SGER: Flow-induced anisotropic thermal energy transport in elongational flows of polymer liquids

本文对聚合物熔体在拉伸变形下的流动诱导各向异性热传导进行了实验研究。 在以前的研究中，我们已经开发并应用了一种新的光学技术，以获得定量测量的热导率张量在剪切流动的聚异丁烯熔体。 这些先前研究的结果与应力-热规则一致，即应力和热导率张量线性相关。 在本研究中，同样的光学技术被应用到聚合物熔体在简单的拉伸流动。 热导率张量的两个分量（平行和垂直于拉伸方向）的随时间变化的测量将作为应变和应变率的函数获得。 此外，机械（应力）和光学（双折射）数据在相同的流量。 的热导率和应力的数据被用来检查的第一次的有效性的应力-热规则在聚合物熔体的拉伸流动，和具有不同的化学性质的聚合物的应力-热规则的有效性。 本研究和以往研究的实验结果被用来发展对聚合物中流动诱导的各向异性热传导的分子水平的理解。聚合物熔体在诸如纤维纺丝和注射成型等制造过程中的流动本质上是非等温的。 因此，这些工艺的有效设计和操作依赖于对流动聚合物熔体中的热传递的良好理解。 尽管这一公认的重要性，在变形的聚合物液体中的热传递，特别是，流动引起的各向异性热传导，是知之甚少。 精确的计算机辅助设计的聚合物工艺需要一个模型来估计的导热系数作为变形或应力的函数。 本研究中获得的实验结果直接满足了这一需求。 从这个调查的结果也将是非常宝贵的预测，或半预测，在聚合物中的流动诱导各向异性thermalconduction.This项目的理论发展是由热传输过程（TTP）计划和流体动力学（FD）计划，化学，生物工程，环境和运输系统（CBET）司在工程局（ENG）的共同资助。

CBET-0837907VenerusAn experimental study of flow-induced anisotropic thermal conduction in polymer melts subjected to elongational deformations is proposed. In previous studies, we have developed and applied a novel optical technique to obtain quantitative measurements of the thermal conductivity tensor in shear flows of poly-isobutylene melts. Results from these previous studies are consistent with the stress-thermal rule, which says the stress and thermal conductivity tensors are linearly related. In the present study, the same optical technique is applied to polymer melts in simple elongational flows. Time-dependent measurements of two components of thermal conductivity tensor (parallel and perpendicular to the stretch direction) will be obtained as functions of strain and strain rate. In addition, mechanical (stress) and optical (birefringence) data are obtained in the same flows. The thermal conductivity and stress data are used to examine for the first time the validity of the stress-thermal rule in elongational flows of polymer melts, and the validity of the stress-thermal rule for polymers having different chemistries. Experimental results from the present and previous studies are used to develop a molecular-level understanding of flow-induced anisotropic thermal conduction in polymers.Flows of polymeric melts in fabrication processes such as fiber spinning and injection molding are inherently non-isothermal. Consequently, the efficient design and operation of these processes relies on a good understanding of thermal transport in flowing polymer melts. Despite this well-accepted importance, heat transfer in deforming polymer liquids, and in particular, flow-induced anisotropic thermal conduction, is poorly understood. Accurate computer-aided design of polymer processes requires a model for estimating the thermal conductivity as a function of deformation or stress. The experimental results obtained in this study directly address this need. Results from this investigation will also be invaluable in the development of predictive, or semi-predictive, theories for flow-induced anisotropic thermal conduction in polymers.This project is jointly funded by the Thermal Transport Processes (TTP) Program and the Fluid Dynamics (FD) Program, both of the Chemical, Bioengineering, Environmental, and Transport Systems (CBET) Division within the Directorate for Engineering (ENG).