การเร่งอัตราการอบแห้งข้าวเปลือกชื้นด้วยเทคนิคสนามไฟฟ้าสถิตแรงสูง

Abstract

The enhancement of paddy drying rate using high voltage electrostatic field project was conducted to study the thermo-physical properties and the drying kinetics of fresh paddy with high electrostatic field treatment. For determining the rice property, apparent density, specific heat capacity, percentage of void and equilibrium moisture content was studied. The results concluded that apparent density, specific heat capacity and percentage of void were linearly related to moisture content. An equilibrium moisture content determined by Henderson (1952) model was the best fitting model to the experimental results for Lek Nok Pattani and Sung Yod rice while Chung and Pfost (1967) model shows good correlation to experimental data of Khao Dawk Mali 105 paddy. To determine drying kinetic of paddy with initial moisture contents of 25.3-34.8% dry-basis, paddy was discharged with high voltages of 6-10 kVa0, electrode gaps of 2 and 3 cm and discharges time of 20-40 min. After electrical treatment paddy was batch dried by hot air temperature of 40-70°C with an air flow rate of 1.9 m/s. The results showed that drying rate directly depended on electrical voltage, electrical discharge time and drying temperature exponentially as a function of drying time. To determine quality of rice, it showed that high voltage had no effect on physical quality (germination, whiteness and yellowness value) however, high voltage has effect to head rice yield. Consequently, high voltage and drying temperature had insignificant effect on the chemical quality of rice. From evaluation of the physicochemical quality and sensory test, it showed that high voltage and drying temperature can accelerate rice aging. The overall acceptability was slightly decreased whilst aroma and glossiness value had insignificantly changed at confidence level of 95 %. Finally, from determination of specific energy consumption, the dried rice with high voltage electric field treatment tended to be slightly lower compared to the control sample.