Abstract:

Carbon capture, transport and storage (CCS) plays an important role in the process of carbon neutralization. The flow and heat transfer process of supercritical CO₂ and supercritical CO₂ mixture in a vertical circular tube was studied with supercritical CO₂, supercritical CO₂+CH₄ mixture (CH₄ mole fraction is 1%, 3%, 5%) and supercritical CO₂+N₂ mixture (N₂ mole fraction is 1%, 3%, 5%) as working fluids at a mass flow rate of 300～600 kg/(m²?s), heat flow density of 80～100 kW/m², and inlet pressure of 8～10 MPa. The results show that with the decrease of CH₄ and N₂ mole fraction in the working medium, the peak value of heat transfer coefficient of the working medium increases gradually, and its corresponding temperature increases gradually; the heat transfer coefficient of the working fluid increases with the increase of the mass flow rate, and the greater the mass flow rate, the greater the change range of the heat transfer coefficient; with the increase of inlet pressure, the peak value of heat transfer coefficient of working fluid decreases, and its corresponding temperature increases gradually. Turbulent kinetic energy, buoyancy and specific heat capacity at constant pressure are closely related to the heat transfer enhancement of supercritical CO₂ and its mixture.

Key words: CCS, CO₂ mixture, Heat transfer, Numerical study

摘要：

碳捕捉、运输和储存（CCS）对实现碳中和具有重要意义。以超临界CO₂、超临界CO₂+CH₄混合物（CH₄摩尔分数分别为1%、3%、5%）及超临界CO₂+N₂混合物（N₂摩尔分数分别为1%、3%、5%）为工质，在工质质量流速为300～600 kg/（m²?s）、热流密度为80～100 kW/m²、入口压力为8～10 MPa的条件下，研究了超临界CO₂及超临界CO₂混合物在竖直圆管内的流动换热过程。结果表明，随着工质中CH₄和N₂摩尔分数的降低，工质的换热系数峰值逐渐升高，且其对应的温度逐渐升高；工质的换热系数随着质量流速的增大而增大，且质量流速越大，换热系数变化幅度越大；随着入口压力的增大，工质的换热系数峰值有所降低，且其对应的温度逐渐升高；湍动能、浮升力及定压比热容与超临界CO₂及其混合物换热强化密切相关。

关键词: CCS, CO₂混合物, 换热, 数值研究