SUMMARY

Stirling and pulse tube cryocoolers represent robust refrigeration systems capable of achieving extremely low temperatures, typically below 123K, and as low as 3 K. Enhancing the efficiency of these cryocoolers and adopting them for new applications, such as In-Situ Resource Utilization (ISRU) in future space missions, requires the development of novel designs and materials and detailed analysis of their components to ensure reliability and optimal performance. A critical component influencing the overall efficiency of these cryocoolers is the regenerator. The design and precise modeling of the hydrodynamic and thermal behavior of regenerator filler materials are essential for successful cryogenic system development.

This research focuses on the design and development of novel regenerators, as well as flow distribution components before and after the regenerators, for a two-stage hybrid Stirling (first stage) – pulse tube (second stage) cryocooler suitable for ISRU where liquefaction of oxygen (first stage) with a cooling power of 150 W at 90 K and hydrogen (second stage) with a cooling power of 20 W at 20 K are the targets. Prototype-size experimental regenerators for both stages are designed and fabricated using microfabrication techniques. Experiments are performed to characterize the hydrodynamic as well as the thermal performance of the regenerators and their replicas, employing the single-blow technique. Detailed pore, component, and system-level CFD simulations are carried out and the performance parameters of the developed regenerators are compared with potential alternatives.

Pore-level Computational Fluid Dynamics (CFD) analysis in conjunction with experiments are also conducted for a novel regenerator design implemented in a compact SmallSat Stirling Cryocooler (SSC). This effort is part of a collaborative initiative involving multiple teams, with the goal of developing a high-frequency Stirling Cryocooler operating at approximately 200 Hz.