自旋扭带强化传热及旋转特性

Enhancement of heat transfer and rotation characteristics of self-rotating twisted tape

旋转扭带是在固定式扭带基础上发展而来的，因其特殊结构所以能在管内流体作用下产生自旋效果。本文对自旋式扭带旋转特性及强化传热特性进行研究。通过理论及实验研究管内自旋扭带旋转特性后得出：扭率越小，扭带克服阻力起始旋转需要的流体速度越小；扭带转速与管内流体流速呈一次线性关系，且扭带节距不变时线性比例基本保持不变。通过实验研究后得出：自旋扭带能达到很好的强化传热性能，扭率越小其强化传热性能越明显，同时阻力特性也越明显，在雷诺数为4×10^3～4×10^4、扭率为3～8时，换热管内摩擦因子增至1.7～3.5倍，努赛尔数增幅为10%～37%。本文使用评估指标η对扭带进行综合评价，得出扭率为7的自旋扭带具有最佳的综合性能。并分别拟合出摩擦因子及努赛尔数与雷诺数、扭率之间的关联式，提出一种工程上自旋扭带选型方法。

Because of its special structure,rotating twisted tape can rotate under the action of fluid in tube. This paper studied the rotation characteristics and heat transfer enhancement characteristics of self-rotating twisted tape. The theoretical and experimental research of rotation characteristics showed that with decreasing twist ratio,the fluid velocity tape needed to overcome resistance and starting rotation reduced;the relationship between rotating velocity and the fluid velocity was linear,and the linear ratio remained constant when the pitch of tape was unchanged. The experiment research of heat transfer and pressure drop demonstrated that Nusselt number in the tube with self-rotating twisted tape was higher than that in plain tube,and increased with the decreasing of twist ratio; when Reynolds number was in the range of 4×10^3—4×10^4,and twist ratio was at 3—8,the Nusselt number increased 10%—37% and Darcy friction factor was 1.7—3.5 times higher compared to plain tube. The comprehensive evaluation was based on evaluation indicatorη,and twisted ratio of 7 was determined to be the best comprehensive performance. The relationship of the friction factor,Nusselt number and Reynolds number with the twist ratio was also obtained.