Dynamic behaviour of compact heat exchangers in aircraft environment control system

Abstract This study presents a dynamic analysis of compact heat exchangers (CHEs) integrated within an aircraft Environmental Control System (ECS), with emphasis on their transient thermal behaviour under varying operating conditions. A dynamic model is developed using the ECS library in a 1-D system simulation platform. Characteristic maps of heat exchanger effectiveness as functions of hot and cold fluid mass flow rates are generated in MATLAB for the primary heat exchanger (PHE), secondary heat exchanger (SHE), reheater (RHX), and condenser (CND), and subsequently imported into the ECS library framework. The model employs pressure–temperature sources at the inlets and temperature–mass flow sinks at the outlets on both hot and cold sides. Dynamic performance is evaluated in terms of hot- and cold-side outlet temperatures, hot-side heat flow rate, and system response time. Parametric analysis reveals that the fluid channel volume has a dominant influence on transient response compared to heat exchanger effectiveness. For an isolated heat exchanger, the dynamic response time increases from approximately 10 s to 25 s as the fluid channel volume increases from 0.5 m³ to 1.5 m³. Stabilised hot-side outlet temperatures of about 86 °C, 162 °C, 369 °C, and 453 °C are obtained for effectiveness values of 0.98 (SHE), 0.84 (PHE), 0.43 (RHX), and 0.25 (CND), respectively, corresponding to hot-side heat flow rates of 339.40 kW, 288.17 kW, 146.84 kW, and 88.37 kW. Furthermore, an integrated ECS configuration combining the PHE and SHE is modelled, demonstrating longer response times for the SHE (≈ 20–40 s) compared to the PHE (≈ 10–25 s) over the same range of fluid channel volumes. The results clearly demonstrate the significance of transient analysis in the design and optimisation of compact heat exchangers for aerospace ECS applications.