Comparison of drying kinetics, thermal and performance parameters during drying guava slices in natural and forced convection indirect solar dryers

The performance of the dryer, thermal properties and the drying kinetics of guava were evaluated in natural convection indirect solar dryer (NCISD) and forced convection ISD (FCISD) and compared. The average final moisture content (MC) of guava slices (kept in all four trays) was reached from 5.5355 to 0.0244 kg/kg of db. The final MC was attained at 14, 18 and 24 h in FCISD, NCISD and open sun drying (OSD) methods, respectively. Effective diffusion coefficient (D-ef), surface transfer coefficients (h and h(m)), collector and dryer efficiencies (eta(coll) and eta(dry)), specific energy consumption and activation energy were estimated for both setups. The Page models were the best models for indicating the drying curve of guava slices in NCISD, FCISD and OSD. The specific energy consumption (SEC) of guava slices was 2.108 and 1.675 kWh/kg in NCISD and FCISD, respectively. The average increment of 34.12% on D-ef, 55.59% of h, 55.55% of h(m), 16.63% of eta(coll), 26.19% of eta(dry) and decrement of 20.54% on SEC were observed in FCISD than NCISD. The activation energy of guava slices was 136.98 and 116.49 kJ/mol in NCISD and FCISD, respectively. 16.63% and 26.19% improvements in eta(coll) and eta(dry), respectively, were noticed in FCISD compared to NCISD. The performance of ISD is improved in FCISD by attaching DC fans driven by PV modules.

Automated summary

The performance, thermal properties, and drying kinetics of guava were evaluated and compared in a natural convection indirect solar dryer (NCISD) and a forced convection ISD (FCISD). FCISD showed better performance with higher efficiency and lower specific energy consumption.