Impact of the Dead State Point Selection on the Exergy Analysis of Aircraft Environmental Control Systems

Abstract

The analysis of energy intensive systems using the exergy analysis is a powerful tool to reveal the weakness of the respective system. But by its nature, it will not give absolute results as exergy is the maximum usable work relative to a reference point. This paper presents the influence of the reference state selection on the results obtained from the exergy analysis of a conventional aircraft air generation unit (pack). The analysis is done for a complete flight mission. Physical and chemical parts of the exergy are considered separately and the relative positions of the thermodynamic states compared to the reference state are taken into account for the calculation of fuel and product exergy. Different approaches for selecting the reference environment are discussed and conclusions are drawn.