Bananas Drying Performance with a Developed Hot Air Dryer Using Waste Heat from Charcoal Production Process

Abstract

The purpose of this research is to develop a hot air dryer using waste heat from a 200 liter kiln for drying bananas, and to investigate its drying performance. The main parts of the dryer consist of the drying chamber that has dimensions 0.71×0.83×0.91 m³, the air circulation system and a heat exchanger, which receives waste heat from the exhaust tube and kiln surface. The dryer was developed by designing a drying chamber on the top of a 200 liter kiln to reduce heat lost in the structure and an exhaust gas heat exchanger was developed using groups of copper tubes for increasing then heat transferred to the air. The drying performances were analyzed by measuring specific drying rates and specific energy consumption. Experiments were performed under different temperatures of 60, 70 and 80 ^oC and at a constant velocity of 1.8 ms^-1. Eucalyptus was selected as the heat source. Thirty kg of peeled bananas were prepared at an initial moisture content of 241.19±31.50 % dry basis and were dried until to final moisture content of 48.47±10.46 % dry basis. All experiments were carried out in duplicate. For temperatures of 60, 70 and 80 ^oC, the average specific drying rates were 0.085±0.0004, 0.114±0.0009 and 0.1277±0.010 kg_waterh^-1kg_solid^-1 and the average specific energy consumptions were 1.42±0.055, 1.21±0.355 and 1.04±0.074 MJ/kg_water respectively. Some dried bananas had burned at a temperature of 80 ^oC so at temperature of 70 ^oC was the optimal condition in this experiment. This produced good color, a high specific drying rate and low specific energy consumption.