Numerical Investigation of CO₂ Contaminant Transport and Deposition in an In-Line Pulse Tube Cryocooler

Pulse tube cryocoolers are widely employed in cryogenic systems, where gas contamination has become a critical factor limiting both performance and service life. To further investigate the condensation behavior of contaminants, this study develops a two-dimensional axisymmetric model of a linear-type cryocooler to simulate the transport and deposition processes of trace CO₂, evaluating the impact of contamination on system pressure drop under various operating conditions. Results indicate that CO₂ diffusion is primarily driven by concentration gradients. The CO₂ deposition rate increases markedly at low temperatures and high concentrations, with over 90% of deposition occurring in the cold-end heat exchanger. Under different concentration distributions, dry ice predominantly accumulates in the cold-end heat exchanger; however, notable differences emerge in the pulse tube. In the uniform distribution case, CO₂ tends to deposit along the inner wall of the pulse tube, whereas in the gradual release scenario, deposition mainly occurs on the cold-end flow straightening mesh screen. Dry ice deposition significantly increases the pressure drop across the system and decreases the pressure wave amplitude, resulting in a degradation of cooling capacity. This study lays a foundation for further investigation into the thermal properties of contaminant layers and provides theoretical guidance for optimizing cold-end components to improve contamination resilience.