SURFACE TEMPERATURE PROFILE, ENERGY-EXERGY ANALYSES AND THERMO-PHYSICAL PROPERTIES OF POTATO CHIPS DRIED IN MICROWAVE AND HYBRID (MICROWAVE + CONVECTIVE) OVENS

Abstract

The present study potato slices were dried at a microwave oven and hybrid (microwave + convective) oven at PR 3 power rate. Effects of drying methods and conditions on surface temperature profile, drying characteristics, effective diffusion, activation energy, thin-layer drying model, specific moisture extraction rate (SMER), specific energy consumption (SEC), energy efficiency (EE), specific exergy loss (SEL), exergy efficiency (EXE), specific heat, thermal diffusivity, thermal conductivity and density were investigated. The lowest surface temperature (39.00 ºC) was observed in 160 W+55 ºC drying treatment and the greatest (128.30 ºC) in 160 W+75 ºC drying treatment. Among the thin-layer drying models, Wang-Sing model was identified as the best model. Effective diffusion values of drying treatments varied between 1.14x10-7- 3.18x10-10, activation energy values between 79.12 kJ/mol (Microwave) and 126.96 kJ/mol (microwave + convective), SMER values between 1006.57 - 1950.14 kg water/kWh, SEC values between 8.86 - 14.31 MJ/kg water, EE values between 2.55 - 19.39%, SEL values between 0.42 - 12.68 kJ/kg. Of thermophysical properties of potato slices, specific heat values varied between 837.69 - 848.13 J/kgºK, thermal conductivity values between 0.07 - 0.27 W/mºK, thermal diffusivity values between 1.163 - 3.774x10-6 m2/s and density values between 700.60 - 839.41 kg/m3.