Investigation of thermal performance, drying characteristics and environomical analysis: direct flow evacuated tube solar drying of okra

A direct flow evacuated tube solar dryer (DF_ETSD), a novel drying system, was used for drying pre-treated okra (Abelmoschus esculentus). The performance of DF_ETSD was analysed by determining thermal profiling, dryer and collector efficiency hourly. The maximum 3-day average ambient temperature, collector outlet temperature and solar radiation were 35.6 °C, 66.4 °C and 976 W m−2 respectively. The collector efficiency increased as solar radiation increased over time due to a higher temperature difference between the collector outlet and ambient temperature. The maximum collector and dryer efficiency observed were 30.19