Prototype and model of passive tropical fruit dryer utilizing a flexible transpired solar collector

Abstract

We explore a novel drying system to preserve tropical fruits, motivated by the needs of a rural farming co-op in Haiti. Most solar drying technologies rely on glazed collectors, but these are not readily accessible in rural communities. A low cost and low maintenance prototype drying system is designed, built and tested. The system comprises a transpired solar absorber made from cheap landscape fabric, a drying chamber, and a chimney. The drying chamber houses the fruit and the chimney induces airflow. In tests on thinly sliced bananas, the novel collector efficiency regularly exceeds 50% with an average temperature rise from inlet to outlet of the device of over 20°C. In one test, 4kg of banana slices per square meter of absorber area are dried from an average moisture content of 73wt% to 8wt% over two days. A preliminary mathematical model for the entire drying system is developed that agrees favorably with experiments.