Heat transfer area optimization of intermediate heat-exchange cycle system for aero engines

•A mathematical model for optimizing intermediate cycle was proposed.•The model was numerically validated for an aero-engine intermediate cycle system.•Total heat transfer area of the intermediate cycle was optimized.•A new approach to determining optimal parameters of intermediate cycle was developed. The present study constructs an intermediate heat-exchange cycle system for aero engines. To explore the impact of circulation parameters on the cycle, a mathematical model has been developed. Based on the mathematical model, a novel and convenient approach to determining intermediate working fluid (IWF) mass flow rate and temperature, achieving the minimum total system heat transfer area, has been proposed. A two-stage heat exchanger combined intermediate heat-exchange cycle system with Chinese aviation kerosene RP-3, high-pressure water, and air as working fluids is taken as an example to verify the analytical results through numerical calculations. The deviation between the analytical and numerical results is relatively small, below 0.03%. For the situation of a given higher intermediate temperature, a wide range of IWF mass flow rates can be selected as the design point without significantly affecting the total heat transfer area. For the situation where both intermediate temperature and IWF mass flow rate are variable, an optimal area exists where the total heat transfer area is very low and does not differ much with each point. Overall, the present findings can serve as reasonably accurate preliminary guidelines for designing and optimizing the intermediate heat-exchange cycle system.