Affecting the Gross Cooling Power of a Pulse Tube Cryocooler with Mass Flow Control

Abstract

To increase the cooling capacity of a pulse tube cryocooler the gas expansion work (pV-work) at the cold end of the pulse tube needs to be increased and the system losses have to be reduced simultaneously. For a given pulse tube volume the gross cooling power is limited. Since the cooling effect originates from the phase shift angle between the mass flow and the temperature, this angle plays a significant role in designing a pulse tube refrigerator. In conventional pulse tube refrigerators, such as orifice or double inlet refrigerators, the phase shift is thermodynamically limited. That phase shift can be enlarged with an active control unit at the hot end of the pulse tube. The control unit manages the gas flows into and out of the pulse tube. In cases of differing mass flows during the working cycle, a further enlargement of the phase shift is possible. Here we present such a system which reaches a cooling power of 85 W at 80 K with an input power of 4.8 kW.