Desenvolvimento de uma bancada experimental de secagem com roda dessecante e aquecimento por energia solar fotovoltaica

Abstract

This study presents the modifications made on a drying testbench with electrical heating of the process airflow to include the installation of a desiccant wheel, that heats and dehumidify the process air The purpose of the bench is to perform sample drying curves at temperature levels regulated by PID controllers, allowing drying curves analysis under different psychometric air conditions. This study includes the reform of the drying test bench with air heating by electric resistances, the desiccant wheel installation, the assembly of a data acquisition system, the drying experiment and the analysis of drying curve results. The components consist of fans, mechanical flow controller and electric heating resistances with temperature controller. The measured variables were dry bulb temperature (DBT), relative humidity and velocity of the air, temperature and mass of a sample in a semi-analytical scale. Drying experiments were performed with banana samples at 50 °C DBT and with apple at 71.5 °C DBT, in order to compare the performance of the drying test bench with desiccant to the bench with sensible heating under the same initial air conditions and sample mass. Also, the economic viability of a photovoltaic system on the drying bench was analyzed. Results showed that the drying time for the bench with desiccant wheel was reduced by 22.7% for banana samples, compared to the electric heating bench, and 50% for apple samples. Power consumption economy, due to temperature PID control on the resistance group during the drying process, was 53.5% for banana and 66% for apple samples compared to the consumption of the continuous use of resistances. The off-grid photovoltaic system sizing at the drying bench presented a 46.7% lower cost for the bench with desiccant wheel compared to the bench with electric resistance heating. The grid-tie photovoltaic systems showed an average cost reduction of 40.13% compared to the off-grid photovoltaic systems.