Heat Transfer and Superfluidity of Helium II

Kapitza, P. L.

doi:10.1103/physrev.60.354

Cited by 249 publications

(140 citation statements)

References 6 publications

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“…In contrast to the transmission to the substrate, the transmission to the helium 7"Snm~=0.32 _+0.5 exceeds the calculated value 7"s,/ne < 0.01 significantly. The enhanced transmission is in accord with the reduced Kapitza resistance found in heat conduction experiments [28]. So far no satisfactory explanation is known for the physical mechanism of the Kapitza resistance [16,17,[28][29][30][31][32][33] reduction.…”

Section: Experimental Data and Proceduressupporting

confidence: 71%

Sources of loss processes in phonon generation and detection experiments with superconducting tunneling junctions

Trumpp

Eisenmenger

1977

Z Physik B

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Observing the phonon yield, i.e. the ratio of the experimental phonon signal amplitude and the corresponding calculated value, phonon losses within the generation-detection system can be localized and determined quantitatively. With tin junctions on pure silicon substrates immersed in liquid helium the phonon yield is 3-5%. Under vacuum conditions the yield rises to 10-12 % indicating strong phonon transmission to the helium bath. The experimental lifetime for 280 GHz phonons in the silicon substrate is longer than 65 las indicating negligible volume losses and losses at the free substrate surface. It is further shown, that volume losses inside the phonon generator and detector are small compared to the total loss of about 90 %. By phonon reverberation measurements we find evidence that the main sources for phonon losses are localized at the boundaries of the tunneling junctions to the substrate. This is supported by an increase of the phonon yield with improved polishing from about 9 % (mechanical), 10% (chemical) to 12 % (sputter etching). A SIMS analysis indicates the presence of carbonhydrates and probably of water in the boundaries. This layer of extraneous molecules together with the nonideal surface structure of the substrate and the evaporated films weakens the mechanical bonding between the tunnel junctions and the substrate and is possibly causing strong phonon splitting by anharmonic forces.

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Section: Experimental Data and Proceduressupporting

confidence: 71%

Sources of loss processes in phonon generation and detection experiments with superconducting tunneling junctions

Trumpp

Eisenmenger

1977

Z Physik B

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“…1 This temperature is just above the limiting temperature for PTRs, which is about 1 K. However, by using a PTR as a precooling stage, the lowest temperature can be brought further down. In this research we have used a PTR as a precooler for a superfluid vortex cooler 2,3 ͑SVC͒. The superfluid vortex cooler is small, simple, and has no moving parts.…”

Section: Introductionmentioning

confidence: 99%

The superfluid vortex cooler

Tanaeva

Waele

Lindemann

et al. 2005

Journal of Applied Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. In this contribution a superfluid vortex cooler ͑SVC͒ is described. A SVC is a cooling device, the operation of which is based on the special properties of superfluid helium ͑He II͒. The SVC is small, simple, has no moving parts, and is gravity independent. It is capable of reaching temperatures as low as 0.65 K. First we have carried out a number of experiments, using a liquid-helium bath as a precooler for the SVC. Various geometries of the cooler components as well as the influence of the working pressure and the base temperature on the performance of the cooler have been investigated. Temperature below 1 K have been reached with a base temperature of 1.4 K. The next step has been combining the SVC with a pulse-tube refrigerator. In a preliminary experiment a lowest temperature of 1.19 K has been reached. Several ways to improve the system are suggested.

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“…The thermal boundary resistance, R b , is an inherent material property and arises due to fundamental mechanisms of thermal transport [15]. It was first measured by Kapitza [16] showing that there is a discontinuity in temperature at a metal/liquid helium interface. If the thermal resistance has a significant impact on the thermal conductivity, the particle size is one of the essential parameters for determining it.…”

Section: Interfacial Boundary Resistancementioning

confidence: 99%

“…Thus, it appears that dimensionless parameter α ranges from 10 to 100. The interfacial thermal resistance, R b can be calculated by using Equation (16) and it is in the range of 2.156 × 10 −6 to 2.156 × 10 −5 . When R b has this range, the effective thermal conductivity can be calculated by applying ACF and IRCF to Equation (1).…”

Section: Particle Shape and Size Effectsmentioning

confidence: 99%

Thermal conductivity of U–Mo/Al dispersion fuel: effects of particle shape and size, stereography, and heat generation

Cho

Sohn

Kim

2015

Journal of Nuclear Science and Technology

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This paper describes the effects of particle sphericity, interfacial thermal resistance, stereography, and heat generation on the thermal conductivity of U-Mo/Al dispersion fuel. The ABAQUS finite element method (FEM) tool was used to calculate the effective thermal conductivity of U-Mo/Al dispersion fuel by implementing fuel particles. For U-Mo/Al, the particle sphericity effect was insignificant. However, if the effect of the interfacial thermal resistance between the fuel particles and Al matrix was considered, the thermal conductivity of U-Mo/Al was increased as the particle size increases. To examine the effect of stereography, we compared the two-dimensional modeling and three-dimensional modeling. The results showed that the two-dimensional modeling predicted lower than the three-dimensional modeling. We also examined the effect of the presence of heat sources in the fuel particles and found a decrease in thermal conductivity of U-Mo/Al from that of the typical homogeneous heat generation modeling.

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Heat Transfer and Superfluidity of Helium II

Cited by 249 publications

References 6 publications

Sources of loss processes in phonon generation and detection experiments with superconducting tunneling junctions

Sources of loss processes in phonon generation and detection experiments with superconducting tunneling junctions

The superfluid vortex cooler

Thermal conductivity of U–Mo/Al dispersion fuel: effects of particle shape and size, stereography, and heat generation

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