Can you clean this pipe? 3-D CFD modeling of compressed-air cleaning of large pipe networks*

This study was conducted to improve the methods for modelling compressed-air cleaning of large complex piping systems. The current industry standard is to model the cleaning operation as an inviscid 1-D gas expansion. This work proposes using Computational Fluid Dynamic software for 3-D viscous turbulent flow. The simulation results were compared with actual industrial cleaning operations. Cleaning is measured by the ratio of the gas flow kinetic energy during the cleaning operation to the kinetic energy of normal operation. Cleaning force ratios (CFR) above 1.5 are acceptable. In one case, a simulation was performed on a 1000-foot, 8-inch pipe with four 90⁰ elbows. The simulation yielded a CFR of 16 near the pipe inlet and a CFR of 2 at the pipe exit. This was an 87.5% overall reduction in CFR along the pipe; however, with the minimum CFR above 1.5, the pipe cleaning should still be effective. Not surprisingly, at each elbow there was a noticeable reduction in total energy and velocity. The proposed model shows improved fidelity and accuracy in predicting the CFR and energy losses in these complex piping systems compared to the current industry model.