涟漪纹管内R22单相传热与流动特性的实验与数值研究

Experimental and numerical study of heat transfer and friction resistance for R22 in the dimpled and textured tube

中文关键词: 湍流  传热  实验研究  数值模拟  优化设计  强化因子

英文关键词: turbulent flow  heat transfer  experimental investigation  numerical simulation  optimal design  enhancement factor

中文摘要:

      涟漪纹管是一种新型三维内外表面强化换热管，内径11.5mm、外径12.7mm，管壁表面有直径为3.5mm的半球凹坑与高度为0.1778mm的涟漪花纹。工质R22在涟漪纹管内的流速设定为40-90kg/h，实验结果表明，涟漪纹管内对流换热努赛尔数（Nu）是相同雷诺数（Re）下光管的2.48倍。同时，对具有不同表面参数（凹坑直径0到4mm，花纹高度0到0.2778mm）的涟漪纹管内湍流换热进行了数值模拟，结果显示，在所研究的范围内，管壁表面凹坑直径越大，Nu越大；花纹虽有助于提高换热效果，但花纹高度越大，Nu越小；而摩擦阻力随着凹坑直径与花纹高度的增大而增大。如果以基于相同泵功的强化因子η''评价其综合强化换热性能，则当凹坑直径为1mm且无花纹存在时，管内的强化换热效果最好。

英文摘要:

      Dimpled and textured copper tube (1EHT tube) is a newly developed heat transfer enhancement tube, which has the outer diameter of 12.7mm and inner diameter of 11.5mm. The surface of the 1EHT tube is enhanced by dimple and texture. In this study, the mass flow rate of R22 is specified from about 40 to 90 kg/h. The results suggest that the heat transfer performance of the 1EHT tube is much higher than the plain tube with an enhancement factor of 2.48. In addition, the numerical analysis of heat transfer and friction resistance for turbulent flow in the tubes has also been performed for different structure parameters (dimple size from 0 to 4mm, texture height from 0 to 0.2778mm) . The numerical results show the Nu number increases with the dimples size, and decreases with the texture height. The friction resistance coefficient f increases with the dimples size and texture height increasing. If using the pump power based enhancement factor η'' to evaluate the heat transfer enhancement effect of the 1EHT tube, the tube with the dimple diameter of 1mm and without texture produces the best heat transfer performance.