Two Years’ Experience in Liquid Helium Transfer with a Maintenance Free Centrifugal Pump
We report on two years of operating experience with low loss liquid helium transfer using cold gas exchange and a centrifugal immersion pump with magnetic bearings and a cold drive motor. Results of further pump developments are given. Depending on the blade height of rotor and guide wheel and rotational speed a wide range of flow rates to and pressure heads Ap with a hydraulic efficiency > 75% is reached. For example, depending on the values chosen for these parameters, one can get Δp = 0.5 bar at ṁ = 50 g/s (1440 L/h) or ṁ = 100 g/s at Δp = 0.2 bar. Just by adapting the blade height of rotor and guide wheel to a given load line the pump can always be operated in the region of maximum total efficiency. Shaft powers up to 40 W are possible.
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