Dynamic Model of Vapor Compression Systems for Aircraft Environmental Control Systems

The optimization of novel aircraft Environmental Control System (ECS) architectures necessitates the support of complex numerical simulations. Within the framework of the more electric aircraft approach, a promising strategy to enhance the overall efficiency of traditional ECS involves the incorporation of vapor compression systems (VCSs), which offer superior cooling efficiency compared to conventional air cycle machines. In this study, a Modelica/Dymola library for simulating VCSs has been developed, with a focused emphasis on three critical attributes: numerical robustness, accuracy, and minimal computational time. To successfully integrate and simulate the VCS model into an entire ECS model, these characteristics are essential. An appropriate tradeoff has been achieved between the computational cost of the VCS model and its ability to accurately predict the system’s physical behavior (the heat exchangers have been modeled using a partial dynamic approach to optimize both robustness and computational efficiency). The VCS model has undergone thorough testing and has been seamlessly integrated into a representative ECS model to replicate a typical commercial airplane flight mission. A comparative analysis of the advantages offered by a variable-speed compressor versus a fixed-speed one has been conducted, revealing potential energy savings of up to 40%. Furthermore, the incorporation of an internal heat exchanger has led to additional energy savings exceeding 5%.