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The rapid increase of liquid cooling demand from high-power and high-density avionics in military aircraft has been a challenge for aircraft cooling system designers. A number of state-of-the-art approaches were presented in SAE 2003-01-2399. This paper is a continuation of that discussion on the advancement of environmental-control-system design to meet the higher demands for liquid cooling. In this paper, another advanced environmental control system will be presented. The advanced system is one of a new generation of “bootstrap” air-cycle cooling systems. Similar to a traditional bootstrap air-cycle system, the advanced system is powered by high-pressure engine bleed air and uses ambient ram air and/or on-board fuel as a heat sink. However, unlike a typical air-cycle system, the advanced system maximizes usage of engine bleed pressure to form a recirculation flow path.

A balance of mission capability, agility, survivability, affordability and mission range is a key to the advanced fighter aircraft design. The advanced fighter aircraft is equipped with high power and density electronic equipment to achieve a superior level of mission capability. Electrical power supplied to this equipment is generated by engine powered generator. The heat generated by this equipment typically is cooled by an onboard environmental control system (ECS) operated by high-pressure pneumatic air from the engine compressor. Both the supplied power and power generating the cooling source are a power extraction from the engine. As fuel is the sole energy resource in the aircraft, this power presents a penalty of the use of fuel and results in reduction in the mission range. The challenge to ECS designer is to maximize the cooling capacity with the minimum energy consumption.