National Superconducting
Cyclotron Laboratory

Pete Knudsen
Pete Knudsen
Senior Cryogenic Process Engineer
Accelerator Engineering
PhD, Mechanical Engineering, Fluid and Thermal Sciences, Old Dominion University, 2016
Joined NSCL in 2016

Pete Knudsen

Cryogenic systems used to cool superconducting devices close to a temperature of absolute zero, are complex thermal-hydraulic process systems comprised of many sub-systems and are very energy intensive by nature, requiring at least three orders of magnitude higher input power for the same cooling.

As in aerospace, these systems are highly specialized and often unique. The process cycles are complex, the sub-systems must operate in concert, and designs are inherently thermally and mechanically coupled and necessitate consideration of non-constant and non-ideal fluid behavior. The demands on the process equipment with respect to efficiency and reliability over the required operating temperature range are quite different than in commercial industry. These factors provide many opportunities for applied research and development.

Our group’s research interests are the modeling, optimization, and trade-off studies of cryogenic process systems. And, the investigation and development related to the performance, efficiency and reliability of key process equipment; such as compressors, purifiers, heat exchangers, turbomachinery, process vacuum, thermal insulation, instrumentation, process controls, and system test hardware. Presently we are developing a freeze-out purifier, involving both the study of the heat and mass transfer occurring during the contaminate solidification and a mechanical design to be used for the FRIB experimental system superconducting magnet clean-up and cool-down. We are also developing a compressor test bed stand to investigate aspects governing the isothermal and volumetric efficiency, including helium-oil mixing and separation. Typically an oil-flooded twin-rotary screw compressor is used. This component provides the thermodynamic availability to the refrigeration system. However, about half of the total input power is lost due to its inefficiency, and it usually comprises two-thirds of the total helium refrigeration system availability losses. We are seeking students interested in these areas, as well as the development of cryogenic turbomachinery and 2 Kelvin (sub-atmospheric) helium refrigeration processes and equipment.

My career began differently than a typical university faculty, starting as Space Shuttle systems engineer, then moving on toward diverse system and equipment designs; such as multi-million dollar launch vehicle ground support fluid systems, the process design of large helium cryogenic refrigeration systems, and specialized test equipment such as a 2 Kelvin helium heat exchanger. It is this background, typical in our group, which emphasizes both our motivation for theoretical and applied research to practical applications.

Selected Publications

Equivalent isentropic expansion efficiency of real fluid subject to concurrent pressure drop and heat transfer, P. Knudsen, V. Ganni, IOP Conf. Ser.: Mater. Sci. Eng. 278 012059 (2018)

Modifications to JLab 12 GeV refrigerator and wide range mix mode performance testing results, P. Knudsen, et al, IOP Conf. Ser.: Mater. Sci. Eng. 171 012015 (2017)

Testing of a 4 K to 2 K heat exchanger with an intermediate pressure drop, P. Knudsen, V. Ganni, IOP Conf. Ser.: Mater. Sci. Eng. 101 012105 (2015)

Performance testing of Jefferson Lab 12 GeV helium screw compressors, P. Knudsen, et al, IOP Conf.: Mater. Sci. Eng. 90 012072 (2015)

Process options for nominal 2 K helium refrigeration system designs, P. Knudsen, V. Ganni, AIP Conf. Proc. 1434, 800 (2012)