Flow and Heat Transfer Characteristics of High-Polymer Flow with Free Gas-Liquid Interface Boundary

在工业应用(注塑等)的高分子材料的熔融和连续相变过程中，由于其非牛顿性质和非线性的温度依赖性，其在流场和传热场中具有几个特征行为。近年来，在材料加工过程中，这些流动和热行为对保持和控制工程质量变得越来越重要。聚合物熔融实验研究的难点主要在于没有合适的实验方法能够高精度地同时测量聚合物熔体的非定常流动和换热场，从而能够检测到具有时间特性的非牛顿性质及其非定常效应。本研究将通过可视化图像和多点非定常测量，用数值层析技术实验地显示具有自由气液界面的聚合物流体熔体前沿的非定常流动和换热现象。The Unst…从视频连续图像中可以检测到更多对整个热场和传热场有重要影响的气液界面的几何形状和熔体前沿的速度矢量场，并通过换热传感器检测到流体的壁面换热。为了验证实验方法，首先进行了室温下液态高聚物的预实验，然后在与实际工程材料加工条件基本相同的条件下进行了几次实验试验。将聚合物材料(PP)放入具有许多固体原始短棒的圆柱管中。在管内，由于电加热器和摩擦热产生的温度高于材料的熔点，材料在传输过程中会改变其相态。通过可控步进电机驱动的活塞，将具有表面张力效应的熔融流体从喷嘴推出管路和矩形通道。将出口的速度条件改变为推力活塞的运动速度，以明确其影响。采用多路图像处理技术，利用CCD摄像机对熔体前沿的连续三维形状和再附着进行了实验检测。并尝试将熔体前沿的流场作为速度矢量和剪应力分量从两幅随时间分开的图像中检测出来。在壁面附近的矢量图上，气液界面的形状随速度的波动而变化，这意味着在分子水平上存在着几种局部的、非均匀的滑移现象。熔体前沿的换热也发生了变化，并与这些现象相关联。这些起源于聚合物性质的现象可以用来建立传热机理模型，以便通过数值模拟来了解所有现象并估计整个熔融过程。较少

In the melting and continuous phase changing of the high-polymer material on industrial applications (injection molding and etc.), there are several characteristic behaviors in the flow field and heat transfer field in depends on its non-newtonian properties and non-liner temperature dependencies. These flow and heat behaviors become more important recently to keep and control engineering quality in the material proctessing. The difficulty of the experimental investigation of the melting high-polymer is mainly that there is no appropriate experimental method to measure the unsteady flow and heat transfer field simultaneously with high accuracy that can detect the time-special non-newtonian properties and its unsteady effects.In this study, the unsteady flow and heat transfer phenomena in melt-front of high-polymer fluid with free gas-liquid interface boundary will be shown experimentally with a numerical tomography by visualization images and multi-point unsteady measurements. The unst … More eady geographic shape of the gas-liquid interface and velocity vector field in melt-front which make important effects on whole heat and transfer field, are detected from the continuos images by video, and heat transfer from fluid into wall detected by the heat transfer sensors. The pre-experiments using liquid high-polymer (PEO) with a room temperature were done at first for checking methods, and then several experimental trials have done with mostly same conditions as real engineering material processing. The high-polymer materials (PP) were put into the cylindrical tube with many solid original short bars. In the tube, as the temperature raise over melting point of material by electric heaters and frictional heat generation, the material change its phase aspect in transit. The melting fluid with the effects of surface tension gets pushed out into the tube and rectangular channel from the nozzle by a piston moved with controllable stepping motor. The velocity conditions at exit are changed as the moving velocity of pushed piston for making clear its effects. The continuous 3-D shape and reattachment of the melt-front are detected experimentally with the multi-image processing by CCD video Camera. And the flow field in the melt-front would be tried to detect as velocity vector and shear stress components from two images separated with the time.From experimental results, several interesting phenomena were detected as below. The gas-liquid interface changes its shape properties time-dependently with velocity fluctuations on vector-map near wall, which mean that there are several local and non-uniform slipping phenomena at molecular levels. Heat transfers in melt-front are also changed and correlated with the phenomena. These phenomena originated in high-polymer properties can be made useful of building the heat transfer mechanism models in order to make clear the all phenomena and to estimate the whole process of melting with a numerical simulation. Less