1.1 BACKGROUND TO THE STUDY
Drying is one of the oldest methods of food preservation. For many years, people have been preserving agricultural products by drying until caning was developed at the end of the 18th century (Ekechukwu and Norton, 1999). The importance of dried foods cannot be overestimated as the kitchens and food stores in any country will confirm the quantity and diversity of dried food in use. Drying is essentially a process of moisture removal due to simultaneous heat and mass transfer. It is a classical method of food preservation which provides longer shelf life,lighter weight for transportation and small space for storage. Drying could be of various methods such as open sundrying,direct and indirect solar drying etc.
Open sundrying which is the most commonly used method to preserve agricultural products like grains, fruits and vegetables in most developing countries. Such drying under hostile climatic conditions leads to severe losses in the quantity and quality of the dried product .This losses related to contamination by dirt, dust, bird droppings and infestation by insects, rodents and animals as well as the quality of the products being degraded due to uncontrolled heat in sundrying even up t the extent that the food products are inedible (whitefield, 2000). Therefore the introduction of solar dryers in developing countries can reduce crop losses and improve the quality of the dried product significantly when compared to the traditional methods.
Solar dryers could be either Natural convection of forced convection solar dryers. The Natural solar dryer is such that it controls the drying process and protects the agricultural produce from contamination by insects, dust, bird droppings, invasions by animals, and in comparison to Natural solar dryers, it generates higher temperatures, lower relative humidity, lower produce moisture content and reduce spoilage during drying process in addition, it takes less time and is relatively inexpensive when compared to artificial mechanical drying method (Ged-Gujur at Energy development Agency, 2003, www.geda.com). Dried foods using natural convection solar dryers are quality products that can be stored for extended nutritive values.
1.2 STATEMENT TO PROBLEM
A country which cannot feed its people is bound to fail, and so food production without adequate preservation amounts to waste. In Nigeria, subsistent agriculture amounts to a major percentage of food produced and so due to inadequacy of storage facilities and proper preservation, all round year availability of farm produce is mostly difficult. Natural convection solar dryers which tackles the major drawbacks of the usual sundrying has been usedin most countries to solve problems associated with economical food preservation. The target has always been to supply this natural convection solar dryers to the rural farmers in a cheap and portable manner.
The focus of this project is to supply drying need at a cheaper price. It is to design and manufacture a natural convection solar dryer which requires little or no maintenance and can be easily accessible to the rural woman.
1.3 AIM AND OBJECTIVES
The aim of this project is to design and fabricate a portable mobile natural convection solar dryer which can be easily moved from place to place and is suitable for drying sliced yam. In order to achieve this aim, the following objectives would be pursued;
To examine different drying methods.
Identify and characterize different factors that affect drying.
Examine annual weather conditions in the Benin city metropolis.
Calculate and determine relevant dimensions.
Identify and characterize different insulating materials.
Fabricate and test the solar dryer.
In pursuance of the objective of this project and with a view to achieve the aim, adequate literature would be reviewed in method of drying, regular data would be collected a basis for designing and fabricating suitable natural convection dryer. The dryer would be tested and the efficiency computed.
1.5 RELEVANCE OF WORK
The outcome of this work would allow food producers to ensure adequate drying of sliced yam produce, allowing for the availability of the dried product all season of the year, reducing food wastage due to crude, ineffective and expensive drying techniques.
1.6 SCOPE OF WORK
This work is limited to the drying of sliced yam produce. It is a natural convection solar dryer and there would be no moving part. Annual data collection is limited to three years. Weather conditions would be suitable for Nigerian environment suitably Benin City.