Date of Award

Spring 2008

Document Type


Degree Name

Master of Science (MS)


Mechanical & Aerospace Engineering

Committee Director

Ayodeji O. Demuren

Committee Member

Sushil K. Chaturvedi

Committee Member

Venkatarao Ganni


Helium refrigeration at temperatures below 4.5-Kelvin (K), but greater than 0.8-K typically employ a sub-atmospheric process utilizing a vacuum pumping system. These types of helium refrigerators are of keen interest to present and future particle physics programs utilizing super-conducting magnet or radio-frequency technology. As such, there is a need for small scale 2-K helium refrigeration systems (i.e., those that operated below the lambda temperature) in small laboratories and test facilities at this time. This study establishes the key process parameter choices of flow ratio, heat-exchanger size, and supply pressure, and how they influence the overall system performance for various process configurations that do not utilize rotating machinery within the cold box (i.e., turbo-machinery for either cryogenic vacuum pumping or expansion) but do utilize a separate commercially available 4.5-K helium liquefier system. Three 2-K process configurations are studied to determine the key process parameter values that yield the best performance. These process configurations are compared to the commonly employed (but inefficient) direct vacuum pumping process, which typically uses a dewar as the 4.5-K liquid helium supply source. It is found that the performance of these configurations is similar and substantially superior to direct vacuum pumping, providing an inverse coefficient of performance of around 1800 W/W.


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