How the convective heat transport at the solid/liquid phase interface influences the stable mode of dendritic growth

2018 ◽  
Author(s):  
Liubov V. Toropova ◽  
Dmitri V. Alexandrov ◽  
Peter K. Galenko
Keyword(s):  
Liquid Phase ◽  
Heat Transport ◽  
Convective Heat ◽  
Dendritic Growth ◽  
Phase Interface ◽  
Stable Mode ◽  
Solid Liquid

scholarly journals Verification of a mathematical model for the solution of the Stefan problem using the mushy layer method

2021 ◽  
Vol 2021 (3) ◽  
pp. 119-125
Author(s):  
R.S. Yurkov ◽  
◽  
L.I. Knysh ◽  
Keyword(s):  
Phase Transition ◽  
Liquid Phase ◽  
Stefan Problem ◽  
Heat Storage ◽  
Storage Systems ◽  
Phase Interface ◽  
Mushy Layer ◽  
Liquid Phase Transition ◽  
Layer Method ◽  
Solid Liquid

The use of solar energy has limitations due to its periodic availability: solar plants do not operate at night and are ineffective in dull weather. The solution of this problem involves the introduction of energy storage and duplication systems into the conversion loop. Among the energy storage systems, solid–liquid phase transition modules have significant energy, ecologic, and cost advantages. Physical processes in modules of this type are described by a system of non-stationary nonlinear partial differential equations with specific boundary conditions at the phase interface. The verification of a method for solving the Stefan problem for a heat-storage material is presented in this paper. The use of the mushy layer method made it possible to simplify the classical mathematical model of the Stefan problem by reducing it to a nonstationary heat conduction problem with an implicit heat source that takes into account the latent heat of transition. The phase transition is considered to occur in an intermediate zone determined by the solidus and liquidus temperatures rather than in in infinite region. To develop a Python code, use was made of an implicit computational scheme in which the solidus and liquidus temperatures remain constant and are determined in the course of numerical experiments. The physical model chosen for computer simulation and algorithm verification is the process of ice layer formation on a water surface at a constant ambient temperature. The numerical results obtained allow one to determine the temperature fields in the solid and the liquid phase and the position of the phase interface and calculate its advance speed. The algorithm developed was verified by analyzing the classical analytical solution of the Stefan problem for the one-dimensional case at a constant advance speed of the phase interface. The value of the verification coefficient was determined from a numerical solution of a nonlinear equation with the use of special built-in Python functions. Substituting the data for the physical model under consideration into the analytical solution and comparing them with the numerical simulation data obtained with the use of the mushy layer method shows that the results are in close agreement, thus demonstrating the correctness of the computer algorithm developed. These studies will allow one to adapt the Python code developed on the basis of the mushy layer method to the calculation of heat storage systems with a solid-liquid phase transition with account for the features of their geometry, the temperature level, and actual boundary conditions.

scholarly journals Inhibition Effect of Kinetic Hydrate Inhibitors on the Growth of Methane Hydrate in Gas–Liquid Phase Separation State

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4482
Author(s):  
Liwei Cheng ◽  
Limin Wang ◽  
Zhi Li ◽  
Bei Liu ◽  
Guangjin Chen
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Methane Hydrate ◽  
Phase Interface ◽  
Major Effect ◽  
Initial Position ◽  
Liquid Phase Separation ◽  
Inhibitory Effects ◽  
Surrounding Water ◽  
Solid Liquid

The effect of kinetic hydrate inhibitors (KHIs) on the growth of methane hydrate in the gas–liquid phase separation state is studied at the molecular level. The simulation results show that the kinetic inhibitors, named PVP and PVP-A, show good inhibitory effects on the growth of methane hydrate under the gas–liquid phase separation state, and the initial position of the kinetic hydrate inhibitors has a major effect on the growth of methane hydrates. In addition, inhibitors at different locations exhibit different inhibition performances. When the inhibitor molecules are located at the gas–liquid phase interface, increasing the contact area between the groups of the inhibitor molecules and methane is beneficial to enhance the inhibitory performance of the inhibitors. When inhibitor molecules are located at the solid–liquid phase interface, the inhibitor molecules adsorbed on the surface of the hydrate nucleus and decreased the direct contact of hydrate nucleus with the surrounding water and methane molecules, which would delay the growth of hydrate nucleus. Moreover, the increase of hydrate surface curvature and the Gibbs–Thomson effect caused by inhibitors can also reduce the growth rate of methane hydrate.

Phase field model for dendritic growth with impurities

2017 ◽  
Vol 28 (08) ◽  
pp. 1750105
Author(s):  
F. L. O. Rodrigues ◽  
M. P. Almeida ◽  
Raimundo N. Costa Filho
Keyword(s):  
Liquid Phase ◽  
Phase Field ◽  
Dendritic Growth ◽  
Field Model ◽  
Solid Phase ◽  
Phase Field Model ◽  
Square Lattice ◽  
A Site ◽  
Solid Liquid Interface ◽  
Solid Liquid

A phase field model is used to study dendritic growth in a media with impurities. The model consists of a square lattice where a parameter [Formula: see text] can take values between [Formula: see text] and [Formula: see text] at each site. A site is in the solid phase for [Formula: see text], in the liquid phase for [Formula: see text], and the solid-liquid interface is expressed by [Formula: see text]. A fraction of the sites are considered impurities that cannot be solidified, i.e. [Formula: see text] is fixed and taken as zero. These impurities are distributed randomly. As the probability [Formula: see text] of impure sites in the lattice increases, the growth loses its dendritic characteristic. It is shown that the perimeter of the growing solid goes from quadratic to a linear function with time. It was also found that as the probability of impurities reaches [Formula: see text], the solid undergoes a transition from anisotropic to isotropic growth.

scholarly journals Numerical Study on Melting Heat Transfer in Dendritic Heat Exchangers

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2504 ◽  
Author(s):  
Xinmei Luo ◽  
Shengming Liao
Keyword(s):  
Heat Exchanger ◽  
Liquid Phase ◽  
Phase Change ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Phase Interface ◽  
Dendritic Structure ◽  
Melting Process ◽  
High Efficient ◽  
Solid Liquid

The dendritic fin was introduced to improve the solid-liquid phase change in heat exchangers. A theoretical model of melting phase change in dendritic heat exchangers was developed and numerically simulated. The solid-liquid phase interface, liquid phase rate and dynamic temperature change in dendritic heat exchanger during melting process are investigated and compared with radial-fin heat exchanger. The results indicate that the dendritic fin is able to enhance the solid-liquid phase change in heat exchanger for latent thermal storage. The presence of dendritic fin leads to the formation of multiple independent PCM zones, so the heat can be quickly diffused from one point to across the surface along the metal fins, thereby making the PCM far away from heat sources melt earlier and faster. In addition, the dendritic structure makes the PCM temperature distribution more uniform over the entire zone inside heat exchangers due to high-efficient heat flow distribution of dendritic fins. As a result, the time required for the complete melting of the PCM in dendritic heat exchanger is shorter than that of the radial-fin heat exchanger.

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