Abstract

Free convection heat transfer over annular finned tubes was studied numerically for more than 60 different cases and verified against two experimental works. In addition, the effect of fin spacing on heat transfer was investigated. As a result, a correlation was proposed to estimate Nusselt number as a function of Rayleigh number. Moreover, it was shown that there was an optimum fin spacing for which the total heat transfer was maximized. Based on the proposed equation, an expression for optimum fin spacing was derived, which proved that the optimum Nusselt number was 0.9035. The presented equation for optimum fin spacing was a general equation in so far that it could also be used to find the optimum spacing between a series of circular disks by letting the tube diameter in the equation be zero. Moreover, a good agreement was observed between the derived equation for optimum fin spacing and the results of the scale analysis method.

摘要

对 60 多种不同情况下的环形翅片管上的自由对流换热进行了数值研究，并针对两个实验工作进行了验证。此外，研究了翅片间距对传热的影响。因此，提出了一种相关性来估计努塞尔数作为瑞利数的函数。此外，结果表明存在一个最佳的翅片间距，使总传热最大化。基于所提出的方程，导出了最佳翅片间距的表达式，证明了最佳努塞尔数为0.9035。到目前为止，所提出的最佳翅片间距方程是一个通用方程，它也可用于通过让方程中的管直径为零来找到一系列圆盘之间的最佳间距。而且，