Performance analysis of scCO2 closed Brayton cycle applied to aero engine thermal protection considering flow and heat transfer characteristics inside the scCO2-fuel heat exchanger

To clarify the cycle performance considering flow and heat transfer characteristics inside the heat exchanger, this paper constructs a calculation model which combines heat exchanger model for an onboard scCO₂ closed Brayton cycle cooling system. Based on the model, the influence of fluid mass flow rate and flow heat transfer characteristics on cycle performance are clarified. The results indicate that the scCO₂ pressure losses inside the heat exchanger is the dominate factor on the cycle performance. The heat transfer deterioration inside heat exchanger caused by laminar flow area of fuel deteriorate the cycle performance. A critical fuel mass flow rate is found that the increase in fuel mass flow rate improves cycle thermodynamics performance below it and remains roughly constant above it. Furthermore, the increase in the heat exchanger’s flow area improves cycle thermal efficiency, however decreases the power-to-weight ratio of the heat exchanger, limiting its feasibility. Ultimately, recuperated layout can enhance system thermodynamic performance but deteriorate cooling performance.