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  • 1
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    Design considerations for a micro-g superfluid helium fluid acquisition system (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The general description, the operation, and the design of a superfluid helium (SFHe) fluid acquisition system (FAS) for use under microgravity conditions is presented. For the type of FAS considered here, where fine-mesh woven screens are used to retain flowing SFHe within a gallery arm (flow) channel, those forces which determine the flow dynamics are the micro-g accelerations, liquid surface tension, and tensile strength and cumulative pressure drops along a flow path that begins at the bulk liquid and ends at the entrance to a pump. For this case, the dimensionless number, N(T) is written as the ratio between the pressure drop across the screen and the surface tension forces at the screen for low fluid velocities. Static Bond number measurements have bene taken for SFHe using 325 x 2300 twilled Dutch screen and have indicated a screen pore hydraulic radius of 0.00031 cm.
    Keywords: ENGINEERING (GENERAL)
    Type: Cryogenics (ISSN 0011-2275); 29; 523-527
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  • 2
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    Superfluid transport and its applications in space (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Various transport modes in superfluid helium are discussed. They include zero net mass flow and finite mass flow for pure superfluid and normal fluid flow. An attempt is made to characterize these transport modes in a common frame of reference. Two dimensionless numbers are used, namely, the dimensionless heat flux number and the dimensionless driving force number. The equations are generalized by the use of a characteristic length so that they can be applied to the transport of HE II in any geometry. The theories are then extended to applications in space. In particular, fountain effect pumps and superfluid management at zero g by vapor-liquid phase separators are discussed in detail.
    Keywords: ENGINEERING (GENERAL)
    Type: Cryogenics (ISSN 0011-2275); 30; 222-229
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  • 3
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    Sintered plug flow modulation of a vapor-liquid phase separator for a helium II vessel (1984)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Presented is a system for modulation of a superfluid (helium II) flow in a vapor-liquid phase separator, for use in cryogenic storage tanks in future space missions. The system consists of a semicircular mechanically operated shutter, downstream of the separator plug, rotated at 0.1 rpm to control the operational surface area of the separator. The mass flow rate was varied from 10 to 22 mg/s. Pressure gradients across the plug are also discussed.
    Keywords: ENGINEERING (GENERAL)
    Type: Advances in cryogenic engineering.; Aug 15, 1983 - Aug 17, 1983; Colorado Springs, CO
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    NASA TECHNICAL REPORTS
  • 4
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    The influence of gas velocity on surface heat pumping for the orifice pulse tube refrigerator (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The basic pulse tube refrigerator produces cooling by a mechanism known as surface heat pumping. Cyclical compression and expansion of a gas within an enclosed tube produces large temperature gradients. The purpose of the tube is to act as 'nodal regenerator'. Heat is stored at node positions along the tube wall and is transported between nodes by moving gas parcels. This process gives rise to refrigeration, with hot temperatures at the closed end and cold temperatures at the open end. Unfortunately, much of the available refrigeration is not realized because the closed end of the basic pulse tube restricts gas movement - gas at the extreme temperatures does not come in contact with the heat exchangers. The orifice pulse tube overcomes this limitation by using a valve and surge volume assembly at the warm, closed end. This allows for a residual gas velocity to remain present during the heat transfer process, thereby permitting more gas to exchange heat at the heat exchangers. This paper describes the pulse tube as a nodal regenerator and the effect residual gas velocity has on the heat transfer mechanism of the orifice pulse tube.
    Keywords: ENGINEERING (GENERAL)
    Type: 1989 Cryogenic Engineering Conference; Jul 24, 1989 - Jul 28, 1989; Los Angeles, CA; United States
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  • 5
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    Turbulent transport of He II in active and passive phase separators using slit devices and porous media (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The turbulent transport mode of vapor liquid phase separators (VLPS) for He II has been investigated comparing passive porous plug separators with active phase separators (APS) using slits of variable flow paths within a common frame of reference. It is concluded that the basic transport regimes in both devices are identical. An integrated Gorter-Mellink (1949) equation, found previously to predict VLPS results of porous plugs, is employed to analyze APS data published in the literature. It is found that the Gorter-Mellink flow rate parameter for 9-micron and 14-micron APS slit widths are relatively independent of the slit width, having a rate constant of about 9 + or - 10 percent. This agrees with the early heat flow results for He II entropy transport at zero net mass flow in wide capillaries and slits.
    Keywords: ENGINEERING (GENERAL)
    Type: Advances in cryogenic engineering.; Jun 14, 1987 - Jun 18, 1987; Saint Charles, IL; United States
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    NASA TECHNICAL REPORTS
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