Development of a reliable and simple pressure wave generator for pulse tube refrigerators

The pressure wave generator is a critical component of a pulse tube refrigerator. Conventionally either a solenoid operated electromagnetic valve or a rotary valve driven by a hermetically sealed motor is used for this. In this article, we present a novel pressure wave generator design based on cam operated valves for use with pulse tube refrigerators. This, when coupled with an inverter drive (variable frequency drive), forms a versatile pressure wave generator in the range between 1 and 10 Hz. In a single stage double inlet pulse tube using this type of pressure wave generator, refrigeration power of about 6 W at 77 K and a no load temperature of about 42 K were obtained. The above results are comparable to those obtained with pulse tube systems based on other two types of pressure wave generators. While the rotary valve based pressure wave generator is prone to developing leaks at the rotating seal, the solenoid valve based system cannot be operated continuously due to coil failure. The cam operated valve based pressure wave generator overcomes the above shortfalls of rotary valve and solenoid valve type pressure generators and is well suited for continuous operation of the refrigerator.