Study On Drying Mathematical Model Of Hawthorn Using Microwave Coupled With Hot Air And Drying Machine Design

Microwave coupled with hot air drying combines microwave drying and hot air dryingprinciples, it is a drying method that microwave and hot air affect on dry material together, andhas the advantages of microwave drying and hot air drying. Hawthorn is a kind of nutrients fruitwith medicinal and edible function. Dried hawthorn film is the main raw material for furtherprocessing, it is also a favorite food. Therefore, it has a great market potential. Not only are thenutrients of hawthorn slices dried with microwave coupled with hot air higher than that ofconventional drying method, but also drying time is shorter, and the drying efficiency of themicrowave coupled with hot air is high. Drying characteristics of the microwave coupled withhot air was analyzed in this paper, and the drying kinetics model and the drying process model ofmicrowave coupled with dry hot air for hawthorn were established, the drying process conditionswere optimized. It was compared to other drying method in terms of the energy consumptionefficiency and quality of the dried product, and a set of microwave coupled with hot air dryingequipment that suitable for fruits and vegetables was developed through detailed analysis anddesign. The main contents are as follows.1. Drying principle and characteristics of microwave coupled with hot air were studied inthis paper. The moisture of dried material was transferred and diffused under the common actionof the difference of temperature, concentration and pressure during microwave coupled with hotair drying, and the moisture of dried material was evaporated from the material surface, and so asto achieve the drying purpose. under the common action of three drying facts, drying time ofmicrowave coupled with hot air is short, drying speed was fast, and so as to achieve the dryingpurpose of improving the production efficiency.2. The influence law of the drying rate and drying moisture ratio that was effected bymicrowave power density, hot air temperature and hot air velocity was researched and analyzed.The effective diffusion coefficient value of hawthorn microwave coupled with hot air drying wasthree times than that of hawthorn hot air drying. It was also shown that the drying rate ofmicrowave coupled with hot air was faster than that of conventional drying methods.3.12mathematical models were selected from classic drying kinetics models and wereregarded as the research object. Weibull distribution model had a maximum value of R2and aminimum value of and RMSE through using R2, and RMSE as evaluation criteria and using experimental data that were fitted, so it was considered to be the best model among12mathematical models, and can represent the drying behavior of hawthorn microwave coupledwith hot air, and can predict drying moisture ratio of hawthorn.4. WHADK model, which was also a drying kinetics model of microwave coupled with hotair, was deduced through using the energy conservation law WHADK model had the averagevalue0.99of the correlation coefficient R2, the average value0.0.001127of and the averagevalue0.030786of RMSE through using R2, and RMSE as evaluation criteria and usingexperimental data that were fitted. This was able to explain that WHADK model can predictdrying moisture ratio of hawthorn. WHADK model of the larger difference between thepredicted values and experimental values was modified according to the difference valuebetween SR and SE. After moisture ratios were revised, graphs of experimental and predictedvalues were consistent. At this time, WHADK model was considered to be reasonable, and it cancomprehesively predict the moisture ratio5. On the basis of single factor analysis, the scope of the microwave power density, hot airtemperature and hot air velocity was determined. We determined the weight drying rate anddrying quality mathematical model according to the secondary orthogonal rotation designprinciple and analysis of variance, and determined the weights of the weight drying rate anddrying quality index according to the hierarchy analysis method, and obtained comprehensiveevaluation mathematical model, and determined optimum drying process and comprehensivedrying process of each evaluation index.6. Drying process of hawthorn microwave coupled with hot air was simulated andoptimized through using BP neural network. Test samples were input to the trained model andsimulated and tested. Relative error values of experimental and simulation results were within10%. This can explain that BP neural network model can roundly predict drying processparameter changes of actual hawthorn microwave coupled with hot air, and further provided atheoretical basis and guidance for the actual production of hawthorn microwave coupled with hotair drying.7. In the aspect of energy consumption efficiency and product quality, the comparison studyof the hawthorn slices that were dried using the method of hot air drying, microwave drying andmicrowave coupled with hot air drying were done. For energy consumption efficiency, Theenergy consumption efficiency of microwave drying and microwave coupled with hot air drying is far better than that of the hot air drying, but the energy consumption efficiency of microwavecoupled with hot air drying was slightly less than that of the microwave drying. For productquality, the rehydration of microwave coupled with hot air drying was better than that of the hotair drying, but the rehydration of microwave coupled with hot air drying was was slightly lessthan that of the microwave drying. The organic acid content, vitamin C content and chromaticaberration of dried hawthorn slices were better than those of hot air drying and microwavedrying.8. According to drying optimization process parameters of hawthorn slices microwavecoupled with hot air, drying machine of microwave coupled with hot air was designed, and theperformance test of drying machine was done.