Vuilleumier Refrigerator Analysis. Low Temperature Refrigerator Design Optimization.

In published analyses of the Vuilleumier refrigeration cycle, it has been assumed that the gas in the various volumes of the system go through variations in pressure isothermally. Actually, the gas approaches isentropic conditions in these volumes, leading to a significant difference. An analysis is presented which includes this effect along with the effects due to void volume, the regenerator inefficiency, motional heat leak, longitudinal conduction, and the pressure drop. The analysis was made considering both sinusoidal and linear displacer motions. The results obtained lead to two useful considerations. The first is that improved performance can be obtained with other than sinusoidal displacer motion. The second is that the big problem in Vuilleumier cycle refrigeration is in obtaining sufficiently high pressure ratios when one takes into account reasonable void volumes and the regenerator pressure drops. This becomes especially true for temperatures below 15K. Author