Evaluation of airflow, temperature, and RH in the deep bed dryer for paddy grain with several combinations of floors and air distribution pipes using CFD

Abstract

Abstract The problem of the varying water content of the dried grain is a common problem in the drying process in the pile of grain. An uneven drying air distribution and reduced air pressure when penetrating the porosity and thickness of the grain pile cause that condition. A deep bed dryer is one of the dryers with a forced convection system to carry water content from the grain pile; the thickness of the pile and grain porosity strongly affect this process. The arrangement of the air distribution pipe in a pile of grain is an effort to facilitate air drying so that it is spread evenly in a grain pile and helps the airflow through the thickness of the pile of grains. The arrangement of the shape of the dryer floor is also essential for the effectiveness of the air input from the blower into the drying chamber so that there is minimal loss of air pressure in the plenum and the distribution of air drying becomes evenly distributed. CFD simulations were conducted for four scenarios using a combination of conical and sloping floor shapes, as well as input airflow pipe models in rectangle and circular formation; that combination arrangement is LT1PU1, LT1PU2, LT2PU1, and LT2PU2. The simulation output is analyzed using the SAW method to determine the best combination for constructing a deep bed dryer. The evaluation results on four design scenarios show that the fourth scenario, the LT2PU2 model, has an average distribution value of airflow velocity, air pressure, temperature, and RH of 0.061 m·s−1, 6.07 Pa, 39.35°C, and 44.30%, respectively. Moreover, it gets a preference value of 0.99 as the best model. So, it is worth developing as a Deep bed dryer prototype for paddy grain.