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Abstract
Many situations exist in rural areas of developing countries where the implementation of simple technology can have a substantial positive impact on living conditions, finance and sustainability. A challenge faced in the sunny region of Melanesia is the means to adequately preserve indigenous food sources such as C. indicum nuts. In this thesis the design and use of a solar dryer to provide a sustainable, low cost approach for drying C. indicum nuts in Port Vila, Vanuatu is demonstrated.
A mixed mode, low-profile solar tunnel dryer typology, utilizing natural building materials where available, was selected to best fulfill the drying requirements for C. indicum nuts in the climatic and economic conditions of Vanuatu. This design incorporates a pre-heating area prior to the drying area, enabling higher internal temperatures to be achieved. DC powered fans, directly coupled to a small photovoltaic module, are used to generate forced convective airflow within the solar dryers.
An equivalent electric circuit has been designed and validated for modelling the thermal performance of the solar tunnel dryer and predicting output temperatures of the pre-heater. Solar dryer prototypes were built in Port Vila, Vanuatu and Sydney, Australia for monitoring and performance testing under load and no-load conditions. Comparison of the simulation model and the prototype dryer showed good agreement in the temperature rise obtained between the ambient air temperature and the pre-heater outlet air temperature, which was found to be 9˚C during the middle of the day.
The average moisture content (wb%) values, of the available C. indicum nut kernels, were determined from initial sample sets which measured 23-27%, as well as samples during and after solar drying. Mass loss profiles were recorded for the nut-in-shell samples exposed to approximately thirty hours of solar drying using the prototype dryer in Sydney. The nuts-in-shell were successfully dried to an acceptable kernel moisture content (wb%), between 2.5-3.5%, which is considered a safe range for storage in controlled environments. Therefore, this low-cost, sustainable solar dryer has met the goal in providing an effective solution for drying C. indicum nuts in remote regions of Melanesia.