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  • 1
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    Heat transfer in space power and propulsion systems (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: NASA's planned Space Station has projected power requirements in the 75-300 kW range; attention is presently given to the range of power system configurations thus far proposed. These are a silicon solar cell system incorporating regenerative fuel cell or battery storage, with a 10-year lifetime, a solar-dynamic power system with phase-change or regenerative fuel cell energy storage, and a combination of these two alternatives. A development status evaluation is also given for the propulsion systems that may be used by next-generation boosters. These include such novel airbreathing systems as turboramjets, air liquefaction cycle rockets, airturboramjet/rockets, and supersonic combustion ramjets.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Mechanical Engineering (ISSN 0025-6501); 108; 40-52
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  • 2
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    Effect of location in an array on heat transfer to a short cylinder in crossflow (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders. All cylinders had a length-to-diameter ratio of 3.0. Both in-line and staggered array patterns were studied. The cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow. The row containing the heated cylinder remained in a fixed position in the channel and the relative location of this row within the array was changed by adding up to five upstream rows. The working fluid was nitrogen gas at pressures from 100 to 600 kPa. The Reynolds number range based on cylinder diameter and average unobstructed channel velocity was from 5,000 to 125,000. Turbulence intensity profiles were measured for each case at a point one half space upstream of the row containing the heated cylinder. The basis of comparison for all the heat transfer data was the single row with the heated cylinder. For the in-line cases the addition of a single row of cylinders upstream of the row containing the heated cylinder increased the heat transfer by an average of 50 percent above the base case. Adding up to five more rows caused no increase or decrease in heat transfer. Adding rows in the staggered array cases resulted in average increases in heat transfer of 21, 64, 58, 46, and 46 percent for one to five upstream rows, respectively. Previously announced in STAR as N82-19493
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 106; 42-48
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  • 3
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    Unsteady heat transfer and direct comparison to steady-state measurements in a rotor-wake experiment (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Circumferentially local and time-resolved heat transfer measurements were obtained for a circular cylinder in crossflow located downstream of a rotating spoked wheel wake generator in a steady flow tunnel. The unsteady heat transfer effects were obtained by developing an extension of a thin film gauge technique employed to date exclusively in short-duration facilities. The time-average thin film results and conventional steady-state heat transfer measurements were compared. Time-averaged wake-induced stagnation heat transfer enhancement levels above the nowake case were about 10 percent for the four cylinder Reynolds numbers. This enhancement level was nearly independent of bar passing frequency and was related directly to the time integral of the heat transfer spikes observed at the bar passing frequency. It is observed that the wake-induced heat transfer spikes have peak magnitudes averaging 30 to 40 percent above the interwake heat transfer level.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 4
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    Convective heat transfer to low-temperature fluids (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Research into forced and natural convection processes in low-temperature (cryogenic) fluids is reviewed with primary emphasis on forced convection. Boundaries of the near-critical region are defined, fluid properties near the critical state are discussed, and heat-transfer processes around the critical point are described. The thermodynamics of the critical point is analyzed together with transport properties of a near-critical fluid, and the quantum states of low-temperature molecular hydrogen (para and ortho) are discussed. Experimental work on heat transfer in free, natural, and forced convection systems is briefly summarized. Graham's (1969) penetration model for near-critical fluids is outlined, near-critical heat transfer is discussed in relation to conventional geometric effects, and the effects of curvature on the properties of near-critical hydrogen are noted. Theoretical considerations in free and forced convection are examined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 5
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    Preliminary results of a study of the relationship between free-stream turbulence and stagnation region heat transfer (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Preliminary results of a study to investigate the relationship between free stream turbulence and heat transfer augmentation in the stagnation region is presented. The effects of free stream turbulence and surface roughness on spanwise averaged heat transfer were investigated. Turbulence was measured upstream of a cylinder placed in the wake of an array of parallel wires that were perpendicular to the cylinder axis. Finally, flow visualization and thermal visualization techniques were combined to show the relationship between vortices in the stagnation region and spanwise variations in heat transfer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Transition in Turbines; p 17-34
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  • 6
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    New Facility to Study Unsteady Wake Effects on Turbine Airfoil Heat Transfer (1985)
    In:  CASI
    Details
    Publication Date: 2014-08-27
    Description: A significant portion of the SSME aerothermal loads program is directed at the heat transfer effects of the unsteady flows, particularly wakes, that occur naturally in turbomachinery. Although these phenomena occur in all turbomachines, we feel they will be more severe in the SSME turbines because of the high heat transfer associated with the very high Reynolds numbers over the SSME airfoils.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Struct. Integrity and Durability of Reusable Space Propulsion Systems; p 41-47
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  • 7
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    Review and assessment of the database and numerical modeling for turbine heat transfer (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The objectives of the NASA Hot Section Technology (HOST) Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high-temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding while the analytical efforts were approximately 25 percent. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Toward Improved Durability in Advanced Aircraft Engine Hot Sections; p 39-55
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  • 8
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    Progress in the prediction of unsteady heat transfer on turbines blades (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Progress toward developing a general method for predicting unsteady heat transfer on turbine blades subject to blade-passing frequencies and Reynolds numbers relevant to the Space Shuttle Main Engine (SSME) is discussed. The method employs an invisid/viscous interactive procedure which has been tested extensively for steady subsonic and transonic external airfoil problems. One such example is shown. The agreement with experimental data and with Navier-Stokes calculations yields confidence in the method. The technique is extended to account for wake generated unsteadiness. The flow reversals around the stagnation point caused by the nonuniform onset velocity are accounted for by using the Characteristic Box scheme developed by Cebeci and Stewartson. The coupling between the inviscid and viscous methods is achieved by using a special procedure, which, with a novel inverse finite-difference boundary-layer method, allows the calculations to be performed for a wide range of flow conditions, including separation. Preliminary results are presented for the stagnation region of turbine blades for both laminar and turbulent flows. A laminar model problem corresponding to a flow on a circular cylinder which experiences the periodic passing of wakes from turbine blades is presented to demonstrate the ability of the method to calculate flow reversals around the stagnation region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Structural Integrity and Durability of Reusable Space Propulsion Systems; p 21-27
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  • 9
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    Buoyancy effects on critical heat flux of forced convective boiling in vertical flow (1966)
    In:  CASI
    Details
    Publication Date: 2019-05-30
    Description: Buoyancy effects on critical heat flux of forced convective boiling in reversed vertical flow of liquid nitrogen
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-TN-D-3672
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  • 10
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    Preliminary results of a study of the relationship between free stream turbulence and stagnation region heat transfer (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The mechanism that causes free stream turbulence to increase heat transfer in the stagnation region of turbine vanes and blades was studied. The work is being conducted in a wind tunnel at atmospheric conditions to facilitate measurements of turbulence and heat transfer. The model size is scaled up to simulate Reynolds numbers (based on leading edge diameter) that are to be expected on a turbine blade leading edge. Reynolds numbers from 13,000 to 177,000 were run in the present tests. Spanwise averaged heat transfer measurement with high and low turbulence were made with rough and smooth surface stagnation regions. Results of these measurements show that the boundary layer remains laminar in character even in the presence of free stream turbulence at the Reynolds numbers tested. If roughness is added the boundary layer becomes transitional as evidenced by the heat transfer increase with increasing distance from the stagnation line. Hot wire measurements near the stagnation region downstream of an array of parallel wires have shown that vorticity in the form of mean velocity gradients is amplified as flow approaches the stagnation region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 85-GT-84
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