Studies on Characteristics and Model of Solar Low-temperature Adsorption Drying for Fresh Apple Slices
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Abstract:
Using fresh apple slices as the research object and the low-temperature solar adsorption drying (LSAD) system developed in our company as the experimental facility, the effects of drying temperature, relative humidity, drying medium flow rate, sample loading amount and slice thickness on the LSAD characteristics of apple slices were investigated. The results showed that the LSAD process could be divided into three stages: Adjustment, constant speed, and decelerating drying stages. The drying temperature had the most significant effect on the drying rate of fresh apple slices e.g. drying at 50 ℃ reduced the drying time by 65.9% than at 10 ℃. The primary and secondary influences of the variables on the drying of apple slices were drying temperature > relative humidity > flow rate of drying medium > slice thickness> sample loading amount. The optimum process conditions for LSAD of apple slices were: drying temperature 50 ℃, relative humidity 20%, flow rate of drying medium 0.9 m/s, sample loading amount 7.5 kg/m2, slice thickness 3 mm. The mathematical software was used to select and fit the experimental data by three models, and the mathematical model of apple slice drying had the highest fitting degree with Page model. The mathematical equation for LSAD of fresh apple slices was MR = exp (-0.00557*t^1.76669). The establishment of such a model provides the theoretical support for the application of LSAD to the production of dehydrated apple slices.
