【作者】 张江；

【导师】 文怀兴；

【作者基本信息】 陕西科技大学 ， 机械制造及其自动化， 2014， 硕士

【摘要】 果蔬低温真空干燥能够有效地减少果蔬干燥过程中营养成分的损失，对于解决果蔬产量相对过剩有着重要的意义。但是，国内少量用于果蔬真空干燥的设备还停留在试验和小规模生产阶段。本文旨在通过一系列的真空干燥试验、软件分析和设计计算，对现行低温真空干燥设备装料面积小，加热不均匀和能耗较高等缺陷进行改良设计。（1）通过真空干燥设备的工艺试验，验证了真空低温干燥设备的可行性，研究了加热水温度、真空度和物料厚度对干燥效率的影响；同时，实验证明了实验真空设备加热搁板传热的不均匀性，发现提高加热介质的流速能够有效提高加热搁板的加热均匀性。（2）针对果蔬实验真空干燥设备真空系统的有效抽速得不到充分利用的情况，本文将计算和实验相结合，根据物料的干燥工艺条件，计算出其最大放气速率，在合理匹配真空系统有效抽速的条件下，确定真空干燥箱的装料面积。另外，对于不同的干燥物料，可以采用本文提出的理论方法，对原真空干燥设备的真空干燥箱装料面积进行匹配设计。（3）通过有限元分析，研究大型真空干燥箱形状对其力学性能的影响，得出在相同条件下，圆筒形真空干燥箱的应变更小，且抵抗屈曲变形的能力更强。因此，本文将真空干燥箱设计为圆筒形。（4）根据圆筒形真空干燥箱的设计压力、设计温度和装料面积，确定了箱体的材料，公称直径和圆筒长度，并用图算法求得箱体的名义壁厚。同时，设计了圆筒形真空干燥箱的箱门、封头和支座，确定了其具体参数。根据圆筒的几何尺寸，改进设计料车，使得干燥箱的装卸料更加便捷。并且根据箱体的参数，设计选配相应的真空泵组。（5）通过传热理论，分析对比了搁板采用辐射传热和传导传热的区别。改进设计加热搁板，传热方式选为辐射传热，并改进其结构，使其传热更加均匀。根据加热搁板的结构，设计了加热搁板的供热管道组和搁板固定架。（6）本文提出了加热冷却系统的改进方案，将真空干燥箱抽出蒸汽的热量和水环式真空泵工作产生的热量回收，用于真空干燥箱的加热；将水环式真空泵的循环水热量回收后，再次用于水环式真空泵的水量供给，实现废热废水的循环利用。本文在真空干燥工艺试验的基础上，通过数据分析，软件分析，设计改进了真空干燥设备的核心部件，增大了设备的装料面积，改善真空干燥箱的传热均匀性，提高了设备的能源利用率。更多还原

【Abstract】 Low-temperature vacuum drying of fruits and vegetables can effectivelyreduce the loss of nutrients in fruits and vegetables drying process, which is greatsignificant for solving the relative excess production of fruits and vegetables.However, domestic vacuum drying equipment for fruits and vegetables is still inexperimental stage and small-scale production. Through the experimental dataanalysis and design calculations, the defects of current low temperature vacuumdrying equipment, such as loading area is small, uneven heating and high energyconsumption, were improved in this thesis.（1）The influence of heating water temperature and vacuum degree andmaterial thickness on the drying efficiency was studied by the test of vacuumdrying equipment. And, the non-uniform heating of vacuum equipment heatingshelf and the cause were found by test.（2）For vacuum system of fruit and vegetable vacuum drying equipmentcan not make full use of effective pumping speed, this thesis combines thecalculation and test, and put forward an improving method. According to thedrying process conditions of the material, the maximum outgassing rate wascalculated, then, the reasonable loading area of the vacuum drying oven wasdetermined. In addition, for different drying materials, matching design ofvacuum drying oven loading area and vacuum system can use the methodsmentioned in this thesis.（3）The effects of different shape on mechanical properties of vacuumoven was compared by finite element analysis. The result of analyze can supplysome basis for the design of large vacuum drying oven.（4）According to the design pressure and temperature of cylindricalvacuum drying oven and the loading area, the oven material and nominal diameter and length of the cylinder were be determined. At the same time, thedoor and the dome head and the pedestal of the cylindrical vacuum drying ovenand the vacuum pump were designed. In order to matching the large oven, a skipwas designed forloading and unloading.（5）Based on the theory of heat transfer, the difference between radiationand conduction of the shelf heat transfer were be compared. In order to the heattransfer more evenly, the structure of heating shelf was be improved. In addition，heating pipe group and fixed frame of the heating shelf were be designed.（6）The heating and cooling system were be designed，and the waste heatof vacuum oven and water ring pumps could be recycling use. While，the wastewater could supply for water ring pump again.Based on the tests of vacuum drying process and data analysis, softwareanalysis, the core components of vacuum drying equipment were improved. Theequipment can improve the energy efficiency and the uniformity of heat transferand the capacity of charging.更多还原