Abstract
Cooling temperature of a pulse tube refrigerator was dramatically improved by adding an orifice valve at the end of the pulse tube. However, there are few experimental results on how oscillatory flow changes upon opening the valve. In this work, we try to understand the gas dynamics in an orifice pulse tube refrigerator by measuring velocity and pressure oscillations. We used Laser Doppler Velocimeter (LDV) for the velocity and small pressure sensors for the pressure to determine the complex acoustic impedance near the cold end of the regenerator. When the phase of the acoustic impedance is the smallest, the lowest cooling temperature was obtained. With opening the orifice valve, a semicircular locus of the acoustic impedance was drawn on the complex plane, from which the roles of the components of the pulse tube refrigerator are discussed.
