Hopper Bottom Semi-Trailer Modified for In-Shell Peanut Drying: Design, Fabrication, and Performance Testing

Abstract

HighlightsComputational fluid dynamics modeling of airflow through the peanut load improved the design process.Peanuts dried using the modified hopper bottom semi-trailer passed inspection at 9.1% moisture content in preliminary tests.Final moisture gradient in the modified hopper bottom semi-trailer consisted of even layers from front-to-back with moisture increasing with depth.Current inspection probe sampling pattern biases inspection moisture measurements lower by not sampling the hopper bottom.Abstract. Hopper bottom semi-trailers (HBST) modified to dry loads of in-shell peanuts would provide several advantages to peanut producers and peanut processing facility operators. Producers who have HBST for transporting grain would have an additional use for their HBST and would reduce harvest delays during peak harvest times when trailer availability is limited from peanut processors. Additionally, smaller processing facilities would gain the economic advantages of semi-trailers without the investment in hydraulic lifts to unload peanut drying van semi-trailers. Before this study, no HBST had been modified to add peanut drying functionality. The objectives of this study were to design, fabricate, and test the performance of drying modifications to a HBST. After review of the functional components needed to dry peanuts and existing structural constrains of the HBST, the components fabricated were an air inlet connection, an enclosed transition space, an air plenum vent, and air exhaust vents on the undersides of the hopper tubs. The number, size, and location of the air exhaust vents were determined using a computational fluid dynamic model. Three test loads of peanuts were dried in the modified HBST during the 2020 peanut harvest season. Measurements were taken at intervals throughout the peanut drying process to assess drying and to monitor air temperature and relative humidity. Results of a test load indicated that the moisture content decreased from 12.9% wet basis (w.b.) to 12.0% w.b. after 8.5 h of drying. Average moisture content was reduced to 11.1% w.b. following an additional 8.6 h without the dryer operating. The sample load official grade moisture content was 9.1% w.b after the rest period. The most important finding was that a moisture gradient persisted in the loads of peanuts after active drying and rest period. The peanuts located at the top of the load had a moisture content of 9% w.b. while those with the highest moisture content of 14% w.b. were at the bottom of the load. The official inspection sampling procedure did not detect the moisture content differences in the test loads. The finding of a persistent moisture gradient will require more investigation and modification of the HBST. Keywords: Computational Fluid Dynamics, CFD, Design, Drying, Hopper-bottom semi-trailer, Moisture distribution, Moisture gradient, Peanuts, Retrofit.