Calculated Regenerator Performance at 4 K with HELIUM-4 and HELIUM-3
Abstract
The helium-4 working fluid in regenerative cryocoolers operating with the cold end near 4 K deviates considerably from an ideal gas. As a result, losses in the regenerator, given by the time-averaged enthalpy flux, are increased and are strong functions of the operating pressure and temperature. Helium-3, with its lower boiling point, behaves somewhat closer to an ideal gas in this low temperature range and can reduce the losses in 4 K regenerators. An analytical model is used to find the fluid properties that strongly influence the regenerator losses as well as the gross refrigeration power. The thermodynamic and transport properties of helium-3 were incorporated into the latest NIST regenerator numerical model, known as REGEN3.3, which was used to model regenerator performance with either helium-4 or helium-3. With this model we show how the use of helium-3 in place of helium-4 can improve the performance of 4 K regenerative cryocoolers. The effects of operating pressure, warm-end temperature, and frequency on regenerators with helium-4 and helium-3 are investigated and compared. The results are used to find optimum operating conditions. The frequency range investigated varies from 1 Hz to 30 Hz, with particular emphasis on higher frequencies.
- Publication:
-
Advances in Cryogenic Engineering
- Pub Date:
- March 2008
- DOI:
- 10.1063/1.2908551
- Bibcode:
- 2008AIPC..985..225R
- Keywords:
-
- 07.20.Mc;
- 25.55.-e;
- 85.25.-j;
- Cryogenics;
- refrigerators low-temperature detectors and other low-temperature equipment;
- <sup>3</sup>H- <sup>3</sup>He- and <sup>4</sup>He-induced reactions;
- Superconducting devices