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Recent advances in aircraft technology have raised much concern over the manner in which aircraft thermal management is carried out. These advances range from the incorporation of high-power electronics to transporting thermal loads at high temperatures. These types of technological advances have brought about a necessity for new aircraft thermal management architectures in order to maintain reasonable cost, size, weight, and power requirements of the overall system. The objective of this study is to address the requirements and performance aspects of existing system configurations in an effort to identify inefficiencies and highlight potential areas for improvement. As a result of this study, a new aircraft thermal management architecture, which can best be described as a vapor-compression thermal bus, is proposed as a replacement for existing technology.

Advances in aircraft technology have brought about a necessity for new aircraft thermal management architectures in order to maintain reasonable cost, size, weight, and power requirements of the overall thermal system. Two-phase cooling technologies such as vapor-compression systems have demonstrated significant benefits and offer a serious option for emerging new aircraft thermal management applications. Although vapor-compression technology offers a steady state solution to many of the limitations of existing aircraft thermal management systems, industry concerns about transient behavior need to be addressed. The purpose of this research was to investigate transient effects on the vapor compression system when the majority of the onboard thermal loads are cooled directly with the vapor-compression system and how these systems operate under the rapid thermal transients that a military aircraft experiences during combat missions.

This paper describes the performance benefits and current technology progress of an active heat pump loop (HPL) thermal control bus for spacecraft and planetary thermal control applications. Having initiated this research more than 14 years ago, this paper also briefly highlights the technical developments and obstacles overcome during this 14-year development. This paper discusses the unique features of the HPL approach that make it an attractive design choice for future manned thermal control applications: the use of an heat pump to reject heat to space at a temperature above the heat acquisition temperature, the use of non-toxic thermally stable working fluids, and the use of high-performance lubrication-free (gravity independent) refrigeration compressors. The HPL approach has the performance benefits of a traditional two-phase pumped loop thermal bus coupled with the simplicity of a single-phase pumped loop.

This paper will describe a patent-pending approach of using a vapor compression system to also provide a forced two-phase indirect heat transfer loop. This system can be configured with water boiler peak cooling thermal control hardware to avoid the high ambient temperatures associated with supersonic low altitude flight. Due to the very short duration of this high ambient condition, water boiler transient cooling techniques have potential. The water boiler can also be used for ground based cooling when flight-line ground cooling carts are unavailable. The use of a PID controller to accurately control the cold plate temperatures when used with a solenoid activated by-pass circuit will be described.