Heat Rejection Capacity in Miniature Thermoacoustic Expanders at Cryogenic Temperature 77 K
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Miniaturized thermoacoustic expanders MTAEs are a new type of expander designed to improve the cooling efficiency of recuperative type cryocoolers without sacrificing their reliability and simplicity. Experimental studies have demonstrated the feasibility of MTAEs, including their ability to remove heat from the expansion of a DC cold-stage flow to a high-temperature reservoir. The heat pumping from the cold-stage to a hot sink by an MTAE relies critically on the behavior of nonlinear wave systems created in miniature-scale channels (several hundreds microns) inside resonant tube bundles of MTAEs. This paper presents an experimental investigation of this heat rejection capacity between a low temperature source and a much higher temperature sink and the influence of such heat energy pumping on the cooling performance of an MTAE operated at a cryogenic temperature of 77�K. The objective is to explore this technology�s feasibility in both scaled down and cryogenic temperature conditions. The characteristics of acoustic wave systems and the cooling power achieved using helium in the MTAE (170�mg/s) with different supply pressures and hot reservoir temperatures are reported. The observations and challenges of the thermoacoustic streaming phenomenon and modeling in miniature or micron-scale channels is also discussed.