Experimental investigation of mixed mode ultraviolet tent house solar dryer under natural convection regime

A mixed mode natural convection ultraviolet (UV) tent house solar dryer is designed and installed at University Teaching Department, Chhattisgarh Swami Vivekanand Technical University, Bhilai, Chhattisgarh (21 degrees 27 ' N, 81 degrees 43 ' E) India for drying potato slices. This solar dryer is equipped with a solar flat plate collector (area 1.12 m2), covered with 5.0 mm thick glass and consists of two trays of the same size (0.57 m X 1.11 m) in a drying chamber on which equal quantities of potato slices were placed. The local atmospheric conditions including relative humidity, atmospheric temperatures, solar intensity, and wind velocity have been recorded for analyzing various parameters. The solar intensity and atmospheric temperature ranges from 134 to 993 W/m2 and 36.2 degrees C to 44.9 degrees C respectively. The initial moisture content value of 85.25% reaches 14.75% for 2.5 mm thick potato slices and for 5.0 mm thickness, the initial & final moisture content values are 85.10% & 14.90% respectively. The upper and lower tray temperature varies from 34.2 degrees C to 59.7 degrees C and 33.6 degrees C to 57.1 degrees C respectively. The open sun drying took 6 h longer than the solar natural convection drying. Moisture ratio for 2.5 mm thickness and 5.0 mm thickness lies 0.475-0.001 and 0.650-0.003 respectively. The maximum dryer efficiency is 26.62% and 21.61% for 2.5 mm and 5.0 mm thick potato slices respectively. All the drying kinetics is superior in the 2.5 mm thickness of the potato in process of drying using natural convection.