Abstract
Small-scale farmers in developing Asian countries have minimal agricultural mechanisms available to them. In the Philippines, postharvest losses in rice production can reach about 36% in the drying process alone. Thus, the inflatable solar dryer (ISD) was developed through the collaboration of the University of Hohenheim, the International Rice Research Institute, and GrainPro Philippines Inc. Although the ISD was successfully tested with different agricultural products, further characterization of the ISD design is required for predicting the drying performance. To this end, the airflow behavior in the ISD was simulated using computational fluid dynamics (CFD) via ANSYS Fluent. Moreover, a thermal model was developed in MATLAB/Simulink by taking into account heat transfer in the heating area and coupled heat and mass transfer within the drying area. Three batches of drying experiments were performed and airflow measurements were taken inside the dryer to validate the models. The MATLAB/Simulink model was further used to predict the drying performance under various weather conditions spanning 10 years. The simulated temperatures and moisture content in the ISD showed high accuracy (mean absolute percentage error (MAPE) < 10%) with the experimental data. The proposed dynamic model provides an efficient computational tool that can be applied to predict the drying performance and to optimize the ISD design.
Highlights
Rice is one of the most produced and consumed staple cereals globally
The results indicate that air velocity decreased along the dryer length and that air velocity magnitude in the x-direction at 0.08 m above the paddy rice verifies the computational results with the experimental data
This study presents computational fluid dynamics (CFD)-Simulink models used to simulate and predict the inflatable solar dryer (ISD)’s performance when drying paddy rice
Summary
Rice is one of the most produced and consumed staple cereals globally. In the AsiaPacific region [1], 144 million rice farms, most of which are less than one hectare in area [2], produce over 90% of the world’s production. In the Republic of the Philippines, postharvest losses found in paddy rice can reach about 36% in the drying process alone [4,5]. The farmers face several challenges when drying paddy rice due to high ambient relative humidity. This can be the case during unfavorable weather conditions or the rainy season, when there is lower solar radiation, or when sudden rainfall occurs. Under these conditions, the safe moisture content of 14% wet basis (w.b.) cannot be reached [6], and grains with high moisture contents are susceptible to attacks by microorganisms, insects, and pests [7]. Some examples are low-cost grain dryers [8], solar tunnel dryers [9], two-stage grain dryers [10,11], and flat-bed dryers [12,13]
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