Thin layer drying kinetics and exergy analysis of turmeric (Curcuma longa) in a mixed mode forced convection solar tunnel dryer

A low cost and user friendly solar tunnel dryer was fabricated for drying of indigenous agro products. Experimental investigation and drying kinetics of turmeric (Curcuma longa) in a mixed mode solar tunnel dryer is reported. The key advantage of the current design is the inclination of the solar air heater which effective harnessing of solar radiation. The presence of detachable trays helps in easy handling of drying samples. The turmeric with an average initial moisture content of 0.779 (kg water/kg dry matter) were dried to 0.070 (kg water/kg dry matter) in the solar tunnel dryer under forced convection. Final drying levels of turmeric were realized in 12 h in the solar dryer while it took 43 h under the open sun drying. Thin layer drying kinetics of turmeric under forced solar tunnel drying was performed. The energy and exergy analysis during the drying process was assessed by employing the first and second law of thermodynamics. Energy utilization ratio of solar tunnel varied in the range of 9.75-33.98%. The mean value of exergetic efficiency of dryer was found to be 49.12%.