Thin-layer drying rates of corn hybrids related to performance of high-speed, high-temperature batch dryer

Jose Helvecio Martins, Purdue University

Abstract

The effect of corn variety on both drying efficiency and thin-layer drying rates was investigated. A farm size batch dryer was modified and used for drying several corn hybrids grown in 1985, 1986 and 1987. Fuel consumption, airflow rates, plenum and grain bed temperatures, and exhaust air relative humidity were determined for the batch drying tests and drying efficiency (kJ/kg of water removed) was calculated for each test. Hybrids with either fast and slow thin-layer drying rates were used in the tests. In the batch drying tests, drying efficiency for a fast drying hybrid (FRB73 x MO17) was significantly (5% to 10%) better than batch drying efficiency for slow drying hybrids (FUNKS G4522 and FR35 x FR20A). High levels of hybrid physical damage also reduced the energy required to dry by approximately 10%. Thin-layer drying tests using a drying temperature of 93.3$\sp\circ$C and air velocity of 0.47 m/s (1.53 m/s in 1985) were performed on samples taken from every batch drying test. Different hybrids had different thin-layer drying rates. Regression analysis demonstrated that drying efficiency was dependent on thin-layer drying rate, initial moisture content, batch drying time, and damage index. For both 1986 and 1987 two hybrids, one with a fast and the other with a slow thin-layer drying rate, were selected for modeling using Thompson's thin-layer drying equation. Equations for the parameters of Thompson's model as a function of temperature and initial moisture were obtained. The new thin-layer models were incorporated into both the Thompson and Michigan State University (MSU) cross flow computer programs. Drying efficiency and time required to dry were predicted by both programs and compared with drying efficiency determined in the field tests. The results predicted by the two models were nearly identical. However, Thompson's model appeared to be more efficient in terms of user time and memory in the computer. The simulation programs showed that fast drying hybrids can reduce the energy required to dry by 5% to 10%. This hybrid effect is greatest for high initial moistures, intermediate drying air temperatures (approximately 80$\sp\circ$C) and high airflow rates (approximately 111 m$\sp3$/min-t which is equivalent to 100 cfm/bu).

Degree

Ph.D.

Advisors

Stroshine, Purdue University.

Subject Area

Agricultural engineering

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