Performance evaluation of green peas drying by using a solar air heater with baffles inserted on the back plate: a numerical and experimental approach
摘要
In this paper, green peas drying was carried out in a forced convection solar dryer with additional electric heater. A numerical approach has been taken to solve the one-dimensional unsteady heat transfer of the air collector and the coupled heat and mass transfer of green peas. Shrinkage of green peas during drying is also considered. Transverse baffles placed on the bottom plate of the collector to improve heat transfer were investigated in this study. The drying chamber includes four trays and has a capacity of 8 kg of fresh green peas. An outdoor experimental model was set up to confirm the calculation results with a maximum error of 8%. Results show that the average moisture content difference between tray 4 and tray 1 is up to 0.25 kg kg−1 (dry basis). The moisture difference in the center of green peas of tray 4 and tray 1 is up to 0.35 kg kg−1. The heat transfer rate of the baffled solar air heater is 1.6 times that of a smooth air collector. Increasing the successive ratio of baffles increases the specific energy consumption from 3.53 to 3.75 MJ kg−1. Also, the payback period of current dryers has increased from 3.36 to 3.66 years. Dryer efficiency reaches 27.4% at a drying temperature of 60 °C. This efficiency decreases with increasing drying temperature and air flow.