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  • 1
    Publication Date: 2006-12-01
    Print ISSN: 0017-9310
    Electronic ISSN: 1879-2189
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 2
    Publication Date: 2013-09-01
    Print ISSN: 1359-4311
    Electronic ISSN: 1873-5606
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 3
    Publication Date: 2008-03-01
    Print ISSN: 0196-8904
    Electronic ISSN: 1879-2227
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 4
    Publication Date: 2018-08-10
    Description: Over the past two decades, risk management and risk analysis have emerged throughout the business community in the United States (US) as prominent planning and development strategies used to mitigate risk of failure and ensure a high return on investment (ROI) for business endeavors (financial and otherwise). They are generic tools that can be applied to any business regardless of the sector (i.e., government, university, private) and have been used by the Federal government in the form of institutional practices aimed at maximizing the probability of success in business activities. One US Federal agency that incorporates risk management and analysis techniques into business and/or engineering activities is the National Aeronautics and Space Administration (NASA). The present work is a discussion on mission, spacecraft and instrument design (as well as technology development) and the role of risk management, analysis and mitigation as a fundamental tool in the design process.
    Keywords: Spacecraft Design, Testing and Performance
    Format: application/pdf
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  • 5
    Publication Date: 2019-07-12
    Description: As part of an effort to identify cost efficient fabrication techniques for Loop Heat Pipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop Heat Pipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.
    Keywords: Mechanical Engineering
    Type: GSFC.O.6854.2012
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-13
    Description: Experiments were conducted to study the effects of spray trajectory angles upon heat flux for flat and enhanced surface spray cooling. The surface enhancement consisted of straight fins machined on the top surface of a copper heater block. Spray cooling curves were obtained with the straight fin surface aligned both parallel (axial) and perpendicular (transverse) to the spray axis. Measurements were also obtained on a flat surface heater block for comparison purposes. Each copper block had a cross-sectional area of 2.0 sq cm. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) conditions. Results show that the maximum CHF in all cases was attained for a trajectory angle of 30' from the surface normal. Furthermore, trajectory angles applied to straight finned surfaces can have a critical heat flux (CHF) enhancement as much as 75% (heat flux value of 140 W/sq cm) relative to the vertical spray orientation for the analogous flat surface case under nominally degassed conditions.
    Keywords: Mechanical Engineering
    Type: HT2005-72634 , ASME 2005 Heat Transfer Summer Conference; Jul 17, 2005 - Jul 22, 2005; San Francisco, CA; United States
    Format: application/pdf
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  • 7
    Publication Date: 2019-07-13
    Description: Experiments were conducted to study the effects of enhanced surfaces on heat transfer during spray cooling. The surface enhancements consisted of cubic pin fins, pyramids, and straight fins (uniform cross sectional straight fins) machined on the top surface of copper heater blocks. Each had a cross-sectional area of 2.0 square cm. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa ) and gassy conditions (chamber with N2 gas at 101 kPa). The results show that the straight fins had the largest enhancement in heat flow. Critical heat flux (CHF) for this surface showed an increase of 55% in comparison to the flat surface for the nominally degassed condition. The cubic pin finned and pyramid surfaces provided slightly more than half the heat flux enhancement (30% - 40% greater than the flat surface) of the straight fins. The gassy case showed that the straight fins again provided the largest enhancement (48%) in CHF relative to the flat surface. This was followed by the cubic pin fins, and pyramids which had increases of 31% and 18% respectively. No significant effect was observed in the surface temperature at which CHF occurs for either portion of the study.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: IMECE2004-61753 , Proceedings of IMECE2004: ASME International Mechanical Engineering Congress; Nov 13, 2004 - Nov 19, 2004; Anaheim, CA; United States
    Format: text
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  • 8
    Publication Date: 2019-07-12
    Description: A method has been developed for improving heat flux performance relat ive to flat surfaces in spray-cooling systems. This study investigat es the effect of foam on spraycooling heat flux.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GSC-15553-1 , NASA Tech Briefs, August 2009; 21
    Format: application/pdf
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  • 9
    Publication Date: 2019-07-13
    Description: This study compares heat flux performance of a Loop Heat Pipe (LHP) wick structure fabricated from compressed carbon foam with that of a wick structure fabricated from sintered soda lime glass. Each wick was used in an LHP containing a fractal based evaporator. The Fractal Loop Heat Pipe (FLHP) was designed and manufactured by Mikros Manufacturing Inc. The compressed carbon foam wick structure was manufactured by ERG Aerospace Inc., and machined to specifications comparable to that of the initial soda lime glass wick structure. Machining of the compressed foam as well as performance testing was conducted at the United States Naval Academy. Performance testing with the sintered soda lime glass wick structures was conducted at NASA Goddard Space Flight Center. Heat input for both wick structures was supplied via cartridge heaters mounted in a copper block. The copper heater block was placed in contact with the FLHP evaporator which had a circular cross-sectional area of 0.88 cm(sup 2). Twice distilled, deionized water was used as the working fluid in both sets of experiments. Thermal performance data was obtained for three different Condenser/Subcooler temperatures under degassed conditions. Both wicks demonstrated comparable heat flux performance with a maximum of 75 W/cm observed for the soda lime glass wick and 70 W /cm(sup 2) for the compressed carbon foam wick.
    Keywords: Mechanical Engineering
    Type: GSFC-500-13-D-0347 , Aerospace Sciences Meeting; Jan 13, 2014 - Jan 17, 2014; Washington, DC; United States
    Format: application/pdf
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  • 10
    Publication Date: 2019-07-13
    Description: Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of cubic pin fins machined on the top surface of copper heater blocks. The structure height, pitch, and width were parametrically vaned. Each copper block had a projected cross-sectional area of 2.0 sq cm. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2 x 2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data were obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 100.7 kPa) with a bulk fluid temperature of 20.5 C. Results for both the degassed and gassy cases show that structure width and separation distance have a dominant effect upon the heat transfer for the size ranges used. Cubic pin fin height had little impact upon heat flux. The maximum critical heat flux (CHF) attained for any of the surfaces was 121 W/sq cm, giving an enhancement of 51% relative to the flat surface case under nominally degassed conditions. The gassy case had a maximum CHF of 149 W/sq cm, giving an enhancement of 38% relative to the flat surface case.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: IPACK2005-73003 , ASME International Electronic Packaging and Technical Conference; Jul 17, 2005 - Jul 22, 2005; San Francisco, CA; United States
    Format: application/pdf
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