Micro Cryogenic Coolers (MCCs) can achieve very small sizes and high efficiencies when operating with a refrigerant mixture, but micro-scale compressors have a limited pressure output. Four refrigerant mixtures were designed to operate between 0.4 MPa and 0.1 MPa, and tested in a MCC system both with and without pre-cooling. For comparison, two pure refrigerants were tested as well. Without pre-cooling, each mixture exhibited considerably lower cooling power than the design value. With pre-cooling, after a period of time each mix exhibited unsteady cooling temperatures accompanied by flow pulsations. The low cooling power, unsteady temperatures, and time required for the pulsations to occur are analyzed in terms of composition change due to liquid hold-up in the annular and intermittent flow regimes.
Pub Type: Journals
Joule-Thomson cooler, microcryogenic cryocoolers, refrigerant mixture