Design and Simulation of Forced Solar Coffee Dryer Using Computational Fluid Dynamics (CFD)

Abstract

The solar drying system is the oldest processing technique utilizes solar energy to heat up air and to dry any food substance loaded, which is beneficial in reducing wastage and preservation of agricultural products used for food such as fruits, vegetables, grains and etc. The current paper outlines the methodology applied for the design and optimization of the solar coffee dryer, which has been achieved through the analysis of the flow field by means of computational fluid dynamics. The prediction of the 3D flow problem was accomplished through the solution of the steady-state incompressible, Reynolds-Averaged Navier-Stoke (RANS) equations with the incorporation of the standard k-ε turbulence model. The measurement and control instrumentation with the inclusion of the innovative, computer-controlled, 3D traverse system that serves detailed surveys of the temperature and velocity inside the drying chamber, are also discussed. The solar collector and dryer system configuration has been optimized for minimal pressure drop by incorporating guide vanes and minimizing flow separation tendency using numerical simulation on ANSYS. High collector outlet temperature and efficiency were observed in a collector with flat absorber plate. The results obtained during the CFD simulation period revealed that the temperatures inside the dryer and solar collector were much higher than the ambient temperature during most hours of the day-light. Within 6hours, coffee bean dried from 29% moisture content to12.1% on a clear sunny day and within 7hours from 17% moisture content to 11.1% on partially overcast day. The dryer exhibited sufficient ability to dry coffee beans reasonably rapidly to a safe moisture level and simultaneously it ensures a superior quality of the dried product. Average thermal efficiency of the dryer was found to be 50.6% for clear sunshine day and 36.8% for partial overcast day.