Design, construction and testing of a novel round the clock solar crop dryer with water recovery :

Abstract

The drying of foods and crops is a major operation in the food industry consuming large quantities of energy. Providing the most suitable drying conditions for a particular crop ensures that it reaches acceptable moisture content for storage with minimum use of energy within a specified time. (Mcdoom et al., 1999). In the food sector, many studies have been laid to optimize the drying operation by rationalizing energy consumption and improving the quality of the dried product. In this regard, solar drying is an adequate solution for developing countries which are poor in conventional energy resources but have an important solar input practically during all the year. Solar energy is preferred because it is abundant, free, inexhaustible and non-polluting. This report describes the use of a refrigeration system as a heat pump to provide heat required for drying during the night and cloudy weather conditions. The use of refrigeration in crop drying is quite limited and perhaps the existing one is freeze drying. However, because of the low temperature and low pressure, the drying rate tends to slow down. Freezer burn, sometimes seen in frozen foods is an example of undesirable freeze drying. Freeze drying is quite expensive compared to many other drying methods because it is limited to drying high value materials. The main objective of this work is to design a solar refrigeration system that will provide energy to the system and recovery 5litres of water from 75kg of maize during the night. Special procedures are described that were applied to ensure effective even drying of the crops to the required moisture content and results in terms of heating load and cooling load were obtained with accompanying quantity of water collected. In my conclusion, there is inadequate satisfactory data at present to justify the effectiveness of drying that was carried out during the night thus more time and attention should be paid to the night drying such that systematic results can be obtained for evaluation. A refrigeration system in this study was developed through data collection which involved literature review, assembly of the system components and the major role it plays towards the drying chamber. The dryer was constructed and testes and results were analysed.