Minimum power requirement for environmental control of aircraft

This paper addresses two basic issues in the thermodynamic optimization of environmental control systems (ECS) for aircraft: realistic limits for the minimal power requirement, and design features that facilitate operation at minimal power consumption. Four models are proposed and optimized. In the first, the ECS operates reversibly, the air stream in the cabin is mixed to one temperature, and the cabin experiences heat transfer with the ambient, across its insulation. The cabin temperature is fixed. In the second model, the fixed cabin temperature is assigned to the internal solid surfaces of the cabin, and a thermal resistance separates these surfaces from the air mixed in the cabin. In the third model, the ECS operates irreversibly, based on the bootstrap air cycle. The fourth model combines the ECS features of the third model with the cabin-environment interaction features of the second model. It is shown that in all models the temperature of the air stream that the ECS delivers to the cabin can be optimized for operation at minimal power. The effect of other design parameters and flying conditions is documented. The optimized air delivery temperature is relatively insensitive to the complexity of the model; for example, it is insensitive to the size of the heat exchanger used in the bootstrap air cycle. This study adds to the view that robustness is a characteristic of optimized complex flow systems, and that thermodynamic optimization results can be used for orientation in the pursuit of more complex and realistic designs. © 2003 Elsevier Ltd. All rights reserved.

Duke Scholars

Author Adrian Bejan Thomas Lord Department of Mechanical Engineering and Materia ...