Commercialisation of Pulse Tube cryocoolers to produce 330 W and 1000 W at 77 K for liquefaction

A free-piston Stirling cryocooler using metal diaphragms

“…A refrigeration power of 390 W was predicted at 77 K with 4.0 kW of input pressure-volume (pV) power resulting in an efficiency of 28% of the Carnot COP. The DPWG's electrical to acoustic efficiency is 70% [8], so this represents an overall efficiency of 20% of the Carnot COP at 77 K. This performance compares well with other cryocoolers [9] and justified the manufacture of a proof-of-concept prototype. The amplitude of displacer movement was 0.41 mm, which is much less than the diaphragm's limit of 1.25 mm indicating that a smaller diaphragm would be suitable.…”

“…To date, 15 metal diaphragm pressure wave generators have been made and operated with swept volumes from 20 cc to 1000 cc and with 500 W to 30 kW input power, respectively. The DPWGs have been successfully used to provide pressure waves for single or multiple pulse tube refrigerators with up to 1200 W of refrigeration at 77 K at an efficiency 15% of the Carnot COP [9,10]. The DPWG employs two opposed metal diaphragms that balance each other's average gas forces.…”