A Tanit Ruangrungchaikul creator Bhattacharya, Sribas C. Chairperson Pham, Hoang-Luong Co-Chairperson Kumar, Sivanappan Examination Committee National Energy Policy Office/ Asian Institute of Technology Partial Scholarship Scholarship Donor text series technical report th Bangkok : Asian Institute of Technology 1999 continuing eng 102 leaves A natural convection dryer for fruits and vegetables using indirectly heated air was designed and fabricated. The dryer could be operated in shade as biomass-fuelled dryer and/or in the sun as a biomass/solar hybrid dryer. The dryer consists of four main pa1is; (1) a gasifier stove for generating the heat supplied to the system, (2) a heat exchanger unit for transferring heat from the hot flue gas to the process air, (3) a drying chamber in which the product to be dried was placed and (4) a temperature control system for controlling the drying air temperature inside the drying chamber at the appropriate level. In addition, a solar collector was provided to heat up process air for hybrid operation and a wind ventilator was installed on the top of the chamber to promote movement of process air tlU"ough the drying chamber. Since the process air flows naturally and the temperature control system works mechanically, it does not need an electrical power supply. The performance of the prototype unit was evaluated in terms of drying air temperature, fuel consumption rate, drying duration, drying efficiency and the quality of the dried product. No-load tests conducted on the biomass-fuelled dryer have shown that the process air temperature could be controlled to be near the permissible level (70 °C) for drying fruits and vegetables when using the temperature control system. The experiments on load condition were conducted with banana and chili (16 kg each). The drying duration and fuel consumption rate were about 20 hours and 2 kg/lU' for both banana and chili. The drying efficiency was measured to be 3.42% for banana and 3.67% for chili. The quality of final dried products obtained was similar to that obtained from open sun drying. The temperature profiles of the drying air, air flow rate, drying time and quality of the products for the dryer operating in the hybrid mode were not different compared to the operation fuelled by biomass alone. For hybrid operation, the fuel consumed in the gasifier stove could be saved by about 15% and the overall system efficiency (with the solar energy input about 72 MJ or about 12% of bioenergy) was about 4.29%. A thesis submitted in pa1tial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development Thesis (M.Sc.) - Asian Institute of Technology, 1999 Biomass energy Drying Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B12034 http://203.159.5.9/ait-thesis/detail.php?q=B12034 070200 20260818223210.0