Modeling Approach of Thermal Decomposition of Salt-Hydrates for Heat Storage Systems

2013 ◽  
Author(s):  
Armand Fopah Lele ◽  
Fréderic Kuznik ◽  
Holger Urs Rammelberg ◽  
Thomas Schmidt ◽  
Wolfgang K. L. Ruck
Keyword(s):  
Thermal Decomposition ◽  
Heat Storage ◽  
Storage Systems ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
The Finite Element Method ◽  
Modeling Approach ◽  
Measurement Results ◽  
Salt Hydrates ◽  
Physical Phenomena

Heat storage systems using reversible chemical solid-fluid reactions to store and release thermal energy operates in charging and discharging phases. During last three decades, discussions on thermal decomposition of several salt-hydrates were done (experimentally and numerically) [1,2]. A mathematical model of heat and mass transfer in fixed bed reactor for heat storage is proposed based on a set of partial differential equations (PDEs). Beside the physical phenomena, the chemical reaction is considered via the balances or conservations of mass, extent conversion and energy in the reactor. These PDEs are numerically solved by means of the finite element method using Comsol Multiphysics 4.3a. The objective of this paper is to describe an adaptive modeling approach and establish a correct set of PDEs describing the physical system and appropriate parameters for simulating the thermal decomposition process. In this paper, kinetic behavior as stated by the ICTAC committee [3] to understand transport phenomena and reactions mechanism in gas and solid phases is taking into account using the generalized Prout-Tompkins equation with modifications based on thermal analysis experiments. The model is then applied to two thermochemical materials CaCl2 and MgCl2 with experimental activation energies and a comparison is made with TGA-DSC measurement results.

Thermal decomposition kinetic of salt hydrates for heat storage systems

2015 ◽  
Vol 154 ◽  
pp. 447-458 ◽  
Author(s):  
Armand Fopah Lele ◽  
Frédéric Kuznik ◽  
Holger U. Rammelberg ◽  
Thomas Schmidt ◽  
Wolfgang K.L. Ruck
Keyword(s):  
Thermal Decomposition ◽  
Heat Storage ◽  
Storage Systems ◽  
Decomposition Kinetic ◽  
Salt Hydrates ◽  
Thermal Decomposition Kinetic

scholarly journals Thermochemical Heat Storage in a Lab-Scale Indirectly Operated CaO/Ca(OH)2 Reactor—Numerical Modeling and Model Validation through Inverse Parameter Estimation

2021 ◽  
Vol 11 (2) ◽  
pp. 682
Author(s):  
Gabriele Seitz ◽  
Farid Mohammadi ◽  
Holger Class
Keyword(s):  
Numerical Model ◽  
Gas Flow ◽  
Reaction Rate ◽  
Heat Storage ◽  
Bulk Material ◽  
Fixed Bed ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Thermochemical Heat Storage ◽  
Speed Up

Calcium oxide/Calcium hydroxide can be utilized as a reaction system for thermochemical heat storage. It features a high storage capacity, is cheap, and does not involve major environmental concerns. Operationally, different fixed-bed reactor concepts can be distinguished; direct reactor are characterized by gas flow through the reactive bulk material, while in indirect reactors, the heat-carrying gas flow is separated from the bulk material. This study puts a focus on the indirectly operated fixed-bed reactor setup. The fluxes of the reaction fluid and the heat-carrying flow are decoupled in order to overcome limitations due to heat conduction in the reactive bulk material. The fixed bed represents a porous medium where Darcy-type flow conditions can be assumed. Here, a numerical model for such a reactor concept is presented, which has been implemented in the software DuMux. An attempt to calibrate and validate it with experimental results from the literature is discussed in detail. This allows for the identification of a deficient insulation of the experimental setup. Accordingly, heat-loss mechanisms are included in the model. However, it can be shown that heat losses alone are not sufficient to explain the experimental results. It is evident that another effect plays a role here. Using Bayesian inference, this effect is identified as the reaction rate decreasing with progressing conversion of reactive material. The calibrated model reveals that more heat is lost over the reactor surface than transported in the heat transfer channel, which causes a considerable speed-up of the discharge reaction. An observed deceleration of the reaction rate at progressed conversion is attributed to the presence of agglomerates of the bulk material in the fixed bed. This retardation is represented phenomenologically by mofifying the reaction kinetics. After the calibration, the model is validated with a second set of experimental results. To speed up the calculations for the calibration, the numerical model is replaced by a surrogate model based on Polynomial Chaos Expansion and Principal Component Analysis.

Catalytic performance and deoxygenation path of methyl palmitate on Ni2P/SiO2 synthesized using the thermal decomposition of nickel hypophosphite

RSC Advances ◽  
2016 ◽  
Vol 6 (37) ◽  
pp. 31308-31315 ◽  
Author(s):  
Qingxin Guan ◽  
Fei Han ◽  
Wei Li
Keyword(s):  
Thermal Decomposition ◽  
Continuous Flow ◽  
Methyl Palmitate ◽  
Fixed Bed ◽  
Catalytic Performance ◽  
Fixed Bed Reactor

Catalytic performance and deoxygenation path of methyl palmitate on Ni2P/SiO2 catalysts were systematically studied in a continuous flow fixed-bed reactor.

Heterogeneous Modeling Approach for Gas‐Limited Reactions in an Inclined Rotating Fixed Bed Reactor

2019 ◽  
Vol 91 (5) ◽  
pp. 637-644 ◽  
Author(s):  
Robert Timaeus ◽  
Uwe Hampel ◽  
Markus Schubert
Keyword(s):  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Modeling Approach
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