Study On Heat And Moisture Transfer In Apple Slices During Hot Air Drying

The hot air drying of apple slices can extend the storage time and effectively increase the incidental value of the fruit.In order to explore the process of heat and moisture transfer and water evaporation in the drying process,and at the same time solve the problems of poor quality,low drying efficiency,too long drying time and unpredictable drying time in the traditional process of apple slice hot air drying,This article studies the apple slice drying process through two parts: experiment and numerical simulation.In the process of hot air drying,the size of apple slices has a greater impact on drying time,rehydration ratio,and slice color.This article takes cylindrical apple slices as an example.Through the hot air drying experiment on apple slices of different thickness and different radius,the The influence of the thickness and diameter of the slice on the drying time,rehydration ratio,and color of the slice,it is determined that the appropriate thickness of the dried slice is about 7mm,and the slice radius is 20 mm.Based on the hot air drying test bed,using Comsol software,by establishing the MPMM(Multi-phase Porous Medium Model)of apple slice drying,numerical simulation analysis found that drying is a process from front to back,from outside to inside,the front of the slice The drying rate is obviously greater than the rear end,and the evaporation of water is mainly carried out in a certain area of the slice surface.By changing the three drying process parameters of apple slices-supply air temp erature,supply air speed and supply air relative humidity,the influence of the change s of the three parameters on the moisture transfer in the slice was analyzed,and the drying time and drying time of the parameter changes were explored The influence law of unevenness,comprehensive comparison selects the best supply air temperature as 50℃ supply air speed as 1m/s,and supply air relative humidity as 40%.Finally,in order to predict the drying time of apple slices during the hot air drying process,the least square method was used to fit the nonlinear multivariate functions under different air supply parameters,and the fitting calculation was performed by the Origin software,which obtained 20%,30%,40 % The functional relationship of drying time t with the change of wind speed v and temperature T at three different relative humidity,and by verifying the accuracy of the fitting function,the accuracy of the fitting data is verified,which provides for the actual process production process Guidance.