OPTIMUM PHASE-ANGLE BETWEEN PRESSURE AND GAS DISPLACEMENT OSCILLATIONS IN A PULSE-TUBE REFRIGERATOR

A study is made to investigate how the phase angle between pressure oscillation and gas displacement affects pulse-tube refrigeration performance. For this purpose, a pulse-tube refrigerator involving a piston at the hot end of the pulse tube is constructed. It is found that the optimum phase angle of piston motion is 142-degrees, and that the lowest temperature is 47 K with an operating speed of 1.3 Hz. Gas displacement due to contraction and expansion is suppressed by the piston motion at this optimum phase angle. Since the optimum phase angle is in the range of 90-degrees-180-degrees, orifice pulse-tube refrigerators cannot achieve optimum phase operation. The improvement achieved with double-inlet pulse-tube refrigerators can be explained by the phase angle versus refrigeration performance relation found in the present experiment.