Experimental Investigation of Melting in Vertical Circular Tubes

2008 ◽  
Author(s):  
L. Fraiman ◽  
E. Benisti ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Melting Point ◽  
Digital Camera ◽  
Melting Process ◽  
Water Bath ◽  
Free Expansion ◽  
Circular Tubes ◽  
Dimensionless Groups ◽  
Different Diameters ◽  
Vertical Tubes ◽  
Rayleigh Numbers

The present study explores experimentally the process of melting of a phase change material (PCM) in vertical circular tubes. The study is performed with a commercially available paraffin-type material with the melting point of about 28 degrees Celsius. The experiments are conducted using vertical tubes of four different diameters, filled with the PCM and immersed in a water bath. In each tube the experiments are performed at the water bath temperatures of 10, 20 and 30°C above the melting point of the paraffin. Three different initial heights of the PCM inside the tubes are considered, thus bringing the total number of cases explored to thirty six. Each tube is thermally insulated at the bottom, and at its top open to atmosphere, to allow free expansion of the melt liquid. The tubes are transparent, and the melting process is monitored and recorded by a digital camera. The digital pictures of the melting process are analyzed, and the results are graphically presented as melt fraction vs. time, showing the effects of tube diameter, PCM height and temperature difference. Generalization of the results is attempted based on the dimensionless groups, including the Fourier, Stefan, and Rayleigh numbers. A correlation connecting the melt fraction with these dimensionless groups is suggested.

Experimental Investigation of Solid-Liquid Phase Change in Cylindrical Geometry

2007 ◽  
Author(s):  
L. Katsman ◽  
V. Dubovsky ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Melting Point ◽  
Phase Change ◽  
Digital Camera ◽  
Melting Process ◽  
Cylindrical Geometry ◽  
Water Bath ◽  
Free Expansion ◽  
Dimensionless Groups ◽  
Different Diameters ◽  
Solid Liquid

The present study explores experimentally the process of melting of a phase change material (PCM) in cylindrical geometry. The study is performed with a commercially available paraffin-type material with the melting point of about 28 degrees Celsius. The experiments are conducted using vertical tubes of four different diameters, filled with the PCM and immersed in a water bath. In each tube the experiments are performed at the water bath temperatures of 10, 20 and 30°C above the melting point of the paraffin. The tubes are transparent, and the melting process is monitored and recorded by a digital camera. Each tube is thermally insulated at the bottom, and at its top open to atmosphere, to allow free expansion of the melt liquid. The digital pictures of the melting process were analyzed, and the results were graphically presented as melt fraction vs. time, showing for the plain tubes the effects of tube diameter and temperature difference. Numerical simulations are performed in order to provide an insight into the mechanisms governing the process. Generalization of the results is attempted based on the dimensionless groups, including the Fourier, Stefan, and Rayleigh numbers. A correlation connecting the melt fraction with these dimensionless groups is suggested.

UGIMA 4404, UGIMA 316L

Alloy Digest ◽  
1998 ◽  
Vol 47 (12) ◽  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Melting Point ◽  
Physical Properties ◽  
Melting Process ◽  
Heat Treating ◽  
Aisi 316L

Abstract UGIMA 4404 (UGIMA 316L) is identical to UGINE 4404 (AISI 316L) in analysis, corrosion resistance, mechanical properties, and forging and welding ability, but not with respect to machinability. A specific melting process creates inclusions of malleable oxides with a low melting point. The inclusions improve machinability by 20-30% compared with AISI 316L (1.4404) stainless steel. This datasheet provides information on composition and physical properties. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: SS-735. Producer or source: Ugine-Savoie.

scholarly journals How Atoms of Polycrystalline Nb 20.6 Mo 21.7 Ta 15.6 W 21.1 V 21.0 refractory High-Entropy Alloys Rearrange during the Melting Process

2021 ◽  
Author(s):  
Shin-Pon Ju ◽  
Chen-Chun Li
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Single Crystal ◽  
Melting Temperature ◽  
Md Simulation ◽  
Melting Process ◽  
Structural Rearrangement ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Melting Mechanism

Abstract The melting mechanism of single crystal and polycrystalline Nb 20.6 Mo 21.7 Ta 15.6 W 21.1 V 21.0 RHEAs was investigated by the molecular dynamics (MD) simulation using the 2NN MEAM potential. For the single crystal RHEA, the density profile displays an abrupt drop from 11.25 to 11.00 g/cm 3 at temperatures from 2910 to 2940 K, indicating all atoms begin significant local structural rearrangement. For polycrystalline RHEAs, a two-stage melting process is found. In the first melting stage, the melting of the grain boundary (GB) regions firstly occurs at the pre-melting temperature, which is relatively lower than the corresponding system-melting point. At the pre-melting temperature, most GB atoms have enough kinetic energies to leave their equilibrium positions, and then gradually induce the rearrangement of grain atoms close to GB. In the second melting stage at the melting point, most grain atoms have enough kinetic energies to rearrange, resulting in the chemical short-ranged order (CSRO) changes of all pairs.

Thermal Convection in Porous Media at High Rayleigh Numbers

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Daniel J. Keene ◽  
R. J. Goldstein
Keyword(s):  
Boundary Layer ◽  
Porous Media ◽  
Thermal Convection ◽  
Thermal Boundary Layer ◽  
Packed Bed ◽  
Horizontal Layer ◽  
Homogeneous Fluid ◽  
Fluid Systems ◽  
Dimensionless Groups ◽  
Rayleigh Numbers

An experimental study of thermal convection in a porous medium investigates the heat transfer across a horizontal layer heated from below at high Rayleigh number. Using a packed bed of polypropylene spheres in a cubic enclosure saturated with compressed argon, the pressure was varied between 5.6 bar and 77 bar to obtain fluid Rayleigh numbers between 1.68 × 109 and 3.86 × 1011, corresponding to Rayleigh–Darcy numbers between 7.47 × 103 and 2.03 × 106. From the present and earlier studies of Rayleigh–Benard convection in both porous media and homogeneous fluid systems, the existence and importance of a thin thermal boundary layer are clearly demonstrated. In addition to identifying the governing role of the thermal boundary layer at high Rayleigh numbers, the successful correlation of data using homogeneous fluid dimensionless groups when the thermal boundary layer thickness becomes smaller than the length scale associated with the pore features is shown.

Thermodynamic Optimization of Phase-Change Energy Storage Using Two or More Materials

1992 ◽  
Vol 114 (1) ◽  
pp. 84-90 ◽  
Author(s):  
J. S. Lim ◽  
A. Bejan ◽  
J. H. Kim
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Phase Change ◽  
Phase Change Material ◽  
Finite Thickness ◽  
Melting Process ◽  
Two Phase ◽  
In Series ◽  
Optimal Melting ◽  
Change Material

This paper documents the relative merits of using more than one type of phase-change material for energy storage. In the case of two phase-change systems in series, which are melted by the same stream of hot fluid, there exists an optimal melting point for each of the two materials. The first (upstream) system has the higher of the two melting points. The second part of the paper addresses the theoretical limit in which the melting point can vary continuously along the source stream, i.e., when an infinite number of different (and small) phase-change systems are being heated in series. It is shown that the performance of this scheme is equivalent to that which uses an optimum single phase-change material, in which the hot stream remains unmixed during the melting process. The time dependence, finite thickness and longitudinal variation of the melt layer caused by an unmixed stream are considered in the third part of the paper. It is shown that these features have a negligible effect on the optimal melting temperature, which is slightly higher than (T∞Te)1/2.

scholarly journals Electric Field Interaction with Hydrocarbon Flames

2018 ◽  
Vol 63 (5) ◽  
pp. 402
Author(s):  
S. G. Orlovskaya ◽  
M. S. Skoropado ◽  
F. F. Karimova ◽  
V. Ya. Chernyak ◽  
L. Yu. Vergun
Keyword(s):  
Melting Point ◽  
Field Strength ◽  
Electric Field ◽  
Fossil Fuels ◽  
Melting Process ◽  
Melting Rate ◽  
Melting Time ◽  
Field Interaction ◽  
Hydrocarbon Flames ◽  
Dc Electric Field

The problem of electric-field-assisted combustion for low-melting point hydrocarbons (paraffin wax, n-alkanes) attracts the attention of scientists in relation to the development of paraffin-based propellants. Our study is aimed at the detailed investigation of the dc electric field interaction with the flame of octadecane droplet. We have studied the melting and combustion of alkane particles in the electric field ranging from 33 kV/m to 117 kV/m. It is found that the melting rate decreases distinctly starting with the electric field strength E ∼ 80 kV/m. This effect is more pronounced at high gas temperatures (Ste >1), when the melting time is about a few seconds. So, the melting process slows down in the dc electric field. At the same time, the burning rate constant rises by more than 10 percents. The obtained results can be used to develop efficient and clean technologies of fossil fuels combustion.

scholarly journals Wall Pressures In a Channel Flow Obstructed By a Line of Inclined Rods: Invariant Groups and Semi-Empirical Correlations

2021 ◽  
Author(s):  
Víctor Herrero ◽  
Hernán Ferrari ◽  
Raul Marino ◽  
Alejandro Clausse
Keyword(s):  
Inclination Angle ◽  
Rectangular Channel ◽  
Momentum Conservation ◽  
Empirical Correlations ◽  
Independence Principle ◽  
Dimensionless Groups ◽  
Conservation Principles ◽  
Different Diameters ◽  
Semi Empirical ◽  
Velocity Projection

Abstract An experiment is conducted in a rectangular channel obstructed by a transverse line of four inclined cylindrical rods. The wall pressure around the perimeter of a central rod and the pressure drop through the channel are measured varying the inclination angle of the rods. Three assemblies of rods with different diameters are tested. The measurements were analyzed applying momentum conservation principles and semi-empirical considerations. Several invariant dimensionless groups of parameters relating the pressure at key locations of the system with characteristic dimensions of the rods are produced. It was found that the independence principle holds for most of the Euler numbers characterizing the pressure at different locations, that is, the group is independent of the inclination angle provided that the inlet velocity projection normal to the rods is used to non-dimensionalize the pressure. The resulting semi-empirical correlations can be useful for designing similar hydraulic units.

Remelting and Addition of Alloy Components

2021 ◽  
pp. 405-449
Author(s):  
Thorvald Abel Engh ◽  
Geoffrey K. Sigworth ◽  
Anne Kvithyld
Keyword(s):  
Melting Point ◽  
Numerical Model ◽  
Melting Process ◽  
Class Ii ◽  
Melting Rate ◽  
Intermetallic Phases ◽  
Class I ◽  
Melt Temperature ◽  
Continuous Feeding ◽  
Conservation Model

This chapter discusses our scientific understanding of alloying. Class I alloy additions have a melting point lower than the bulk melt temperature, whereas class II additions have a melting point higher than the bulk melt temperature. This means that magnesium is a class I element when added to aluminium, and silicon and manganese are class II alloy additions. An energy conservation model for melting is presented and compared to measurements. A numerical model is presented for continuous feeding and melting of aluminium plates into aluminium melt. For class II alloy additions it is shown from the literature that the melting rate can be strongly affected by the formation of intermetallic phases during the melting process. Therefore, it is virtually impossible to put up a general model for the melting of these types of alloying elements. Safety regarding alloying operations is also addressed.

Heat Transfer During Melting Inside a Horizontal Tube

1983 ◽  
Vol 105 (2) ◽  
pp. 226-234 ◽  
Author(s):  
H. Rieger ◽  
U. Projahn ◽  
M. Bareiss ◽  
H. Beer
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Numerical Data ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Melting Process ◽  
Mapping Technique ◽  
Transfer Coefficients ◽  
Melting Front ◽  
Rayleigh Numbers

The melting process of a phase change material (PCM) enclosed in a horizontal, isothermal circular tube has been investigated analytically and by experiment for an interesting range of parameters. The physical process was analyzed by numerical methods, whereby the underlying mathematical model involves heat conduction as well as natural convection as the basic heat transport mechanisms. Difficulties associated with the complex and timewise changing melt region whose shape is also part of the solution, have been overcome by applying a numerical mapping technique. Computations and experiments were performed for Rayleigh numbers in the range 105 ≤ Ra ≤ 106. For lower Rayleigh numbers the numerical calculations predict a streamlined design of the PCM at later times, similar to the experiment. At higher Rayleigh numbers, three-dimensional Bernard convection was observed in the bottom region of the melt layer, which was unsteady in their timewise behaviour. The appearance of several roll-cells have also been predicted by the calculations, although the mathematical model was restricted to two-dimensional flow. The experiments were performed with n-octadecane (Pr ≃ 50) as PCM. The test cell basically consists of a short tube filled with the PCM. The tube is closed with plexiglass disks on both ends, thus allowing the melting front to be recorded photographically with time. As a result, the interface positions as well as the overall and local heat transfer coefficients are presented as function of time. The agreement between experimental and numerical data is reasonably good.

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