螺旋管内迪恩涡强化传热的试验研究

Experimental Study of the Dean Vortex-enhanced Heat Transfer Inside a Spiral Tube

在第一类边界条件下,从迪恩涡理论出发,采用7种不同几何参数的螺旋铜管以及直铜管进行了传热试验,得到了螺旋管内流体的努塞尔特数、压降以及强化传热综合评价因子随雷诺数、曲率比以及扭率的变化规律。试验结果表明:螺旋管的努塞尔特数和压降均高于直管,且随着曲率比、雷诺数的增大而增大;扭率对努塞尔特数的影响不明显,但扭率增大会引起压降降低;螺旋管的强化传热综合性能评价因子在任何雷诺数、曲率比、扭率下均大于1。在较低雷诺数条件下螺旋管具有很好的强化传热性能。

Under the boundary conditions in the first category,based on the Dean vortex theory,seven kinds of spiral copper tube and straight tube with various geometrical parameters were used to perform a heat transfer test and changes of the Nusselt number,pressure drop and enhanced heat transfer comprehensive performance evaluation coefficient of the fluid inside the spiral tube with Reynolds number,curvature ratio and twist rate were obtained.The test resultsshow that the Nusselt number,and pressure drop of the fluid inside the spiral tube are all higher than those inside the straight tube and will increase with an increase of the curvature ratio and Reynolds number.The influence of the twist rate on the Nusselt number is not evident,however,to increase the twist rate can lead to a decrease of the pressure drop.The enhanced heat transfer comprehensive performance evaluation coefficient of the spiral tube is invariably greater than 1 at any Reynolds number,curvature ratio and twist rate.Under the condition of low Reynolds numbers,the spiral tube has very good enhanced heat transfer performance.