Heat transfer and pressure drop characteristics of supercritical CO₂ in horizontal semicircular channels was investigated numerically. Comparison study of flow and heat transfer characteristics of semicircular and circular channels at the same inlet velocity and mass flux was conducted respectively with the bulk temperature ranging from 27 °C to 67 °C. It is shown that the fluid heat transfer coefficient and pressure drop in the circular channel are slightly higher than those of the semicircular channel, but the fluid temperature drop through the circular channel is lower than that of the semicircular channel under the same hydraulic diameter. The effect of heat flux and channel hydraulic diameters on the heat transfer coefficient and pressure drop was analyzed for horizontal cooling semicircular channels. It is found that smaller hydraulic diameter enhances heat transfer, but the channel flow resistance increases significantly. The numerical results also indicate that the pressure drop decreases with the increase of heat flux, and the heat transfer coefficients depend on both bulk temperature and cooling heat flux.

超临界CO _2的传热和压降特性在水平半圆形通道中进行了数值研究。在相同的入口速度和质量通量下，在整体温度范围为27°C至67°C的情况下，分别进行了半圆形和圆形通道的流动和传热特性的比较研究。结果表明，在相同的水力直径下，圆形通道内的流体传热系数和压降略高于半圆形通道，但通过圆形通道的流体温度降幅小于半圆形通道。分析了水平冷却半圆形通道的热通量和通道水力直径对传热系数和压降的影响。发现较小的水力直径可增强热传递，但通道流动阻力显着增加。数值结果还表明，压降随热通量的增加而减小，并且传热系数取决于体温和冷却热通量。