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This study explores modifying refrigeration compressors for Joule-Thomson coolers supplied with gas mixtures to improve efficiency and performance. Key points include open vs. closed systems, compressor cooling, hermetic compressors, and results from test modifications. The research emphasizes the possibility of using compressors for coolers with gas mixtures and highlights factors affecting performance. Findings suggest modifications can enhance efficiency in high-efficiency scenarios. The study was conducted at Wroclaw University of Technology in Poland and presented at CEC-ICMC 2015.
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Adaptation of refrigeration compressors for Joule-Thomson cryocoolers fed with gas mixturesAgnieszka Piotrowska, Maciej Chorowski, Pawel DoroszWroclaw University of Technology, PolandCEC-ICMC 2015, June 29th, 2015
Outlines • Joule-Thomson coolers – open system • Joule-Thomson coolers supplied with gas mixture – closed system • Refrigeration compressors • The possibility of the compressor cooling • Conclusions
Joule-Thomson coolers – open system • Simple construction • No moving parts working at low temperatures • Short start-up time High workingpressure, min. 80 bar for N2, up to inversionpressure Lowthermodynamicefficiency Limited workingtime (need of pressure tank replacement)
Joule-Thomson coolers J-T coolers Micro capacity below 1 W Low capacity up to 10 W Medium capacity up to 50 W Cooling power: Wroclaw University of Technology, Poland CLOSED SYSTEM REQUIRED (reduction of working pressure) University of Twente, Netherlands
Joule-Thomson cooler – closed system NITROGEN HEAT EXCHANGER AZOT AFTERCOOLER JT VALVE HEAT EXCH. COMPRESSOR MIXTURE MIESZANINA
J-T cooler with hermetic piston compressor COMPRESSOR ELEMENTS ELECTRIC MOTOR
Compression process Poisson equation Nitrogenk = 1.40 Methanek = 1.31 Ethanek = 1.19 Propanek = 1.13 I-butanek = 1.10 Mixturek = (1.10 - 1.40)
Compressor test stand aftercooler throttling valve compressor
Test results Nitrogen Methane Ethane Propane I-butane 5-components mixture
Solutions of the compressor cooling Compressor located in the stream of theafter-cooler air - refrigeration technology v
Hermetic compressors Calculation results of the required compressor surface Compressors: Danfoss VTZ serie nitrogen mixture
Solutions of the compressor cooling Process modification To decrease inlet temperature of the working mixture:
DTexpected = 22K Process modification Test results: DTmeasured = 6 K
Solutions of the compressor cooling Modification of the construction Additionalcooling of the oil Outlet temperatureof gas – no additionalcooling Outlet temperatureof gas – additionalcooling Temperatureof the compressorshell – no additionalcooling Temperatureof the compressorshell – additionalcooling
J-T coolers designed, manufactured and tested at WUT CRYOGENIC SUB-SYSTEM REFRIGERATION SUB-SYSTEM CRYOGENIC SUB-SYSTEM REFRIGERATION SUB-SYSTEM
Test results – min. temp. 84 K Nitrogen 20%, Methane 30%, Ethane 10%, Propane 20%, I-butane 20% Temperature, K Pressure, bar Time, min
Summary • Laboratory tests confirm the possibility of using refrigeration compressors for Joule-Thomson coolers supplied with gas mixtures. • Temperature of oil (directly depending on the final temperature of compressionprocess) is main limit factor. • Depending on the volumetric efficiency, the hermetic refrigeration compressors can be used without any modifications (for low efficiencies), for high efficiencies the modifications are the must.
