Pulsating Heat Pipes

Large radiator panels, based upon state of the art conventional heat pipes with attached fins for thermal load distribution and dissipation is the current baseline design for NASA�s Fission Power System. The initial 1 kWe FPS requires a total radiating surface of 2.5 m2. Higher power designs will require corresponding larger radiating surfaces. In order to achieve optimum radiator performance, the face sheets of these radiators should present waste heat loads as isothermal sheets pointed to the sink of space. The current state of the art designs do not meet this requirement and rely upon heat pipes to axially carry the waste thermal loads while radiating fins, with typical thermal gradients and losses, provide thermal distribution away from the heat pipes via simple conduction. Under Phase I, Peregrine has successfully demonstrated an alternative design which promises to be lower in mass while improving performance based upon pulsating heat pipes (PHPs). PHPs can directly acquire and then readily distribute thermal loads across the face of radiator panels to create highly efficient near isothermal designs. PHPs are an autonomous, self-contained, low profile, lightweight, high performance thermal transport system based upon heat of vaporization. Phase II will characterize a titanium/water pulsating heat pipe system, build prototypes of a Pulsating Heat Pipe (PHP) radiator for a 1 kWe FPS, and also build a conventional heat pipe design in order to provide a side by side comparison of performance increases of PHPs versus the conventional design. Phase II will provide objective data through empirical results for future efficient lightweight, isothermal radiator designs.

The following potential NASA applications will benefit from this pulsating heat pipe technology. 1. The production of high efficiency (isothermal) radiators for NASA in General. Fission Power Systems will benefit directly. 2. Heat spreaders to acquire high heat fluxes and to transfer and distribute high thermal loads over both short and long distances. Most NASA systems can consider this advantage. 3. An autonomous thermal control device that operates by simple introduction of a thermal load (on startup) and dissipation via a sink (i.e. radiator). 4. PHPs can be stacked for redundancy and for improved performance, allowing instrument temperatures to be maintained within a narrow range. 5. PHPs can be placed within thin sheet metal and formed or rolled in order to provide complex or flexibility in their use.

Pulsating heat pipes can also be used in the following areas. 1. As heat spreaders/thermal transport devices for cell phones, laptops, tablets, sensors, and ignition switches on automobiles. 2. As a thermal control device for GaN power amplifiers that have very high heat fluxes. This can assist in the replacement of conventional traveling wave tubes, thermal control of high power microwave devices, and power systems. 3. Autonomous thermal control devices in order to heat or cool buildings and residences.

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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