Experimental study of a mixed refrigerant JouleaThomson cryocooler using a commercial air-conditioning scroll compressor

• Published in: Cryogenics (Guildford) Vol. 55-56; pp. 47 - 52
• Main Authors: Lee, Jisung, Lee, Kyungsoo, Jeong, Sangkwon
• Format: Journal Article
• Language: English
• Published: 01.07.2013
• Subjects: Air conditioning; Compressors; Cryogenic temperature; Discharge; Durability; Overheating; Ports; Refrigerants
• ISSN: 0011-2275

Mixed refrigerant JouleaThomson (MR JaT) cryocoolers have been used to create cryogenic temperatures and are simple, efficient, cheap, and durable. However, compressors for MR JaT cryocoolers still require optimization. As the MR JaT cryocooler uses a commercial scroll compressor developed for air-conditioning systems, compressor overheating due to the use of less optimized refrigerants may not be negligible, and could cause compressor malfunction due to burn-out of scroll tip seals. Therefore, in the present study, the authors propose procedures to optimize compressor operation to avoid the overheating issue when the MR JaT cryocooler is used with a commercial oil lubricated scroll compressor, and the present experimental results obtained for a MR JaT cryocooler. A single stage 1.49 kW (2 HP) scroll compressor designed for R22 utilizing a mixture of nitrogen and hydrocarbons was used in the present study. As was expected, compressor overheating and irreversible high temperatures at a compressor discharge port were found at the beginning of compressor operation, which is critical, and hence, the authors used a water injection cooling system for the compressor to alleviate temperature overshooting. In addition, a portion of refrigerant in the high-pressure stream was by-passed into the compressor suction port. This allowed an adequate compression ratio, prevented excessive temperature increases at the compressor discharge, and eventually enabled the MR JaT cryocooler to operate stably at 121 K. The study shows that commercial oil lubricated scroll compressors can be used for MR JaT cryocooling systems if care is exercised to avoid compressor overheating.