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烘干机干燥的物理过程及机理!

2019-09-27 来源:http://www.zhongyanjixie.com 发布人:admin 浏览量:
  物料的干燥过程可以通过干燥试验来确定。在干燥机干燥条件下,即干燥机干燥介质的温度、湿度、流量以及与物料在干燥过程中的接触量均设置为数值不变,观察干燥机干燥物料在干燥过程中的水分、温度以及干燥速度的变化。如果测试。应用一定的温度、湿度、风速的热风干燥器来干燥少量的湿物料,基本上是接近干燥机恒定的干燥条件。
  The drying process of materials can be determined by drying test. Under the drying condition of the dryer, that is, the temperature, humidity, flow rate of the drying medium and the contact amount with the material in the drying process are set to the same value. The changes of moisture, temperature and drying speed of the drying material in the drying process are observed. If tested. The application of a certain temperature, humidity, wind speed of the hot air dryer to dry a small amount of wet materials is basically close to the constant drying conditions of the dryer.
  根据物料在干燥过程中的变化(物料中的水分和干燥速度随时间的变化),可以将It本体物料的干燥速度曲线分为以下几个阶段。
  According to the change of material in drying process (the change of moisture content and drying speed with time), the drying speed curve of It bulk material can be divided into the following stages.
  1. 热身阶段
  1. Warm-up phase
  当物料与热风(烘干机干燥介质)接触时,热风将热量传递到物料表面。此时,单位时间内传递到材料表面的热量远远大于地表水蒸发所需的热量,材料表面温度迅速升高。当热空气达到湿球温度时,单位时间内传递到材料表面的热量等于材料表面蒸发所需的热量。这是处于平衡状态。在预热阶段,材料中的水在减少。表面温度在升高。干燥机的干燥速度增加。热身时间很短,没有多少水被移走。
  When the material is in contact with the hot air (drying medium of the dryer), the hot air transfers heat to the surface of the material. At this time, the heat transferred to the surface of the material in unit time is far greater than the heat required for surface water evaporation, and the surface temperature of the material rises rapidly. When the hot air reaches the wet bulb temperature, the heat transferred to the material surface in unit time is equal to the heat required for evaporation on the material surface. This is in equilibrium. In the preheating stage, the water in the material is decreasing. Surface temperature is rising. The drying speed of the dryer increases. The warm-up time was short, and not much water was removed.
  2. 干燥机干燥阶段均匀
  2. Dryer drying stage uniformity
真空烘干机厂家
  在干燥机干燥前释放,物料的干燥速率恒定的干燥阶段称为干燥阶段恒定。在恒速干燥阶段的干燥,因为它的高含水物质,材料内部水分很容易扩散到表面,材料内部迁移率可以适应材料表面的水表面水的蒸发速度,使材料表面润湿结合水,传热速率和水蒸发速度维度保持不变。这个阶段的干燥机的干燥速度与材料的粒径和初始含水率的盆地,但与干燥机的干燥温度,空气的湿度和气流的速度和方向。它的特点是表面总是保持湿润。该材料的温度不上升,这消除了材料的非连接水。
  The drying stage in which the material is released before drying is called the constant drying stage when the drying rate is constant. In the constant drying stage, because of its high moisture content, the moisture in the material can easily diffuse to the surface. The internal mobility of the material can adapt to the evaporation rate of water on the surface of the material, so that the wetting and binding water on the surface of the material, heat transfer rate and water evaporation rate dimension remain unchanged. The drying speed of the dryer at this stage is related to the size of the material and the initial water content of the basin, but with the drying temperature of the dryer, the humidity of the air and the speed and direction of the airflow. Its characteristic is that the surface always keeps wet. The temperature of the material does not rise, which eliminates the unconnected water of the material.
  3.干燥机减速干燥阶段
  3. Deceleration drying stage of dryer
  当物料含水率降至临界含水率时,物料干燥机的干燥速度随含水率的降低而降低
  When the moisture content of material decreases to the critical moisture content, the drying speed of material dryer decreases with the decrease of moisture content.
  物料干燥机的干燥速率随着含水率的降低而降低,这意味着水分向物料表面迁移的速率低于物料表面水分的蒸发速率。材料的表面,特别是突出部分,会变得干燥,单位时间内的水分蒸发速率会降低。因此,地表水汽化所需热量降低,物料表面温度逐渐升高,干燥机的干燥速度降低。干燥器的干燥速度逐渐下降,然后下降得更快
  The drying rate of material dryer decreases with the decrease of moisture content, which means that the rate of water migration to material surface is lower than the rate of evaporation of water on material surface. The surface of the material, especially the prominent part, will become dry and the rate of water evaporation per unit time will decrease. Therefore, the heat required for surface water vaporization decreases, the surface temperature of the material increases gradually, and the drying speed of the dryer decreases. The drying speed of the dryer decreases gradually and then more rapidly.。
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