Objective Supercritical/dense-phase CO₂ pipeline transmission serves as a crucial component in Carbon Capture, Utilization, and Storage (CCUS) technology. However, various factors, such as unstable gas source outputs or terminal consumption fluctuations, induce dynamic responses of internal mediums, expressed by variations in their hydraulic and thermal parameters. Continuous or significant fluctuations can potentially result in pipeline and equipment instability. Existing hydraulic and thermal calculation models for supercritical/ dense-phase CO₂ pipeline transmission predominantly focus on steady-state calculations and economic evaluations, resulting in a deficiency of transient calculation models.

Methods Based on the fundamental conservation equations of fluid mechanics and taking into account the properties of CO₂ phases, a one-dimensional transient simulation calculation model was established to capture flow fluctuations within supercritical/dense-phase CO₂ pipelines containing impurities. Following this, numerical calculations were conducted to solve this model, producing dynamic simulation results that shed light on the changing rules of hydraulic and thermal parameters along the pipeline under transient conditions at varying flow rates. A comparative analysis was performed between this model and OLGA, another industrial transient simulation software.

Results The results from the proposed model exhibited trends consistent with those from OLGA. The pressure and temperature responses calculated by the model were marginally higher than those produced by OLGA. The differences in the relative variations of outlet temperature and pressure responses calculated using the two tools remained within 2%, thereby meeting the accuracy requirements for engineering calculations. Furthermore, in the process of transient calculations, the model exhibited higher reliability than OLGA, attributed to the absence of numerical oscillations. Consequently, the proposed model proved proficient in predicting dynamic responses in temperature and pressure within supercritical/dense-phase CO₂ pipelines under transient conditions at varying flow rates.

Conclusion The comparison between simulation results derived from the proposed model for supercritical/dense phase CO₂ pipelines and those from OLGA highlights the enhanced calculation accuracy of the former. The research outcomes offer theoretical backing for the development and implementation of localized design and process simulation software tailored specifically for CO₂ pipelines.