Wang Xuesong, Qiu Xiaoyi, Zhang Xincheng, Zhao Ling, Xi Zhenhao
State Key Laboratory of Chemical Engineering and Low-Carbon Technology, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
Shanghai Key Laboratory of Multiphase Materials Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
Polymers (Basel). 2025 May 19;17(10):1393. doi: 10.3390/polym17101393.
The viscoelasticity of fluids have a significant impact on the process of heat and mass transfer, which directly affects the efficiency and quality, especially for highly viscous functional polymer materials. In this work, the effect of elasticity on hydrodynamic behavior of pipe flow for highly viscous non-Newtonian fluids was studied using viscoelastic polyolefin elastomer (POE). Two constitutive rheological equations, the Cross model and Wagner model, were applied to describe the rheological behavior of typical POE melts, which have been embedded with computational fluid dynamics (CFD) simulation of the laminar pipe flow through the user-defined function (UDF) method. The influence of both viscosity and elasticity of a polymer melt on the flow mixing and heat transfer behavior has been systematically studied. The results show that the elastic effect makes a relative larger velocity gradient in the radial direction and the thicker boundary layer near pipe wall under the same feed flow rate. That leads to the higher pressure drop and more complex residence time distribution with the longer residence time near the wall but shorter residence time in the center. Under the same conditionals, the pipeline pressure drop of the viscoelastic fluid is several times or even tens of times greater than that of the viscous fluid. When the inlet velocity increases from 0.0001 m/s to 0.01 m/s, the difference in boundary layer thickness between the viscoelastic fluid and viscous fluid increases from 3% to 12%. Similarly, the radial temperature gradient of viscoelastic fluids is also relatively high. When the inlet velocity is 0.0001 m/s, the radial temperature difference of the viscoelastic fluid is about 40% higher than that of viscous fluid. Besides that, the influence of elasticity deteriorates the mixing effect of the SK type static mixer on the laminar pipe flow of highly viscous non-Newtonian fluids. Correspondingly, the accuracy of the simulation results was verified by comparing the pressure drop data from pipeline hydrodynamic experiments.
流体的粘弹性对传热传质过程有重大影响，这直接影响效率和质量，对于高粘性功能高分子材料尤其如此。在本工作中，使用粘弹性聚烯烃弹性体（POE）研究了弹性对高粘性非牛顿流体管流流体动力学行为的影响。应用两个本构流变方程，即Cross模型和Wagner模型，来描述典型POE熔体的流变行为，并通过用户自定义函数（UDF）方法将其嵌入到层流管流的计算流体动力学（CFD）模拟中。系统研究了聚合物熔体的粘度和弹性对流动混合和传热行为的影响。结果表明，在相同进料流速下，弹性效应使径向速度梯度相对更大，管壁附近的边界层更厚。这导致更高的压降和更复杂的停留时间分布，靠近管壁处的停留时间更长，而中心处的停留时间更短。在相同条件下，粘弹性流体的管道压降比粘性流体大几倍甚至几十倍。当入口速度从0.0001 m/s增加到0.01 m/s时，粘弹性流体和粘性流体之间的边界层厚度差异从3%增加到12%。同样，粘弹性流体的径向温度梯度也相对较高。当入口速度为0.0001 m/s时，粘弹性流体的径向温差比粘性流体高约40%。除此之外，弹性的影响会降低SK型静态混合器对高粘性非牛顿流体层流管流的混合效果。相应地，通过比较管道流体动力学实验的压降数据验证了模拟结果的准确性。
