Microwave drying characteristics of rice and its thermal model injection
There are two stages in grain drying process under microwave drying. The drying power is 0.2W/g or below 0.2W/ g, the germination rate is high, and the waist burst rate is low. The fatty acid content of dried storage is lower than that of hot air. A moisture and heat transfer model for microwave drying of cereals was established, and the coefficient of moisture diffusivity was determined.
Keywords: microwave drying model for rice drying
Different from hot air and other drying methods, microwave drying has broad application prospects because of the uniform diffusion of moisture on the inner surface and the fast drying speed caused by the direct heating of materials after absorbing microwave energy. After harvest, the rice needs to be dried and stored safely. The drying method and reasonable process are very important. Up to now, little research has been done on microwave drying of rice, and the drying characteristics are not clear yet. In this paper, the microwave drying characteristics of paddy were studied, and a mass-heat model was established to provide reference for further research and production application.
Experimental equipment: microwave drying equipment. It is improved by the WEG 600 microwave oven. The working frequency is 2450 Hz, and the output power can be fixed. The change of exhaust humidity is realized by changing the speed of fan.
Rice: late japonica rice. Harvest the wet valley after threshing with plastic seal.
It is stored at about 4 degrees Celsius. Before drying, the initial moisture was determined according to GB5479 -85 standard. When dry, evenly distribute the grain on the insulation network.
Radiation thermometer: TH I -400 (made in Japan), precision +
1 degrees centigrade.
Thermal analysis balance: JA 5001, precision + 0.01g. 1 test method
The moisture content at each time was calculated by grain weight and initial moisture. The wind speed is measured by the thermo sphere anemometer QDF -3, with an accuracy of + 0.1 m/.
S. The germination rate was measured according to GB5520 -85 in the electrothermic thermostat.
The detonation rate was determined by GB5496 -85. Fatty acids were extracted by GB5510 -85.
3.1 the drying process of rice can be divided into two stages under microwave drying.
3.2 when the drying power is 0.2W/ g or less, the germination rate of rice is high and the waist burst rate is low. After 3~6 months of microwave drying, the content of fatty acid in paddy was lower than that in hot air drying.
3.3 a model of moisture and temperature changes during microwave drying of rice was established.
The calculated results are basically the same as those measured.