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  • 1
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    Thermal conductance of pressed brass contacts at liquid helium temperatures (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An apparatus has been designed and fabricated which will measure the thermal conductance of pressed contacts at liquid helium temperatures as a function of applied force, with surface finish as a parameter. The apparatus is automated and was used to measure thermal conductance at temperatures from 1.5 to 6.5 K at applied forces up to 700 N for brass sample pairs having surface finishes from 0.1 to 1.6 micron rms. The experimental data were found to fit a simple power law where the thermal conductance is given by k = alpha T exp n, where k is the thermal conductance, T is the absolute temperature, and alpha and n are empirically determined constants.
    Keywords: ENGINEERING (GENERAL)
    Type: Cryogenics (ISSN 0011-2275); 26; 217-221
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Performance of all-metal demountable cryogenic seals at superfluid helium temperatures (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Two all-metal demountable cryogenic seals with an outside diameter of 36.6 mm, inside diameter of 27.2 mm and thickness of 0.51 mm were leak-tested at room temperature (300 K), liquid nitrogen temperature (21 cycles at 77 K), liquid helium temperature (nine cycles at 4.2K) and superfluid helium temperature (four cycles at 1.6 K). Each seal was mounted and demounted for 13 cycles. Thickness measurements at 90 deg intervals along the circumference showed a maximum seal compression of 0.038 mm. Leak rate measurements at all temperatures showed no detectable leak above the helium background level, typically 0.1 x 10 exp -9 std cu cm/s, during testing.
    Keywords: MECHANICAL ENGINEERING
    Type: Cryogenics (ISSN 0011-2275); 31; 993-995
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    NASA TECHNICAL REPORTS
  • 3
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    Thermal conductance of pressed copper contacts at liquid helium temperatures (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 22; 1810-181
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    NASA TECHNICAL REPORTS
  • 4
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    Thermal conductance of pressed aluminum and stainless steel contacts at liquid helium temperatures (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The thermal conductance of aluminum and stainless steel 304 sample pairs with surface finishes ranging from 0.1 to 1.6 microns rms roughness was investigated over a temperature range from 1.6 to 6.0 K. The thermal conductance follows a simple power law function of temperature, with the exponent ranging from 0.5 to 2.25, increases asymptotically with increasing applied force, and exhibits an anomaly for surface finishes in the 0.4 micron region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Thermal conductance measurements of pressed OFHC copper contacts at liquid helium temperatures (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The thermal conductance of oxygen-free high conductivity (COFHC) copper sample pairs with surface finishes ranging from 0.1 to 1.6-micrometers rms roughness was investigated over the range of 1.6 to 6.0-K under applied contact forces up to 670 N. The thermal conductance increases with increasing contact force; however, no correlation can be drawn with respect to surface finish.
    Keywords: ENGINEERING (GENERAL)
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  • 6
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    Thermal conductance of pressed aluminum and stainless steel contacts at liquid helium temperatures (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thermal conductance of aluminum and stainless steel 304 sample pairs with surface finishes ranging from 0.1 to 1.6 microns rms roughness was investigated over a temperature range from 1.6 to 6.0 k. The thermal conductance follows a simple power law function of temperature, with the exponent ranging from 0.5 to 2.25, increases asymptotically with increasing applied force, and exhibits an anomaly for surface finishes in the 0.4 micron region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86855 , A-86033 , NAS 1.15:86855
    Format: application/pdf
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  • 7
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    Thermal conductance of augmented pressed metallic contacts at liquid helium temperatures (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thermal conductance of uncoated oxygen-free high conductivity (OFHC) copper, 6061-T6 aluminum, free-machining brass, and 304 stainless steel sample pairs which were augmented with a gold coated 6061-T6 aluminum washer inserted between the contact surfaces was measured over the temperature range of 1.6 to 6.0 K, with applied forces from 22 to 670 N. The contact surfaces of the sample pairs were prepared with a 0.8 micron lapped finish, while the finish of the aluminum washer was 0.2 micron lapped. The contribution to the overall thermal impedance by the bulk conductance of the aluminum washer was negligible. It was found that addition of the washer offered no significant conductance improvement over an uncoated single contact pair; any benefits from using the gold plated washer were counteracted by the addition of two more contact surfaces. Additionally, the thermal conductance of a 'combination' aluminum sample pair having one gold coated and one uncoated surface was measured and compared to the washer pair. The ratio of the conductance of the washer pair to half the conductance of the 'combination' pair was found to be constant and near unity over the temperature range of the data obtained, within experimental error.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-103917 , A-92055 , NAS 1.15:103917
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  • 8
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    Thermal conductance measurements of pressed OFHC copper contacts at liquid helium temperatures (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thermal conductance of oxygen-free high conductivity (OFHC) copper sample pairs with surface finishes ranging from 0.1 to 1.6-micrometers rms roughness was investigated over the range of 1.6 to 6.0-K under applied contact forces up to 670 N. The thermal conductance increases with increasing contact force; however, no correlation can be drawn with respect to surface finish.
    Keywords: PHYSICS (GENERAL)
    Type: NASA-TM-85861 , A-9542 , NAS 1.15:85861
    Format: application/pdf
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  • 9
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    Thermal conductance of pressed contacts at liquid helium temperatures (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is pointed out that the optimum design of cryogenic instruments requires accurate thermal models. The present models are limited by a lack of knowledge of the low temperature thermal conductance of the bolted joints which are typically used in the instrument-to-system interface. In connection with studies of pressed contacts, it has been found that the thermal conductance does not obey the Wiedemann-Franz law. The present investigation is concerned with the characterization of the thermal conductance of pressed contacts at liquid helium-4 temperatures, taking into account the dependence of thermal contact conductance on applied force and temperature. It is shown that for the 0.4 micron OFHC copper pressed contact pair, the thermal conductance varies roughly as the second power of the temperature, and increases with increasing applied force.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 83-1436
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  • 10
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    Thermal conductance of pressed contacts at liquid helium temperatures (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thermal contact conductance of a 0.4 micrometer surface finish OFHC copper sample pair has been investigated from 1.6 to 3.8 K for a range of applied contact forces up to 670 N. Experimental data have been fitted to the relation Q = the integral alpha T to the nth power dt by assuming that the thermal contact conductance is a simple power function of the sample temperature. It has been found that the conductance is proportional to T squared and that conductance increases with an increase in applied contact force. These results confirm earlier work.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-TM-84365 , A-9323 , NAS 1.15:84365
    Format: application/pdf
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