【作者】 王磊；

【导师】 郑先哲；

【作者基本信息】 东北农业大学 ， 农业机械化工程， 2016， 硕士

【摘要】 针对现有活性米干燥设备存在的效率低、品质差等问题,本文通过活性米微波干燥工艺参数优化,微波干燥活性米过程传热传质过程模拟,微波干燥腔内电磁场分布均匀性分析,设计了一套适用于活性米干燥的连续式微波干燥设备,有望提高活性米干燥效率及保证干后品质。在连续式微波干燥机上,进行了活性米干燥试验。以干燥的温度、含水率、爆腰率、GABA含量为指标,采用三因素五水平响应曲面试验设计,分别建立了不同影响因素对各指标的回归模型,优化工艺参数,得到连续式微波干燥活性米的合理工艺条件:微波强度为4.00W/g、风速为2.50 m/s、每循环干燥时间为3.00 min。建立连续微波干燥活性米过程的质热传递模型,可获得活性米微波干燥机内的温度和含水率分布,并在微波强度为1.16 W/g、2.75 W/g、4.34 W/g的条件下,进行活性米温度和水分模型的试验验证,确定传热传质模型的正确性。模拟与实测结果表明,在连续式微波干燥机的干燥末段温度上升缓慢,相应控制微波功率,既减少微波干燥的能耗,同时可以提高干燥品质;连续式微波干燥过程应在干燥段后接缓苏阶段,使活性米物料内外温度达到平衡,干燥效果更为均匀,又可以保证干燥品质。对活性米的微波加热工艺确定及控制过程设计具有实际指导意义。应用电磁仿真软件HFSS对微波干燥腔体的电磁场分布进行分析,比较磁控管不同排列方式下干燥室内电磁场分布的均匀性。通过改变物料层距底部的距离,分析不同高度物料上的电磁场分布。仿真结果表明:料层与磁控管的距离对电磁场分布与强度有很大的影响,且料层距离微波源越近,电磁场强度越大。当物料层距底部100 mm时,磁控管并列排布的方式电磁场分布较为均匀,但当物料层距底部150 mm时,n型排布方式电磁场较为均匀,但以上两种料层位置的品质因数较小,能量利用效率低;当物料层距底部200 mm、磁控管n型排布的电磁场分布更为均匀,整体来看电磁场大部分在3000-4000 V/m范围内,且品质因数较高,微波干燥腔体储存能量的能力强,根据研制微波干燥设备的研制,提高微波干燥的均匀性及微波能的利用效率。根据活性米的微波干燥工艺优化、模拟和仿真结果,设计新型微波干燥设备,由定量进料装置、微波干燥装置、缓苏装置、控制装置部分组成,实现了微波干燥的连续性;微波干燥过程分为干燥—缓苏—再干燥三个阶段,每段干燥均按照电磁场分布均匀性较好和能量利用效率高的原则进行设计,实现活性米的高效率和高品质的连续式微波干燥。更多还原

【Abstract】 For the problem of germinated brown rice(GBR) dryer with low efficiency and poor quality, some researches were conducted to optimize the parameter of germinated brown rice microwave drying process, simulate and analyze the process of the microwave drying of the germinated brown rice. By meansof the analysis of distribution uniformity of electromagnetic field in the microwave drying chamber, a continuous drying microwave dryer was designed for the germinated brown rice to increase drying efficiency and ensure quality.In the microwave drying experiments of germinated brown rice the intensity of microwave, surface velocity, drying duration of per cycle were slected as influencing factors, and temperature, moisture content, fissuring rate, GABA were selected as the objective factors. Response surface design method with three factors and five levels was employed to establish regression models to describe the influcencing factors and objective factors. Optimization of germinated brown rice under conditions of continuous microwave drying were obtained as microwave intensity of 4 w/g, surface velocity of 2.50m/s, the drying time per cycle of 3.00 min.A heat-mass transfer model was built to describe the distribution of temperature and moisture of GBR under continous microwave drying condition. The verification test were done under microwave intensity of 1.16 W/g, 2.75 W/g, 4.34 W/g to deterimine the validity of model developed. Results from simulation and experiments showed the slow temperature increment at later stage of drying process. The control of microwave input rate may decrease of energy consumption of microwave energy, and increase the drying quality of GBR. Tempering stage following the drying stage may increase the temperature consistency within GBR to improve the drying uniformity and quality of GBR. These researches give the guidance for the determination and design of control system of continous microwave dryer.HFSS software was employed to simulate the electric-magnetic fileld within the drying cavity by means of the comparison of magnetron array at different modes. The distributions of electric-magnetic fileld were simulated under different distance of load location to the bottom of microwave dryer. The simulation results show the the distance of material surface and the wave guidance ports of magnetron has the obvious effect on the distribution and intensity of electric-magnetic field. Closed distance may result in the high intensity of electric-magnetic field. Side by side arrangement of magnetrons may generate the uniform distribution of electric-magnetric fileld at material surface under the distance of100 mm to the bottom of microwave dryer. If the distance of material surface to bottom of microwavedryer is in the range of 150-200 mm, n-type arrangement of magnetrons may generate the uniform distribution of electric-magnetic field. However, the distance of 100 and 150 mm had lower the Q-factor than that of 200 mm. The electric field intensity is in range of 3000-4000 V/m at distrance of 200 mm with high stored energy. These researches help to design the new microwave dryer to improve the drying uniform and energy utilization.Based on the results from the optimization and simulation of microwave drying technology, a new continous microwave dryer was designed including the ration feed, microwave drying section, tempeing section, control system. Three stages drying technologies were developed as drying stage, tempering stage and next drying stage considering the distribution uniform of electric-magnetric field and microwave energy utilization. A continous microwave drying process will be achieved by the new microwave dryer to gain the high efficient and qulity.更多还原