PCHE内轴向导热对局部换热性能的影响研究

通过改变印刷电路板式换热器（PCHE）通道壁厚、直径以及冷热侧CO₂进口温度差，数值分析了层流条件下，轴向导热对PCHE内超临界压力CO₂流动换热的影响。结果表明，考虑轴向导热时，局部热通量沿程变化更加平缓，冷侧对流传热系数在小于拟临界温度区域变小，而热侧对流传热系数在小于拟临界温区域增大；轴向导热仅对热效率峰值附近区域有所影响，其使得峰值略有增大且向低温侧移动；传热熵产主要发生在高温区域，轴向导热可有效降低局部传热熵产。增大壁厚和直径可增大轴向导热的影响，而增大进口温差，轴向导热的影响变化不大。

Investigations of axial conduction effect on local heat transfer performance in PCHE

Numerical investigations of the axial conduction effect on the local heat transfer performance of the printed circuit heat exchanger (PCHE), which has straight channels and use supercritical pressure carbon dioxide (SCO₂) as working fluid, were conducted under laminar conditions. Variations of local heat flux, heat transfer coefficient, heat effectiveness and entropy generation due to heat transfer in PCHEs were obtained under the conditions with or without axial conduction, when the wall thickness, diameter as well as the inlet temperature difference between the two sides get changed. Then, the effect of the axial heat conduction could be analyzed by comparing the results with/without the axial conduction. It was found that the axial conduction could greatly impact the temperature distributions in both solid and fluid domains and lead to significant changes to the convective heat transfer of SCO₂ in PCHEs. When the axial conduction exists, the local heat flux variations get more even along the flow direction, and smaller heat transfer coefficient of the cold side as well as larger heat transfer coefficient of the hot side in the region of T _pc are also observed. The axial conduction would enlarge the peak heat effectiveness slightly and bring it to a lower bulk temperature. The heat transfer entropy production mainly occurs in the high temperature region, and the axial heat conduction can effectively reduce the local heat transfer entropy. Increasing the wall thickness and diameter can increase the influence of axial heat conduction, while increasing the inlet temperature difference, the influence of axial heat conduction does not change much.