Solar, Biomass and Hybrid Dryers - BioEnergy Discussion Lists

Technical specifications of the improved solar tunnel dryer are given in Table 6.1.Table 6.1: Technical specifications of the solar tunnel dryerSl. ParameterNo.1. Mode of drying Direct2. No. of glazing Single3. No. of trays 16Specifications4. Air circulation Forced, 370 W, AC exhaust fan5. Collector area 24 m 26. Drying capacity 70 kg-fresh7. Constructionmaterials8. Approx. cost NRs. 200,000**1 US$ = 74 NRs (Nepalese Rupees), March 2004Wood, steel section, aluminum sheets, GIsheets, window glass, glass wool, aluminiumscrews and rivetsSolar Collector modulesSix solar collector modules heat the ambient air forced into the tunnel by the blowerfixed at one end. Four of the six collector modules are fixed at one end, next to theblower, while two collectors are located in the middle. These two solar collectormodules help prevent condensation of moisture on the inner surface of the glasses,by maintaining the temperature of air inside the tunnel at reasonably high levels.The design details of the individual solar collector modules are presented in Figure6.3. Each module has an outer box and an inner box, with glass wool insulationbetween them. The collector frame is made of wood and mild steel sheet. Acorrugated sheet GI absorber, coated with flat black paint, is fixed inside the innerbox. 4mm thick window glasses are used for glazing the collector.Mild steel angles provide the necessary structural support for the collector-dryerassembly.Dryer modulesEight dryer modules are fixed between the solar collector modules, as shown inFigure 6.2. Each dryer module has two partitions, and each partition has two traysand a glass door hinged at one side of the door frame. The glass doors can be openedat the top, for loading and unloading of the product. The trays are made ofaluminum frames and stainless steel wire mesh, on which the products to be driedare loaded in a thin layer. Figure 6.4 illustrates the design of a single dryer module.33