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

在工业应用（注塑等）中高分子材料的熔融和连续相变中，在流场和传热场中存在几种特征行为，这取决于其非牛顿特性和非线性温度依赖性。这些流动和热行为对材料加工过程中工程质量的保持和控制显得尤为重要。高分子熔体流动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非稳态流动和传热场，从而检测出熔体的非牛顿特性及其非稳态效应。研究了含自由气体高聚物熔体前沿的非稳态流动与传热现象，液体界面边界将通过可视化图像和多点非稳态测量用数值层析成像实验显示。国次区域工作队 关于我们 通过视频从连续图像中检测出对整个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，并通过传热传感器检测出流体向壁面的传热。首先在室温下进行了液态高分子材料（PEO）预处理实验，并在与真实的工程材料基本相同的条件下进行了多次实验。将高分子材料（PP）放入带有许多实心原始短棒的圆柱形管中。在管内，由于电加热和摩擦生热的作用，物料的温度升高到熔点以上，物料在输送过程中发生相变。熔融流体在表面张力的作用下，由可控步进电机带动活塞运动，从喷嘴喷出，进入圆管和矩形流道。为了明确被推活塞的运动速度对出口速度的影响，将出口速度条件作为被推活塞运动速度的变化来考虑。用CCD摄像机对多幅图像进行处理，对熔体前缘的连续三维形状和再附着进行了实验检测。并尝试从两幅随时间分离的图像中检测熔体前沿的流场，作为速度矢量和剪应力分量。从实验结果来看，发现了以下几个有趣的现象。在近壁面矢量图上，气液界面的形状随速度涨落而随时间变化，这意味着在分子水平上存在着一些局部的、非均匀的滑移现象。熔体前沿的传热也发生了变化，并与这些现象相关联。这些现象源于高分子材料的特性，通过建立传热机理模型，可以对熔融过程进行数值模拟，从而更好地了解熔融过程中的各种现象，并对熔融过程进行预测。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