螺杆熔融段构型对传热效率的影响

Effect of Molten Section Configuration of Screw on Heat Transfer Efficiency

采用数值模拟的方法,对比了普通的和分别放置扭转元件、Maddock元件的螺杆熔融段处的传热效率,并从流体速度场和温度梯度场的协同性解释差异产生的原因。模拟结果表明,扭转元件的特殊流道设计能够有效提高流道内速度场和温度梯度场的协同性,显著增强对流传热,无论元件放置在熔融段的入口还是出口,装有扭转元件的螺杆的传热效率都远远高于装有Maddock元件的螺杆和纯螺纹螺杆;同时,扭转元件对物料的剪切力相对Maddock元件小得多,从而使螺杆产生的黏性耗散热降低,局部过热的现象得到很好的控制。从模拟结果来看,场协同理论的结果与模拟的实际结果具有良好的一致性,因此场协同理论可以用于解释聚合物加工中高黏度非牛顿流体的传热特性。

Numerical simulation was used to compare the heat transfer efficiency of general screw and the screws assembled with torsion element and Maddock element at compression zone.Reasons of the differences were proposed from the viewpoint of the synergy of velocity field and temperature gradient field.Simulation results showed that the torsion element with elaborately designed flow channel would effectively improve the synergy of velocity field and temperature gradient field,significantly enhancing the convective heat transfer.Heat transfer efficiency of screws assembled with torsion element were much higher than those with Maddock element and general screw,no matter on the inlet or outlet of compression zone.At the same time,the torsion element applied much less shear stress compare to Maddock element.Thus,the heat caused by viscous dissipation would reduce significantly and local overheating phenomenon could be well-controlled.Moreover,the results obtained from field synergy theory were consistent with the actual simulation results,so field synergy theory could be used to explain the heat transfer properties of non-newtonian fluid with high viscosity in polymer processing.