SBIR-STTR Award

Iris Technology, in collaboration with Georgia Tech and Raytheon, proposes to perform advanced 3D CFD modeling to guide the architecture selection for a tactical 4K Cryocooler. Iris will lead the System Design and Program Management efforts. Georgia Tech is the lead organization on the Analysis. Raytheon is providing the underlying mechanical cryocooler technology. The preliminary technical baseline is a three stage Raytheon hybrid Stirling / pulse tube cryocooler. The first stage is a Stirling stage, which provides gravitational insensitivity, high efficiency, and operational adjustability. The second and third stages are pulse tubes to avoid the cost and complexity of moving cryogenic seals that additional Stirling stages would require. CFD and other modeling techniques will be pursued to either show that the baseline provides the best technical solution or to select an alternative, probably all pulse tube, design.

Benefit:
The 4K Cryocooler developed on this program will be more efficient, more compact, and more operationally flexible than any competing low temperature cryocoolers by virtue of its unique architecture. Therefore, it is expected to make the use of low temperature superconducting electronics practical for a wide range of tactical communications applications. Commercial applications include medical (magnetic resonance imaging, MRI) and communications.

Keywords:
Stirling, Stirling, cryogenic, Computational Fluid Dynamics, hybrid, cryocooler, Pulse Tube

The primary objective of Phase II is to obtain experimental test data to substantiate the analytic predictions developed during Phase I (4.0 W at 60.0K, 0.30 W at 11.5K, and 0.196W at 4.0K for 800 W of input pressure-volume (PV) power). This will be accomplished by leveraging a new purpose-built pulse tube cold head with existing cryocooler assets to be provided by the United States Air Force. This creative programmatic approach makes possible the build of a complete three-stage Stirling/Pulse Tube/Pulse Tube cryocooler on a limited budget. Successful build and test of this cryocooler will represent the first build of this type of three-stage cryocooler, thus establishing the viability of the concept, and it will provide an invaluable tool for model correlation to inform productized versions to follow.

Benefit:
At present, the only presently available 4K cryocoolers are large and require maintenance. They also tend to be audibly loud. These are cryocoolers based upon the low frequency (1-2 Hz, typical) Gifford-McMahon (G-M) Cycle. The Stirling / pulse tube / pulse tube hybrid 3-stage (RSP3, R 0x9D for Raytheon, a partner in this development)cryocooler that will be built during Phase II will operate at greater than 20 Hz. The higher frequency means more cooling cycles per second, which enables it to be about an order of magnitude smaller than the G-M type cryocoolers because the required swept volume 0x9D of moving gas is about an order of magnitude lower. (Cooling power is roughly proportional to the product of the operating frequency times the displaced mass in the cold head during a half-cycle). The first stage is a Stirling stage, which provides gravitational insensitivity, high efficiency, and operational adjustability. The second and third stages are pulse tubes to avoid the cost and complexity of moving cryogenic seals that additional Stirling stages would require, which would almost certainly never lead to a cost-effective or viable long-life solution under high vibration conditions. This combination of Stirling and pulse tube stages yields a 3-stage design that is superior to either monolithic Stirling or monolithic pulse tube designs. In addition to cooling superconducting electronics, this cryocooler is expected to have application in the medical filed, possibly supplanting the G-M cryocoolers for magnetic resonance imaging applications.

Keywords:
cryocooler, Pulse Tube, regenerator, RSP3, Stirling