مطالعه كاهش رطوبت ورقه هاي سير به شيوه ي الكتروهيدروديناميك و جريان هواي داغ

چكيده انگليسي :

127 Electrohydrodynamic and Hot air Dehydration of Garlic Slices Mohammad Javad Salighe MJ Salighe@ag iut ac ir January15 2014 Department of Agricultural Machinery Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Language Farsi Degree M Sc Ali Esehaghbeygi esehaghbeygi@cc iut ac ir AbstractDrying is the most common method of food preservation which extends the food self life and minimiziespackaging storage and transport costs Using high voltage electric field for drying be namedelectrohydrodynamic EHD This method is used for fruits and vegetables drying The principlemechanism of electrohydrodynamic drying is convective without involving heat so is useful in dryingheat sensitive materials The high electric field generates electric wind that is the main driving force forspeeded up drying of the agricultural products In the present study a multiple point to plate high voltageelectric field was made to conduct the 15 dehydration of garlic slices It mainly consisted of 30 needle point electrodes with 0 15 mm in diameters a copper and aluminum square plates 150 150 mm Thedistance between needle point electrodes was 32 16 mm To produce the electric field a high voltagepower supply was used with a maximum output voltage of 22 kV at 1 mA The slices with 2 mm inthickness were investigated using electrohydrodynamic field at 4 5 and 6 kV cm 1 and Hot air drying at30 40 and 50 C with the constant air velocity of 0 5 and 1 m s 1 Consumed energy drying time waterabsorpation color parameters L a b and E shrinkage and biot number of dehydrated sampleswere investigated A completely randomized arrangement in factorial experimentation was used Moisturereduction kinetics was investigated through moisture content versus time and drying rate versus time Theresults showed with increasing the electric field temperature and air flow rate dehydration rateincreased Empirical modeling of dehydration data was done by fitting to 6 commonly used for thin layerdrying models To performe these models was assesed by statistical procedure According to themaximum coefficient of determination R2 and minimum value of root mean square of error RMSE between the observed and predicted moisture ratios the Midilli and Logaritm models forelectrohydrodynamic and Hot air drying method showed the best prediction to the observed data Theanalytical modeling of dehydration data was done using Crank equation considering biot number Theelectric field had a significant effect on the drying time water absorpation consumed energy and colorparameters Meanwhile the hot air had a significant effect on biot number and the flow rate had asignificant effect on shrinkage Consumed energy of dehydration of garlic slices with 0 5 m s 1 air flowrate at 30 C was 1811 kJ g 1 and for 6 kV cm 1 electric field 1 m s 1 air flow rate at 50 C was 845 kJ g 1 The mean value of drying time of garlic slices decreased with increasing the electric field airtemperature and its flow rate Considering low consumed energy and drying time 6 kV cm 1 electric fieldwith 1 m s 1 air flow rate at 50 C was economic treatment Keywords Energy shrinkage water absorpation biot number analytical modeling

سليقه، محمدجواد

مطالعه كاهش رطوبت ورقه هاي سير به شيوه ي الكتروهيدروديناميك و جريان هواي داغ

انرژي , چروكيدگي , ظرفيت جذب آب , عدد بايوت , مدل سازي تحليلي