新型横纹螺旋盘管强化传热的数值模拟

为了增强螺旋盘管的传热性能,对现有的普通螺旋盘管进行优化设计,提出一种管壁向内凸起形成环肋的异型管,称为横纹螺旋盘管。通过数值模拟方法对横纹螺旋盘管和普通盘管内部流动和传热过程进行模拟。应用场协同原理对其速度场和温度场的协同作用进行分析。实验数据与仿真结果的误差在5%以内,验证了数值模拟方法的正确性。在不同Re(雷诺数)条件下,计算两种盘管的Nu(努塞尔数),进而与Gnielinski(格尼林斯基)修正公式计算结果进行比较,误差在10%以内。结果表明:环肋结构通过工质旋转流动破坏边界层厚度,改善了管内速度场与温度场的协同程度,从而实现了强化传热。在较高的Re范围内,横纹螺旋盘管的Nu为普通盘管的1.29~1.43倍。因此,横纹螺旋盘管具有更好的传热性能,为异型螺旋盘管的研究及工程应用提供一定的理论依据。

Numerical Simulation of the Enhanced Heat Transfer of a Novel Transversally Corrugated Coil Tube

In order to improve the heat transfer performance of a coil tube and optimize the design of currently available common coil tubes,proposed was a special section tube in which a ring-rib was formed by an embossed tube wall towards the internal of the tube,named as a transversally corrugated coil tube.The flow and heat transfer process inside a transversally corrugated coil tube and common coil tube were simulated by using the numerical simulation method.The field synergy principle was used to analyze the synergetic action of the speed and temperature field.It has been found that the errors between the data tested and ones simulated are within 5%,thus verifying that the numerical simulation method is sound and correct.Under the condition of various Reynolds numbers,the Nusselt numbers in both types of tube were calculated and then compared with the results calculated by using the Gnielinski correction calculation formulae.The errors between the Nusselt numbers and those calculated by using the Gnielinski correction calculation formulae were in a range of 10%.The research results show that through the rotating flow of the working medium destroying the thickness of the boundary layer,the ring rib structure can improve the synergetic extent of the velocity and temperature field inside the tubes,thus realizing an enhancement of the heat transfer.In the range of relatively high Reynolds numbers,the Nusselt number of the transversally corrugated coil tube will be 1.29 to 1.43 folds of that of a commonly-used coil tube.As a result,the transversally corrugated coil tube enjoys better heat transfer performance,thus offering a theoretical basis for further studies of the special section coil tubes and their applications in engineering projects.