Aircraft Thermal Management Using Loop Heat Pipes

Abstract : The objective of this thesis was to determine the feasibility of using loop heat pipes to dissipate waste heat from power electronics to the skin of a fighter aircraft and examine the performance characteristics of a titanium-water loop heat pipe under stationary and elevated acceleration fields. In the past, it has been found that the boundary condition at the condenser can be a controlling factor in the overall performance of this type of thermal management scheme. Therefore, the heat transfer removed from the aircraft skin has been determined by modeling the wing as a flat plate at zero incidence as a function of the following parameters: airspeed: 0.8 </_Ma infinity </- 1.4; altitude: 0 </- H</- 22 km; wall temperature: 105 </- Tw</-135 degrees C. In addition, the effects of the variable properties of air have been taken into account. Heat transfer due to thermal radiation has been neglected in this analysis due to the low skin temperatures and high airspeeds up to Ma infinity = 1.4. It was observed that flight speed and altitude have a significant effect on the heat transfer abilities from the skin to ambient, with heat rejection becoming more difficult with increasing Mach number or decreasing altitude. An experiment has been developed to examine operating characteristics of a titanium-water loop heat pipe (LHP) under stationary and elevated acceleration fields. The LHP was mounted on a 2.44 m diameter centrifuge table on edge with heat applied to the evaporator via a mica heater and heat rejected using a high-temperature polyalphaolefin coolant loop.