Drying of fruits and vegetables: using a concentrating parabolic through solar collector

A high performance parabolic trough solar collector was developed during this study and was used for drying of vegetables and fruits. The materials used are easily available in the markets and included steel sheet with high power of reflecting light, steel pipe, angle iron and fully insulated drying box. The concentrating collector was a tilted at 34°south (Equivalent to the latitude of Peshawar). The concentrating reflector has a reflecting surface area of 2.9 m2 and focal length of 0.17 m. The length and width of the collector were 2.4 m and 1.21 m, respectively. The absorber having a surface of 0.376 m2 was fixed in front of the reflector at the distance equal to focal length. The heated air was flowing through fan from absorber tube to drying box. The maximum temperature of the absorber was 140 oC. The drying box was a 1 m x 0.57 m x 0.55 m box fully insulated. All Fruits and vegetable were dried with high air flow rate (1.72 kg.min-1). Efficiency was determined by taking the ratio of heat available at the collector in