A heat transfer dataset for supercritical carbon dioxide flowing in three directly heated tubes with internal diameters equal to 4.6, 8.0 and 22.0 mm under closely incremented and widely ranging operating conditions

All experimental results were collected in the multi-fluid Supercritical University of Ottawa Loop (SCUOL). This facility was designed to operate at a maximum pressure of 10 MPa and contained carbon dioxide as the working fluid. Measurements were collected in three electrically heated circular tubes with inner diameters D = 4.6, 8.0 and 22.0 mm, wall thicknesses 0.89, 1.00, and 1.50 mm and heated lengths of 1200, 1940 and 2000 mm, respectively; each heated test section was preceded by an unheated section of the same tube. Wall temperature was measured by closely spaced, surface mounted, T-type thermocouples. The bulk fluid specific enthalpy along the heated test section was calculated using the energy equation. Local values of the carbon dioxide thermophysical properties were computed from specified values of pressure and temperature using the NIST software. The three datasets, one for each test section, include wall temperature, bulk temperature, and heat transfer coefficient profiles for each condition measured. The conditions include a reduced pressure that was 1.13 times the pressure of supercritical carbon dioxide. The mass flux (G) was incremented by increments of 100 kg/m^2s up to G = 700 kg/m^2s, with measurements also taken at G = 1000 and 1500 kg/m^2s for the 4.6 and 8 mm test sections. For each G, measurements were taken for three or four different wall heat fluxes (q) at levels slightly below and above the corresponding value at heat transfer deterioration onset. For each of the mass flux and heat flux combinations, tests were performed for inlet temperatures in the range 0 ◦C所有实验数据均采集自多流体超临界渥太华大学回路（Supercritical University of Ottawa Loop，SCUOL）。该实验装置设计最大工作压力为10 MPa，以二氧化碳作为工质。实验数据采集于三根电加热圆管，其内径D分别为4.6、8.0和22.0 mm，管壁厚度分别为0.89、1.00和1.50 mm，加热段长度分别为1200、1940和2000 mm；每段加热测试段前均设有一段同规格的非加热段。壁面温度通过密集布设的表面安装式T型热电偶测得。沿加热测试段的主流流体比焓由能量方程计算获得。二氧化碳的局部热物理性质通过NIST软件，由指定的压力和温度参数计算得到。三个测试段各对应一套数据集，包含各测试工况下的壁面温度、主流温度以及换热系数分布数据。本次测试的对比压力为超临界二氧化碳压力的1.13倍。质量流速（mass flux，G）以100 kg/(m²·s)为步长递增，直至G=700 kg/(m²·s)；针对内径4.6 mm和8.0 mm的测试段，额外采集了G=1000和1500 kg/(m²·s)工况下的实验数据。针对每一个质量流速工况，分别在略低于和略高于传热恶化起始点对应的壁面热流密度（heat flux，q）的3~4个不同水平上采集实验数据。针对每一组质量流速与热流密度的组合工况，实验测试了入口温度处于0 ℃范围内的工况。