Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Abstract

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

Operation and Multi-Objective Design Optimization of a Plate Heat Exchanger with Zigzag Flow Channel Geometry

“…It repeats periodically, as shown in Figure 2b. The entire PHE can be approximated by such a simplified model with periodic boundaries on the top and bottom surfaces, and since the simulation focuses on the vertical heat transfer, the lateral surface boundaries are set to be adiabatic [26][27][28], as shown in Figure 4, to save computation time. The channel geometry is the same as the practical PHE geometry and simplified into three zigzag channels with semicircular cross-sections.…”

“…The smaller the bending angle, the more pronounced the Dean vortices. The occurrence of vortices in the flow can enhance collisions between fluid parcels but cause more pressure loss [28]. As a result, design point A' presents a higher effectiveness value but a more significant pressure loss.…”