Drying kinetics and thermo-economic analysis of drying hot water blanched ginger rhizomes in a hybrid composite solar dryer with heat exchanger

Abstract

This research aimed to examine the need of adding hot water blanching pre-treatment on the drying of ginger rhizomes using a hybrid solar-dryer with paraffin liquid as thermal storage infused into a copper tube to form a compact heat exchanger. Blanching duration quickened the drying rate of the ginger rhizomes and the average drying rate for blanching at 90 s, 60 s, 30 s and un-blanched ginger varied between 0.0147 kg/h to 0.0245 kg/h at a sensible heat ratio of 4.12 × 10−5 to 2.53 × 10−3. The optimal drying rate varied from 0.01161 kg/h to 0.0263 kg/h for all treatment at a collector temperature range of 39.5 °C–40.5 °C and collector efficiency range of 14.3%–30%. The logarithmic model better predicted the drying kinetics of un-blanched and blanching for 30 s with an R2 value of 0.9875 and 0.97247 respectively while the modified Henderson and Pabis model better predicted drying of blanched ginger rhizomes at 60 s and 90 s with R2 values of 0.96252 and 0.98188 respectively. Using the hybrid solar dryer instead of artificial dryers with fossil energy sources can save about $75.731 to $757.31 of the running cost as the usage increased from 10 to 100%. The payback period decreased from 2.88 years to 0.31 years as the rate of usage increased from 10 to 100%. Using the presented solar dryer instead of coal, diesel or grid base electricity can prevent 15.96 to 186, 7.62 tones of CO2 from entering the atmosphere. The earned carbon credit if the dryer is to be powered by coal, diesel or grid base electricity were $ $6245364, $27080.52, and $231.45 per year respectively which can be used to compensate other non-renewable energy sources deployed within an energy enterprise.

Keywords

• Agricultural products
• Decarbonisation
• Drying kinetics
• Hot water blanching
• Solar thermal storage