Radebaugh, R.
(2013),
Thermodynamic Analysis of Cascade Microcryocoolers with Low Pressure Ratios, Advances in Cryogenic Engineering, Anchorage, AK, [online], https://doi.org/10.1063/1.4860693
(Accessed December 14, 2024)
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Thermodynamic Analysis of Cascade Microcryocoolers with Low Pressure Ratios
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Abstract
The vapor-compression cycle for refrigeration near ambient temperature achieves high efficiency because the isenthalpic expansion of the condensed liquid is a rather efficient process. However, temperatures are limited to about 200 K with a single-stage system. Temperatures down to 77 K are possible with many stages. In the case of microcryocoolers using microcompressors, pressure ratios are usually limited to about 6 or less. As a result, even more stages are required to reach 77 K. If the microcompressors can be fabricated with low-cost wafer-level techniques, then the use of many stages with separate compressors may become a viable option for achieving temperatures of 77 K with high efficiency. We analyze the ideal thermodynamic efficiency of a cascade Joule-Thomson system for various temperatures down to 77 K and with low pressure ratios. About nine stages are required for 77 K, but fewer stages are also analyzed for operation at higher temperatures. For 77 K, an ideal second-law efficiency of 83 % of Carnot is possible with perfect recuperative heat exchangers and 65 % of Carnot is possible with no recuperative heat exchangers. The results are compared with calculated efficiencies in mixed-refrigerant cryocoolers over the range of 77 K to 200 K. Refrigeration at intermediate temperatures is also available. The use of single component fluids in each of the stages is expected to eliminate the problem of pulsating flow and temperature oscillations experienced in microcryocoolers using mixed refrigerants.Proceedings Title
Advances in Cryogenic Engineering
Volume
1573
Issue
132
Conference Dates
June 17-21, 2013
Conference Location
Anchorage, AK
Conference Title
Cryogenic Engineering Conference
Pub Type
Conferences
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Keywords
Cascade, microcompressors, cryocoolers, cryogenics, efficiency, heat exchangers, Joule-Thomson, recuperative, stages, vapor-compression cycle
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Created June 17, 2013, Updated November 10, 2018