Thermoacoustics

Lihan cryocooler series include Stirling cryocoolers and Stirling-type pulse tube cryocoolers. Sometimes they are all referred as Stirling-type cryocoolers for conciseness. The main difference between them is the mechanism of tuning the gas movement inside the cold-head. While the former one uses a moving displacer, which is more efficient and compact, the latter one uses a hollow tube (i.e., the pulse tube) and inertance tube, which is much simpler and easier to manufacture. Underlying the different configurations, the fundamental working mechanisms are exactly the same, which has been interpreted in a unified thermoacoustic perspective.

For Stirling type cryocoolers, the oscillating piston driven by the linear motor generates a high frequency pressure wave inside the system, i.e., the acoustic wave. Depending on the tuning mechanisms, gas moves back and forth inside the system. Inside the most critical component, the regenerator, the gas compresses and expands accompanied by its movement, and exchanges heat with the local solid materials. Through proper phasing between the gas displacement and pressure wave, heat can be pumped from the cold region to the ambient. This is the source of the cooling power. Such a process can also be used in a reversed way to realize a thermoacoustic engine.