同心双扭旋元件内外叶片数量对管内传热性能的影响

为探究同心双扭旋元件组合方式变化对换热管传热特性的影响规律，采用数值模拟方法对雷诺数Re=200~1 800范围内恒壁温条件下的管内传热进行了分析，并进行了实验验证。研究结果表明：在Re=200~1 800的范围内，含有4-4同心双扭旋元件换热管的努赛尔数Nu值最大，其次为3-3同心双扭旋元件，2-4与2-2同心双扭旋元件的Nu相差不大，最大仅相差5%；4-4同心双扭旋元件换热管的阻力系数f最大，其次为3-3同心双扭旋元件，2-4同心双扭旋元件的阻力系数略高于2-2同心双扭旋元件；2-2同心双扭旋元件换热管的综合传热性能评价因子（PEC）值最大，为1.50，且明显高于其他3种换热管，其余3种换热管的PEC值相差不大；4-4同心双扭旋元件换热管的场协同数F_c值最大，其余3种换热管的F_c值相差不大。

Effect of a concentric double twisted element combination on the heat transfer characteristics in heat exchange tubes

Numerical simulation methods and experimental verification have been employed to investigate the influence of concentric double-twisted elements on the heat transfer characteristics in heat exchange tubes. The heat transfer characteristics in the tubes were analyzed under the condition of constant wall temperature with Reynolds number in the range Re=200-1 800. It was found that the Nusselt number (Nu) of the heat exchange tube with 4-4 concentric double-twisted elements was the best, followed by that with 3-3 concentric double-twisted elements. The maximum difference between tubes with 2-4 and 2-2 concentric double-twisted elements was only 5%. Tubes with 4-4 concentric double-twisted elements had the largest resistance coefficient f, followed by tubes with 3-3 concentric double-twisted elements. The resistance coefficient of tubes with 2-4 concentric double-twisted elements was slightly higher than that of those with 2-2 concentric double-twisted elements. The tube with 2-2 concentric double-twisted elements had the largest performance evaluation criterion (PEC) value, with a maximum of 1.50. This was significantly higher than the values for the other heat exchange tubes, which were not significantly different. The field synergy number (F_c) of the 4-4 concentric double-twisted element heat exchange tube was the largest, and the F_c values of the other tubes were not significantly different.