Numerical investigation on maldistribution of S-CO2 flow inside PCHE under rolling conditions

Abstract

Heat exchangers with mini-channels, such as the printed circuit heat exchanger (PCHE), are key components for supercritical carbon dioxide (S-CO2) Brayton cycle due to advantages in compactness and structural rigidity. Flow distribution plays an important role for PCHE performance and it is affected by environment conditions like rolling and heaving motions. The flow distributions and heat transfer characteristics among parallel mini-channels for S-CO2 flow under the steady and rolling conditions would be simulated in this paper. Two plateaus/shoulders were observed on the nonuniformity-Reincurve: one was caused by the flow regime changing from laminar to turbulence regime, and another due to the compromise of “heating up” and “flow rate” effects. The rolling effects on the thermal-hydraulic characteristics of S-CO2 flow inside PCHE would be further investigated. In general, the response of thermal-hydraulic characteristics would be slightly delayed, and the rolling effects increase with the rolling frequency, amplitude and radius. As the rolling period increases, the shapes of heat transfer coefficient and friction factor curves would no longer be sinusoidal. The heat transfer characteristics in each channel were also investigated and it could be found that the heat transfer coefficient increases with the flow flux (Re). The effects of rolling conditions could not be neglected for low flow mass rate and high rolling frequency. Adding baffles at manifolds significantly improves the flow distribution under rolling conditions.

Keywords

• PCHE
• Rolling condition
• CFD
• Flow uniformity