In evaporating system design of large subcritical pressure natural circulation boiler sometime expensive rifled tube will be used unavoidably in part, so that the film boiling Can be avoided.

在大容量、亚临界自然循环锅炉蒸发系统设计中，有时不可避免地需要部份地采用价格昂贵的内螺纹管，以避免出现膜态沸腾。