Infineon Advances Cryogenic Cooling With Highpower Stirling Refrigerator

As demand for low-temperature refrigeration grows, particularly in applications where market constraints and user requirements differ significantly from traditional cooling systems, developing high-performance, efficient refrigeration solutions becomes increasingly critical. Infinia Technology Corporation (ITC) is actively developing a high-power, single-stage Stirling cycle cryocooler designed to meet these emerging market needs.

The cryocooler employs a highly modular design concept from inception, allowing adaptation to various applications without major changes to the core high-power linear drive system. The unit can utilize up to 8 kW of electrical input power depending on operating conditions, with dimensions of 1000 mm length, 530 mm height (without insulation), 300 mm depth, and a total mass of 160 kg (excluding power supply/controller).

The system features two opposed linear drive pressure wave generators that effectively cancel out all drive motor vibrations. The net residual vibration from piston movement remains minimal. ITC rates the cryocooler at 650 W net cooling capacity at 77K with 5800 W electrical input, though it operates across a broad temperature range. The current model provided to the U.S. Navy delivers 300 W cooling at 50K.

The modular cold-end assembly—comprising piston assembly, heat rejector, regenerator, and cold head heat exchanger—is optimized for specific operational requirements. ITC's system differs from other large-capacity cryocoolers in physical size, performance, and operating characteristics. The company employs Gedeon Associates' SAGE Stirling cycle simulation model, which shows excellent correlation with actual hardware test results.

ITC's pressure wave generator module incorporates proven flexure bearings to provide gas gap sealing while eliminating wear as a degradation mechanism. The resulting compact assembly achieves >87% power conversion efficiency (Stirling cycle piston PV power/drive motor electrical power) relative to its 8 kW electrical input capacity.

For the 60-110K temperature range of particular interest, the Stirling cycle configuration demonstrates 20-50% performance advantages over pulse tube alternatives. These advantages grow significantly at higher operating temperatures (175K and above). Reliability concerns about additional moving parts in Stirling systems are mitigated by ITC's extensive experience with flexure bearing designs that have demonstrated continuous operation exceeding 100,000 hours.

The cryocooler's waste heat rejection system represents a critical design consideration, particularly when transitioning from laboratory to field conditions. Performance impacts from elevated coolant temperatures necessitate careful optimization of the complete thermal management system, including Stirling cycle rejector heat exchanger, air-side heat exchanger, coolant circulation pump, and cooling fans.

The system's modular architecture enables multiple configuration options currently under development:

• Two-stage arrangements for 20-30K superconducting applications
• Dual cold head configurations for improved balance with large piston assemblies
• Quad-drive modules (four pressure wave generators) for increased cooling capacity

Ongoing linear motor development aims to double current drive capacity from 4 kW to 8 kW per module while maintaining or reducing cost per kilowatt, enabling future systems with input power exceeding 30 kW.