EXPERIMENTAL INVESTIGATIONS ON HEAT TRANSFER OF CO2 UNDER SUPERCRITICAL PRESSURE IN HEATED HORIZONTAL PIPES - EXPERIMENTAL DATASET

This publication provides a dataset of 54 experiments, carried out with supercritical CO2 (sCO2) in two heated horizontal pipes with inner diameters of 4 and 8 mm at a pressure of approximately 7.75 MPa. The mass fluxes were set to 400 and 800 kg/m2s and the heat flux was varied from 30 to 130 kW/m2, resulting in a heat to mass flux ratio of 38 to 225 J/kg. The influences of the inner pipe diameter, the Reynolds number and the heat to mass flux ratio on the thermal stratification were studied. Temperature differences up to 90 K between the bottom and the top of the pipe have been detected. By varying the bulk fluid inlet temperature, the thermal inflow lengths have been quantified for a fully developed temperature stratification with up to 180 inner pipe diameters. The Petukhov and Richardson buoyancy criteria show that the experimental results are strongly influenced by buoyancy. For the Jackson buoyancy criterion, a new threshold of higher than 160 is proposed. The validation of four empirical Nusselt correlations shows that the Bishop correlation has the lowest total average deviation of 52 %, especially for the bottom site of both pipes with an average deviation of 29 %.

本研究公开了一套包含54组实验的数据集，实验以超临界二氧化碳（supercritical CO2，sCO2）为工质，在内径分别为4 mm与8 mm的两根水平加热圆管中开展，实验压力约为7.75 MPa。实验设定的质量流速为400 kg/(m²·s)与800 kg/(m²·s)，热流密度范围为30~130 kW/m²，由此得到的热流-质量流速比区间为38~225 J/kg。本研究探讨了管内径、雷诺数以及热流-质量流速比对热分层现象的影响规律。实验观测到管底部与管顶部间的最大温差可达90 K。通过改变流体主体入口温度，本研究量化了充分发展温度分层下的热流入长度，其最大可达180倍管内径。基于Petukhov与Richardson浮力准则的分析表明，实验结果受浮力作用影响显著。针对Jackson浮力准则，本研究提出了大于160的全新阈值。对4项经验努塞尔（Nusselt）关联式的验证结果表明，Bishop关联式的总平均偏差最低，仅为52%；尤其在两根圆管的底部区域，其平均偏差仅为29%。