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Glicksman, M. E.

Publications and source records attributed to Glicksman, M. E..

62 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Boundary-layer analysis for the convection/diffusion transition in dendritic growth

The supercooling dependence of dendritic growth kinetics under the influence of convective heat transport is investigated theoretically and experimentally with emphasis on theoretical prediction of the supercooling level at which the transition from diffusion-controlled to convection-controlled dendritic growth occurs. It is shown that the crossover between diffusive and convective transport depends on the relative thickness of the Stefan length compared with the thermal boundary layer. These lengths become equal at a supercooling which may be calculated from diffusion theory and fluid mechanics. It is also shown that the crossover supercooling varies weakly with the gravitational acceleration, melt viscosity, and the volumetric expansion coefficient.

Glicksman, M. E.↗
NASA NTRS1980

A temperature fixed point near 58 C

Triple-point cell contrains about 300 g of high-purity succinontrile. Experiments show that lower 4 cm of thermometer well are virtually isothermal, making placement of thermometer not very critical. Bulb at bottom of well helps to prevent solid succinontrile mantel from slipping.

Glicksman, M. E.↗
NASA NTRS1979

Convective heat transfer during dendritic growth

Axial growth rate measurements were carried out at 17 levels of supercooling between 0.043 C and 2 C, a temperature range in which convection, instead of diffusion, becomes the controlling mechanism of heat transfer in the dentritic growth process. The growth velocity, normalized to that expected for pure diffusive heat transfer, displays a dependence on orientation. The ratio of the observed growth velocity to that for convection-free growth and the coefficients of supercooling are formulated. The dependence of normalized growth rate in supercooling is described for downward growing dendrites. These experimental correlations can be justified theoretically only to a limited extent.

Glicksman, M. E.↗
NASA NTRS1979

Convection and diffusion effects during dendritic solidification

A report is presented of the first quantitative measurements of dendritic growth at supercooling levels where convection instead of diffusion is the controlling heat transfer mechanism. Precautions similar to that used in an investigation conducted by Glicksman et al. (1976) were taken to insure 'free' dendritic growth conditions. Dendritic growth velocity was measured as a function of growth orientation at seventeen supercoolings which ranged from 0.043 C to 2 C. Selected but representative measurements of velocity versus orientation angle are shown in a graph. The relative growth velocity of a downward growing dendrite is found to be greater than that of a diffusion-limited dendrite. This result is consistent with that expected from the enhanced heat transfer arising from natural convection.

Glicksman, M. E.↗
NASA NTRS1979

Convective flow during dendritic growth

A review is presented of the major experimental findings obtained from recent ground-based research conducted under the SPAR program. Measurements of dendritic growth at small supercoolings indicate that below approximately 1.5 K a transition occurs from diffusive control to convective control in succinonitrile, a model system chosen for this study. The key theoretical ideas concerning diffusive and convective heat transport during dendritic growth are discussed, and it is shown that a transition in the transport control should occur when the characteristic length for diffusion becomes larger than the characteristic length for convection. The experimental findings and the theoretical ideas discussed suggest that the Fluid Experiment System could provide appropriate experimental diagnostics for flow field visualization and quantification of the fluid dynamical effects presented here.

Glicksman, M. E.↗
NASA NTRS1978

Materials science experiments in space

The criteria for the selection of the experimental areas and individual experiments were that the experiment or area must make a meaningful contribution to the field of material science and that the space environment was either an absolute requirement for the successful execution of the experiment or that the experiment can be more economically or more conveniently performed in space. A number of experimental areas and individual experiments were recommended for further consideration as space experiments. Areas not considered to be fruitful and others needing additional analysis in order to determine their suitability for conduct in space are also listed. Recommendations were made concerning the manner in which these materials science experiments are carried out and the related studies that should be pursued.

Gelles, S. H.↗
NASA NTRS1978

Convective heat transfer during dendritic solidification

Experiments on succinonitrile are described in which the dependence of dendritic growth velocity is studied as a function of orientation with respect to gravity. Growth rate measurements were carried out at a relatively small supercooling, requiring high specimen purity as well as extreme thermal stability and precision temperature measurement. The normalized growth velocity showed a dependence on orientation described by the ratio of observed growth velocity to that expected for convection-free growth being equal to 3.52 times the n-th power of Cos half the orientation angle, where n lies between 0.5 and 0.75.

Glicksman, M. E.↗