Computational fluid dynamics modeled air speed through in-shell peanuts in drying wagons compared to measured air speed

Authors: McIntyre, Joseph; Butts, Christopher - Chris; Read, Quentin

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2022
Publication Date: 6/13/2022
Citation: Mcintyre, J.S., Butts, C.L., Read, Q.D. 2022. Computational fluid dynamics modeled air speed through in-shell peanuts in drying wagons compared to measured air speed. Applied Engineering in Agriculture. 38(3):489-508. https://doi.org/10.13031/aea.14771.
DOI: https://doi.org/10.13031/aea.14771

Interpretive Summary: After harvest, peanuts are placed into trailers for transporting from the field and for drying. Drying peanuts to a marketable moisture content of 7% is achieved by blowing air with fans through the peanuts while in the trailers. The market quality and price of peanuts is greatly affected by the conditions and consistency of the drying process. The profitability of peanut production is affected by how efficiently energy is used and the amount of time involved in the drying process. Understanding air flow in loaded peanut drying trailers is essential for understanding how the peanut drying process proceeds in a peanut mass in a trailer. Computational Fluid Dynamics (CFD) modeled air flow in a peanut drying trailer loaded with in-shell (farmer stock) peanuts was compared to actual air flow measurements to determine CFD model accuracy and usefulness for studying air flow in peanut masses. CFD modeling makes it possible to investigate the difficult to measure air flow inside drying trailer air plenums and peanut loads. CFD model results reproduced the actually measured air flow rates to within the accuracy limits of the experimentally measured values. The air flow and pressure in trailer plenums was found to be complex even when the resistance to air flow of the peanut load was the same for the entire load which is usually not the case. Model results revealed trailer plenum air flow patterns and pressure distribution could explain the general velocity distribution of low peanut surface flow velocity near the inlet wall and increasing velocity along the length of the trailer. Air flow resistance variations within the peanut load can explain localized areas of increased and decreased velocity in air flow at the top surface of a trailer load of peanuts which has been observed while taking actual measurements.

Technical Abstract: Computational Fluid Dynamics (CFD) modeled air flow in a peanut drying trailer loaded with in-shell (farmer stock) peanuts was compared to actual air flow measurements to determine CFD model accuracy and usefulness for studying air flow in peanut masses. CFD models allow for the investigation of air flow inside the trailer air plenum and peanut load. A trailer load of in-shell peanuts was modeled as a solid with distributed resistance with flow behavior following Darcy’s law. CFD simulations were undertaken using the reported average air volume flow rate and trailer plenum air pressure and with flow rate and pressure reproducing the performance of the fan used in the measurements. To match the computational model to actual air flow measurements the trailer load of peanuts was divided into 40 segments or blocks in the shape of a three-dimensional rectangular grid. The permeability of each of the segments or blocks was varied in a trial-and-error fashion to increase or decrease the surface velocity to match the actual air flow distributions reported at the surface of the peanuts. Model results reproduced the measured air flow rate values to within the accuracy limits of the original measurements. The air flow and pressure distribution in the trailer plenum was found not to be simple even when the permeability of the peanut load blocks had a single value. Model results revealed trailer plenum air flow patterns and pressure distribution could explain the general velocity distribution of low peanut surface flow velocity near the inlet wall and increasing velocity along the length of the trailer. Permeability variations within the peanut load can explain localized variations in air flow at the surface of the peanuts.