Study On The Combined Drying Characteristics Of Banana Chips With High Voltage Electric Field And Heat Pump

Banana(scientific name: Musa Nana Lour)is one of the important economic crops in China.It contains a variety of essential nutrients for human beings.Fresh bananas are soft and difficult to store,which brings great inconvenience to preservation,transportation and storage.In order to solve this problem,drying banana slices is one of the means to extend its shelf life.At present,there are few studies on banana slices drying by combined drying of high voltage electric field and heat pump.In this paper,banana slices as the research object,and through the establishment of combined drying test bed by high voltage electric field and heat pump drying,the drying characteristics of banana slices under different drying conditions were studied.The results are as follows:(1)In order to determine the best form of air supply and return in the drying room,the gas flow state of three kinds of air supply and return forms,i.e.upper supply and upper return,upper supply and middle return and upper supply and lower return,are simulated.It is found that the upper supply and lower return has the maximum average velocity and the minimum velocity non-uniformity coefficient.Therefore,the upper supply and lower return is the best form of air supply and return in the drying room.(2)Using fresh banana as raw material,the drying characteristics of banana slices under different drying temperature(50,55,60),different slice thickness(1 mm,3 mm,5 mm),different electric field intensity(50 k V,75 k V,100 k V)and different number of needle electrodes(1,3,5)were studied by single factor experiment.The results showed that the drying process of banana slices was mainly slow drying.The drying rate of banana slices is directly proportional to the drying temperature,electric field intensity and the number of needle electrodes,and inversely proportional to the slice thickness;the time of moisture content reaching the end of drying is directly proportional to the drying temperature,electric field intensity and the number of needle electrodes,and inversely proportional to the slice thickness.(3)In order to obtain the mathematical model of banana slices under the condition of combined drying of high voltage electric field and heat pump,6 thin-layer drying models were used to fit and analyze the experimental data,and the Page model could best describe the moisture change law of banana slices during drying.The factors influencing the drying process were as follows: thickness > temperature > number of needle electrodes > electric field intensity,and the activation energy of banana slices drying by combined drying of high voltage electric field and heat pump is 26.45 k J/mol.