Exergy analysis of a solar thermal energy powered tea withering trough

Abstract

Abstract Tea leaves undergo drying (withering) at low temperatures after they are plucked. Withering consumes around 6.48\xa0MJ/kg of conventional thermal energy in tea production. The quantity of energy intake may be partially reduced by using sustainable energy. Solar thermal energy meets the demand for such resources readily. The present study evaluates the exergetic efficacy of a solar thermal energy powered laboratory scaled tea withering trough. For this purpose, the withering trough was coupled with a solar air-heating unit equipped with a corrugated plate absorber. The weights of the sample trays loaded with fresh tea leaves in the withering trough were taken after every hour in a digital weighing balance till the desired moisture content was attained. The temperature within the withering chamber was maintained between (298–308) K. The relative humidity was maintained in the range of (75–85)%. The air mass fluxes considered were 0.03 and 0.04\xa0kg/s. The maximum energy efficiencies for the air heater with the considered mass flow rates were obtained as 45.32% at the radiation of 1047\xa0W/m2 and 54.46% at 1060\xa0W/m2 solar radiation accordingly. The exergetic efficiencies of the withering trough were found within 36.62% to 89.79% at 0.03\xa0kg/s and 59.03% to 94.23% for 0.04\xa0kg/s.