OPTIMIZATION OF THERMAL-HYDRAULIC PERFORMANCE OF A ZIGZAG CHANNEL PRINTED CIRCUIT HEAT EXCHANGER EMPLOYED AS IHX IN HTGR SYSTEMS

摘要

Intermediate heat exchangers are one of the most critical devices in the safety of facilities with very high temperature nuclear reactors. In this application, the printed circuit heat exchanger (PCHE) design has shown the greatest advantages in terms of heat transfer, compactness and structural strength. In this work, a thermal-hydraulic model of the zigzag channels PCHE was developed using computational fluid dynamics (CFD) techniques. The Nusselt number and the Fanning friction factor obtained from the CFD model was validated by comparison with correlations published by other authors and found by experimental data. Four geometric parameters of zigzag channels such as: zigzag length, zigzag angle, zigzag radius and zigzag phase-shift were chosen to optimize the PCHE design. With this in view, the model was set up with three channels for each cold and hot fluid, achieving a good accuracy. To consider the interaction among parameters with a reduced computing time, the Taguchi method was used to reduce the quantity of analyzed geometric designs. The zigzag angle was found like the most important geometric parameter in the thermal-hydraulic performance of the PCHE. The maximum value of the Nusselt number had the maximum value of zigzag angle and the minimum friction factor had the minimum value of zigzag angle. This is caused by the increment of the real length of the channels and the appearance of reverse flow zones for higher angles.