In the study, the thermal-hydraulic performance of the zigzag channels with circular cross-section was analyzed by Computational Fluid Dynamics (CFD). The standard K-Ꜫ turbulent scalable wall functions were used for modeling. The wall temperature was assumed constant 353 K and water was used as the working fluid. The zigzag serpentine channels with bend angles of 5 - 45° were studied for turbulent flow from 4000 to 40,000 Reynolds number (Re). The thermal performance of the zigzag 45° channel was better than the other channels and also it had the highest friction factor (f). The bends caused secondary flow, and as the bend angle increased, the secondary flow increased. This Phenomenon had a positive effect on thermal performance and a negative effect on hydraulic performance by increasing the friction factor. The obtained CFD data used to develop correlations for predicting the Nu and f as the functions of Re and bend angles. The correlation constants were optimized by the genetic algorithm method which leads to the mean relative errors of 3.32% and 6.94% for Nu and f estimation, respectively.
