A new air recirculation system for homogeneous solar drying: Computational fluid dynamics approach

Improvement of air flow distribution, air velocity and temperature inside a mixed greenhouse dryer was numerically investigated using 3D CFD ANSYS FLUENT code. The study was performed considering six different locations of axial fans inside the greenhouse. Additional elements such as a false ceiling and front and back internal walls were included in some configurations to analyze their contribution in improving the air distribution. Numerical simulations were focused on dynamic fluid models in order to select the best configuration to achieve homogeneous air distribution and velocity among the six proposals. Then, the temperature distribution was analyzed considering the contribution of solar energy in the best-selected greenhouse configuration. Additionally, the Discrete Ordinate (DO) model was used to simulate the mechanism of heat transfer from solar radiation to the greenhouse. The results showed that installing an air recirculation system (including: axial fan, false ceiling, back and front walls), into the greenhouse can increase the air velocity in the drying chamber from 0.71 m/s to 1.5 m/s and the temperature from 315 K to 360 K, which represent an increase of approximately 111.26% y 11.11%, respectively, compared with the greenhouse without an air recirculation system. This improvement could result in the reduction of drying time and a homogeneous moisture content in dry products.