冷却条件下渐扩/渐缩管内超临界压力二氧化碳的传热特性

Heat transfer characteristics of supercritical pressure CO_(2)in diverging/converging tube under cooling conditions

采用SSTk-ω湍流模型,数值计算了冷却条件下超临界压力二氧化碳(SCO_(2))在三种水平管(等截面管、渐扩管和渐缩管)内的传热特性,研究了不同运行参数(压力、质量流量及热通量)对传热性能的影响。结果表明,与等截面管相比,渐扩管有效地强化了传热,采用渐扩管时,SCO_(2)的总传热系数最大提高了47.98%。然而,相比等截面管,渐缩管却削弱了传热。最后,从类冷凝和湍流场分布的角度阐明了传热强化的物理机理。为SCO_(2)冷却器的优化设计提供了新的思路和理论指导。

Using the SST k-ωturbulence model,the heat transfer characteristics of supercritical carbon dioxide(SCO_(2))in three kinds of horizontal tubes(uniform cross-section tube,diverging tube and converging tube)were numerically calculated under cooling conditions,and different operating parameters were studied(pressure,mass flow and heat flux)on heat transfer performance.The computational results demonstrate that the diverging tube effectively strengthen heat transfer compared with the uniform cross-section tube.A maximum improvement of 47.98%in overall heat transfer coefficient can be observed with the employment of diverging tubes.However,the converging tube weakens the heat transfer.According to the distribution of quasi-liquid film and turbulent kinetic energy,the physical mechanism of heat transfer enhancement is clarified by the dual-effect of quasi-liquid film and turbulent kinetic energy on this account.Our work provides a new idea and theoretical guidance for the optimal design of SCO_(2)cooler.