Abstract Three different types of axially nonuniform heat fluxes are imposed on the outer surface of a vertical circular tube with turbulent supercritical carbon dioxide (S-CO2) flowing upward. The aim is to explore the potential in adjusting the axial heat flux distribution to optimize heat transfer. Numerical simulations are conducted to investigate how varying the heat flux in the axial direction influences several convective heat transfer behaviors (DHT: deteriorated heat transfer, NHT: normal heat transfer, EHT: enhanced heat transfer). It was found that DHT can be restrained by decreasing the local heat flux in the entrance region. Superior local heat transfer performance is realized for cases with a nonuniform heat flux defined by a piecewise linear function. The present study provides fundamental insight into the mechanisms of heat transfer under a varying axial heat flux and shows the promise of adjusting the axial heat flux distribution to obtain NHT, or even EHT, for S-CO2 flowing upward in a vertical tube.

中文翻译：

---

超临界 CO2 在受轴向不均匀加热的垂直管中向上流动

摘要 三种不同类型的轴向不均匀热通量施加在垂直圆管的外表面，湍流的超临界二氧化碳 (S-CO2) 向上流动。目的是探索调整轴向热通量分布以优化传热的潜力。进行数值模拟以研究轴向热通量的变化如何影响几种对流传热行为（DHT：劣化传热，NHT：正常传热，EHT：增强传热）。发现可以通过降低入口区域的局部热通量来抑制 DHT。对于由分段线性函数定义的非均匀热通量的情况，实现了卓越的局部传热性能。