To further discover the flow resistance characteristics of liquid nitrogen in bellows in wider application range

dimensionless variables namely the ratio of wave-height over bellows-diameter (e/d) and the ratio of wave-pitch over wave-height (p/e) are introduced. CFD modeling has been conducted on the behaviors of both pressure drop and Darcy friction factor (f) at different geometries of the bellows

either with or without an insert. Effects on the f by different Reynolds numbers at certain ratios e/d or p/e in wide ranges were investigated. The results shows that the vortex forming inside the bellows trough is the main cause of the flow resistance increment. When the e/d and p/e remain unchanged

changing of the inner diameter of the bellows has little influence on the friction factor. If a rod is inserted into the bellows

the larger the rod diameter

the smaller the Darcy friction factor. When the diameter of the insert reduces to zero

the friction factor approaches that of the hollow bellows

which is consistent with the experimental results.