Analysis of Two-Dimensional Melting in Rectangular Enclosures in Presence of Convection

1984 ◽  
Vol 106 (1) ◽  
pp. 20-26 ◽  
Author(s):  
A. Gadgil ◽  
D. Gobin
Keyword(s):  
Solid Phase ◽  
Equations Of Motion ◽  
Melting Process ◽  
Two Dimensional ◽  
Governing Equations ◽  
Finite Difference Technique ◽  
Liquid Boundary ◽  
Solid Liquid ◽  
Change Material ◽  
Good Agreement

Two-dimensional melting of a solid phase change material in a rectangular enclosure heated from one side is simulated numerically. The simulations are carried out by dividing the process in a large number of quasi-static steps. In each quasi-static step, steady-state natural convection in the liquid phase is calculated by directly solving the governing equations of motion with a finite difference technique. This is used to predict the shape and motion of the solid-liquid boundary at the beginning of the next step. The predictions are found to be in good agreement with experiment. Influence of some of the governing parameters on the time development of the melting process is studied using the numerical simulation procedure.

The Lattice Boltzmann Investigation for the Melting Process of Phase Change Material in an Inclined Cavity

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Zhonghao Rao ◽  
Yutao Huo ◽  
Yimin Li
Keyword(s):  
Heat Flux ◽  
Phase Change ◽  
Lattice Boltzmann ◽  
Melting Process ◽  
Clockwise Rotation ◽  
Linear Distribution ◽  
Left Wall ◽  
Inclined Cavity ◽  
Solid Liquid ◽  
Change Material

The solid–liquid phase change process is of importance in the usage of phase change material (PCM). In this paper, the phase change lattice Boltzmann (LB) model has been used to investigate the solid–liquid phase change in an inclined cavity. Three heat flux distributions applied to the left wall are investigated: uniform distribution, linear distribution, and parabolic symmetry distribution. The results show that for all the heat flux distributions, the slight clockwise rotation of the cavity can accelerate the melting process. Furthermore, when more heat is transferred to the cavity through the middle part (parabolic symmetry distribution) or bottom part (linear distribution) of left wall, clockwise rotation of cavity leads to larger temperature of PCM.

Unusual liquid-solid transition effects in a methoxypentamethylflavan

1958 ◽  
Vol 243 (1235) ◽  
pp. 518-533 ◽  
Keyword(s):  
Solid Phase ◽  
Polarized Light ◽  
Melting Process ◽  
X Rays ◽  
Melting Range ◽  
Crystalline Materials ◽  
External Conditions ◽  
Transition Effects ◽  
Solid Liquid ◽  
Crystal Boundaries

The solid phase of the compound 2'-methoxy-2 : 4 : 4 : 7 : 4'- pentamethylflavan differs in many respects from normally crystalline materials, yet is not amorphous. It tends to form spherical masses which exhibit no regular crystal boundaries, even when seen under the microscope. The solid melts over a range of up to 3° C and the actual temperatures at which melting begins and ends vary according to the thermal treatment previously received by the specimen. The temperature at which the melt starts to solidify on cooling is always several degrees below the melting range; this is not due to normal supercooling. Solidification from the melt presents several other interesting features, including some rhythmic effects. Variations in the external conditions during solidification can give rise to three superficially different forms of the solid phase. The solid-liquid and liquid-solid transitions have been followed by measurements of density, rigidity and dielectric constant, all of which give further indications of the diffuse nature of the melting process and the existence of hysteresis between melting and solidifica­tion. These effects recall the behaviour of some crystalline high polymers and examination of solid methoxypentamethylflavan by polarized light, X-rays and electron microscopy has revealed further analogies with such materials. It is tentatively concluded that the solid is composed of submicroscopic crystalline regions which are organized into larger spherulitic aggregates, but no definite explanations of the failure of the compound to form macroscopic crystals or of the similarities between it and polymers seem possible at present.

Numerical Simulation of Thermal Energy Storage in Cylindrical Cells

2002 ◽  
Author(s):  
Horacio Ramos-Aboites ◽  
Abel Hernandez-Guerrero ◽  
Salvador M. Aceves ◽  
Raul Lesso-Arroyo
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Fluid Flows ◽  
Melting Process ◽  
Inlet Temperature ◽  
Transient Model ◽  
Storage Cell ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Change Material

This paper presents the results of a -numerical transient model for phase change in a storage cell filled with a phase change material (PCM). Phase change occurs under the presence of natural convection. The PCM is encapsulated in a cylindrical energy storage cell. Two cases of PCM melting are analyzed, (1) the surface temperature of the bottom half of the cylindrical cell is kept at a constant temperature, which is higher than the melting temperature of the PCM, and (2) a fluid flows under the cell with an inlet temperature that is higher than the melting point of the PCM. The results show the evolution of the solid-liquid interface, isotherms and flow lines during the melting process.

scholarly journals Natural convection melting of nano-enhanced phase change material in a cavity with finned copper profile

2018 ◽  
Vol 240 ◽  
pp. 01006 ◽  
Author(s):  
Nadezhda Bondareva ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Melting Process ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Dimensional Approximation ◽  
Change Material

Present study is devoted to numerical simulation of heat and mass transfer inside a cooper profile filled with paraffin enhanced with Al2O3 nanoparticles. This profile is heated by the heat-generating element of constant volumetric heat flux. Two-dimensional approximation of melting process is described by the Navier-Stokes equations in non-dimensional variables such as stream function, vorticity and temperature. The enthalpy formulation has been used for description of the heat transfer. The influence of volume fraction of nanoparticles and intensity of heat generation on melting process and natural convection in liquid phase has been studied.

Boundary-layer development at a two-dimensional rear stagnation point

1972 ◽  
Vol 56 (1) ◽  
pp. 161-171 ◽  
Author(s):  
A. J. Robins ◽  
J. A. Howarth
Keyword(s):  
Boundary Layer ◽  
Stagnation Point ◽  
Equations Of Motion ◽  
Two Dimensional ◽  
Initial Value ◽  
Boundary Layer Development ◽  
Leading Term ◽  
Layer Development ◽  
Rear Stagnation Point ◽  
Good Agreement

This paper examines the nature of the development of two-dimensional laminar flow of an incompressible fluid at the rear stagnation point on a cylinder which is started impulsively from rest. Proudman & Johnson (1962) first examined this type of flow, andobtainedasimilarity solution of the inviscid form of the equations of motion. This solution describes the nature of the flow at large distances from the surface, for large times after the start of the motion. Here, the flow at the rear stagnation point is examined in greater detail. The solution found by Proudman & Johnson constitutes the leading term in an asymptotic expansion, valid for large times. Further terms in this expansion are now calculated, and the method of matched asymptotic expansions is used to obtain an inner solution describing the flow near the surface. A numerical integration of the full initial-value problem gives good agreement with the analytical solution.

Thermohydrodynamic Analysis of Solid-Liquid Lubricated Journal Bearings

1988 ◽  
Vol 110 (2) ◽  
pp. 367-374 ◽  
Author(s):  
M. M. Khonsari ◽  
V. Esfahanian
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Solid Particles ◽  
Governing Equations ◽  
Transfer Processes ◽  
Flow And Heat Transfer ◽  
Experimental Findings ◽  
Solid Liquid ◽  
General Computer Program ◽  
Good Agreement

Thermohydrodynamic theory is extended to include the effect of solid particles in hydrodynamically lubricated journal bearings. Appropriate governing equations and boundary conditions are derived for the fluid flow and heat transfer processes taking place in a finite journal bearing. A general computer program is developed to numerically solve the governing equations. Results are provided for biphase lubricants containing oil with molybdenum disulfide and polytetrafluoroethylene particles. The computational results are in good agreement with experimental findings. The results indicate that the bearing temperature field is affected significantly by the presence of particles in oil. Moreover, it is found that inclusion of particles in the lubricant results in a higher coefficient of friction in the mid-range of the Sommerfeld number compared to that of the clean oil.

scholarly journals A modification of the CABARET scheme for numerical simulation of multicomponent gaseous flows in two-dimensional domains

2015 ◽  
pp. 436-445
Author(s):  
А.В. Данилин ◽  
А.В. Соловьев ◽  
А.М. Зайцев
Keyword(s):  
Numerical Simulation ◽  
Initial Conditions ◽  
Experimental Studies ◽  
Two Dimensional ◽  
Governing Equations ◽  
Cabaret Scheme ◽  
Gaseous Flows ◽  
Multicomponent Gas ◽  
Good Agreement ◽  
Made In

Предложен явный численный алгоритм для расчета течений смесей идеальных газов в двумерных областях. Приведены физическая модель и уравнения движения смеси в консервативной и характеристической формах. Дискретизация уравнений движения произведена по методике Кабаре. Алгоритм испытан на задачах о прохождении ударной волны в воздухе через неоднородности из легкого и тяжелого газов, начальные условия для которых адаптированы из рассмотренных другими авторами натурных и численных экспериментов. Показано хорошее совпадение расчетов по предложенному алгоритму с результатами этих экспериментов. An explicit numerical algorithm for calculation of two-dimensional motion of multicomponent gas mixtures is proposed. A physical model as well as conservative and characteristic forms of governing equations are given. The discretization of the governing equations is made in accordance with the CABARET (Compact Accurately Boundary Adjusting-REsolution Technique) approach. The proposed algorithm is tested on problems of air shock waves passing through dense and dilute volume inhomogeneities with initial conditions adopted from numerical and experimental studies of other authors. A good agreement between the results of these studies and those obtained by the CABARET approach is shown.

scholarly journals A miniaturized method for fast, simple, and sensitive pesticide analysis in soils

2021 ◽  
Author(s):  
Marcel Pierre Simon ◽  
Dennis Knuth ◽  
Leonard Böhm ◽  
Katrin Wiltschka ◽  
Marlene Schatz ◽  
...  
Keyword(s):  
World War Ii ◽  
Solid Phase Microextraction ◽  
Agricultural Soils ◽  
Solid Phase ◽  
Sample Volume ◽  
World War ◽  
Quechers Method ◽  
Solid Liquid ◽  
Good Agreement ◽  
Different Soils

Abstract Purpose Organochlorine pesticides (OCPs) like lindane and DDT have been used extensively after World War II until the 1990s. Still, residues of these pesticides can be found in agricultural soils all over the world, especially in developing countries. Often, they occur in extensive areas and elevated concentrations so that food safety is jeopardized. Hence, simple, cheap, and fast analytical methods are needed for a straight-forward assessment of risks. A miniaturized solid–liquid extraction combined with solid-phase microextraction (SPME) based on a proven ISO method is presented. Methods The performance of the method is evaluated by extracting three different soils which were spiked with HCH and DDT congeners, and trifluralin, and aged for 35 days. The results are compared with those of a modified quick, easy, cheap, efficient, rugged, and safe (QuEChERS) method. For further validation, both methods are applied to three environmental soil samples. Results Validation results show limits of detection and quantification as well as recovery rates in good agreement with standard requirements. The new method was found to be quicker than QuEChERS, which requires time-consuming preparation of reagents. Conclusion Merits include low time and sample volume requirements (0.5 g) and the possibility to extract many samples simultaneously, which allows the screening of large sample sizes to determine the pollution status of whole landscape regions. However, access to an automated SPME apparatus is assumed. The authors can recommend this method as a cheap and fast alternative where SPME is available.

scholarly journals Numerical investigation on the phase change process of different shaped macro encapsulated PCM

2018 ◽  
Vol 7 (4.5) ◽  
pp. 587
Author(s):  
Jay R. Patel ◽  
Manish K. Rathod
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Complex Flow ◽  
Ansys Fluent ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Convection Dominated ◽  
Change Material

Latent heat energy storage using macro encapsulated phase change material is an emerging technique for thermal energy storage applica- tions. The main aim of the present investigation is to investigate the melting process of phase change material filled in different shaped configurations. The selected different cavities are square, circular and triangular. A mathematical model based on convection dominated melting is required to be developed, especially in view of the complex flow geometries encountered in such problems. Thus, an attempt has been made to develop a model using ANSYS Fluent 16.2 to investigate the heat transfer rate and solid-liquid interface visualization of PCM filled in different shapes of cavity. It is found that triangular shaped macro encapsulated PCM melts faster than square and circu- lar shaped encapsulated PCM.   

scholarly journals Kazantsev model in non-helical 2.5-dimensional flows

2016 ◽  
Vol 806 ◽  
pp. 627-648 ◽  
Author(s):  
K. Seshasayanan ◽  
A. Alexakis
Keyword(s):  
Turbulent Flows ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Control Parameters ◽  
Governing Equations ◽  
Field Correlation ◽  
Good Agreement

We study the dynamo instability for a Kazantsev–Kraichnan flow with three velocity components that depend only on two dimensions $\boldsymbol{u}=(u(x,y,t),v(x,y,t),w(x,y,t))$ often referred to as 2.5-dimensional (2.5-D) flow. Within the Kazantsev–Kraichnan framework we derive the governing equations for the second-order magnetic field correlation function and examine the growth rate of the dynamo instability as a function of the control parameters of the system. In particular we investigate the dynamo behaviour for large magnetic Reynolds numbers $Rm$ and flows close to being two-dimensional and show that these two limiting procedures do not commute. The energy spectra of the unstable modes are derived analytically and lead to power-law behaviour that differs from the three-dimensional and two-dimensional cases. The results of our analytical calculation are compared with the results of numerical simulations of dynamos driven by prescribed fluctuating flows as well as freely evolving turbulent flows, showing good agreement.

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