Comparison of solar dryer and solar-assisted heat pump dryer for cassava

The performance of a solar dryer (SD) and a solar-assisted heat pump dryer (SAHPD) for drying of cassava chips have been investigated. The SD and SAHPD decreased the mass of cassava from 30.8 kg to 17.4 kg within 13 and 9 h at average temperatures of 40 °C and 45 °C, respectively. The moisture content of cassava decreased from 61% (wet basis) to 10.5%, with a mass flow rate of 0.124 kg/s. The average thermal efficiencies were 25.6% and 30.9% for SD and SAHPD respectively. The average drying rate (DR) and specific moisture extraction rate (SMER) were 1.33 kg/h and 0.38 kg/kW h, respectively, for SD as well as 1.93 kg/h and 0.47 kg/kW h, respectively, for SAHPD. The pick-up efficiencies varied from 3.9% to 65.8% and 15.9% to 70.4% for SD and SAHPD, with average values of 39.3% and 43.6%, respectively. The average solar fractions were 66.7% for SD and 44.6% for SAHPD. The coefficient of performance of the heat pump ranged from 3.23 to 3.47, with an average of 3.38.