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Evaluation of Pressure Oscillator Losses



Peter E. Bradley, Michael A. Lewis, Ray Radebaugh


Efficiencies of regenerative cryocoolers are influenced by losses within the pressure oscillator (compressor). An evaluation of these losses is important when searching for ways to improve the overall cryocooler efficiency. Typically, compressor efficiency is taken as the ratio of PV power to electrical input power. This definition ignores blowby and irreversible heat transfer losses within the compressor. The actual PV power delivered to the cold head is less than that measured at the face of the piston(s). We discuss a simple set of measurements for evaluating the total loss within the compressor. One measurement is of the input power, both electrical and PV, required for a blanked off compressor to provide a given pressure ratio. The second measurement is of the input power for a given stroke with the compressor connected to a large reservoir. In the third measurement a load is added to the compressor for the loss measurements. With these measurements the compressor loss during system operation can be estimated. We compare such estimations with actual system measurements using hot wire anemometry at the compressor outlet to determine the PV power delivered by the compressor. Measurements for different mean pressures from 1.5 to 2.5 MPa, pressure ratios from 1.0 to 1.3 and for the corresponding mass flows are presented.
Proceedings Title
Evaluation of Pressure Oscillator Losses
Conference Dates
August 29-September 2, 2005
Conference Location
Keystone, CO
Conference Title
2005 Cryogenic Engineering Conference adn International Cryogenic Materials Conference


Bradley, P. , Lewis, M. and Radebaugh, R. (2005), Evaluation of Pressure Oscillator Losses, Evaluation of Pressure Oscillator Losses, Keystone, CO, [online], (Accessed July 17, 2024)


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Created August 29, 2005, Updated January 27, 2020