The Self-cleaning and Heat Transfer Enhancement Technology of the Twisted Strip with Oblique Teeth Used in Condensing Tubes of Refrigerating Units

摘要

The smooth twisted strip, which can not only self clean away fouling in condensing tubes but also enhance heat transfer, cannot be directly used for condensers of low flowing velocity. It is mainly because the force movement of self-rotation is too small. For this reason, the authors have successfully developed another kind of twisted strip, i.e. the twisted strip with oblique teeth, according to the principle of momentum movement of particle system. The operation movement can be enhanced by times by the action of the teeth. Thus, the modified twisted strip can self-rotate and remove fouling reliably even at low flowing velocity. All the structure parameters of the twisted strip with oblique teeth have different effect on its performance, such as the teeth shape, oblique angle, intersection angle, etc, and their interrelationship is quite complex. So, many experiments were conducted including the tracer determination of flowing distance of an eddy after a tooth and comparison experiments of different parameter structure. Among many kinds of twisted strips with oblique teeth, the strip "Q" can increase the self-rotation movement by 277% over the smooth twisted strip. The overall flowing resistance of equipment is not great although the resistance coefficient of the strip with teeth is much greater than the smooth strip. Therefore, the twisted strip with teeth has good development prospects in condensers and other shell-tube heat exchangers of low flowing velocity.