scholarly journals Sensitivity of Numerical Predictions to the Permeability Coefficient in Simulations of Melting and Solidification Using the Enthalpy-Porosity Method

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4360 ◽  
Author(s):  
Amin Ebrahimi ◽  
Chris R. Kleijn ◽  
Ian M. Richardson
Keyword(s):  
Mushy Zone ◽  
Phase Change ◽  
Permeability Coefficient ◽  
Numerical Predictions ◽  
Fluid Velocities ◽  
Increased Sensitivity ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
High Degree ◽  
Melting And Solidification

The high degree of uncertainty and conflicting literature data on the value of the permeability coefficient (also known as the mushy zone constant), which aims to dampen fluid velocities in the mushy zone and suppress them in solid regions, is a critical drawback when using the fixed-grid enthalpy-porosity technique for modelling non-isothermal phase-change processes. In the present study, the sensitivity of numerical predictions to the value of this coefficient was scrutinised. Using finite-volume based numerical simulations of isothermal and non-isothermal melting and solidification problems, the causes of increased sensitivity were identified. It was found that depending on the mushy-zone thickness and the velocity field, the solid–liquid interface morphology and the rate of phase-change are sensitive to the permeability coefficient. It is demonstrated that numerical predictions of an isothermal phase-change problem are independent of the permeability coefficient for sufficiently fine meshes. It is also shown that sensitivity to the choice of permeability coefficient can be assessed by means of an appropriately defined Péclet number.

Experimental Validation of Numerical Predictions for the Transient Performance of a Simple Latent Heat Storage Unit (LHSU) Utilizing Phase Change Material (PCM) and 3-D Printing

2017 ◽  
Author(s):  
Navin Kumar ◽  
Debjyoti Banerjee
Keyword(s):  
Phase Change ◽  
Experimental Validation ◽  
Numerical Models ◽  
Dominant Mode ◽  
Storage Unit ◽  
Latent Heat Storage ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Change Material ◽  
Melting And Solidification

Experimental validation was performed in this study to verify the efficacy of numerical models for predicting the location of solid-liquid interface in an axi-symmetric configuration during both melting and solidification in a Latent Heat Storage Unit (LHSU). Development of analytical solutions for predicting the location of the solid-liquid interface is often intractable in LHSU due to non-linear temperature distribution in the Phase Change Material (PCM). This is further complicated by the moving boundary problem with free convection within the liquid phase of the PCM. Analytical solutions available in the contemporary literature are based on simplified transient heat conduction models and often fail to reliably predict the charging and discharging time constants for LHSU with complex configurations. This study is designed with the goal of developing more sophisticated numerical models for the estimation of transient thermal performance of an LHSU with a simple configuration involving a shell and tube heat exchanger (HX). The LHSU utilized in this study is realized by integrating various types of Phase Change Materials (PCM) contained in the shell side of a HX. The LHSU is charged or discharged by pumping hot or cold fluids in the tube side of the HX (i.e., by pumping water at a fixed inlet temperature from a commercial chiller apparatus). This study enabled the characterization of the transient response of a LHSU subjected to conduction and forced convection heat transfer. The PCM used in this material was paraffin wax (PURETEMP 29). The HX in the LHSU consisted of a single pass straight tube (½ inch copper pipe) mounted within a single shell configuration. The shell was fabricated from plastic material using additive manufacturing (i.e., “3D Printing”). The temperature variation during melting and solidification of the PCM were measured at different radial and axial locations within the cylindrical shell that was mounted vertically. Temperature measurements were performed at different mass flowrate ranging from 0.004 Kg/sec to 0.007 Kg/sec for the same fluid temperature. The water bath temperatures were maintained at a constant temperature of 40°C for melting and 15°C for solidification. The experiment results show that the transient response of the LHSU for charging and discharging (i.e., time required for melting and solidification of the PCM) vary significantly. Comparison of the experimental data with analytical results (involving quasi-stationary models for phase change) demonstrate that natural convection is the dominant mode during the melting process, while conduction is the dominant mode during the solidification process.

Heat Transfer During Melting From an Isothermal Vertical Wall

1984 ◽  
Vol 106 (1) ◽  
pp. 12-19 ◽  
Author(s):  
C.-J. Ho ◽  
R. Viskanta
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Vertical Wall ◽  
Local Heat ◽  
Source Surface ◽  
Interface Motion ◽  
Numerical Predictions ◽  
Buoyancy Driven Convection ◽  
Solid Liquid Interface ◽  
Solid Liquid

This paper reports basic heat transfer data during melting of n-octadecane from an isothermal vertical wall of a rectangular cavity. The shadowgraph technique was used to measure local heat transfr coefficents at the heat source surface and the solid-liquid interface motion during phase change was recorded photographically. Experimental results clearly showed that, except in the very early stages of melting, the rates of melting and of heat transfer were greatly affected by the buoyancy-driven convection in the liquid. Initial subcooling of the solid substanially impeded the phase change process. A numerical simulation of the corresponding two-dimensional melting in the presence of natural convection was performed, and the numerical predictions are compared with experimental data.

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 Approximate Analytical Solution for One-Dimensional Solidification Problem of a Finite Superheating Phase Change Material Including the Effects of Wall and Thermal Contact Resistances

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Hamid El Qarnia ◽  
Fayssal El Adnani ◽  
El Khadir Lakhal
Keyword(s):  
Analytical Solution ◽  
Phase Change ◽  
Phase Change Material ◽  
Liquid Interface ◽  
Solid Shell ◽  
Interface Position ◽  
Temperature Distributions ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Change Material

This work reports an analytical solution for the solidification of a superheating phase change material (PCM) contained in a rectangular enclosure with a finite height. The analytical solution has been obtained by solving nondimensional energy equations by using the perturbation method for a small perturbation parameter: the Stefan number,ε. This analytical solution, which takes into account the effects of the superheating of PCM, finite height of the enclosure, thickness of the wall, and wall-solid shell interfacial thermal resistances, was expressed in terms of nondimensional temperature distributions of the bottom wall of the enclosure and both PCM phases, and the dimensionless solid-liquid interface position and its dimensionless speed. The developed solution was firstly compared with that existing in the literature for the case of nonsuperheating PCM. The predicted results agreed well with those published in the literature. Next, a parametric study was carried out in order to study the impacts of the dimensionless control parameters on the dimensionless temperature distributions of the wall, the solid shell, and liquid phase of the PCM, as well as the solid-liquid interface position and its dimensionless speed.

scholarly journals Numerical Solution of Heat Transfer Process in PCM Storage Using Tau Method

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
B. Heydari ◽  
F. Talati
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Numerical Approach ◽  
Heat Transfer Process ◽  
Liquid Interface ◽  
Tau Method ◽  
Two Dimensional ◽  
Interface Location ◽  
Solid Liquid Interface ◽  
Solid Liquid

Thermal energy storage units that utilize phase change materials have been widely employed to balance temporary temperature alternations and store energy in many engineering systems. In the present paper, an operational approach is proposed to the Tau method with standard polynomial bases to simulate the phase change problems in latent heat thermal storage systems, that is, the two-dimensional solidification process in rectangular finned storage with a constant end-wall temperature. In order to illustrate the efficiency and accuracy of the present method, the solid-liquid interface location and the temperature distribution of the fin for three test cases with different geometries are obtained and compared to simplified analytical results in the published literature. The results indicate that using a two-dimensional numerical approach can predict the solid-liquid interface location more accurately than the simplified analytical model in all cases, especially at the corners.

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.   

Numerical and Experimental Investigation of Phase Change Heat Transfer in the Presence of Rayleigh–Benard Convection

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Mohammad Parsazadeh ◽  
Xili Duan
Keyword(s):  
Nusselt Number ◽  
Phase Change ◽  
Local Heat ◽  
Liquid Interface ◽  
Interface Location ◽  
Local Heat Flux ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Abstract This research investigates the melting rate of a phase change material (PCM) in the presence of Rayleigh–Benard convection. A scaling analysis is conducted for the first time for such a problem, which is useful to identify the parameters affecting the phase change rate and to develop correlations for the solid–liquid interface location and the Nusselt number. The solid–liquid interface and flow patterns in the liquid region are analyzed for PCM in a rectangular enclosure heated from bottom. Numerical and experimental results both reveal that the number of Benard cells is proportional to the ratio of the length of the rectangular enclosure over the solid–liquid interface location (i.e.,, the liquified region aspect ratio). Their effect on the local heat flux is also analyzed as the local heat flux profile changes with the solid–liquid interface moving upward. The variations of average Nusselt number are obtained in terms of the Stefan number, Fourier number, and Rayleigh number. Eventually, the experimental and numerical data are used to develop correlations for the solid–liquid interface location and average Nusselt number for this type of melting problems.

Simulation of the Solidification Parameters of Single Crystal Casting

2010 ◽  
Vol 638-642 ◽  
pp. 2251-2256 ◽  
Author(s):  
H.P. Jin ◽  
Jia Rong Li ◽  
Shi Zhong Liu
Keyword(s):  
Boundary Conditions ◽  
Mushy Zone ◽  
Single Crystal ◽  
Liquid Interface ◽  
Physical Parameters ◽  
Element Analysis ◽  
Solidification Parameters ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Thermal Physical Parameters

The effects of thermal physical parameters and boundary conditions on investment solidification parameters were obtained using a computer simulation system. Directional solidification parameters of single crystal superalloy include the temperature distribution, the position and the shape of the solid/liquid interface in the mushy zone of the solidifying blade casting. Commercial finite-element analysis software, ProCAST, was used to simulate the solidification processes of the castings of single crystal DD6. The simulation results indicate that the predictions of the temperature show little sensitivity to the thermal physical parameters and boundary conditions. Further, it has also been shown that the location and the shape of solid/liquid interface is related to the boundary conditions of simulation. Increasing the value of interface heat transfer coefficient decreases the width of mushy zone.

Numerical Simulation of the Effect of the Size of Nanoparticles on the Solidification Process of Nanoparticle-Enhanced Phase Change Materials

2012 ◽  
Author(s):  
Yousef M. F. El Hasadi ◽  
J. M. Khodadadi
Keyword(s):  
Particle Size ◽  
Phase Change ◽  
Phase Change Materials ◽  
Concentration Field ◽  
Solidification Process ◽  
Liquid Interface ◽  
Constitutional Supercooling ◽  
Fluid Mixture ◽  
Solid Liquid Interface ◽  
Solid Liquid

Nanoparticle-enhanced phase change materials (NEPCM) were proposed recently as alternatives to conventional phase change materials due to their enhanced thermophysical properties. In this study, the effect of the size of the nanoparticles on the morphology of the solid-liquid interface and evolving concentration field, during solidification had been reported. The numerical method that was used is based on the one-fluid-mixture model. The model takes into account the thermal as well as the solutal convection effects. A square cavity model was used in the simulation. The NEPCM that was composed of a suspension of copper nanoparticles in water was solidified from the bottom. The nanoparticles size used were 5 nm and 2 nm. The temperature difference between the hot and cold sides was 5 degrees centigrade and the loading of the nanoparticles that have been used in the simulation was 10% by mass. The results obtained from the model were compared with those existing in the literature, and the comparison was satisfactory. The solid-liquid interface for the case of NEPCM with 5 nm particle size was almost planar throughout the solidification process. However, for the case of the NEPCM with particle size of 2 nm, the solid-liquid interface evolved from a planar stable shape to an unstable dendritic shape, as the solidification process proceeded with time. This was attributed to the constitutional supercooling effect. It has been observed that the constitutional supercooling effect is more pronounced as the particle size decreases. Furthermore, the freezing time increases as the particle size decreases.

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