Integrative thermodynamic optimization of the environmental control system of an aircraft

In this paper we propose to optimize the geometric configuration of a component by maximizing the global thermodynamic performance of the much larger system that contains the component. This “integrative” approach departs from current thermodynamic optimization practice in which the configuration of a component (e.g., heat exchanger) is optimized by itself, in isolation. In the present example the larger system is an aircraft and the component is its environmental control system (ECS). We show that the configuration of the ECS impacts the performance (exergy destruction, fuel consumption) of the aircraft in two ways, not one: through its own irreversibility, and its weight-related contribution to the power required to sustain the flight. By minimizing the thermodynamic losses at the aircraft level, we deduce all the geometric details of the cross-flow heat exchanger that dominates the weight and structure of the ECS. The optimized geometry is robust with respect to changes in some of the operating parameters that have to be specified. The integrative method illustrated in this paper is generally applicable to the optimization of architecture in other systems where all the functions are driven by the exergy of the fuel installed onboard.