Study on the Influencing Factors of Gas Mixing Length in Nitrogen Displacement of Gas Pipeline

The gas pipeline commissioning replacement is a vital section before the pipes being put into operation. It is related to the gas mixture length of segment regardless the replacement method, the gas mixing length theory formula is derived based on diffusion theory and convection diffusion equation. Taking the impact factors of gas movement into account, with software FLUENT, this paper simulated different flow regimes, pipe length, diameter, velocity, back pressure and temperature to influence the gas mixing length, the general influence law of various factors is identified. That is the gas mixing length increases with the increasing of pipe length, diameter, velocity, back pressure and temperature, the corresponding mixing length and displacement time are longer at laminar flow. The research results provide theoretical basis for the natural gas pipeline commissioning replacement to determine reasonable parameters.