In military aircraft, electronics are often subjected to
operating environments well beyond their survival temperatures and
with limited heat sinks. The current approach is to use a Liquid
Cooling System (LCS) with either vehicle fuel or Polyalphaolephin
(PAO) to cool electronics. However, advanced military platforms
have found this approach limits their operational effectiveness. A
thermal management system for electronics cooling in high
temperature avionics environments is under development using Loop
Heat Pipe (LHP) and heat pipe-based technology. The system reduces
thermal energy transport inefficiencies within electronics
enclosures, identifies potential sinks to provide continuous heat
rejection over the operating envelope of the platform, and provides
passive thermal energy transport from the electronics enclosure to
selected sinks.
The system developed to accomplish these tasks is divided into
two subsystems. The first subsystem is responsible for improving
thermal transport within the electronics enclosure and consists
primarily of heat pipe assemblies. Model results of the first
subsystem show considerable improvements over the current
implementation. The overall temperature gradient within a generic
electronics box decreased from 42.7°C (76.9°F) to 17.8°C (32.0°F),
increasing the allowable sink temperature from 66.7°C (152.1°F) to
91.7°C (197.1°F). This increase allows for more freedom in sink
selection, which is typically limited aboard military platforms.
The second subsystem transports thermal energy from the external
surface of the enclosure to appropriate sinks and consists
primarily of a LHP. At this stage, several sinks have been
identified and evaluated. Final sink selection is underway.
Depending on sink temperature and capacity throughout the operating
envelope of the platform, multiple sinks may be used. During
operation, the LHP will passively select the appropriate sink.