of the agricultural products Inthe present study a multiple point to plate high voltage electric field system was made to conduct the dryingexperiments It mainly consisted of 25 needle point electrodes with 2 5 mm in diameters and a steel square plate 150 150 mm The distance between needle point electrodes was 34 6 mm In order to produce the electric field a high voltage power supply was used with a maximum output voltage of 22 kV at 1 mA Banana slices with 3 5mm in thickness were investigated using electrohydrodynamic field at 6 8 and 10 kV cm 1 oven at 50 60 and 70 C and hot air drying at 50 60 and 70 0C with the constant air velocity of 1 5 m s 1 In order to evaluate0electrohydrodynamic oven and hot air drying methods consumed energy drying time rehydration capacity color parameters L a b and E and the shrinkage of dried samples were investigated The data weredesigned based on a completely randomized arrangement The mean comparisons of treatments were examinedthrough the LSD test at the probability level of P 0 05 Moisture reduction kinetics was investigated throughmoisture content versus time drying rate versus time and drying rate versus moisture content curves Inelectrohydrodynamic method with increasing the electric field and in the oven and hot air drying methods withincreasing the temperature the values of drying rate increased The effective moisture diffusivity values werecalculated using Crank s solution of second Fick s equation for infinite plane sheet and were obtained between3 12 10 10 and 4 23 10 10 m2 s 1 for electrohydrodynamic 2 85 10 10 and 7 27 10 10 m2 s 1 for oven and4 10 10 10 and 1 34 10 9 m2 s 1 for hot air drying Empirical modeling of drying data was done by fitting to 12commonly used thin layer drying models The performance of these models was assesed by statistical procedure According to the maximum coefficient of determination R 2 and minimum value of root mean square of error RMSE between the observed and predicted moisture ratios the Diffusion model for electrohydrodynamic andhot air drying methods and Midilli model for oven method showed the best close prediction to the observed data The theoretical modeling of drying data was done using numerical implicit solution of second Fick s equation The predicting model based on numerical solution of second Fick s equation showed a good correlation with theexperimental data for electrohydrodynamic method but not good correlation with the experimental data for ovenand hot air drying methods Drying method had a significant effect on the drying time shrinkage andrehydration capacity and color parameter E of dried samples The mean values of consumed energy forelectrohydrodynamic oven and hot air drying methods were 0 34 487 55 and 1096 31 kJ g 1 respectively Themean values of drying time until the moisture content of banana slices reached 17 5 were 335 8 321 3 and199 7 min for electrohydrodynamic oven and hot air drying methods respectively Although drying time ofelectrohydrodynamic method was more than dryi

پيرنظري، كيانوش

تحقيق و مدل سازي فرايند خشك كردن ورقه هاي موز به شيوه الكتروهيدروديناميك

باد الكتريكي , انرژي , چروكيدگي , ظرفيت بارجذب آب , مدل سازي