Energy Simulation in Aviation

XRG develops tools and applications for the analysis and optimization of complex thermodynamic systems in aviation. This includes analysis and dynamic simulation of air conditioning and pressurization control, ventilation, pressure regulation, heating, cooling, humidification, as well as regulation and control of air distribution including consideration of air quality (e.g., contaminants, smoke, viruses).
With our methods, the thermal behavior of various systems can be modeled and examined. This includes, for example, the temperature and flow distribution within the pressure hull, starting from the initial design through prototype tests of future cabin architectures to existing customer-specific system layouts. Another focus of our work is the modeling of the supply and thermal management of new propulsion systems such as fuel cells.


Our simulations and modeling include:

  • Environmental Control System (ECS) architectures
  • Air conditioning units (packs)
  • Cabin air distribution
  • Fuel Cell Systems (FCS) including controls
  • Media models (moist air-H2, -N2+O2)
  • Hydrogen storage technologies
  • Thermal management of aviation components and systems
  •  Air and moisture transport in aircraft cabins and insulations 

With the help of these models, XRG is able to answer various questions at the component level, but also for the interaction of entire subsystems (virtual demonstrator). Innovative simulation methods, uncertainty analyses, surrogate modeling, and reinforcement learning complete the offering.

In cooperation with renowned institutes and companies, XRG researches various projects in the field of aviation. 

These include simulation-based thermal aircraft designs, the development of a Modelica-based multi-physics compartment model (EEBAY), as well as the investigation of model reduction techniques for surrogate models and model coupling to a larger system model (direct Modelica and co-simulation). 

In another aviation project, XRG has researched aircraft cooling systems with natural circulation. Innovative Modelica pipe models for detailed flow analyses (Euler-Euler method for multi-phase flows) have been developed, and new interpolation methods have been investigated to increase simulation robustness and reduce simulation time.

Case Study - Cabin Humidity 

The humidity in aircraft has both positive and negative effects. Moist air has a positive effect on passenger comfort. At the same time, it increases condensation or freezing of water on cold surfaces and in insulation. Therefore, higher humidity is generally avoided. The condensate increases the weight of the aircraft (up to several hundred kilograms in large aircraft), causes corrosion, and moves uncontrollably in the aircraft fuselage ("rain in the aircraft"). 

The Mohicab project was conducted in cooperation with the Hamburg University of Technology and AIRBUS Operations GmbH and aimed to investigate various insulation layers through numerical simulation. XRG's contribution consisted of developing the MohicabLib model library: This detailed insulation model library (DIM) enables the analysis of water paths and water storage within insulation layers. Since its creation, the DIM model has been successfully applied and further developed in several projects, such as SINTEG I / II, INDIKAR, and other joint projects with AIRBUS.

Case Study 2 - Innovative Device Cooling 

NAKULEK stands for “NAturumlaufKUehlung für LEistungselektroniK” (natural circulation cooling for power electronics). In the context of this project, a new aircraft cooling system based on natural circulation is being investigated. With natural circulation cooling, high reliability can be ensured as the system operates without active components like a pump. Additionally, the total mass of the system can be reduced since the high enthalpy of evaporation of refrigerants allows for very small pipe diameters. Possible applications include cooling systems for power electronics, batteries, and fuel cells. 

XRG is researching new modeling techniques for digital development. Three research areas are at the core of the project:

  • Development of an innovative interpolation method for calculating fluid data. This allows the investigation of new refrigerants, which is crucial as environmental restrictions demand the replacement of existing cooling fluids. Additionally, the new interpolation method enables an increase in simulation speed.
  • Modeling of a new fluid-pipe model (Six-Equation or Euler-Euler multi-phase Models), where liquid and gas phases and their interactions are individually modeled. With these models, a detailed model of the cooling flow can be realized, e.g., different flow directions / flow velocities of gas and liquid phases as well as non-thermodynamic equilibrium (different temperatures).
  • Modeling of aircraft motion to investigate the influence of aircraft roll, yaw, and pitch angles. This allows the influence of aircraft motion on the cooling system performance to be studied. 

The successful implementation of these project topics enables the project partner to develop cooling systems with natural circulation.