Design And Numerical Simulation Of Vegetable Vacuum Drying Equipment

The production of fruits and vegetables in China is largest in the world,and the amount of dried fruits and vegetables account for about 60% of the world's total trade.With the improvement of technology and the increasing demand of the market,the annual output of fruits and vegetables show an increasing trend in our country.Fresh fruits and vegetables is sensitive to storage conditions,room temperature storage will lead to the loss of nutrition,and even rotting deterioration,and the preservation of fruits and vegetables become very difficult,especially the vegetable products which is sensitive to heat.It is very favorable that vacuum drying can achieve low temperature drying for the drying of heat-sensitive material.Vacuum drying technology of China has gradually developed,but the overall quality is not high,those machine which is old-fashioned,low degree of automation,and drying effect is not ideal for fruits and vegetables has been unable fully to apply.Therefore,it is very urgent to develop a kind of fruit and vegetable drying equipment with low cost,low energy consumption and stable performance for the vacuum drying of fruits and vegetables.The research contents of this paper including:(1)With cilantro as test material,using the existing vacuum drying equipment,vacuum drying tests were carried out to obtain the vacuum drying characteristics of the parsley and using the existing equipment of dry parsley optimum vacuum drying process conditions.This vacuum drying equipment has the following problem: uneven drying phenomenon existed during drying process,sometimes,the instability of vacuum degree is difficult to maintain,increasing energy consumption of drying process.It provides a reliable experimental basis for vegetable vacuum drying equipment design through drying test.(2)Through the structure analysis of the traditional vacuum drying equipment and the problems existing in vacuum drying equipment,combining with the basic principles of vacuum drying,drying process and design methods,SolidWorks software is used to build three dimensional model of the drying box and hot water coil which are two key components of this equipment.ANSYS that finite element analysis software was used to analyze and optimize the box with different stiffeners,and choose 6.5 channel steel as body reinforcement material.Make the drying oven enclosure structure to meet the design requirements.(3)FLUENT that computational fluid dynamics software is used to simulate the flow field distribution of 3D model for the optimized vacuum drying equipment.Combining with the optimal condition of parsley vacuum drying experiment process,the temperature of the material layer,and the temperature,pressure,fluid velocity of the drying chamber during the vacuum drying process is analyzed through simulation.The simulation results show that the internal chamber temperature,pressure,and the temperature distribution of material layer are evenly distributed,thus,the optimized vacuum drying equipment can solve the problem of uneven drying.The simulation results provide a theoretical basis and technical support for the study of vacuum drying process.The existing problems of the current equipment is found by vacuum drying experiment,the box model is established by SolidWorks software,the ANSYS finite element analysis software is used to optimize the model,and the FLUENT software was used to simulate the internal flow field.Results show that the optimized vacuum drying equipment can eliminate the drying uneven phenomenon in the existing vacuum drying equipment.The instability problem of vacuum degree which is difficult to maintain sometimes can be solved through the choice of appropriate vacuum pump and give a good sealing.This research provided a technical basis for the dried vegetable processing and related equipment design.