Design and simulation of an integrated solar cooker - dryer system

Abstract

Several solar drying technologies exist in Uganda, but marred with multiple deficiencies such as inefficient conversion of trapped solar radiations into thermal energy, prolonged drying times, among others. The aim of this study was to design and simulate an integrated solar cooker-dryer system with a simple biomass cooker using locally available technology and materials. The major component of this study entailed an assessment of existing solar drying technologies. Through purposive sampling, four existing dryers were assessed to gather information that guided the development of a better drying technology. The results from performance evaluation of the existing solar dryers showed a substantial drop in ascorbic acid content by about 27.9 mg/100g of pineapple (Ananas comosus) dried in natural convection drying and 14.5 mg/100 g during forced air drying. It showed that the natural convection solar mode of operation was slowest in drying the samples, with the solar forced air mode being fastest under the prevailing meteorological conditions (which were generally unfavorable from November through to December). The results showed a considerable advantage of forced air solar dryer over the natural convection solar dryer in terms of drying rate and reduced risk of spoilage. In view of alleviating the weather restriction experienced by farmers in crop drying especially for pineapples, it is recommended that dryers be designed with backup cooker for supplementing the solar energy and enhancing airflow to increase the drying air temperature. This results into increase in the drying rate and reduced spoilage. Using performance results as boundary conditions, the temperature distribution of the airflow inside the dryer was visualized using OpenFOAM CFD. Uniform temperature distribution was achieved as a result of forced air system and incorporation of a biomass cooker.