Air Conditioning for Aerospace
Consideration of the comfort felt by passengers and crew is of great importance in the design phase of air-conditioning system for an aircraft. The thermal comfort in the aircraft cabin is influenced by the interaction of several factors including pressure, temperature, air speed and humidity.
The environmental control system (ECS) supplies conditioned air to maintain the desired temperatures, ventilation rates and pressurization within the cabin zones and flight deck. A typical environmental control system consists of the air-conditioning packs, the mixer unit, the air distribution and recirculation system and the pressurization system, including the associated fans.
The air-conditioning packs consist of heat exchangers, compressors, water extraction and turbines and provide conditioned air to the mixer unit. In the mixer unit, the conditioned air is mixed with recirculated and filtered cabin air (extracted out of the cabin, usually at floor level), which is fed by recirculation fans to the mixer unit. The air-conditioning packs and mixer unit also receive hot bleed air from the engines or auxiliary power unit (APU). The air from the mixer unit is distributed to the cabin temperature control zones, the flight deck and cargo compartments. The independent temperatures for the different compartments can be achieved by directing hot trim air to the distribution ducts. In addition ventilation has to be provided for the electrical and electronic racks. The cabin pressure is regulated automatically by the outflow valve position depending on the required cabin pressure change rate and differential pressure between cabin and ambient.
To model this complex system in Dymola and to optimise the control and efficiency of the system to meet the passenger comfort targets throughout the cabin a number of libraries can be combined to model the complete system. The Air Conditioning library can provide the components to model the air-conditioning packs, mixer unit and distribution network with the Modelica Standard Library being used to develop the cabin models and control system models.
Dymola Air Conditioning Library
Dymola and the AirConditioning library allows you to optimize and verify the design of your air conditioning system from the early design phases through control design and implementation. Dymola’s multi-engineering capabilities let you fully integrate the HVAC system design with vehicle energy management for conventional and hybrid vehicles. The Air Conditioning library features an open, object-oriented architecture with access to the model source code in Modelica.
Our unique advantage makes the AirConditioning library the preferred solution for design engineers. The library models are based on several years of experience and validation in advanced research applications. The library is adapted to the particular needs of automotive air conditioning systems. Users can connect components freely as they desire, which makes it is easy to realize non-standard configurations such as parallel evaporators.
A/C System Modeling
All commercial refrigerants, (R134a, CO2, R404a, R410a, etc) can be used as working media. The new refrigerant blends that are discussed as global alternative refrigerants, Fluid H from Honeywell and others, are also available. The selection of correlations for friction pressure losses and heat transfer is based on up to date research and is under constant review. The airflow distribution across the face of the heat exchangers can be inhomogeneous and use CFD result data as inputs. The hierarchical structure of the library and a clean separation between the underlying physics and the geometrical parameterization are key features that make adaptation to new components and technologies easy.
Template models of typical automotive A/C-cycles and dialogs with detailed graphical information about the components make the library convenient and easy to use. The modular, hierarchical structure of the library enables power users to integrate their own correlations and component models seamlessly into their system models.
For hybrid vehicles of all types, electrically driven compressors are discussed as a possibility to improve the overall energy management and reduce the fuel impact of the AC-system. Dymola lets you combine the electric drive and its control from the Smart Electric Drives Library or a conventional powertrain from the PowerTrain Library with a cabin model and AC-cycle from the AirConditioning Library. AirConditioning supports the design engineer during all development phases: from early concept studies through detailed component selection to system and control design. High fidelity models lets you perform virtual charge optimization experiments for cycle variants.
An interface to MS Excel simplifies calibration of component models with test rig measurements. The German automotive manufacturers, DaimlerChrysler, BMW, Audi and Volkswagen, have jointly decided to use Dymola and the new AirConditioning library as a tool for model exchange and simulation of automotive air conditioning systems. Key reasons for choosing Dymola and the Air Conditioning library were the flexibility and openness of the model libraries and Modelica as an open modeling standard. Several Tier 1 automotive A/C equipment manufacturers are using the Air Conditioning library for their internal development and model exchange with the OEM. To find out more about the library why not download the brochure.
DaimlerChrysler, BMW, Audi and Volkswagen choose Dymola for modeling and simulation of air conditioning systems
The German automotive manufacturers, DaimlerChrysler, BMW, Audi and Volkswagen, have jointly decided to use Dymola and the new AirConditioning Library as a tool for model exchange and simulation of automotive air conditioning systems. After an extensive benchmark study Dymola was chosen in competition with several other modeling and simulation tools. Dymola and the AirConditioning Library provide exciting possibilities for simulating automotive air conditioning systems.
The flexibility and openness of the model libraries in Dymola was a significant factor for choosing Dymola. The open architecture allows users to adapt models of the library to in-house know-how and users are not forced to work with a fixed set of proprietary component models.
As Daimler Chrysler, BMW, Audi and Volkswagen have chosen a common tool for simulation of air conditioning systems, suppliers of air conditioning components are intended to supply models to the above mentioned automotive manufacturers. This means that component suppliers will be integrated in the design process and the automotive manufacturers will be able to simulate components from different suppliers using one simulation platform. The combination of the manufacturer’s knowledge of vehicle performance goals and the component expertise of the supplier ensure reliable simulation results and an accelerated integration and time-to-market process.
Aerospace
