Experimentation
Natural rubber sheet drying experiments were conducted in designed and fabricated solar drying systems during October 2008 to January 2009 from 09:00 to 18:00 h. Drying chamber has even spanned roof structure, made from polycarbonate sheets and concrete floor. Two sets of experiments were conducted separately for mixed-mode and indirect solar drying. Solar radiations were coming through the roof and sidewalls of drying chamber of the mixed mode solar dryer. These were utilized directly in heating air and natural rubber sheets inside the chamber. At the same time, hot air was also coming from the bottom of mixed-mode solar dryer through the solar air heating collectors. Whereas in indirect solar dryer, walls and roof of drying chamber made opaque and painted black to absorb solar radiation to from heat. Heat from the walls was transferred to the chamber via conduction.
Each set of experiments was performed for 4 days with 30 numbers of rubber sheets (50 cm × 90 cm × 0.4 cm). Global solar radiation, mass of the rubber sheet, temperature & humidity inside and outside the dryer, inlet & outlet velocity of supply air and other ambient parameters were recorded at regular intervals of time.