| Paddy rice is the main grain crop in China.It’s important to study the basic thermo physical parameters and changes in actual storage of it.It’s of great significance to minimize the postpartum loss of rice and ensure it quality and safety.In this paper,we mainly study changes of thermal conductivity,specific heat capacity and respiration intensity of rice during processing and storage,and the influencing factors.The model is simulated and verified.Mainly include the following aspects:(1)Determination of thermal conductivity of rice by DRE-20 thermal conductivity tester.The bursting rate and thermal conductivity of rice were measured by natural wind drying,thin layer hot air drying,fluidized bed drying.The effects of different drying methods on the thermal conductivity of thermal probe and the relationship between bursting rate and thermal conductivity were investigated.The results showed that the thermal conductivity of rice increased linearly with the water content,and the thermal conductivity of different rice varieties was different.There was a significant correlation between precipitation rate and bursting rate,thermal conductivity and bursting rate.With the same drying method,the higher the drying temperature,the faster the precipitation rate and the greater the bursting rate.The thermal conductivity showed a non-linear increase.The same treatment temperature,thermal conductivity values:fluidized bed drying>thin layer of hot air drying>natural drying.The effect of fluidized bed drying on the thermal conductivity of rice is greater than that of thin layer hot air drying.(2)Determination of specific caloric value of rice by specific heat capacity tester.The specific caloric values of rice under different varieties and water conditions were studied.The results showed that the linearity of the specific caloric value and the water content of japonica rice and indica rice were linear.The linearity formula of japonica rice was Cm = 0.091 M + 0.3477 and R2=0.9328.The linear formula of specific caloric value of indica rice was Cm = 0.0719M + 0.6867,R2 = 0.9736.The empirical formula is more similar to that of the indica rice fitting formula,and the Wratten empirical formula is more suitable than the Haswell empirical formula.(3)The natural late maturing of late japonica rice was carried out with natural drying,fluidized bed drying and hot air drying.The indexes of physiological quality,processing quality index and taste quality index were measured during maturing period.Correlation analyzed between the different qualities.The results show:Paddy’s respiratory heat is closely related to the ripening time,which is less affected by the treatment.The respiration heat of rice in the early maturing stage was large,and the later stage became stable and gradually decreased.Drying treatment can reduce the respiration rate of rice to a certain extent and reduce the degree of inhibition of aerobic respiration.The correlation between physiological quality and processing quality,respiration heat,germination rate and roughness rate and whole milled rice rate were significant,and the correlation with water was significant,and the correlation with the bursting rate was not significant.The correlation between the physiological quality and the taste quality,the germination rate and the taste value and the fatty acid value were significant,and the correlation between the respiratory heat and the taste value and the fatty acid value was significant.The quality of natural drying rice is closest to the quality of natural ripening rice.The dryness of rice during the ripening period should be given priority to natural drying,and the second is the low temperature thin layer hot air drying.(4)The quality of rice under different storage conditions was studied.The changes of respiration intensity of rice were studied under the conditions of temperature,moisture,impurities and pests.The numbers of pests,molds,the values of fatty acids and the taste value were measured to monitor the change of rice quality.The results showed that water had a significant effect on the respiration rate of rice,and the temperature had a significant effect on respiration intensity,and the impurity content had no significant effect on respiration intensity.During the storage of rice priority control of water,followed by temperature.In a certain range,with the increase of water and temperature,pest damage to rice increased.In high temperature and high humidity environment mold is the main factor affecting the rice loss.Therefore,In high temperature and humidity environment,rice storage should first pay attention to the impact of mold,otherwise we should pay attention to pests(5)The temperature fluctuation of 0.5m,2.0m,3.5m,5.0m and 6.5m grain depth was analyzed by software Fluent6.3.26,and the temperature distribution cloud was analyzed and analyzed.The following conclusions:cooling and ventilation,the bottom of the grain near the ground cage into the outlet at the grain temperature drop faster than the top grain layer.The relative error between the actual value of the temperature of the grain and the simulated value is between 3.4%and 7.2%.The model can be used to simulate the mechanical ventilation. |
