Molecular dynamics simulation of periodic flow containing contaminant in the regenerator

The lifespan of regenerative refrigerators is predominantly influenced by contamination. This paper studies the interaction between N2 and regenerator wire at a microscopic scale for the first time. A section of regenerator wire is simulated using molecular dynamics to investigate the impacts of temperature, charging pressure, and contamination amount. Based on the single-wire model, it indicates that N2 initially forms clusters and then adheres to the wire surface when the temperature is below 80 K. Clusters decrease in size as the temperature rises from 80 K to 90 K. The quantity of N2 attached to the wire decreases by 50 % when the temperature reaches 130 K and decreases to 0 at 170 K. Charging pressure and contamination amount slightly affect adsorption. When a row of wires is aligned perpendicular to the flow, adsorption rates are fast and the adsorption process is completed in several cycles. At 50 K, the size of the largest cluster decreases by 80.6 %, marking the greatest reduction. Based on this, the paper proposes that N2 will mostly congeal within the regenerator between 90 K and 70 K while the refrigerator operates. This study establishes a theoretical foundation for further exploration of contamination-induced failure mechanisms.