Numerical Simulation Of Melting Research Articles

Analysis of different factors on the features of thermal destruction of a fuel pin

The presented work studies the influence of various factors that affect the specific features of fuel pins melting. For this purpose, fuel pins with different geometries and energy release are considered. Numerical simulation of melting is carried out using a program module for calculating the destruction of fuel rods. Comparison with theoretical calculations is made. The analysis of the convergence of calculations with respect to the time step value and the number of calculated cells along the radius and height is carried out. As a result of work with the use of numerical methods, the characteristic times of destruction of fuel elements during an accident with a loss of coolant flow rate (an accident of the ULOF type) and the dependence of weight loss on time are obtained under various conditions.

Numerical simulation of paraffin wax melting in a rectangular cavity using CFD

ABSTRACT The study presents the numerical simulation of the melting process of phase change material, paraffin wax in a rectangular cavity using ANSYS fluent. The simulation is done for three different Stefan numbers 0.13, 0.18 and 0.28. Enthalpy porosity model and volume of fluid model is used to solve the governing equations. The presence of natural convection and sinking of the solid phase is observed in the density contours. The presence of air content in the cavity is taken into account during estimation of un-melted solid fraction in the cavity which is the novelty of this work. An empirical equation is also derived to calculate solid fraction at different times with different Stefan numbers. This type of empirical equation is proposed for the spherical cavity but not very common in a rectangular cavity. This empirical equation can be useful for designing of latent heat energy storage unit, heat exchanger using phase change material and for the study of metal casting processes. The melting process is also simulated with three different initial shapes of solid paraffin wax in the rectangular cavity. The study reveals that the melting time is not linearly proportional to the volume of paraffin wax.

Experimental and numerical studies of heat and mass transfer in low-temperature heat accumulator with phase transformations of accumulating material

Accumulation of thermal energy is produced with the aim of storing at certain times, when there is an overabundance of this energy and its further use in other periods of time when there is a deficit thermal energy. Thermal energy storage may be carried out under heating of any material (water, solid materials etc.) or by using the phase or chemical transformation of the material (melting and crystallization processes, direct and reverse chemical reaction). Thermal accumulators with phase or chemical transformations are allowed to concentrate a large amount of energy in a relatively small volume of accumulating material. In this paper an experimental study and numerical modeling of heat and mass transfer in the heat accumulator during phase transformations of the accumulating material are presented. The experimental plant consists of a chamber filled with paraffin. In experimental studies, the changes of the temperature distribution in heat accumulating material and tube bundles have investigated. Numerical simulation of melting and solidification of heat accumulating material during the heated and cooled of tube bundles were performed. As the results of research, the basic laws of melting and crystallization processes in heat accumulator during phase transformations of heat accumulating material were determined.

Numerical simulation of melting between two elliptical cylinders

In this paper, melting process between two elliptical cylinders is simulated and analyzed. The shapes of the shell and the central tube are assumed to be circular or elliptical. Since the ellipse can be oriented vertically and horizontally, three possibilities can be accounted for each of the cylinders which lead to nine different heat exchangers. In order to study the effect of the orientations, melting front and flow field are presented for same shell shape. The process is more comprehensively investigated via presenting melt fraction versus time. Results show that regardless of the tube shape and orientation, horizontal ellipse is the best shape for the shell whereas vertical elliptical tube leads to faster pace of heat absorption.

Numerical Simulation of Melting of Phase Change Material in a Square Cavity with a Heat Source

Melting and solidification problems are important in applications of many industries. In the present work mathematical simulation of natural convection with phase transition inside an enclosure with a local heat source has been carried out. Partial differential equations with corresponding initial and boundary conditions have been solved using the finite difference method. The effect of temperature differences on fluid flow and heat transfer has been discussed.

Numerical Simulation of Melting in Porous Media via an Interfacial Tracking Model

Numerical Simulation of Melting in Porous Media via an Interfacial Tracking Model

Numerical Simulation of Melting in Porous Media via an Interfacial Tracking Model

extension. The results are obtained by using the interfacial tracking method, which is validated by comparing with the existing experimental and numerical results. The results show that the interfacial tracing method is capable of solving natural convection-controlled melting problems in porous media at both high and low Prandtl numbers.

Numerical simulation of melting and solidification in laser welding of mild steel

Melting and solidification which is mainly responsible for weld pool geometry in a laser welding process is analysed following two different transient models: (1) without fluid flow, that is, pure conduction and (2) with surface tension driven flow considering various beam power, beam diameter and scanning speed. Based on these models, numerical simulations for laser welding of mild steel has been carried out using commercial software, Fluent. By solving the conservation equations of energy, momentum and mass, the temperature distribution, liquid fraction and flow fields has been predicted and the fusion zone and Heat Affected Zone (HAZ) were obtained. Using predicted results, this present study investigates the effects of laser beam power, beam diameter and scanning speed on heat transfer and the weld pool geometry. Analysis shows that the effect of consideration of fluid motion has pronounced effects on the thermal field and weld pool geometry. [Received 20 January 2007; Accepted 14 September 2007]

Simulation of dynamics of phase transitions in CdTe by pulsed laser irradiation

Numerical simulation of melting and solidification processes induced in CdTe by nanosecond radiation of ruby laser (λ=694nm, τ=20 and 80ns) and KrF excimer laser (λ=248nm, τ=20ns) taking into account components diffusion in melt and their evaporation from the surface has been carried out. Cd atoms evaporation has shown to essentially affect the dynamics of phase transitions in the near-surface region. Thus, in the case of the influence of ruby laser irradiation intensive surface cooling results in the formation of nonmonotone temperature profile with maximum temperature in semiconductor volume at the distance of ∼20nm from the surface. The melt formed under the surface extends both to the surface and to the semiconductor volume as well. As a result of cadmium telluride components evaporation and diffusion in the melt the near-surface region is enriched with tellurium. The obtained melting threshold value of irradiation energy density is in a reasonable agreement with experimental data.

Numerical simulation of melting and evaporation of a cold foil target irradiated by a pre-pulse

Melting and evaporation of matter due to pre-pulse irradiation of a high-peak-power ultra-short pulse laser onto a cold foil target and the expansion of laser-produced plasma are numerically evaluated using a hydrodynamic code based on CIP (cubic-interpolated propagation) and modified C-CUP (CIP-combined unified procedure) methods. The material properties of the solid, equation of state, laser absorption coefficient, skin depth, and thermal conductivity are consistently implemented. The formation and propagation of laser-produced plasmas are obtained with good numerical stability.

A Numerical Simulation of Melting of Ice Heated from above

Melting of ice in a cubical enclosure partially heated from above was studied. Half of the upper surface was maintained at room temperature and the other half at 70°C. The ice cube was maintained at its melting point at the bottom. The other side surfaces were insulated. The process was first modeled by ignoring the effect of natural convection in the liquid phase. The resulting equations of conservation of energy were solved in each phase. The motion of melting front was governed by an energy balance at the interface. This conduction model was verified by applying it to a I-D phase change problem for which an analytical solution is available. Preliminary experiments conducted resulted in a progress of the phase front faster than that predicted by the conduction model and the interface was smoother due to strong effects of natural convection in the liquid phase, except for the initial start of melting The model was then extended to include convective heat transfer in such a way that the liquid phase was assumed to be a mixed body subjected to natural convection from the top surface and the liquid-solid interface. The flux at the interface was obtained by finding a heat transfer coefficient for natural convection with a cold plate facing upward. The predictions of this convection model agreed well with the experimental results.

Numerical Simulation of Melting and Resolidification of a Phase Change Material Around Two Cylindrical Heat Exchangers

A computational methodology is presented for solving natural convection dominated melting and resolidification of a phase change material around two horizontal cylindrical heat sources /sinks spaced vertically. A finite difference method with body-fitted coordinates is employed to handle the irregular boundaries, and a fixed grid enthalpy method is adopted for the phase change problem. Results show that the phase front during the melting and resolidification of the liquid from the upper cylinder is strongly affected by the surface temperature of the lower cylinder. Also, cyclic melting and freezing of the phase change material can result in complex shapes of the solid-liquid interfaces as well as in multiple phase fronts. The shapes of the melted and solidified regions depend on the imposed thermal boundary and the melting and freezing period.