Mathematical Modeling of a Cross-Flow Rice Dryer

Abstract

Abstract. Cross-flow dryers are the most popular industrial-scale rice dryers used in the U.S., yet few mathematical models have been developed and rigorously validated for such dryers. In addition, the glass transition states of rice kernels have never been predicted using a deep-bed drying model. In this study, a mathematical model was developed that describes the distribution of grain and air properties throughout a cross-flow dryer column. The model was validated by performing experiments in a lab dryer that was fabricated to simulate cross-flow drying. The model predictions of grain and air properties were observed to be very close to the measured values in the drying experiments; the root mean square error between the predicted and measured values of rice MC, air temperature, and air RH were less than one percentage point, 5°C, and ten percentage points, respectively. The model was then used to predict the glass transition state of starch present in rice kernels throughout the dryer column. The impact of initial MC on the glass transition states of rice kernels during cross-flow drying was also illustrated. Such predictions of rice kernel material states allow the model to be used for rice fissuring research. Additionally, the model could be applied to optimize drying operation parameters as well as improve dryer design, so as to achieve greater drying capacity, milling quality, and energy efficiency in a commercial drying operation. Keywords: Cross-flow drying, Glass transition, Mathematical model, Rice drying.