Speaker
Mr
Christopher Dodson
(Spacecraft Component Thermal Research Group, Kirtland AFB)
Description
In predicting Pulse-Tube Refrigerator (PTR) performance, One-Dimensional design and analysis tools such as Gedeon Associates SAGE® typically include models for performance degradation due to thermodynamically irreversible processes. SAGE®, in particular, accounts for convective loss, turbulent conductive loss and numerical diffusion “loss” via correlation functions based on analysis and empirical testing.
While the simplicity of 1-D simulation tools facilitates PTR design and analysis, this convenience comes at the cost of modeling detail. An investigator wanting to drill-down into the constitutive relationships or governing principles can be shielded from low-level physical details that may otherwise lead to design insights. In these types of investigations, a higher-order Computational Fluid Dynamics (CFD) simulation complements a 1-D simulation. Whereas 1-D simulation is a sufficient starting point for PTR design, Two-Dimensional and Three-Dimensional CFD models enable an investigator to refine the design—to explore and visualize “real” physical heat-transfer and fluid flow behavior that has been condensed, simplified or omitted in 1-D modeling tools. In a 2-D or 3-D CFD model, the system dynamics and complexity between the input and output of a particular PTR component are not hidden. In this regard, higher order CFD is also a means of validating 1-D models, or of tuning lower-order design tools to new performance spaces before physical functional validation or prototyping.
In this study, we compare CFD and SAGE® estimates of PTR refrigeration performance for four distinct pulse-tube lengths. Performance predictions from PTR CFD models are compared to SAGE® predictions for all four cases, and also compared to select published analytical and empirical models. Then, to further demonstrate the benefits of higher-fidelity and multidimensional CFD simulation, the PTR loss mechanisms are characterized in terms of their spatial and temporal locations.
Primary author
Mr
Christopher Dodson
(Spacecraft Component Thermal Research Group, Kirtland AFB)
Co-authors
Dr
Arsalan Razani
(The University of New Mexico)
Mr
Jorge Esguerra
(Glacier Technical Solutions, LLC.)
Kyle Martin
(ATA/AFRL)
