In this paper, single-phase heat transfer characteristics of water inside internal enhanced tubes were investigated. Refrigerants are boiling or condensing outside the tube. The experimental tubes have internal helical rib heights of 0.25−0.36 mm, helix angles of 40−60°, rib base thicknesses of 0.40−0.79 mm, rib tip thicknesses of 0.078−0.283 mm, and N_s (starts number per circle) of 40−50. It shows that the heat transfer enhanced ratios usually range from 2.3 to 3.64. The friction factors relative to the smooth tube are about 1.8 to 3.3 times higher. Analyzing the effect of rib geometry on flow and heat transfer, it was found that the higher the height of the internal rib, the better the enhancement of convective heat transfer in the tube. Also, the greater the thickness of the rib tip and base, the more detrimental to the friction factor in the tube. There was no noticeable influence on the heat transfer performance as the helix angle increased from 45° to 50°. For the increase of N_s, it appears that 45 ribs per circle is the best value in the present study when considering the increase in pressure loss. The thermal-hydraulic performance of 11 tubes was also evaluated. It shows that Tube-1 had the best performance in the condensing tubes and Tube-7 had the best performance in the boiling tubes.

中文翻译：

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几何参数对内螺旋肋管热工性能的影响

本文研究了内强化管内水的单相传热特性。制冷剂在管外沸腾或冷凝。实验管的内螺旋肋高度为 0.25~0.36 mm，螺旋角为 40~60°，肋底厚度为 0.40~0.79 mm，肋顶端厚度为 0.078~0.283 mm，N _s（每圈起始数）为40−50。结果表明，传热强化比通常在2.3~3.64之间。摩擦系数相对于光滑管大约高1.8至3.3倍。分析肋片几何形状对流动和传热的影响发现，内部肋片高度越高，对管内对流换热的增强效果越好。而且，肋顶端和基部的厚度越大，对管内的摩擦系数就越不利。当螺旋角从45°增加到50°时，对传热性能没有明显影响。对于 N _s的增加，考虑到压力损失的增加，似乎每圈 45 个肋是本研究中的最佳值。还评估了 11 根管子的热工水力性能。结果表明，Tube-1 在冷凝管中性能最佳，Tube-7 在沸腾管中性能最佳。