The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Moghtada Mobedi - One of the best experts on this subject based on the ideXlab platform.
-
A new formulation for nondimensionalization heat transfer of phase change in porous media: An example application to closed cell porous media
International Journal of Heat and Mass Transfer, 2020Co-Authors: Chunyang Wang, Moghtada MobediAbstract:Abstract The problem of solid/liquid phase change in a cavity assisted by a closed cell porous medium is analyzed by pore scale and volume average approaches. The volume average governing equations are non-dimensionalized by using the porous media stagnant Thermal diffusivity and Sparrow number appears automatically. The study consists of four parts as the derivation of new formulation based on Sparrow number, proving the validation of volume average method based on the given formulation for the closed cell porous media, discussion on the change of interfacial heat transfer coefficient with time and finally presenting a Thermal Equilibrium chart in terms of Sparrow number and Thermal diffusivity ratio for prediction of Local Thermal Equilibrium state. A good agreement between the pore scale and volume average results is observed. Based on the established Thermal Equilibrium chart, it is found that the possibility of Local Thermal Equilibrium is high for the large values of Sparrow number (such as 500) and for the Thermal diffusivity ratio around 1. The established Equilibrium chart is verified by prediction of Local Thermal Equilibrium state for two different closed cell porous media and then the validation of predication is proved by using the results of pore scale study.
-
numerical study on latent Thermal energy storage systems with aluminum foam in Local Thermal Equilibrium
Applied Thermal Engineering, 2019Co-Authors: Bernardo Buonomo, Hasan Celik, Davide Ercole, Oronzio Manca, Moghtada MobediAbstract:Abstract The paper analyzes the behavior of a Latent Heat Thermal Energy Storage system (LHTES) with a Phase Change Material (PCM), with and without aluminum foam. A numerical investigation in a two-dimensional domain is accomplished to investigate on the system Thermal evolution. The enthalpy-porosity method is used to describe the PCM melting. The open-celled aluminum foam is described as a porous medium by means of the Darcy-Forchheimer law. A hollow cylinder represents the considered Thermal energy storage and it consists of the enclosure between two concentric shell tubes. The external surface of the internal tube is at assigned temperature with a value greater than the melting PCM temperature, while the other surfaces are adiabatic. Local Thermal Equilibrium (LTE) is numerically adopted for modelling the heat transfer between the PCM and the solid matrix in aluminum foam. In the case with metal foam, simulations for different porosities are performed. A comparison in term of liquid fraction, average temperature of the system, temperature fields, stream function and a performance parameter are made between the clean case and porous assisted case for the different porosities. A scale analysis is developed for evaluating the time and the melting zone in different regimes (i.e. conduction, mixed conduction-convective and convective) during the melting processes of the PCM in porous media. Numerical simulation shows that aluminum foam increases overall heat transfer by a magnitude of two, with respect to the clean case.
Moh’d A. Al-nimr - One of the best experts on this subject based on the ideXlab platform.
-
Validation of the Thermal Equilibrium Assumption in Periodic Natural Convection in Porous Domains
International Journal of Thermophysics, 2005Co-Authors: A. F. Khadrawi, Montasser S. Tahat, Moh’d A. Al-nimrAbstract:The validity of the Local Thermal Equilibrium assumption in the periodic free convection channel flow is investigated analytically. Two cases are considered where in the first case transverse conduction in the solid domain is included while in the second case transverse conduction in the fluid domain is included. The periodic disturbance in the free convection flow is due to a periodic Thermal disturbance imposed on the channel walls. The Darcy–Brinkman model is used to model the flow inside the porous domain. It is found that four dimensionless parameters control the Local Thermal Equilibrium assumption in the first case and five parameters control the Local Equilibrium assumption in the second case. The criteria that secure the validity of the Local Thermal Equilibrium assumption are derived.
-
Thermal Equilibrium in Transient Forced Convection Porous Channel Flow
Transport in Porous Media, 2004Co-Authors: Bassam Abu-hijleh, Moh’d A. Al-nimr, M. A. HaderAbstract:The validity of the Local Thermal Equilibrium assumption in the transient forced convection channel flow is investigated numerically. Axial conduction in both fluid and solid domains is included. It is found that five dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the Thermal diffusivity ratio αR, the volumetric Nusselt number Nu, the dimensionless channel length ξmax, Peclet number Pe, and the solid to fluid total Thermal capacity ratio CR. The qualitative and quantitative aspects of the effects of these five parameters on the channel Thermalization time are investigated.
-
Examination of the Thermal Equilibrium Assumption in Transient Natural Convection Flow in Porous Channel
Transport in Porous Media, 2003Co-Authors: A. F. Khadrawi, Moh’d A. Al-nimrAbstract:The Local Thermal Equilibrium assumption in the transient natural convection channel flow is investigated numerically. The Darcy–Brinkman–Forchheimer model is used to model the flow inside the porous domain. The effect of different parameters on the validity of the Local Thermal Equilibrium assumption is examined. It is found that the volumetric Nusselt number has the most significant effect on the Local Thermal Equilibrium assumption.
-
Thermal Equilibrium IN TRANSIENT CONJUGATED FORCED-CONVECTION CHANNEL FLOW
Numerical Heat Transfer Part A-applications, 2003Co-Authors: Bassam Abu-hijleh, Moh’d A. Al-nimr, M. A. HaderAbstract:The validity of the Local Thermal Equilibrium assumption in transient conjugated forced-convection channel flow is investigated numerically. Axial conduction in both fluid and solid domains is included. It is found that five dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the Thermal diffusivity ratio f R , the Biot number Bi, the dimensionless channel length \xi_{\max} , the Peclet number Pe, and the solid-to-fluid total Thermal capacity ratio C R . The qualitative and quantitative aspects of the effects of these five parameters on the channel Thermalization time are investigated.
-
Validation of Thermal Equilibrium Assumption in Transient Forced Convection Flow in Porous Channel
Transport in Porous Media, 2002Co-Authors: Moh’d A. Al-nimr, Bassam Abu-hijlehAbstract:The validity of the Local Thermal Equilibrium assumption in the transient forced convection channel flow is investigated analytically. Closed form expressions are presented for the temperatures of the fluid and solid domains and for the criterion which insures the validity of the Local Thermal Equilibrium assumption. It is found that four dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the porosity ∈, the volumetric Biot number Bi, the dimensionless channel length ξ_max and the solid to fluid total Thermal capacity ratio C _R. The qualitative and quantitative aspects of the effects of these four parameters on the channel Thermal Equilibrium relaxation time are investigated.
Mohamed Sassi - One of the best experts on this subject based on the ideXlab platform.
-
experimental validation of Local Thermal Equilibrium in a mw plasma torch for hydrogen production
International Journal of Hydrogen Energy, 2013Co-Authors: Babajide Ogungbesan, Rajneesh Kumar, Liu Su, Mohamed SassiAbstract:In this paper, experimental and numerical studies are made to investigate Local Thermal Equilibrium in a microwave plasma torch at atmospheric pressure for hydrogen and carbon black production from methane dissociation. The microwave induced plasma can be operated up to 2 kW power at 2.45 GHz frequency. Methane is dissociated in argon, air or nitrogen plasma and optical emission spectroscopy is used to characterize the plasma. C2, CN and OH ro-vibrational bands are used for rotational and vibrational temperature estimation while stark broadening of H-line is used for electron temperature calculation. Temperatures are determined at varying operating parameters of microwave power, axial gas flow rate, and methane flow rate. The rotational (heavy particle), vibrational, and electron temperatures are found to be equal to 5000 ± 500 K. The plasma is thus at Local thermodynamic Equilibrium.
Stephen Whitaker - One of the best experts on this subject based on the ideXlab platform.
-
Local Thermal Equilibrium for transient heat conduction theory and comparison with numerical experiments
International Journal of Heat and Mass Transfer, 1995Co-Authors: Michel Quintard, Stephen WhitakerAbstract:Abstract Local Thermal Equilibrium refers to the state in which a single temperature can be used to describe a heat transfer process in a multiphase system. When this condition occurs, a one-equation model can be used and the analysis of the heat transfer process is greatly simplified. In this paper we first develop the constraints that must be satisfied in order that the principle of Local Thermal Equilibrium be valid, and we then compare these constraints with numerical experiments for transient heat conduction in two-phase systems. Reasonable agreement between the estimates and the numerical experiments is obtained.
-
improved constraints for the principle of Local Thermal Equilibrium
Industrial & Engineering Chemistry Research, 1991Co-Authors: Stephen WhitakerAbstract:In this work we distinguish between filtered and unfiltered constraints in the closure problem, and we show how to derive an approximate governing differential equation for the difference between the temperatures of two individual phases. The heat-transfer process in a packed bed catalytic reactor is used to illustrate the development of constraints associated with Local Thermal Equilibrium, and the same approach can be used to understand the concept of Local mass Equilibrium
Bassam Abu-hijleh - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Equilibrium in Transient Forced Convection Porous Channel Flow
Transport in Porous Media, 2004Co-Authors: Bassam Abu-hijleh, Moh’d A. Al-nimr, M. A. HaderAbstract:The validity of the Local Thermal Equilibrium assumption in the transient forced convection channel flow is investigated numerically. Axial conduction in both fluid and solid domains is included. It is found that five dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the Thermal diffusivity ratio αR, the volumetric Nusselt number Nu, the dimensionless channel length ξmax, Peclet number Pe, and the solid to fluid total Thermal capacity ratio CR. The qualitative and quantitative aspects of the effects of these five parameters on the channel Thermalization time are investigated.
-
Thermal Equilibrium IN TRANSIENT CONJUGATED FORCED-CONVECTION CHANNEL FLOW
Numerical Heat Transfer Part A-applications, 2003Co-Authors: Bassam Abu-hijleh, Moh’d A. Al-nimr, M. A. HaderAbstract:The validity of the Local Thermal Equilibrium assumption in transient conjugated forced-convection channel flow is investigated numerically. Axial conduction in both fluid and solid domains is included. It is found that five dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the Thermal diffusivity ratio f R , the Biot number Bi, the dimensionless channel length \xi_{\max} , the Peclet number Pe, and the solid-to-fluid total Thermal capacity ratio C R . The qualitative and quantitative aspects of the effects of these five parameters on the channel Thermalization time are investigated.
-
Validation of Thermal Equilibrium Assumption in Transient Forced Convection Flow in Porous Channel
Transport in Porous Media, 2002Co-Authors: Moh’d A. Al-nimr, Bassam Abu-hijlehAbstract:The validity of the Local Thermal Equilibrium assumption in the transient forced convection channel flow is investigated analytically. Closed form expressions are presented for the temperatures of the fluid and solid domains and for the criterion which insures the validity of the Local Thermal Equilibrium assumption. It is found that four dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the porosity ∈, the volumetric Biot number Bi, the dimensionless channel length ξ_max and the solid to fluid total Thermal capacity ratio C _R. The qualitative and quantitative aspects of the effects of these four parameters on the channel Thermal Equilibrium relaxation time are investigated.
-
Validation of the Thermal Equilibrium assumption in the transient conjugated forced convection channel flow
Heat and Mass Transfer, 2001Co-Authors: Moh’d A. Al-nimr, Bassam Abu-hijlehAbstract:The validity of the Local Thermal Equilibrium assumption in the transient conjugated forced convection channel flow is investigated analytically. Closed form expressions are presented for the temperatures of the fluid and solid domains and for the criterion which insure the validity of the Local Thermal Equilibrium assumption. It is found that three dimensionless parameters control the Local Thermal Equilibrium assumption. These parameters are the Biot number Bi, the dimensionless channel length ξmax and the solid to fluid total Thermal capacity ratio C R. The qualitative and quantitative aspects of the effects of these three parameters on the channel Thermalization time are investigated.
