Mathematical modeling of grain cooling in bunker systems with radial air distribution
DOI:
https://doi.org/10.31734/agroengineering2023.27.101Keywords:
grain, cooling, heat exchange, air, bunker, radial airflowAbstract
The need to create or improve the existing grain cooling systems after drying, which operate separately from grain dryers (portable grain coolers), is currently caused by the requirements to increase the efficiency of dryers on farms (by using cooling chambers as drying units) and the emergence of integrated grain dryers with solid fuel furnaces that operate with periodic loading. One way to address the challenges of creating portable grain coolers after drying is to utilize ventilated bunkers with radial distribution of external atmospheric air for grain cooling. To ensure their effective operation and to align the productivity of the cooler with that of the dryer, it is essential to study the patterns of heat exchange in non-steady-state conditions and determine optimal structural and operational parameters. Such research is best conducted by developing mathematical models of non-steady-state thermal processes during the cooling of heated and dried grain. The present work proposes a developed mathematical model of the grain cooling process in bunker systems with radial air distribution based on a two-level hierarchy: microkinetics and macrokinetics of grain cooling.
At the microkinetics level, the equation of non-steady-state heat conduction for a grain particle (or a grain layer element) with a negative heat source is employed, along with the boundary conditions for convective heat exchange. At the second level, the grain cooling model is represented by a differential equation for heat exchange of a ring-shaped grain element with radially moving cooling air. The solution to this equation is implemented in the Mathematica computer environment for two airflow scenarios: from the center of the bunker to the outer surface and in the opposite direction. The results of the calculations are graphically illustrated. It has been determined that the temperature non-uniformity of grain along the radial coordinate of the layer during the final stage of the process, with air filtration from the external cylinder to the central one, is 20-30 % lower than when air filtration is carried out in the reverse direction.
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