Cost Reduction and Maximized Performance of Pulse-Tube Cryocooler Heat Exchangers

Cryocoolers are a critical enabling technology for space-based infrared sensing and missile detection systems. The pulse tube cryocooler architecture is particularly advantageous for this application due to its high efficiency, high reliability, and low vibration due to a lack of moving parts. Unfortunately, high cryocooler costs are a barrier to broader implementation in a variety of defense applications. The hot and cold end heat exchangers are the most expensive components and their performance is critical to overall system efficiency. These heat exchangers have abnormally high-aspect-ratio features. This has led to high component costs and compromised designs from an efficiency standpoint. This reduced efficiency leads directly to greater energy consumption, larger related subsystems, and larger overall packaging – all of which negatively affect mission affordability and platform flexibility. Therefore, developing more capable and affordable manufacturing methods for pulse tube cryocooler heat exchangers is a linchpin to reducing both manufacturing and system costs. Voxel Innovations is proposing the use of pulsed electrochemical machining (PECM) to create the critical heat exchanger features for pulse tube cryocooler. PECM, which operates through a zero-stress, anodic dissolution-based mechanism is highly effective at machining high-aspect ratio, non-cylindrical geometries. It is expected that implementation of PECM into the manufacturing chain for pulse-tube cryocooler heat exchangers could lead to MDA mission cost reduction by reducing heat exchanger costs by 50% and improving the cryocooler efficiency by 15-20%, leading to a smaller and lighter cryocooler with reduced electrical requirements. Under this Phase I SBIR, thermodynamic modeling will be performed to determine the optimal heat exchanger geometry under the expanded design space enabled by PECM. Two primary electrode concepts will be explored conceptually and demonstrated in hardware to examine the strengths and weaknesses of each approach. Approved for Public Release | 20-MDA-10643 (3 Dec 20)