Research Results on Designing Drying System for Litchi Using Combined Thermal Convection and Radiation Method 

Equipment system SV-1.0 for drying litchi by combining convection and radiation method has been designed and manufactured at Department of Agricultural products Processing and Storage, Faculty of Engineering, Hanoi University of Agriculture. This drying system has simple structure and the heat are supplied by combining thermal convection and radiation method. As a result, heat transfer effect was improved. The effect of temperature, drying air velocity, density of material in drying chamber on drying material heterogeneity of dried product and specific fuel consumption was identified. In comparison with common drying systems being used, the drying system SV-1.0 has several advantages: drying time was reduced (70.5 hours), equal to 55.7% of manual drying ovens and 94% of improved drying equipmen. The heterogeneity of dried product is 2.1%, reduced by 2.2% in comparison with manual drying oven and by 1.6% with the improved drying equipment. Specific fuel consumption is 0.45 kg of coal for 1kg of dried product, equal to 46.1% of manual drying oven and 74% of the improved drying equipment. The dried litchi product has good quality with nice shape and colour.