This project continues the application of a numerical model to the design of cryocoolers. These are low temperature refrigerators used to cool infrared detectors, medical devices, and some electronic devices. The group led by Ray Radebaugh has been involved in research and design for these devices for many years.
The numerical model, developed at NIST over the years, involves one dimensional time dependent fluid flow and heat transfer for compressor driven helium gas in a porous media. It is a difficult problem to model because of the porous media and the heat transfer. There is no suitable commercial model available.
This year, numerical experiments with the model were conducted to assist Ray with the design of devices for several groups including Yaron Consulting, Creare, NASA, Lockheed, Cryenco and ARPA . The production code was sent to users at Lockheed and also at NASA. Tests were run on a fully implicit version of the model and comparisons were made with the older explicit model. In addition, there is a collaboration with a Chinese visitor on a comparison of our model with one that he has developed. This comparison will be presented at a cryocooler conference this June. Also, research was conducted on the extension of the model to include more realistic geometry. This involved adding a variable compressor volume to the model and testing various difference schemes, such as the preconditioning ideas of Turkel, and various versions of upwind differencing and finite volume methods.
In the future the implicit version, currently a research code, will be improved so that it is suitable for production use. Research will continue on extending the model to include more of the actual device.