Experimental studies on a parabolic-shaped solar tunnel dryer for Andrographis paniculata drying

Andrographis paniculata was dried using a parabolic-shaped solar tunnel dryer developed in the Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, Thailand. It is constructed with local materials, and then tested experimentally in food stuff drying Andrographis paniculata. With this dryer, 50kg of Andrographis paniculata can be dried within 4 hours. The dryer reduces drying losses as compared to sun drying and shows lower operational costs than the artificial drying. The color and the flavor of the food stuff dried with this dryer are comparable to that of a high- quality dried in markets. The dryer could be used for Andrographis paniculata of 80% (wb) moisture content, and they could be dried within 4 hours, with 0% (wb) remaining moister. The products being dried in the dryer got the heat from both the sunlight and the collectors. They were completely protected from rain, animals, insects and the dried products are of high quality. However, the temperature of the drying air was varied between 31 - 46 o C, depending on the weather conditions.