Passive Thermal management for avionics in high temperature environment
*Passive Thermal Management for
Avionics in High Temperature
• Avionics are the electronic systems used on
aircraft, artificial satellites, and spacecraft.
• Avionic systems include communications, navigation,
the display and management of multiple systems.
• The cockpit of an aircraft is a typical location for
*Under a program funded by the Air Force
Research Laboratory(AFRL), Advanced Cooling
Technologies(ACT) has developed a series of
Passive Thermal Management techniques for
*The rejection of the waste heat generated by the
electronics in the avionics to the surrounding
environment, results in a significant ambient heat
*As a result this high temperature reduces the life of
*Heat must be transported to a sink.
*The only viable sink is aircraft fuel, some times the
fuel temperature can become too high to effectively
*Two passive thermal approaches for avionics
1. Heat Pipe Assemblies(To reduce the internal
2. Loop Heat Pipe(to transport thermal energy to
*Heat pipe assemblies were capable of reducing the
internal temperature gradient by approximately 25
*This reduction translates directly to an increase in the
allowable sink temperature that will still provide
sufficient cooling for the electronic components.
*LHP was designed to transport thermal energy from
the fuel to two heat rejection section.
*Two heat rejection sections were necessary as
aircraft sink condition can vary considerably
throughout the flight.
*Since these sinks can approach temperature much
higher than the intended operating temperature of the
*Two sinks that together were capable of providing
heat rejection over the entire flight envelope.
*Methanol was selected as the working fluid.
*Stainless Steel was used for the evaporator body,
compensation chamber and transport lines.
*Both condenser exchanged waste heat with Liquid
*The flow of LN was controlled to maintain the sink
temperature at the desired value.
*Each condenser also had a surface exposed to an
*This allowed the sink temperature to be raised above
the LHP vapor temperature.
*Heat pipes transport Heat by two phase flow of a