Electron paramagnetic resonance studies of a viscous nematic liquid crystal. II - Evidence counter to a second-order phase change.
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Shutt, W. E.↗
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Phase change paint tests to investigate effects of TPS tiles on heating rates of the Rockwell space shuttle orbiter (test OH4C, model 21-0)
Information and data from wind tunnel tests conducted on 0.0175-scale models of the space shuttle orbiter are presented. The primary objective of the tests was to evaluate aerodynamic heating effects of the tiles in the thermal protection system (TPS). Tile gap depth and flow orientation effects on the TPS were investigated. Tile patterns were cut into the undersides of the orbiter models to simulate the gaps. One model was left smooth for comparison.
Quan, M.↗
A device for rapid determination of thermophysical properties of phase-change wind-tunnel models
An experimental method for direct measurement of the thermophysical properties of wind tunnel heat transfer models was developed. The technique consists of placing the model under a bank of high intensity, radiant heaters so that the fast opening water cooled shutters, which isolate the heater bank from the model, allow a step-input heat rate to be applied. Measurements of the heat transfer rate coupled with a surface-temperature time history of the same material are sufficient to determine the material thermophysical properties. An infrared thermometer is used to measure model surface temperature and a slug calorimeter provides heat transfer rate information. The output from the infrared thermometer and calorimeter is then fed into an analog-to-digital converter which provides digitized data to a computer. This computer then calculates combined thermophysical properties and a teleprinter prints out all the data. Thus, results are available within 7 minutes of test initiation as opposed to the weeks or months required using prior techniques.
Creel, T. R., Jr.↗
Effect of temperature on the electronic instability and the crystalline phase change at low temperature of V3Si type compounds
Equations assuming a Jahn-Teller type effect for the d band electrons in V3Si compounds are given, and the results of free-energy change calculations by using some approximations based on these equations are depicted. The tetragonal structure is converted to cubic as the temperature rises past T sub m which is calculated as 13 K. by the Batterman-Barrett method and is measured to be 20-5 K. Other parameters such as change of C sub p with temperature are predicted better.
Labbe, J.↗
Development of a phase-change thermal storage system using modified anhydrous sodium hydroxide for solar electric power generation
A thermal storage system for use in solar power electricity generation was investigated analytically and experimentally. The thermal storage medium is principally anhydrous NaOH with 8% NaNO3 and 0.2% MnO2. Heat is charged into storage at 584 K and discharged from storage at 582 K by Therminol-66. Physical and thermophysical properties of the storage medium were measured. A mathematical simulation and computer program describing the operation of the system were developed. A 1/10 scale model of a system capable of storing and delivering 3.1 x 10 to the 6th power kJ of heat was designed, built, and tested. Tests included steady state charging, discharging, idling, and charge-discharge conditions simulating a solar daily cycle. Experimental data and computer-predicted results are correlated. A reference design including cost estimates of the full-size system was developed.
Cohen, B. M.↗
Investigation of medium and high temperature phase change materials
A detailed description of the programs for acquisition and analysis of the test results is given. Basically it concerns three programs. The TEST program controls the recording of the test data. With the THELLI program it is possible to follow the temperature curve recorded for each individual thermoelement during the test. With the AUSW program the test data can be analyzed, to determine, for example, the melting point and the start of melting. The first results of the service life tests are discussed. From these it is attempted to draw inferences for the subsequent tests. An attempt is made to focus on the determination of the area-related mass loss, the reduction in thickness and the corrosion rate as well as optical and scanning electron microscope evaluation.
Heine, D.↗
Evaluation of alternative phase change materials for energy storage in solar dynamic applications
The performance of fluoride salt and metallic thermal energy storage materials are compared in terms of basic performance as applied to solar dynamic power generation. Specific performance considerations include uniformity of cycle inlet temperature, peak cavity temperature, TES utilization, and system weights. Also investigated were means of enhancing the thermal conductivity of the salts and its effect on the system performance.
Crane, R. A.↗
Laboratory and field studies of stratospheric aerosols: Phase changes under high supersaturation
It is well known that water in the form of isolated small droplets supercool as much as 40 C below their equilibrium melting point. Solutions similarly supercool (with respect to water) and supersaturate (with respect of the solute). Experiments are described in which bulk solutions typical of atmospheric aerosols (nitric acid, sulfuric acid, and hydrates; ammonium sulfate; ammonium bisulfate; sodium chloride) are supercooled and/or supersaturated and nucleated to initiate crystal growth. Supersaturation of 300 percent is readily attainable, with linear growth of crystals increasing roughly as (supercooling/supersaturation)sup 2. The implication of the experiments is that the situation of metastability in polar stratosphere clouds is very likely, with nucleation only occuring under a high degree of supercooling or supersaturation.
Hallet, John↗
The effect of volume phase changes, mass transport, sunlight penetration, and densification on the thermal regime of icy regoliths
The present quantitative modeling of convective, condensational, and sublimational effects on porous ice crust volumes subjected to solar radiation encompasses the effect of such insolation's penetration of visible bandpass-translucent light, but opaque to the IR bandpass. Quasi-steady-state temperatures, H2O mass fluxes, and ice mass-density change rates are computed as functions of time of day and ice depth. When the effects of latent heat and mass transport are included in the model, the enhancement of near-surface temperature due to the 'solid-state greenhouse effect' is substantially diminished. When latent heat, mass transport, and densification effects are considered, however, a significant solid-state greenhouse effect is shown to be compatible with both morphological evidence for high crust strengths and icy shell decoupling from the lithosphere.
Fanale, Fraser P.↗
Two-dimensional simulation of a two-phase, regenerative pumped radiator loop utilizing direct contact heat transfer with phase change
An innovative pumped loop concept for 600 K space power system radiators utilizing direct contact heat transfer, which facilitates repeated startup/shutdown of the power system without complex and time-consuming coolant thawing during power startup, is under development. The heat transfer process with melting/freezing of Li in an NaK flow was studied through two-dimensional time-dependent numerical simulations to characterize and predict the Li/NaK radiator performance during startup (thawing) and shutdown (cold-trapping). Effects of system parameters and the criteria for the plugging domain are presented together with temperature distribution patterns in solid Li and subsequent melting surface profile variations in time.
Rhee, Hyop S.↗
Coupled structural, thermal, phase-change and electromagnetic analysis for superconductors, volume 2
Two families of parametrized mixed variational principles for linear electromagnetodynamics are constructed. The first family is applicable when the current density distribution is known a priori. Its six independent fields are magnetic intensity and flux density, magnetic potential, electric intensity and flux density and electric potential. Through appropriate specialization of parameters the first principle reduces to more conventional principles proposed in the literature. The second family is appropriate when the current density distribution and a conjugate Lagrange multiplier field are adjoined, giving a total of eight independently varied fields. In this case it is shown that a conventional variational principle exists only in the time-independent (static) case. Several static functionals with reduced number of varied fields are presented. The application of one of these principles to construct finite elements with current prediction capabilities is illustrated with a numerical example.
Felippa, Carlos A.↗
Isentropic phase changes in dissociating gases and the method of sound dispersion for the investigation of homogeneous gas reactions with very high speed : Conclusion
The analytical results of Part I are also applied to sound dispersion by friction and heat conduction, An irreversible change of momentum, energy, and type of particle corresponding to friction, heat conduction, and diffusion effects can appear both in the direction of the sound field and traverse to it. Longitudinal damping, the coupling of longitudinal damping and that due to chemical and physical changes, and coupling of diffusion and compositional changes are treated for a plane sound wave of infinite extent. The same principles are also applied to sound effects in cylindrical tubes. The limitations of the method are discussed in some detail.
SOUND VELOCITY - GASES↗
Isentropic phase changes in dissociating gases and the method of sound dispersion for the investigation of homogeneous gas reactions with very high speed
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GASES - DISSOCIATION↗
Thin Film Mediated Phase Change Phenomena: Crystallization, Evaporation and Wetting
We focus on two distinct materials science problems that arise in two distinct microgravity environments: In space and within the space of a polymeric network. In the former environment, we consider a near eutectic alloy film in contact with its vapor which, when evaporating on earth, will experience compositionally induced buoyancy driven convection. The latter will significantly influence the morphology of the crystallized end member. In the absence of gravity, the morphology will be dominated by molecular diffusion and Marangoni driven viscous flow, and we study these phenomena theoretically and experimentally. The second microgravity environment exists in liquids, gels, and other soft materials where the small mass of individual molecules makes the effect of gravity negligible next to the relatively strong forces of intermolecular collisions. In such materials, an essential question concerns how to relate the molecular dynamics to the bulk rheological behavior. Here, we observe experimentally the diffusive motion of a single molecule in a single polymer filament, embedded within a polymer network and find anomalous diffusive behavior.
Wettlaufer, John S.↗
Microgravity Disturbance Characterization of the Quench Module Insert (QMI) Phase Change Device (PCD)
The Materials Science Research Facility (MSRF) is a multi-user, multi-purpose facility for materials science research. One experiment within the MSRF will be the Quench Module Insert (QMI), a high-temperature furnace with unique capabilities for processing different classes of materials. The primary functions of the QMI furnace are to melt, directionally solidify, and quench metallic samples, providing data to aid in understanding the effects of the microgravity environment on the characteristics of these processed metals. The QMI houses sealed individual sample ampoules containing material to be processed. Quenching of the samples in the QMI furnace is accomplished by releasing low-melting-point metallic shoes into contact with the outside of the sample ampoule, dissipating heat and cooling the sample inside. The impact from this method of quench will induce sample vibrations which could be large enough to adversely affect sample quality. Utilizing breadboard hardware, the sample quench sequence, releasing the shoes, was conducted. Data was collected from accelerometers located on the breadboard sample cartridge, indicating the maximum acceleration achieved by the sample. The primary objective of the test described in this presentation was to determine the acceleration imparted on the sample by the shoe contact. From this information, the science community can better assess whether this method of quench will allow them to obtain the data they need.
Gattis, Christy↗
Direct numerical simulation of multicomponent-fuel drop-laden temporal mixing layers with phase change
A model of a temporal three-dimensional mixing layer laden with a multitude of drops of a fuel containing a large number of species is derived.
multicomponent-fueld mixing layer↗
Phase Change Materials for Advanced Mars Thermal Control
Future missions to Mars for the 1998 launch opportunity and beyond will require advanced thermal control for electronics to minimize enclosure mass, power and volume.
Mars missions to Mars thermal control enclosure ma↗
Growth method for chalcongenide phase-change nanostructures
A method for growth of an alloy for use in a nanostructure, to provide a resulting nanostructure compound including at least one of Ge.sub.xTe.sub.y, In.sub.xSb.sub.y, In.sub.xSe.sub.y, Sb.sub.xTe.sub.y, Ga.sub.xSb.sub.y, Ge.sub.xSb.sub.y,Te.sub.z, In.sub.xSb.sub.yTe.sub.z, Ga.sub.xSe.sub.yTe.sub.z, Sn.sub.xSb.sub.yTe.sub.z, In.sub.xSb.sub.yGe.sub.z, Ge.sub.wSn.sub.xSb.sub.yTe.sub.z, Ge.sub.wSb.sub.xSe.sub.yTe.sub.z, and Te.sub.wGe.sub.xSb.sub.yS.sub.z, where w, x, y and z are numbers consistent with oxidization states (2, 3, 4, 5, 6) of the corresponding elements. The melt temperatures for some of the resulting compounds are in a range 330-420.degree. C., or even lower with some compounds.
Yu, Bin↗