According to the statistics about civil transportation aircraft EnvironmentalControl system (ECS), the three-wheel high pressure water separation system(HPWS) and low pressure water separation system (LPWS) are the mostcommon choices for the 150-seat airliners. Although the former has become themainstream configuration for air conditioning pack, the latter is still used onBoeing 737-600/700. In order to compare the two configurations and choose thebetter one for a specific aircraft, simulation and analysis are done.The cabin heat load is calculated at first in order to calculate required enginebleed air mass flow. Then a specific aircraft is defined so that required structuraldimensions and cabin comfort indexes can be obtained based on Airbus 320.Thirdly, the component models are built by Matlab/Simulink according to thefundamental knowledge of heat transfer and aerodynamics, the workingprinciples and mechanical dimensions of the components, the ambientenvironmental parameters and some data from Airbus 320. Consequently, thecomplete system model can be assembled. After confirming the validity of themodel by checking the required ram air mass flow and temperature deviation ofthe state points referred to Airbus 320, the simulation model is used to doanalyze the specific aircraft. Finally, through comparing the different values ofram air mass flow and turbine expansion ratio, as well as the system mass,economic cost and reliability, the better configuration is selected.It can be summarized that the three-wheel LPWS requires less ram air massflow (0.012kg/s) and a little lower expansion ratio (0.02) than the HPWS, and italso has lower weight (63% of HPWS), lower (83% of HPWS) cost and higherreliability (140% of HPWS), thus it is the suitable configuration for the specificaircraft.
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