Computational fluid dynamics modeling of airflow through walnuts in drying bins and bin modification effect upon airflow

Authors: McIntyre, Joseph; Tumuluru, Jaya Shankar; FUNK, PAUL - Retired ARS Employee; Haff, Ronald - Ron; Breksa, Andrew; BUTTS, CHRISTOPHER - Retired ARS Employee

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Researchers investigating how to improve walnut drying equipment need a way to quickly and easily determine airflow through walnuts drying in a bin. A computer modeling method developed for airflow through drying in-shell peanuts was tested to see if it would also work to determine airflow through drying in-shell walnuts. The computer modeling method for in-shell peanuts was found to also determine airflow through in-shell walnuts with model results comparing favorably to results of experimentally measured airflow through in-shell walnuts. The computer modeling method was then used to investigate if adding multiple air tubes to the bottom of drying bins that extended up into the drying walnuts improved airflow. The computer model results indicated that adding multiple air tubes to the bottom of a walnut drying bin did change the airflow but did not effectively improve drying batches of walnuts.

Technical Abstract: Drying walnuts by blowing heated air up through them in conventional drying bins can result in uneven drying and reduce quality and storage time of the walnuts. Experimental testing of new configurations of drying bins is expensive and time-consuming. Researchers need a more rapid and less expensive way to investigate drying bin designs. Computational fluid dynamics (CFD) modeling can be performed much more rapidly than experimental testing and can provide researchers valuable information about airflow through drying walnuts that was previously unavailable to them. The new information from a CFD model also would make it possible for researchers to obtain more precise experimental test results CFD modeling allows researchers to visualize and quantify airflow of the heated air blown up through walnuts and to compare airflow between different bin designs. The CFD modeling method employed to model airflow through drying in-shell peanuts in a drying trailer was successfully applied to modeling airflow through drying in-shell walnuts in drying bins. The airflow patterns rendered from CFD analysis corresponded to measurements obtained from experimental walnut drying bins which validated model results. The experimental walnut drying bins investigated in the study had multiple vented end air tubes of various lengths added to the bottom of the drying bins that extended up into the drying walnuts. Study results indicated airflow quickly slowed moving away from the air tubes and airflow between air tubes was slower when compared to airflow in bins without air tubes. Addition of the air tubes to walnut drying bins did not appreciably increase the overall rate of airflow or result in more even distribution of airflow in the drying walnuts. CFD model analysis indicated that the addition of multiple air tubes to drying bin was not expected to enhance the drying effectiveness of the bins.