Abstract:

The drying characteristics of apple slices in a heat pump by filling nitrogen and lowering oxygen were studied.The results showed that drying temperature and material thickness had noticeable effects on drying rate. However, theeffects of air velocity and oxygen concentration were little. By logarithmic transformation of drying curves and linear fitting,the Page model for describing the heat pump drying of apple slices was obtained. Using a stepwise regression method,the expressions of modeling coefficients (k and n) were established with respect to drying temperature, material thickness,air velocity and oxygen concentration. Only slight differences were found between the predicted and calculated results.Therefore, this mathematical model could be used to sufficiently predict and describe the heat pump drying process of appleslices by filling nitrogen and lowering oxygen.

Key words: pump drying, apple slices, filling nitrogen and lowering oxygen, mathematical model