论文部分内容阅读
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。
In the first kind of boundary conditions, starting from the Dean vortex theory, seven kinds of different geometric parameters of the spiral copper tube and the straight copper tube heat transfer test was conducted, the Nusselt number of fluid in the coil, the pressure drop and Intensified heat transfer comprehensive evaluation factor with Reynolds number, curvature ratio and the variation of torsion. The experimental results show that the Nusselt number and pressure drop of spiral tube are both higher than those of straight tube and increase with the increase of curvature ratio and Reynolds number. The effect of twist on Nusselt number is not obvious, The increase of twist rate will lead to the decrease of pressure drop. The evaluation index of comprehensive performance of spiral heat transfer enhancement is greater than 1 under any Reynolds number, curvature ratio and twist ratio. Spiral tubes have good heat transfer enhancement properties at lower Reynolds numbers.