| Chrysanthemum is one of the most important economic crops,and the selection of drying technology has a great influence on the quality of chrysanthemum.At present,there is no lack of research on the drying process of chrysanthemum,but most of the existing studies are only limited to a specific process,and lack of in-depth study on the drying characteristics and heat and mass transfer in the drying process.In the actual production,in view of the high moisture content of chrysanthemum,the mechanical drying method is used to dry the chrysanthemum.Only when we fully understand the drying characteristics of chrysanthemum and master the heat and mass transfer mechanism in the drying process,we can better guide the practical production.The chrysanthemum as the research object,based on the study on the drying characteristics on the attempt on the flow field distribution of Chrysanthemum in drying process was simulated by FLUENT software.in order to improve the drying effect of chrysanthemum.The main contents and results are as follows:(1)Based on the experimental research on several fixing technology of chrysanthemum,the closely related indexes and chrysanthemum aroma quality,establish an evaluation index system of chrysanthemum quality.According to the factor weight to calculate the comprehensive score of microwave heating was 8.55,far higher than other fixation methods,and through the comprehensive scoring situation and the fixation treatment of chrysanthemum better than non fixation treatment.So as to get the microwave heating chrysanthemum can effectively improve the aroma quality of chrysanthemum.(2)The treatment of microwave heating after using for Chrysanthemum by microwave hot air drying experiment,and using the software of Design-Expert 8.05 surface design of experiment.Experiment with chrysanthemum color value,response power consumption,amino acid content,the electronic nose value as the objective function,establishes the mathematical regression model of dry chrysanthemum,are obtained the interaction of various factors influence on the objective function,the research on the drying characteristics of chrysanthemum finished.On the basis of considering the drying quality and drying energy consumption of chrysanthemum,the optimum drying process of Chrysanthemum under this experimental condition is as follows:the Microwave Power 400W,the layer thickness of 3cm,the fixing time of 3min,the temperature of hot air 55.(3)The basic physical parameters of chrysanthemum were determined by experiments.The actual density and bulk density of chrysanthemum were 465.6Kg/m3 and 211.8Kg/m3,respectively.The porosity of chrysanthemum was 54.51%,and the average diameter of chrysanthemum was 0.031m.Based on the law of conservation of mass,momentum and energy,combined with the theory of multiphase flow,the governing equations and mathematical models of hot air drying were established,which laid a foundation for the simulation of flow field.(4)For drying equipment,set up the physical model of the dryer;through the pretreatment,the GAMBIT solver of FLUENT software,the model was meshed,parameter determination and calculation,the distribution of the field in the dryer internal velocity field,pressure field,temperature of Chrysanthemum in the drying process,the numerical simulation of flow field distribution chrysanthemum drying process.The simulation results show that there are obvious differences in air distribution between different drying layers.When the drying time is 3h,the uniformity of temperature field presents Z=0.11m plane,>Z=0.7m plane and>Z=1.38m plane.(5)In order to ensure the accuracy of the simulation results,the simulation results of the temperature field and the measured results are compared and analyzed.The relative errors are found to be within 8%,which fully confirms the reliability of the simulation results.The analysis results also show that the flow field simulation analysis has a certain reference value for improving drying quality and optimizing drying method. |
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