Performance Investigation of a Chimney-Dependent Solar Crop Dryer for Different Inlet Areas with a Fixed Outlet Area

The paper describes the performance of a direct-mode solar crop dryer with a solar chimney. Tests were performed for three differently inclined drying-chamber roofs, each with three inlet areas for a given exit area. Cassava was used as the test crop. The results show that the increase in the inlet area for a given exit area can improve the ventilation in the dryer. However, this does not necessarily improve the drying performance of the direct-mode dryer. A wide inlet area for a given exit area can only improve the drying performance of the direct-mode dryer in a geographical location of low relative humidity. It is therefore not advisable to just copy the design of a direct-mode dryer from one location to another without regard to the ambient relative humidity. The designer and builder of the dryer must consider the relative humidity as a prime factor in the design and construction of direct-mode dryers, which are highly sensitive to the ambient relative humidity. 1. Introduction The majority of the citizens of most developing countries live as rural-based farmers. The economies of those countries are heavily dependent on agriculture. The proportion of rural-based farmers in Ghana in 2004 stood at 65% [1]. Yet, the food security remains a great challenge in developing countries. There is normally an overabundance of farm production during the harvest season. Farmers are then forced to sell their production at very cheap prices due to lack of appropriate facilities for processing and storage. The production becomes scarce off-season, even for the farmers. Such a development discourages farmers from more food in the following year. Thus, farming in the rural areas becomes increasingly unattractive. In Ghana, the youth keep drifting from the rural areas into the cities for nonexistent jobs, leading to slum development with increased crime rates. Furthermore, this problem of food insecurity affects the agricultural economy of Ghana negatively. The farmers need to add value to their crops by drying them to reduce the moisture content to an appreciably low level so that the crops can be preserved in their prime marketable condition to enable them receive remunerative prices. The farmers normally dry their crops by spreading them on mats in the open sun. This way of crop drying is not that efficient, and the crop is exposed to rain, pest, and other forms of unhygienic conditions. Crop drying involves the removal of moisture from a crop into the surrounding air. Generally, moisture evaporates from a crop into the surrounding air whenever the vapour pressure