Thermodynamic analysis of a triple-pass solar dryer for drying potato slices

An indirect-type triple-pass forced convection solar dryer has been developed and the performance parameters such as thermal, pickup and exergy efficiency are studied for drying potato slices. The triple-pass solar dryer consists of a blower, triple-pass solar collector integrated with sensible heat storage (sand) bed along with absorber plate and aluminum wire mesh and drying chamber. The experiments were conducted at the optimum value of air mass flow rate of 0.062 kg s⁻¹. The experimental results showed that the maximum collector outlet air temperature of 62 °C was observed at 1.00 pm and the respective solar irradiance of 998 W m⁻². The initial moisture content of the potato slices was reduced from 76% (wet basis) to the final moisture content of 13% (wet basis) in 4.5 h. The solar collector thermal efficiency was varied from 12 to 66%, and the mean value of 45% was observed. The pickup efficiency of the solar dryer for drying potato slices was varied from 2.5 to 62.9%, and an average of 29.9% was observed. The exergy efficiency varies from 2.8 to 87.02%, and the mean value for the day was obtained as 53.57%. The thin-layer drying characteristics of potato slices have been studied, and Midilli and Kucuk model was proposed as most suitable drying model.