Heat Transfer and Hydraulic Characteristics of Supercritical CO2 in Cooled and Heated Horizontal Semicircular Channels

Heat transfer characteristics of supercritical CO2 in horizontal semicircular channels are numerically investigated using Computational Fluid Dynamics method validated with experimental data. Comparison study is conducted for semicircular and circular channels with the same hydraulic diameter and boundary condition at the bulk temperature range including pseudocritical point. The results show that the heat transfer coefficients of the semicircular channel are significantly smaller than those of the circular channels due to the blocking effect at the corner area of the channel cross section, and the fluid thermophysical properties near the wall have a significant effect on the convective heat transfer performance in both heating and cooling cases. A modified model was proposed based on Olson correlation of the semicircular channel considering the channel geometry and near-wall fluid viscosity influence. Further study was conducted to discuss the effect of hydraulic diameter and boundary conditions on the heat transfer performance of the semicircular channel and indicate that the modified correlation shows a reasonable prediction of the heat transfer coefficients in the heated semicircular channel.