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Transient Heat Transfer to Helium II Due to a Sudden Loss of Insulating Vacuum

Title: Transient Heat Transfer to Helium II Due to a Sudden Loss of Insulating Vacuum.
Name(s): Bosque, Ernesto, author
Van Sciver, Steven, professor directing dissertation
Kopriva, David, university representative
Ordoñez, Juan, committee member
Clark, Jonathan, committee member
Department of Mechanical Engineering, degree granting department
Florida State University, degree granting institution
Type of Resource: text
Genre: text
Issuance: monographic
Date Issued: 2014
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
Physical Form: online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: Rapid heat deposition is a natural consequence of an insulating vacuum jacket failure around a He II-cooled system. This loss of vacuum is often referred to as the worst-case scenario, as it seriously endangers its surroundings and the low temperature equipment cooled within. In the case of a vacuum break, air floods into the vacuum jacket, impinging on the inner vacuum wall. The air carries with it a significant amount of energy (~500 kJ/kg) that is ultimately transferred to the He II coolant. Given large magnitudes, the heat flux results in rapid pressurization due to the expansion of the helium as it boils to its vapor phase. An experimental rig has been designed, built, and successfully operated to simulate such a sudden loss of insulating vacuum incident confined to one-dimension in space. The rig consists of an evacuated tube that dead-ends to a He II-cooled disk, beneath which is a column of He II near 1.8 K, open to its bath. A wide range of mass flow rates are studied for warm gas flooding into the evacuated tube, causing the gas to cryodeposit and transfer its internal energy through the disk and to the He II. Thermometry in the disk and axially through the He II column is used to quantify the heat transport generated by the cryodeposition process. In general, it is found that the heat flux to the He II is indeed limited by peak heat flux theory. It is further confirmed that noisy film boiling, though mechanically violent, reduces the heat transfer to the He II. The cryodeposition behavior of warm gas onto a He II-cooled surface is also shown to be somewhat stochastic. In summary, an accurate conceptual model is developed to fundamentally describe and predict the coupled mass and heat transport phenomena that result after such a vacuum failure.
Identifier: FSU_migr_etd-8734 (IID)
Submitted Note: A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Spring Semester, 2014.
Date of Defense: April 4, 2014.
Keywords: Cryodeposition, Helium II, Superfluid Helium, Vacuum Break
Bibliography Note: Includes bibliographical references.
Advisory Committee: Steven Van Sciver, Professor Directing Dissertation; David Kopriva, University Representative; Juan Ordoñez, Committee Member; Jonathan Clark, Committee Member.
Subject(s): Mechanical engineering
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Owner Institution: FSU