Evaluation of drying kinetics of carrot and thermal characteristics of natural and forced convection indirect solar dryer

Abstract

The thermal characteristics of natural (setup-A) and forced (setup-B) convection indirect solar dryers were evaluated and compared by drying carrot slices. Several modifications were made to setup-A to promote setup-B, including a trapezoidal tunnel, and central processing unit fans which were powered by photovoltaic panels. From the experimental solution, the performance terminologies and the drying characteristics of the carrot were examined. The actual rate of heat supplied to setup-A was 705.64 W and setup-B was 789.55 W. In the respective tests, collectors had an average efficiency of 56.84% and 68.74%. Accordingly, the drying efficiencies for the same were 7.5% and 9.55%, respectively. As a result of the aforementioned calculations, activation energy, effective diffusion coefficient, mass and heat transfer coefficients for setup-A and setup-B were 42.71 kJ/mol and 37.85 kJ/mol, 6.32 × 10−9 m2/s and 7.25 × 10−9 m2/s, 0.0055 m/s and 0.0065 m/s, and 6.32 W/m2 K and 7.25 W/m2 K, respectively. The setup-B showed a better effective moisture extraction rate and energy consumption. Characteristic relationships between moisture content vs diffusion, heat and mass transport coefficients were derived. Uncertainty estimations were performed to verify the precision of the findings.

Keywords

• Carrot
• Efficiency
• Drying performance
• Drying kinetics
• Natural convection
• Forced convection