| Seed is the most fundamental agricultural production material.Its quality guarantees the national food safety.The seed quality in storage is affected by many factors,such as ambient temperature,relative humidity,gas composition,microbes,and pests.If these factors are not controlled well,it will accelerate seed deterioration and threaten seed health.Based on the analyzing the matching characteristics of seed and storage environment,This dissertation concentrated on experimental studying the key technique for temperature regulation of cold storage strip,the key technique for dehumidification regulation of warehouse environment,the key technique for controlled atmosphere(CA),designing and fabricating an intelligent gas regulation case.To guarantee the safety storage for rice seed,the main work were shown as follows:(1)Matching characteristics of seed and storage environmentThe effect of the relative humidity of the environment and packing materials was studied.Results showed that the relative humidity of the environment had great influence on the rice seed moisture content.The greater the relative humidity was,the faster the seed water absorbed,the higher the seed moisture content increased.The sorting of wet insulation property of packing materials under high humidity(95%)environment was aluminum foil bag > plastic bag > woven bag > kraft paper bag > stainless steel plate.A gas regulation insect test platform was developed.Taking two pests Tribolium castaneum Herbst and Sitophilus oryzae Linnaeus as examples,the effect of gas composition on the insecticidal effect of rice seed in storage was studied.Results showed that different storage insects had varying reaction to carbon dioxide(CO2)gas;the lower the oxygen(O2)concentration was,the higher the mortality of the two insects was;Tribolium castaneum Herbst was more sensitive to die for the oxygen than Sitophilus oryzae Linnaeus at initial stage.However,the mortality of the two insects became very close with time going on.The mortality of the mixture of O2 and CO2 to the insects was higher than every one of the two gases.The effect of the temperature on the mortality of insects was coupled by the gas composition.The proper gas parameters of the temperature,CO2 concentration and O2 concentration was 16±1℃,30% and 5% respectively.(2)Temperature regulation of cold storage strip.The temperature regulation test device for cold storage strip was set up.The effect of some key factors such as air duct length,air duct cross-sectional area and wind speed of fan on the temperature regulation of cold storage was studied.Results showed that the air duct length had no significant effect on the temperature of various points in the storage room,but had significant effect on the relative humidity;the standard deviation of the temperature and variation coefficient of the relative humidity of sampled points in the storage room were both the smallest;the increase or decrease of air duct had disadvantage to the distribution of the temperature and relative humidity fields.The air duct cross-sectional area had more influence on the relative humidity than the temperature.With the decrease of the opening area of the air duct,the flow field became smaller,leading to the uniform distribution of the temperature filed and relative humidity field.Considering the combination of refrigeration speed and flow uniformity,the air volume would be suggested to select 0.09 m3/s.When the fan gear was in the tenth,the standard deviation of temperature and variation coefficient of relative humidity were both the smallest and the comprehensive performance was better.(3)Dehumidification regulation of warehouse environmentThe dry air duct form of the converter dehumidification system was designed.The effect of air duct location,air duct diameter and the number of holes on the duct on the effect of dehumidification was studied.Results showed that the dehumidification ability and efficiency were both best when the air duct located 0.65 m from the central of storage,and the diameter of the duct and the number of holes were 40 mm and 20 respectively.The dehumidification quantity in the unit time reached 71.74g/kg which three times of the lowest.The sorting of the factors affecting the dehumidification effect were the number of holes,the diameter of the duct and the position of the duct.Numerical simulation and test of moisture content of moisture field and different packaging seeds in dehumidification process were perin the software environment of COMSOL Multiphysics 5.0 version.Results indicated that the environment with 50% RH was suitable for seed storage;the maximum relative error between the simulation and the test was only 1.2%,indicating that the model was effective.(4)Controlled atmosphere for the storage environmentThe gas mixture system for insects control and liquid filling gas regulation system were designed.The liquid nitrogen source and liquid CO2 gas source were added to the design of the gas regulation system to adjust the concentration of CO2 and O2.The effect of the opening area and wind speed on the oxygen decrease time,distribution uniformity of oxygen concentration,temperature and humidity in the storage room was studied.Results showed that the greater the wind speed was,the more full the air exchanged,leading to more uniform distribution of oxygen concentration.The larger the opening area was,the more uniform the distribution of oxygen was.The greater the wind speed was,the better the uniformity of temperature and relative humidity was.The increasing of opening area can help to accelerate the exchange of flow field and the uniform distribution of temperature and humidity fields.The results of germination rate showed that short term pneumatic storage did not affect seed germination.(5)Design and test of smart storage caseAn intelligent pneumatic storage case was designed and fabricated.The control system was based on distributed control system of CAN bus,achieving multi task parallel operation.The man-machine interface was developed for a touch screen.Test result of bus communication indicated that the utilization rate was good,the bandwidth allowance is enough,the error rate is 0%,and system ran stably and reliably.Cold strip temperature,temperature and humidity in storage room were tested during charging and discharging process.It took 9h to charging once in a natural state,and can keep the storage room temperature with 13-15℃ for 12 h.Results indicated that the storage box has good heat preservation and closeness,and satisfies the requirements of seed storage. |
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