4. Conclusions and recommendations for future work
One of the most important potential applications of solar energy is the solar drying of agricultural products. Losses of fruits and vegetables during their drying in developing countries are estimated to be 30-40% of production. The postharvest losses of agricultural products in the rural areas of the developing countries can be reduced drastically by using well-designed solar drying systems. Among the different types of solar dryers, the indirect mode forced convection solar dryer has been demonstrate to be superior in the speed and quality of drying. Since the solar air heater is the most important component of the indirect solar drying system, improvement of the solar air heater would led to better performance of the drying system. Therefore: more studies to investigate and improve the thermal performance of double pass flat, v-corrugated and finned plate solar air heaters is still of considerable interest. Incorporating of sensible and/or latent heat storage media within the solar drying systems accelerate the drying process during the night time and low intensity solar radiation periods and exclude the need for using auxiliary heat sources during low solar radiation seasons. The latent storage media is preferable compared to the sensible store media to achieve nearly constant drying air temperature during the drying process. However, the phase change materials should be investigated in view of their chemical stability and compatibility with the containing materials before their integration within the drying system. Purthermore, before using the drying systems on large scale, computer simulation models must be performed to simulate the short and long terms performance of the drying systems with and without the storage media to estimate the solar drying curves of the dried products and investigate the cost benefits of the solar drying of agricultural products.