Abstract:

Three sets of industrial-scale dense phase CO₂ pipelines (length 258 m, inner diameter 233 mm) leaking experiments with different pore sizes (50, 100 and 233 mm) were carried out, and the time-history curves of CO₂ pressure and temperature at different positions in the tube were recorded. The change of CO₂ density, enthalpy value and Prandtl number (Pr) was obtained by using REFPROP software. The variation of thermodynamic characteristics of dense CO₂ pipeline leakage and pressure loss process was studied. The results show that after the pipeline leaks, the dense phase CO₂ is rapidly converted into gas-liquid two-phase. The gas-liquid two-phase is converted into the gas phase with the experiment, and the solid phase dry ice is formed. The phase change causes the median enthalpy value in the pipeline to increase, the density of the medium to drop sharply, and the smaller the diameter, the more obvious the parameter change. Since the medium in the pipeline forms a multi-phase flow fluid flow, the temperature change is closer to the top of the leak port, and the convective heat transfer intensity is greater. As the leakage diameter increases, the CO₂ phase changes significantly, Pr increases, and the heat transfer in the pipeline moves from the bottom of the pipeline to the top of the pipeline. The heat transfer effect inside the pipeline is the best at the critical point of the CO₂ phase transition.

Key words: carbon dioxide, pipeline leakage, thermodynamics, phase change, Prandtl number

摘要：

开展了3组不同孔径（50、100和233 mm）工业规模密相CO₂管道（长258 m、内径233 mm）泄漏实验，记录了管内不同位置处CO₂压力和温度的时程曲线。应用REFPROP软件，获得CO₂密度、焓值和Prandtl数（Pr）的变化，研究了密相CO₂管道泄漏失压过程的热力学特性变化规律。结果表明：管道发生泄漏后，密相CO₂迅速转为气液两相，随着实验进行气液两相转为气相，并伴随固相干冰生成。相态变化导致管内介质焓值增大，介质密度突降，口径越小其参数变化越明显。由于管内介质形成多相流流体流动，越靠近泄漏口管顶位置温度变化越大，对流换热强度越大。随泄漏口径增大，CO₂相变明显，Pr增大，管内介质换热从管底向管顶移动。管内换热效果在CO₂相变临界点位置达到最好。

关键词: 二氧化碳, 管道泄漏, 热力学, 相变, Prandtl数