【作者】 马琳；

【导师】 尹文庆；

【作者基本信息】 南京农业大学 ， 机械设计及理论， 2004， 硕士

【摘要】 我国果品蔬菜资源丰富，其干制加工正在迅速发展，综合效益日益显著。但是该类物料为含水量高又富含维生素的热敏性体，干燥时间长，干制品的品质难以保证。常规的热风循环干燥因为温度较高、能耗大，已经无法达到生产高品质果蔬干制品的要求。采用冷冻干燥虽然产品质量好，但是设备价格昂贵，生产成本过高。因此，我们采用热泵干燥法来对果蔬进行干制，可以达到品质较高，节省能源的效果。 虽然在国内，使用热泵干燥机来干燥木材、食品、农副产品等的例子不少，但是对于多数使用热泵干燥机进行干燥的厂家来说，他们对干燥现场的温度、湿度等参数的检测还是通过人工的方法来实现的。这样即浪费了大量的人力物力，又不能达到控制所需的精度，还不能完成实时监控的效果。所以，现阶段对热泵干燥工艺参数的自动检测和控制的研究是非常重要的。 本课题根据热泵干燥机的工作原理以及对干燥过程的研究，自行设计并组装了一套热泵干燥装置。该装置主要由以下几个部分组成：蒸发器、冷凝器、压缩机、膨胀阀、辅助加热器和干燥室。电气控制部分采用了西门子可编程控制器；在进风口、出风口以及干燥室内安置了多个温湿度和风速传感器；设计了干燥室内的干燥吊架，其上使用称重传感器来实时测量物料的重量。 由于在食品的干燥过程中，干燥介质(空气)的温度、湿度、风速对干燥物料的影响显著，所以我们要检测这几个因素的变化范围。作者根据试验所需，设计了热泵干燥机计算机数据采集系统。软件系统采用Visual C++6.0编写，主要面向了干燥生产的管理者和技术人员，它可以实时的采集干燥室内的温度、湿度、风速以及物料的重量，采集的数据可以用图像和数据列表两种方式显示。这样就起到了实时监控的作用。其次，在不同温度下对苹果进行多次干燥试验，根据试验测得的数据，对物料的干燥特性进行研究，可以绘制实时干燥曲线和干燥速率曲线等，分析含水率和时间的关系、干燥速率与时间的关系、温度对干燥过程的影响等等。 本课题实现了热泵干燥机工艺参数的实时数据采集，它可以准确、及时的反映水果的干燥过程特性；实时的干燥过程数据记录也可以为自动控制提供基础。更多还原

【Abstract】 In our country, fruit and vegetable resources are rich. At present, companying the rapid development of their dryness technology, the integrated economic benefit is becoming more and more prominent. But fruit and vegetable, often containing lots of water and rich vitamin, are sensitive to heat and need long time to be dried, so the quality of them after drying courses cannot be guaranteed. The traditional drying method, in which fruit and vegetable is dried by constant hot wind, cannot meet the requirement to produce high quality fruit and vegetable products anymore because of the high temperature and huge energy consumption. In another method, which is called the cooling drying method, high quality products can be produced but the equipments are expensive and the productive cost is very high. So we developed this heat pump drying method hi purpose of improving products quality and reducing energy consumption.At present, some plants are using heat pump dryers to dry material such as wood, food and other agricultural products, but in these plants online parameters such as temperature, humidity and material weight are detected manually, thus large quantity of human power and material resource are wasted. At the same time, precision of auto-control and effect of real-time surveillance cannot be achieved. So at present, the research of the parameter auto-detection and auto-control of the heat pump dryer is of great importance.In this paper, the general drying process and the working principles of heat pump dryer are discussed, and the design of a set of heat pump drying equipment is described. This equipment mainly includes six parts: evaporator, condenser, compressor, expanding valve, assistant heater, and drying chamber. Its electric control part is the SIMENSE PLC; at the wind-in entrance, wind-out entrance and in the drying chamber one wind speed sensor and five temperature and humidity sensors are installed; in the drying chamber a drying nacelle for material is designed on which a weight sensor is installed to detect the real-time weight of the material.During the food drying process, the temperature, humidity and wind speed of the drying medium (air) can affect the quality of the drying material, so the variance of these parameters must be detected and controlled. The author designed a computer dataacquisition system according to this requirement. The software system, which is compiled by the Visual C++6.0 and which is mainly faced by the managers and workers, can acquire the values of temperature, humidity, wind speed and the weight of the material in a real-time mode. The acquired data can be browsed in two ways: data list mode and image section mode. In the research work, several drying experiments on apple under different temperatures have been done. According to the data from the test, the software can draw out the drying curve and drying speed curve, and can analyze the relationship between the moisture content and the time, the relationship between the drying speed and the time, and the effect of the temperature in the drying process.The data acquisition system discussed in the paper can complete the real-time data acquisition of the heat pump dryer accurately and timely, and can show the drying features during drying process; and the data acquired can provide a basis for the auto-control system of the heat pump dryer.更多还原