Pipelines transporting impure supercritical carbon dioxide in the carbon capture, utilization, and storage (CCUS) chain exhibit varying decompression characteristics due to engineered emissions or accidental leakage, resulting in diverse temperature drops and heat transfer mechanisms in the media and pipe walls. Therefore, studying heat transfer characteristics during slow and instantaneous decompression is crucial to investigating pipeline operational risks. In this work, supercritical CO₂ pipeline valve release and rupture disc release experiments were performed with a 1.5% molar ratio of N₂ content in an experimental pipeline (16 m long, 100 mm inner diameter). The evolution of the medium and pipe wall's physical properties was measured and discussed. Two methods of depressurization were employed to analyze the phase changes and heat transfer processes in the pipe. The instantaneous decompression process has a shorter decompression time and undergoes fluctuating and stable decompression stages. The slow decompression process has a slower temperature drop rate, but the wall during the process can reach a lower minimum temperature. Both release methods cause a larger temperature drop and Nusselt number at the bottom of the pipe wall due to evaporation heat transfer compared to the middle and top. The slow decompression process demonstrates a higher peak Nusselt number at the bottom, resulting in superior heat transfer efficiency compared to the instantaneous decompression process. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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含N2 S-CO2管道不同减压过程中的热物理演化

由于工程排放或意外泄漏，在碳捕获、利用和储存 (CCUS) 链中运输不纯超临界二氧化碳的管道表现出不同的减压特性，导致介质和管壁中出现不同的温度下降和传热机制。因此，研究缓慢减压和瞬时减压过程中的传热特性对于调查管道运行风险至关重要。本工作在实验管道（长16 m，内径100 mm）中，以摩尔比1.5%的N ₂含量进行了超临界CO ₂管道阀门释放和爆破片释放实验。测量并讨论了介质和管壁物理特性的演变。采用两种降压方法来分析管道内的相变和传热过程。瞬时减压过程减压时间较短，经历波动和稳定减压阶段。慢速减压过程的降温速度较慢，但​​过程中管壁能达到的最低温度较低。与中部和顶部相比，两种释放方法都会因蒸发传热而导致管壁底部出现更大的温降和努塞尔数。缓慢减压过程在底部表现出更高的峰值努塞尔数，与瞬时减压过程相比，具有更高的传热效率。 © 2023 化学工业协会和 John Wiley & Sons, Ltd.