Energy efficiency and moisture diffusivity of apple slices during convective drying

Abstract

The present study aimed at investigating the influences of drying air temperature and flow rate on energy parameters and dehydration behaviour of apple slices. For this purpose, apple slices were dried in a convective dryer at air temperatures of 50, 60 and 70 °C, and air velocities of 1, 1.5 and 2 m s^–1. Dehydration rate increased as the air temperature and flow rate increased from 50 to 70 °C and 1 to 2 m s^–1, respectively. The effective moisture diffusivity was determined to be in the range of 6.75×10^–10-1.28×10^–9 m² s^–1. Results of data analysis showed that the maximum energy consumption (23.94 kW h) belonged to 50 °C and 2 m s^–1 and the minimum (13.89 kW h) belonged to 70 °C and 1 m s^–1 treatment. Energy efficiency values were in the range of 2.87-9.11%. Moreover, the results indicated that any increment in the air temperature increases thermal and drying efficiencies while any increment in the air flow rate decreases both of them.

Keywords:
apple; moisture diffusion; thermodynamic parameters; energy efficiency