Experiments on Remelting and Solidification of Molten Metal Droplets Deposited in Vertical Columns

2006 ◽  
Vol 129 (2) ◽  
pp. 311-318 ◽  
Author(s):  
M. Fang ◽  
S. Chandra ◽  
C. B. Park
Keyword(s):  
Column Height ◽  
Conductive Heat ◽  
Droplet Temperature ◽  
Droplet Generator ◽  
One Dimensional ◽  
Spherical Mass ◽  
Temperature Constant ◽  
Uniform Diameter ◽  
Surface Tension Forces ◽  
Metal Droplets

Experiments were done to determine conditions under which vertical columns could be built by metal droplets landing sequentially on top of each other. Molten tin droplets (0.6mm diameter) were deposited using a pneumatic droplet generator on an aluminum substrate. The primary parameters varied in experiments were those found to most affect bonding between droplets: droplet temperature (250-345°C), substrate temperature (60-200°C), and deposition rate (1-15Hz). At lower deposition rates the substrate cooled down too much to induce remelting whereas at higher rates the tip of the column remained liquid and surface tension forces pulled it into a spherical mass. Assuming one-dimensional conductive heat transfer in a column a simple analytical model was developed to calculate the temperature at the tips of the column. It predicts that deposition frequency should be decreased as column height increases to hold the tip temperature constant. Droplet coalescence was best achieved when the tip temperature of a column was maintained at the melting point of the metal. Columns fabricated following the deposition frequency predicted by the model show good bonding between droplets and uniform diameter.

Experiments on Remelting and Solidification of Molten Metal Droplets Deposited in Vertical Columns

2005 ◽  
Author(s):  
M. Fang ◽  
S. Chandra ◽  
C. B. Park
Keyword(s):  
Column Height ◽  
Conductive Heat ◽  
Droplet Temperature ◽  
Droplet Generator ◽  
One Dimensional ◽  
Spherical Mass ◽  
Temperature Constant ◽  
Uniform Diameter ◽  
Surface Tension Forces ◽  
Metal Droplets

Experiments were done to determine conditions under which vertical columns could be built by metal droplets landing sequentially on top of each other. Molten tin droplets (0.6 mm diameter) were deposited using a pneumatic droplet generator on an aluminum substrate. The primary parameters varied in experiments were those found to most affect bonding between droplets: droplet temperature (250°C to 345°C), substrate temperature (60°C to 200°C) and deposition rate (1 Hz to 15 Hz). At lower deposition rates the substrate cooled down too much to induce remelting whereas at higher rates the tip of the column remained liquid and surface tension forces pulled it into a spherical mass. Assuming one-dimensional conductive heat transfer in a column a simple analytical model was developed to calculate the temperature at the tips of the column. It predicts that deposition frequency should be decreased as column height increases to hold the tip temperature constant. Droplet coalescence was best achieved when the tip temperature of a column was maintained at the melting point of the metal. Columns fabricated following the deposition frequency predicted by the model show good bonding between droplets and uniform diameter.

Building Vertical Walls by Deposition of Molten Metal Droplets

2005 ◽  
Author(s):  
M. Fang ◽  
S. Chandra ◽  
C. B. Park
Keyword(s):  
Surface Layer ◽  
Analytical Solution ◽  
Substrate Temperature ◽  
Layer By Layer ◽  
Droplet Temperature ◽  
Droplet Generator ◽  
One Dimensional ◽  
Metallurgical Bonding ◽  
Experimental Parameters ◽  
Vertical Walls

Experiments were conducted to determine conditions under which good metallurgical bonding was achieved in vertical walls composed of multiple layers of droplets that were fabricated by depositing tin droplets layer by layer. Molten tin droplets (0.75 mm diameter) were deposited using a pneumatic droplet generator on an aluminum substrate. The primary parameters varied in experiments were those found to most affect bonding between droplets on different layers: droplet temperature (varied from 250°C to 325°C) and substrate temperature (varied from 100°C to 190°C). Considering the cooling rate of droplet is much faster than the deposition rate previous deposition layer cooled down too much that impinging droplets could only remelt a thin surface layer after impact. Assuming that remelting between impacting droplets and the previous deposition layer is a one-dimensional Stefan problem with phase change an analytical solution can be found and applied to predict the minimum droplet temperature and substrate temperature required for local remelting. It was experimentally confirmed that good bonding at the interface of two adjacent layers could be achieved when the experimental parameters were such that the model predicted remelting.

An Experimental and Analytical Study of Radiative and Conductive Heat Transfer in Molten Glass

1972 ◽  
Vol 94 (2) ◽  
pp. 224-230 ◽  
Author(s):  
N. D. Eryou ◽  
L. R. Glicksman
Keyword(s):  
Molten Glass ◽  
Analytical Study ◽  
Heat Fluxes ◽  
Conductive Heat ◽  
Spectral Absorption Coefficient ◽  
Strong Function ◽  
One Dimensional ◽  
Helium Neon Laser ◽  
Glass Slab ◽  
Helium Neon

One-dimensional temperature profiles and heat fluxes within a slab of molten glass were measured experimentally. The glass slab was contained between two parallel platinum-lined ceramic plates. The plate temperatures were kept above 2000 deg F so that radiation heat flux was always equal to or larger than conduction. An optical method of temperature measurement was developed in which a helium–neon laser beam was directed along an isothermal path through the glass. The attenuation of the beam was a strong function of temperature and was used to evaluate the local temperatures within the glass slab. In order to perform a theoretical analysis the spectral absorption coefficient of the glass was measured from 2000 to 2300 deg F. Two analyses were performed: one for a diffuse platinum–glass boundary and the other for a specular boundary. The calculated temperatures agree with the measured values within 5 deg F throughout the slab, and the measured and predicted heat fluxes agree within 10 percent.

The packaging unit: a basic structural feature for the condensation of late cricket spermatid nuclei

1978 ◽  
Vol 33 (1) ◽  
pp. 265-283
Author(s):  
A.L. Kierszenbaum ◽  
L.L. Tres
Keyword(s):  
Phosphotungstic Acid ◽  
Liquid Surface ◽  
Sodium Dodecyl ◽  
Thin Sections ◽  
Liquid Surface Tension ◽  
Detergent Treatment ◽  
Binding Forces ◽  
Limited Protein ◽  
Uniform Diameter ◽  
Surface Tension Forces

The alignment, folding and packaging of cricket chromatin was examined during late spermiogenesis by an electron-microscope study of nuclei dispersed by air—liquid surface tension forces after detergent treatment. Late developing spermatid genomes arrange themselves in multiple packaging units in a stepwise process which includes: (1) a loss of the beaded repeating structure of chromatin as nucleoprotein fibres become smooth and gradually assume a uniform diameter; (2) a side-by—side alignment of structurally modified chromatin fibres; and (3) a regular folding into packaging units. Alignment and folding of chromatin fibres are presumably mediated by intermolecular bonds easily disrupted by spreading forces. In very late spermatids, interfibre binding forces are difficult to overrride by spreading alone, indicating a stronger cross-linking of increasingly coalescent packaging units. ‘Unit to unit’ coalescence stabilizes the nuclear structure, first limiting and afterwards denying penetration of phosphotungstic acid, as displayed in thin sections of extremely cricket spermatid nuclei. Binding of phosphotungstate by nuclear basic proteins can be facilitated by limited protein solubilization after disulphide reduction of unfixed cricket tests with sodium dodecyl sulphate and dithiothreitol. Results of this study permit the proposal of model experiments useful for clarifying the organization of highly condensed spermatid genomes and for evaluating the structure of genome segments in systems wherein changes of chromatin-associated protein occur.

Modelling of T-Junction Droplet Generator in the Transition Regime

2010 ◽  
Author(s):  
Tomasz Glawdel ◽  
Caglar Elbuken ◽  
Carolyn Ren
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
Continuous Phase ◽  
Main Channel ◽  
Dispersed Phase ◽  
Transition Regime ◽  
Operational Mode ◽  
Droplet Generator ◽  
Shear Forces ◽  
Surface Tension Forces

One of the most commonly used microfluidic droplet generator designs is the T-junction as shown in Figure 1. In this design, the dispersed phase microchannel, usually containing an aqueous solution, perpendicularly intersects the main channel, which contains the continuous phase (oil). The T-junction design has been widely adopted because of its simplicity and the superior control it offers over droplet size. Two primary operational regimes have been identified where breakup is dominated by confinement of the emerging droplet within the microchannel, known as the squeezing regime (Ca<0.002), or by the balance of shear and surface tension forces known as the dripping regime (Ca>0.02). The operational mode of the T-junction generator is primarily characterized by the Capillary number (Ca = μU / γ), which describes the competition between the aforementioned forces. In between the two regimes exists the transition regime where both confinement and shear forces are important.

The One-Dimensional Analysis of Fin Assembly Heat Transfer

1983 ◽  
Vol 105 (3) ◽  
pp. 646-651 ◽  
Author(s):  
M. Manzoor ◽  
D. B. Ingham ◽  
P. J. Heggs
Keyword(s):  
Convective Heat ◽  
Heat Dissipation ◽  
Electric Circuit ◽  
Convective Heat Exchange ◽  
Conductive Heat ◽  
One Dimensional ◽  
Fin Efficiency ◽  
Conductive Heat Flow ◽  
The One ◽  
Two Stages

The design of finned surfaces is conventionally performed in two stages. First the fin efficiency is determined by simultaneously analyzing the conductive heat flow within the fin, and the convective heat dissipation from the surface of the fin. Then, the effects of the thermal interaction between the supporting interface and the fins and the convective heat exchange at the plain side of the supporting interface are incorporated by employing a technique based on electric circuit theory. In this study, it is shown that this technique in fact has a mathematically rigorous foundation. It is also shown that, for design purposes, there is a far superior alternative to the fin efficiency.

One-dimensional transient conductive heat transport

2009 ◽  
pp. 216-219
Author(s):  
Jean Braun ◽  
Peter van der Beek ◽  
Geoffrey Batt
Keyword(s):  
Heat Transport ◽  
Conductive Heat ◽  
One Dimensional
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