Abstract:

Supercriticl CO₂ has shown great potential in the fields of tower solar thermal power generation and nuclear energy industry. In order to study the heat transfer characteristics of supercritical CO₂ in an inclined upward tube under cooling conditions, numerical simulation methods were used to simulate it by dividing it into liquid like zone, quasi critical zone, and gas like zone according to temperature, analyze the density and temperature field distribution of supercritical CO₂ in an inclined upward tube, as well as the variation of its convective heat transfer coefficient and average resistance coefficient along the tube length, and study the effects of different tilt angles, mass fluxes, and pressures on the heat transfer performance of supercritical CO₂. The research results indicate that the change in tilt angle has an impact on the convective heat transfer coefficient and average resistance coefficient of supercritical CO₂ in the liquid like region, but has no effect on the gas like region. An increase in mass flux can increase the convective heat transfer coefficient and reduce the average drag coefficient. The change in pressure has a significant impact on the convective heat transfer characteristics in the quasi critical and gas like zone.

Key words: supercritical carbon dioxide, flow, heat transfer, numerical simulation, turbulent flow

摘要：

超临界CO₂在塔式太阳能热发电和核能工业领域中展现出了巨大潜力，为了研究超临界CO₂在冷却条件下倾斜上升管内的换热特性，采用数值模拟方法，将其分为类液区、跨临界区、类气区分别进行模拟，分析了倾斜上升管中超临界CO₂的密度场与温度场分布及其对流传热系数和平均阻力系数沿管长的变化规律，并研究了不同倾斜角度、不同质量通量以及不同压力对超临界CO₂换热性能的影响。研究结果表明：倾斜角度变化对于类液区超临界CO₂的对流传热系数和平均阻力系数有所影响，对类气区则没有影响；质量通量的增大能够提高对流传热系数，减小平均阻力系数；压力的改变对拟临界区及类气区的对流传热特性影响较大。

关键词: 超临界二氧化碳, 流动, 传热, 数值模拟, 湍流