Enhancement of linear compressor power and performance improvement of pulse tube refrigerator

Abstract

The performance of pulse tube refrigerator (PTR) is investigated by amplifying the power of the cold linear compressor. In a previous research, the cold linear compressor which operated at liquid nitrogen temperature successfully demonstrated producing sufficient acoustic power for operating a PTR to reach 20 K. Although the PTR using a cold compressor achieved the cooling power of 0.4 W at 20 K, it was found that the regenerator performance was poor because of the insufficient output power from the compressor. To increase the output power using the same linear motor, a new piston-cylinder assembly has been fabricated. The diameter of the piston is enlarged from 27 mm to 33 mm and the surfaces of the piston and the cylinder are coated with polytetrafluoroethylene (PTFE) and nickel, respectively. The linear compressor using new piston produces about 56 W of acoustic power, which is 43% larger than the previous result. The cooling performance of the PTR is, therefore, improved accordingly with more input power. The PTR with modified compressor achieves no load temperature of 17.8 K and the cooling capacity of 1.1 W at 20 K. The paper elucidates the detailed design issues of incorporating a cold linear compressor for PTR.