Newswise — Column thickness, grain flow throughput, temperatures and airflow rates—these must be taken into account when improving the efficiency of a grain dryer, according to thermodynamics experts, Michael Twedt and Stephen Gent of the South Dakota State University Mechanical Engineering Department.
They’ve been developing a simulation to optimize the performance of corn dryers for Brock Grain Systems of Frankfort, Indiana. Most of the comprehensive work on the thermodynamics of grain dryers was done in the 1960s, according to Brent Bloemendaal, engineering manager at Brock. Recent work has dealt with parts of the process, but no one has tackled the entire system. Evaluating parametersTo optimize the dryer design, Gent and Twedt had to investigate what happens within a column grain dryer, identifying operating conditions and determining how various designs affect the rate at which corn dries.
The drying process affects both the quality of the corn and the amount of energy consumed. “If corn dries too quickly, this can cause stress cracks in the kernels,” Gent says. “If it takes too long, it reduces the throughput.”
Gent and Twedt looked at different dryer designs, configurations and operating conditions. They researched grain drying theory, applying the fundamentals of thermodynamics, heat transfer and fluid dynamics to accurately model what happens within the dryer. Building and validating models experimentallyGent developed three numerical models—one using MATLAB, one with Excel and one using computational fluid dynamics. With each iteration, the simulations have grown increasingly sophisticated and accurate. Feedback from Brock indicates that what the researchers have created is both unique and cutting edge.
All of the models have also been validated experimentally. As part of the project, a small-scale grain dryer was built at the SDSU Feed Processing Unit, a mile north of campus. While the typical drying system processes about 1,500 bushels of corn per hour, the experimental unit processes 25 to 40 bushels per hour. However, the height of the experimental dryer is comparable to a farm-scale dryer. This setup allows the researchers to document what is happening in real time. While they run the dryer, they take measurements, get data and confirm predictions that then validate Gent’s models. The researchers have run tests for three drying seasons: 2011, 2012 and 2013. “We see how everything is converging,” Twedt says. The simulations are continuously improving to more accurately predict what is occurring experimentally.Twedt explains, “We are delivering what the company wants and doing it in a research-based way.” Though the corn-drying project is nearing completion, Bloemendaal hopes to continue working with the researchers to improve and expand the model so that it can eventually be applied to other grains and hybrids. About South Dakota State UniversityFounded in 1881, South Dakota State University is the state’s Morrill Act land-grant institution as well as its largest, most comprehensive school of higher education. SDSU confers degrees from eight different colleges representing more than 175 majors, minors and specializations. The institution also offers 29 master’s degree programs, 13 Ph.D. and two professional programs.
The work of the university is carried out on a residential campus in Brookings, at sites in Sioux Falls, Pierre and Rapid City, and through Cooperative Extension offices and Agricultural Experiment Station research sites across the state.
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