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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 09 Nov 2024 13:28:40 GMT2024-11-09T13:28:40ZDevelopment and validation of a local thermal non-equilibrium model for high-temperature thermal energy storage in packed beds
http://hdl.handle.net/10985/24863
Development and validation of a local thermal non-equilibrium model for high-temperature thermal energy storage in packed beds
LIU, Shaolin; AHMADI-SENICHAULT, Azita; LEVET, Cyril; LACHAUD, Jean
High-temperature thermal energy storage (TES) in packed beds is gaining interest for industrial energy
recovery. The wide range of temperature distributions causes significant variations in thermophysical properties
of the fluid and solid phases, leading to inaccuracies of classical TES models and heat transfer correlations.
The objective of this work is to develop and validate a detailed but pragmatic model accounting for
high-temperature effects. Based on a literature survey spanning over several communities interested in high-
temperature porous media, we propose a generic local thermal non-equilibrium model for granulate porous
media accounting for conservation of mass, momentum and energy (two-equation temperature model). The
effective parameters needed to inform the model are the effective thermal conductivities of the different
phases and the heat transfer coefficient. An experimental-numerical inverse analysis method is employed to
determine these parameters. A dedicated experimental facility has been designed and built to study a model
granulate made of glass bead of 16 mm diameter. Experiments are conducted using the Transient Single-Blow
Technique (TSBT) by passing hot air (ranging from 293 K to 630 K) through cold particles at various mass
flow rates, covering a Reynolds number range of 58 to 252. The new model was implemented in the Porous
material Analysis Toolbox based on OpenFoam (PATO) used to compute the transient temperature fields.
Two optimization algorithms were employed to determine the parameters by minimizing the error between
experimental and simulated temperatures: a Latin Hypercube Sampling (LHS) method, and a local optimization
method Adaptive nonlinear least-squares algorithm (NL2SOL). The results indicate that the value of heat
transfer coefficient ℎ�� in the two-equation model falls in the range of 1.0 × 104 ∼ 1.93× 104 W/(m3 K) under
the given conditions. The axial dispersion gas thermal conductivity was found to be around 5.9 and 67.1 times
higher than the gas thermal conductivity at Peclet numbers of around 55 and 165, respectively. Furthermore,
two improved correlations of Nusselt number (���� = 2+1.54����(�� )0.6�� ��(�� )1∕3) and of axial dispersion gas thermal
conductivity (��������,∥ = 0.00053����(�� )2.21�� ��(�� ) ⋅ ���� ) are proposed and validated for a range of Reynolds number
from 58 to 252. The overall approach is therefore validated for the model granulate of the study, opening new
perspectives towards more precise design and monitoring of high-temperature TES systems.
Thu, 01 Feb 2024 00:00:00 GMThttp://hdl.handle.net/10985/248632024-02-01T00:00:00ZLIU, ShaolinAHMADI-SENICHAULT, AzitaLEVET, CyrilLACHAUD, JeanHigh-temperature thermal energy storage (TES) in packed beds is gaining interest for industrial energy
recovery. The wide range of temperature distributions causes significant variations in thermophysical properties
of the fluid and solid phases, leading to inaccuracies of classical TES models and heat transfer correlations.
The objective of this work is to develop and validate a detailed but pragmatic model accounting for
high-temperature effects. Based on a literature survey spanning over several communities interested in high-
temperature porous media, we propose a generic local thermal non-equilibrium model for granulate porous
media accounting for conservation of mass, momentum and energy (two-equation temperature model). The
effective parameters needed to inform the model are the effective thermal conductivities of the different
phases and the heat transfer coefficient. An experimental-numerical inverse analysis method is employed to
determine these parameters. A dedicated experimental facility has been designed and built to study a model
granulate made of glass bead of 16 mm diameter. Experiments are conducted using the Transient Single-Blow
Technique (TSBT) by passing hot air (ranging from 293 K to 630 K) through cold particles at various mass
flow rates, covering a Reynolds number range of 58 to 252. The new model was implemented in the Porous
material Analysis Toolbox based on OpenFoam (PATO) used to compute the transient temperature fields.
Two optimization algorithms were employed to determine the parameters by minimizing the error between
experimental and simulated temperatures: a Latin Hypercube Sampling (LHS) method, and a local optimization
method Adaptive nonlinear least-squares algorithm (NL2SOL). The results indicate that the value of heat
transfer coefficient ℎ�� in the two-equation model falls in the range of 1.0 × 104 ∼ 1.93× 104 W/(m3 K) under
the given conditions. The axial dispersion gas thermal conductivity was found to be around 5.9 and 67.1 times
higher than the gas thermal conductivity at Peclet numbers of around 55 and 165, respectively. Furthermore,
two improved correlations of Nusselt number (���� = 2+1.54����(�� )0.6�� ��(�� )1∕3) and of axial dispersion gas thermal
conductivity (��������,∥ = 0.00053����(�� )2.21�� ��(�� ) ⋅ ���� ) are proposed and validated for a range of Reynolds number
from 58 to 252. The overall approach is therefore validated for the model granulate of the study, opening new
perspectives towards more precise design and monitoring of high-temperature TES systems.Experimental investigation on the validity of the local thermal equilibrium assumption in ablative-material response models
http://hdl.handle.net/10985/25587
Experimental investigation on the validity of the local thermal equilibrium assumption in ablative-material response models
LIU, Shaolin; AHMADI, Azita; LEVET, Cyril; LACHAUD, Jean
Thermal Protection Systems (TPS) material response models rely on the assumption of local thermal equilibrium (LTE) between the solid phase and the gas phase. This assumption was challenged and investigated by several authors but a sufficiently precise knowledge of heat transfer coefficients in TPS materials was lacking to reach final conclusions. The objective of this work is to contribute to filling this gap by providing a literature review of available data in other communities (thermal energy storage, heat exchangers) and by performing an experimental characterization of Calcarb, a commercial carbon preform used for manufacturing thermal protection systems. Heat transfer within Calcarb was studied experimentally in the Through-Thickness and in the In-Plane directions for Reynolds numbers of 1 to 4 - representative of the TPS application - using the transient single-blow technique. Numerical parameter estimation was performed using the Porous material Analysis Toolbox based on OpenFoam (PATO) and the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). The heat transfer coefficient hv is found to be greater than or equal to 108 W/(m3K) and the LTE assumption is shown to be valid in the conditions of the experiment. To assess the validity of the LTE assumption for other conditions, the above bound of hv may now be used in combination with a local thermal non-equilibrium model.
Sun, 01 Oct 2023 00:00:00 GMThttp://hdl.handle.net/10985/255872023-10-01T00:00:00ZLIU, ShaolinAHMADI, AzitaLEVET, CyrilLACHAUD, JeanThermal Protection Systems (TPS) material response models rely on the assumption of local thermal equilibrium (LTE) between the solid phase and the gas phase. This assumption was challenged and investigated by several authors but a sufficiently precise knowledge of heat transfer coefficients in TPS materials was lacking to reach final conclusions. The objective of this work is to contribute to filling this gap by providing a literature review of available data in other communities (thermal energy storage, heat exchangers) and by performing an experimental characterization of Calcarb, a commercial carbon preform used for manufacturing thermal protection systems. Heat transfer within Calcarb was studied experimentally in the Through-Thickness and in the In-Plane directions for Reynolds numbers of 1 to 4 - representative of the TPS application - using the transient single-blow technique. Numerical parameter estimation was performed using the Porous material Analysis Toolbox based on OpenFoam (PATO) and the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). The heat transfer coefficient hv is found to be greater than or equal to 108 W/(m3K) and the LTE assumption is shown to be valid in the conditions of the experiment. To assess the validity of the LTE assumption for other conditions, the above bound of hv may now be used in combination with a local thermal non-equilibrium model.