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Dimosthenis Trimis - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of complete liquid vapour phase change Process inside porous media a comparison between local thermal equilibrium and non equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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simulation of complete liquid vapour phase change Process inside porous evaporator using local thermal non equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
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Simulation of complete liquid–vapour phase change Process inside porous evaporator using local thermal non-equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
Domingo A. Tarzia - One of the best experts on this subject based on the ideXlab platform.
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A sensitivity analysis for the determination of unknown thermal coefficients through a Phase-Change Process with temperature-dependent thermal conductivity☆
International Communications in Heat and Mass Transfer, 2011Co-Authors: Natalia N. Salva, Domingo A. TarziaAbstract:Abstract In Tarzia, Int. Comm. in Heat and Mass Transfer, 25 (1998), 139–147, explicit formulas for the simultaneous determination of unknown thermal coefficients of a semi-infinite material through a Phase-Change Process with temperature-dependent thermal conductivity were obtained. Moreover, ten different cases were studied: four cases of free boundary problems (i.e. Stefan-like problems) and six cases of moving boundary problems (i.e. inverse Stefan-like problems). The goal of this paper is to obtain a numerical sensitivity analysis of the mentioned ten cases for the simultaneous determination of unknown thermal coefficients and to determine the coefficients which are more sensitive with respect to the given parameters. We show numerical result for the aluminum.
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Determination of unknown thermal coefficients for Storm’s-type materials through a Phase-Change Process
International Journal of Non-linear Mechanics, 1999Co-Authors: Adriana C. Briozzo, María F. Natale, Domingo A. TarziaAbstract:Abstract Unknown thermal coefficients of a semi-infinite material of Storm’s type through a Phase-Change Process with an overspecified condition on the fixed face are determined. We follow the ideas developed in C. Rogers (Int. J. Non-Linear Mech. 21 (1986) 249–256) and in Tarzia (Adv. Appl. Math. 3 (1982) 74–82; Int. J. Heat Mass Transfer 26 (1983) 1151–1157). We also find formulae for the unknown coefficients and, the necessary and sufficient conditions for the existence of a similarity solution.
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Estimation of the occurance of the Phase-Change Process in spherical coordinates
International Communications in Heat and Mass Transfer, 1999Co-Authors: Domingo A. Tarzia, Cristina TurnerAbstract:Abstract We study heat conduction problems in spherical coordinates with mixed boundary conditions. We obtain sufficient and/or necessary conditions among the data in order to get a Phase-Change Process. For the spherical coordinates case we consider a problem in a hollow sphere r1 0) on the surface r = r1 and the temperature the surface (b > 0) on the surface r = r2, and an initial condition in the hollow sphere is also considered. We analyse both, the case with or without source. We explicit the relation between the heat flux q, the fixed temperature b and the thermal conductivity k of the initial phase, in order to have a change of phase in the material.
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Experimental-numerical determination of thermal coefficients through a Phase-Change Process
International Communications in Heat and Mass Transfer, 1996Co-Authors: Jorge C. Arderius, Miguel Ángel Lara, Domingo A. TarziaAbstract:Abstract The present paper shows the correlation between the analytical formulae for the determination of thermal coefficients of semi-infinite materials through a Phase-Change Process with an overspecified condition on the fixed face and a simple device which determines some auxiliary parameters. 'File method is approachable for some thermal coefficients because of the dispersion of the theoretical and experimental results.
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On the determination of the unknown coefficients through phase change problems with temperature-dependent thermal conductivity
1993Co-Authors: Domingo A. TarziaAbstract:We study the determination of unknown thermal coefficient of a semi-infinite material through a Phase-Change Process with an overspecified condition on the fixed face with temperature-dependent thermal conductivity. We determine necessary and sufficient conditions on data in order to obtain the existence of the solution. We also give formulae for the unknown coefficients.
Omar Rafae Alomar - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of complete liquid vapour phase change Process inside porous media a comparison between local thermal equilibrium and non equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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simulation of liquid vapour phase change Process inside porous media using modified enthalpy formulation
International Journal of Thermal Sciences, 2016Co-Authors: Subhashis Ray, Omar Rafae AlomarAbstract:Abstract In the present article, after critically analysing the drawbacks of the existing h -formulation based on Two Phase Mixture Model (TPMM), a modified formulation has been developed that can easily accommodate substantial density variations in the single phase regions. The results for steady one-dimensional complete liquid–vapour phase change problems of water inside a porous evaporator, obtained from the modified h - and the existing H -formulations, have been compared and excellent agreements have been observed for all tested cases. It has been also observed that the modified h -formulation requires significantly less computation time, although all variants of TPMM requires smoothing of effective diffusion coefficient in order to avoid “jumps” in the predicted properties. Since the proposed formulation does not require the definition of any artificial variable and in view of the identified advantages, the method is strongly recommended for the future use. Nevertheless, it should now be extended in order to accommodate the local thermal non-equilibrium condition and multi-dimensional phase change problems in presence of substantial density variations in the single phase regions.
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simulation of complete liquid vapour phase change Process inside porous evaporator using local thermal non equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
Subhashis Ray - One of the best experts on this subject based on the ideXlab platform.
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simulation of liquid vapour phase change Process inside porous media using modified enthalpy formulation
International Journal of Thermal Sciences, 2016Co-Authors: Subhashis Ray, Omar Rafae AlomarAbstract:Abstract In the present article, after critically analysing the drawbacks of the existing h -formulation based on Two Phase Mixture Model (TPMM), a modified formulation has been developed that can easily accommodate substantial density variations in the single phase regions. The results for steady one-dimensional complete liquid–vapour phase change problems of water inside a porous evaporator, obtained from the modified h - and the existing H -formulations, have been compared and excellent agreements have been observed for all tested cases. It has been also observed that the modified h -formulation requires significantly less computation time, although all variants of TPMM requires smoothing of effective diffusion coefficient in order to avoid “jumps” in the predicted properties. Since the proposed formulation does not require the definition of any artificial variable and in view of the identified advantages, the method is strongly recommended for the future use. Nevertheless, it should now be extended in order to accommodate the local thermal non-equilibrium condition and multi-dimensional phase change problems in presence of substantial density variations in the single phase regions.
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simulation of complete liquid vapour phase change Process inside porous evaporator using local thermal non equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
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Simulation of complete liquid–vapour phase change Process inside porous evaporator using local thermal non-equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media using smoothing of diffusion coefficient
International Journal of Thermal Sciences, 2014Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present paper deals with numerical simulations of complete phase change Process inside porous media, based on the two-phase mixture model, using finite volume method for discretisation. The investigation proposes a successful remedy in order to eliminate the occurrence of “jump” in predicted properties, by introducing an efficient smoothing algorithm for the effective diffusion coefficient. A thorough parametric study also indicates that the adoption of proposed remedy does not alter the true or expected solution. All tested cases, covering applicable ranges of parametric variations, could be physically interpreted. The methodology is, therefore, recommended for future simulations of complete phase change Processes within porous media.
Miguel A A Mendes - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of complete liquid vapour phase change Process inside porous media a comparison between local thermal equilibrium and non equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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Numerical simulation of complete liquid–vapour phase change Process inside porous media: A comparison between local thermal equilibrium and non-equilibrium models
International Journal of Thermal Sciences, 2017Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis TrimisAbstract:Abstract The Complete liquid-vapour phase change Process inside an asymmetrically heated porous channel has been numerically investigated in this article, based on the Two-Phase Mixture Model (TPMM), while employing both Local Thermal Equilibrium (LTE) and Non-Equilibrium (LTNE) conditions. For the latter condition, four different models have been considered for the partitioning of imposed wall heat flux. All simulations have been carried out by applying the recently proposed smoothing algorithm for the effective diffusion coefficient, without which, the occurrence of non-physical “jump” in the predicated properties, across the interface between the single and the two-phase regions could not be always avoided. The governing equations have been discretised using the finite volume method on a fixed staggered grid layout and solved iteratively in a SIMPLE-like manner. Only the imposed wall heat flux has been varied, while all other parameters and properties have been kept fixed during the present investigation. It has been observed that LTE model fails to produce realistic predictions, particularly when the superheated vapour phase is formed inside the evaporator. On the other hand, the conduction heat transfer through the solid phase and the internal heat exchange between the solid and the fluid phases across the interface separating the superheated vapour and the two-phase mixture regions provide two additionally required mechanisms for LTNE model for the realistic predictions. As far as different models for the partitioning of wall of heat flux is concerned, Model-2 appears to be the most realistic, while Model-1 has been found to be the most stable.
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simulation of complete liquid vapour phase change Process inside porous evaporator using local thermal non equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.
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Simulation of complete liquid–vapour phase change Process inside porous evaporator using local thermal non-equilibrium model
International Journal of Thermal Sciences, 2015Co-Authors: Omar Rafae Alomar, Miguel A A Mendes, Dimosthenis Trimis, Subhashis RayAbstract:Abstract The present article demonstrates the necessity and the usefulness of a newly proposed smoothing algorithm for the effective diffusion coefficient in order to avoid non-physical “jump” in the predicted properties during numerical simulations of the complete liquid–vapour phase change Process within porous media. The formulation is based on the two-phase mixture model (TPMM) along with the assumption of local thermal non-equilibrium (LTNE) condition where the governing equations have been solved using the finite volume method. For the purpose of demonstration, one-dimensional phase change problem of water has been considered. Comparison between results obtained with the local thermal equilibrium (LTE) and LTNE models indicates that wherever applicable, particularly for lower inlet Reynolds number and higher heat input, the latter should be used. The effect of employing different models for the partitioning of wall heat flux using LTNE model has been found negligible owing to the very high convective heat transfer coefficient between the solid and the fluid phases. A representative parametric study suggests that the diffusive energy transport Process in the upstream direction through the solid and the fluid phases has a strong influence on the initiation and the termination of the phase change Process.