Transporting CO₂ through pipelines is essential for large-scale, long-distance carbon movement, playing a crucial role in the carbon capture, utilization, and storage industry. This method helps achieve “dual carbon” targets. To understand phase transitions and flow parameters in CO₂ pipeline transportation, which are essential for ensuring safe and efficient design and operation, we have designed and constructed a CO₂ visualization loop experimental device.

This state-of-the-art CO₂ visualization loop experimental device comprises four key components: gas supply and phase transition, circulation pipeline, depressurization and release, and advanced data and image acquisition systems. Each component is strategically integrated to address the inherent challenges in CO₂ transportation experiments, mainly in controlling crucial initial conditions such as temperature, pressure, and phase states. These factors often present substantial obstacles by causing significant data collection inconsistencies and complicating operational procedures. To overcome these challenges, the device utilizes high-precision and stable instruments alongside cutting-edge equipment to precisely control the initial experimental conditions. This setup significantly enhances the accuracy of capturing flow parameters, including in situ temperature and pressure readings throughout the transportation pipeline. A sophisticated control software was developed for the CO₂ visualization loop experimental device, complementing its physical hardware. This software provides researchers with real-time monitoring by continuously recording pipeline parameters such as pressure, temperature, and flow rate. Furthermore, it allows dynamic control over the initiation, cessation, and operational frequency of crucial components such as booster and circulation pumps. These features offer significant convenience to researchers, significantly enhance experimental safety, and streamline the operational workflow, creating an ideal environment for conducting rigorous scientific investigations.

Empirical investigations utilizing this device have explored gaseous and supercritical CO₂ pipeline release scenarios. The findings reveal that during discharge, pipelines experience pronounced changes in pressure and temperature. The data also reveals that pressure response curves converge across various axial nodes along the pipeline, indicating a uniform pressure drop distribution. Conversely, temperature variations are significant across different nodes, with regions closer to the release endpoint experiencing more pronounced temperature reductions. This is attributed to the progressively intense Joule-Thomson cooling effect near the outlet. Moreover, during the release of supercritical CO₂, a notable gas–liquid phase transition occurs, primarily driven by the sustained vaporization of the supercritical fluid, which modifies the fluid dynamics within the pipeline.

This study highlights the development and capabilities of a CO₂ visualization loop experimental device that adeptly simulates steady-state transportation and transient release conditions within CO₂ pipeline systems. Practical applications and tests confirm the remarkable device measurement accuracy, safety, and ease of use. Beyond CO₂ pipeline research, this versatile device is also well-suited for educational purposes in fields such as oil and gas storage and transportation engineering, carbon storage science, and environmental engineering. The adaptability of the device underscores its immense potential for widespread adoption in various laboratory and educational contexts.