Abstract:

An experimental investigation of the pressure drop and friction factor of supercritical CO₂ in circular tube is presented. Experimental length and inner diameter of the circular tube are 2000 mm and 10 mm. The experimental pressure ranges from 8 MPa to 16 MPa, mass flux ranges from 1000 kg·m^-2·s^-1 to 1525 kg·m^-2·s^-1, and heat flux on the inner wall ranges from 96.5 kW·m^-2 to 283.2 kW·m^-2. The variation of flow resistance was obtained and the effects of pressure, mass flux, heat flux and bulk fluid enthalpy on the frictional flow resistance coefficient of the circular tube were analyzed. The results showed that the frictional pressure drop increases significantly with increasing mass flux and pressure, particularly when the bulk enthalpy surpasses the pseudo-critical enthalpy, increased speed has become more intense, and meanwhile, it is found that the influence of heat flux on the friction pressure drop is not too great. The assessment of correlations demonstrated that constant-property-based correlations fail to predict the friction factor of supercritical CO₂. Therefore, a new empirical correlation is proposed, and the experimental data accounts for 83.31% within the ±20% error band.

Key words: supercritical carbon dioxide, frictional pressure drop, flow, gas-liquid flow, riser

摘要：

对超临界二氧化碳在圆管内流动时的压降和摩擦系数进行了实验研究。实验段长为2000 mm，内径为10 mm。该实验压力范围为8～16 MPa，质量流量范围为1000～1525 kg·m^-2·s^-1，内壁热通量范围为96.5～283.2 kW·m^-2。得到了不同工况下竖直圆管内流动阻力的变化规律，分析了压力、质量流速、主流焓值和热通量对圆管内摩擦阻力的影响。实验结果表明摩擦压降随着质量流量和压力的增加而显著增加，特别是当主流焓值超过拟临界焓值后，其增加的速度变得更加剧烈，同时发现热通量对摩擦压降的影响较小。对于预测常物性摩擦因子的经验关联式并不能预测超临界CO₂的摩擦因子。因此提出了一个新的经验关联式，其实验数据在±20%误差范围内占83.31%。

关键词: 超临界二氧化碳, 摩擦压降, 流动, 气液两相流, 上升管