翅片螺距对锯齿螺旋翅片换热管特性的影响

Effects of fin pitch on heat transfer and flow resistance of serrated spiral-finned-tube banks

在连续螺旋翅片管基础上发展而来的锯齿螺旋翅片管具有易于制造、翅化比大,传热系数和翅片效率更高等优点,已广泛应用于各类大型气体换热设备中。为获得翅片螺距对锯齿螺旋翅片换热管特性的影响,在分析其影响机理的基础上对5个锯齿螺旋翅片管错列管束进行了实验研究。实验结果表明:在实验研究的翅片螺距范围(3.831～4.167mm),相同Re下随翅片螺距增大,管束翅侧Nu增大19%,Eu减小8%;因锯齿螺旋翅片中气流更易渗透和冲刷充分,翅片螺距大于4mm时其对翅侧Nu的影响已不明显;随气流Re增大,管束综合传热性能j/f(Colburn传热因子与摩擦因子比值)先增大后减小,在Re=7000～10000范围j/f较大;相同Re下管束j/f随翅片螺距增大而增大,在实验的翅片螺距范围内管束j/f可增大28%。将实验结果与文献中已有的相关计算关联式预测结果进行了比较。提出了包含翅片螺距、管束横向节距及纵向节距影响的锯齿螺旋翅片管束换热与阻力特性计算关联式,供相关工程设计参考。

Serrated spiral-finned-tube,developed from solid spiral-finned-tube,has been widely applied in large-scale heat-exchange facility due to its advantages such as easier manufacture,more extended heat transfer surfaces,higher heat transfer coefficient and fin efficiency.For the effects of fin pitch on heat transfer and flow resistance of serrated spiral-finned-tube banks（SSBs）,nine SSBs with staggered layouts in terms of various fin pitch were tested based on the analysis on its influencing mechanism.The experimental results are as follows.At the same fin-side Re,Nu increases 19% and Eu decreases 8% with the fin pitch increased from 3.831mm to 4.167mm.The effect of fin pitch on fin-side Nu becomes little when the fin pitch is larger than 4 mm since the gas penetrates the fin-gap more easily and fully flushes the fin-surface.The comprehensive heat transfer performance index j/f（ratio of Colburn heat transfer factor and friction factor）of fin-side first increases and then decreases as Re increases,with higher j/f in Re=7000—10000.At the same fin-side Re,the index j/f is higher as the fin pitch is larger,increased about 28% with the fin pitch increased from 3.831 mm to 4.167 mm.The experimental results were compared with the correlations in literature.The correlations for Nu and Eu on SSBs with staggered layouts, which take fin pitch,transverse pitch and longitudinal pitch of tube banks into accounts,were presented for engineering applications.