The influence of the cross section shape of microchannels on the thermos-hydraulic performance of the supercritical CO₂ fluid is an important issue in the design of industrial compact heat exchangers, but few studies have been conducted about this issue. In this paper, comparative studies of the flow and heat transfer performance of SCO₂ fluid in horizontal microchannels with circular, semicircular, rectangle, and trapezoidal cross sections were conducted numerically. The comparison is based on the same hydraulic diameter and length for all channel types and is carried out under the same mass flux, outlet pressure, and wall heat flux. The fluid bulk temperature in this analysis ranges from 285 K to 375 K, which covers the pseudocritical point of SCO₂. The results show that the circular channel has the highest average heat convection coefficient, while the trapezoidal channel has the worst convective heat transfer performance under the same hydraulic diameter and boundary conditions. The results also indicate that the effect of cross section shape on the heat convection coefficient is significantly greater than that on the channel pressure drop, and the existence of the corner region in the cross section, especially the acute angle, will weaken the heat transfer performance.

中文翻译：

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超临界CO2流体微通道不同截面形状的热工水力性能对比研究

微通道横截面形状对超临界CO ₂流体热工水力性能的影响是工业紧凑型换热器设计中的一个重要问题，但关于这个问题的研究很少。本文对SCO ₂流体在圆形、半圆形、矩形和梯形横截面的水平微通道中的流动和传热性能进行了数值比较研究。比较基于所有通道类型的相同水力直径和长度，并在相同的质量通量、出口压力和壁面热通量下进行。该分析中的流体整体温度范围为 285 K 至 375 K，涵盖了 SCO ₂的伪临界点. 结果表明，在相同水力直径和边界条件下，圆形通道的平均热对流系数最高，梯形通道的对流换热性能最差。结果还表明，截面形状对热对流系数的影响显着大于对通道压降的影响，截面角部特别是锐角的存在会削弱传热性能.