Optimization and heat transfer correlations development of zigzag channel printed circuit heat exchangers with helium fluids at high temperature

Abstract

The printed circuit heat exchanger (PCHE) is an important candidate to be used as intermediate heat exchanger (IHX) in a High Temperature Gas-cooled Reactor (HTGR) plant due to its advantages in terms of safety, heat transfer and compactness. In this work, an analysis of the thermal-hydraulic performance of the zigzag channel PCHE within wide parameter ranges was conducted using computational fluid dynamics (CFD) techniques. The Nusselt number and the Fanning friction factor obtained from simulation were validated using experimental data available. To consider the interaction among parameters with a reduced computing time, the Taguchi method was used, which reduces the quantity of analyzed geometric designs. Optimized designs were proposed to reach the highest Nusselt number and lowest friction losses using the signal to noise ratio as objective function. It was found that the zigzag angle has contribution ratios around 50% and 70% on the values of pressure drop and heat transfer, respectively. Although the zigzag phase-shift was the parameter of least influence, its contribution ratio was close to 10% in the turbulent regime, which is comparable to the zigzag pitch length and bend radius contributions. As the most important contribution, Nusselt number and Fanning friction factor correlations were proposed as functions of the Reynolds number and the geometrical parameters. The new correlations were found to be more accurate as compared to existing ones in the literature.