Research And Design Of Hot-airvacuum Drying Equipment And Control System For Fruits And Vegetables

In 2017,according to the statistics,production of fruits and vegetables reached more than one billion tons in China.However,fresh fruits and vegetables are prone to deterioration due to high moisture content and improper storage.After the fresh fruits and vegetables are dried,not only the nutrients of fruits and vegetables can be preserved to a large extent,but also the storage time of fruits and vegetables can be improved.Therefore,fruits and vegetables drying technology is worthy of be researched and promoted.There are many advantages of hot-air vacuum drying technology,such as simple structure,strong adaptability and low cost,etc.The temperature and humidity detection function has been achieved during the drying process for the control system of drying equipment.However,there are few reports on the detection of the moisture content of the material and the image acquisition of the color change during the drying process.In order to solve the problem above,the main contents of this project are as follows:(1)According to the experimental results and drying parameters of hot-air drying,vacuum drying and their combination of fruits and vegetables,the drying box and vacuum system of the hot-air vacuum drying equipment and the real-time weighing device were designed.And the 3D model is built based on the various dimensions of the designed drying box by SolidWorks.The static finite element analysis of the 3D model was carried out by ANSYS,and the force and deformation of the drying box under vacuum environment were simulated.The results show that the dry box design can meet the requirements.According to the working environment of the real-time weighing device,it is designed as a lever structure,which realizes the real-time weighing function of the drying equipment.(2)According to the drying experiment and process parameters of various fruits and vegetables,the drying parameters and control system design requirements for the drying process are determined.The design scheme was proposed and the hot-air vacuum drying control system for fruits and vegetables was designed.In the hardware design of this system,Siemens S7-200 SMART series PLC is adopted as the lower computer ofthe system.The industrial control touch screen with WinCC configuration software is designed as the host computer of the system.The hardware selection of modules such as image acquisition and material quality inspection was determined.In the software design,it is divided into the lower computer PLC program design and the host computer WinCC configuration software design.According to the MODBUS communication protocol,the PLC program establishes communication with the gravity value meter.The real-time moisture content detection function of the system is realized.The man-machine interface is established in the design of the WinCC configuration software of the host computer.The image acquisition function of the control system is implemented.(3)The experiment of the hot-air vacuum drying control system for fruits and vegetables was carried out based on the laboratory equipment.The laboratory’s hot-air vacuum drying equipment was retrofitted.And the hot-air vacuum combined drying experiment of the apple chip was completed based on the device equipped with the control system.The temperature control is accurate during the drying process,and the moisture content of material detection is normal,as well as the image acquisition result is clear.Finally,a comparative analysis results of the apple crisp drying experiment was completed.The results show that the test data is basically the same as the comparison process drying results.The control system achieves the desired control effect.In this project,the main structural design of the hot-air vacuum drying equipment for fruits and vegetables is completed,such as drying box and weighing device,etc.And the hot-air vacuum drying control system was designed,real-time moisture content detection of material and material image acquisition were realized.This project provides technical support for the further research and popularization of hot air vacuum drying technology and its control system for fruits and vegetables.