The intermittency of renewable power generation systems on the low carbon electric grid can be alleviated by using nuclear systems as quasi-storage systems. Nuclear air-Brayton systems can produce and store hydrogen when electric generation is abundant and then burn the hydrogen by co-firing when generation is limited. The rated output of a nuclear plant can be significantly augmented by co-firing. The incremental efficiency of hydrogen to electricity can far exceed that of hydrogen in a standalone gas turbine. Herein, we simulate and evaluate this idea on a 50 MW small modular liquid metal/molten salt reactor. Considerable power increases are predicted for nuclear air-Brayton systems by co-firing with hydrogen before the power turbine.
The intermittency of renewable power generation systems on the low carbon electric grid can be alleviated by using nuclear systems as quasi-storage systems. Nuclear Air-Brayton Combined Cycle systems can produce and store hydrogen when electric generation is abundant and then burn the hydrogen by Co-Firing when generation is limited. The rated output of a nuclear plant can be augmented by several hundred per cent by Co-Firing. The incremental hydrogen to electricity efficiency can far exceed that of hydrogen in a stand-alone gas turbine.
In the power plant industry, the turbine inlet temperature (TIT) plays a key role in the efficiency of the gas turbine and, therefore, the overall — in most cases combined — thermal power cycle efficiency. Gas turbine efficiency increases by increasing TIT. However, an increase of TIT would increase the turbine component temperature which can be critical (e.g., hot gas attack). Thermal barrier coatings (TBCs) — porous media coatings — can avoid this case and protect the surface of the turbine blade. This combination of TBC and film cooling produces a better cooling performance than conventional cooling processes. The effective thermal conductivity of this composite is highly important in design and other thermal/structural assessments. In this article, the effective thermal conductivity of a simplified model of TBC is evaluated. This work details a numerical study on the steady-state thermal response of two-phase porous media in two dimensions using personal finite element analysis (FEA) code. Specifically, the system response quantity (SRQ) under investigation is the dimensionless effective thermal conductivity of the domain. A thermally conductive matrix domain is modeled with a thermally conductive circular pore arranged in a uniform packing configuration. Both the pore size and the pore thermal conductivity are varied over a range of values to investigate the relative effects on the SRQ. In this investigation, an emphasis is placed on using code and solution verification techniques to evaluate the obtained results. The method of manufactured solutions (MMS) was used to perform code verification for the study, showing the FEA code to be second-order accurate. Solution verification was performed using the grid convergence index (GCI) approach with the global deviation uncertainty estimator on a series of five systematically refined meshes for each porosity and thermal conductivity model configuration. A comparison of the SRQs across all domain configurations is made, including uncertainty derived through the GCI analysis.
The evaluation of effective material properties in heterogeneous materials (e.g., composites or multicomponent structures) has direct relevance to a vast number of applications, including nuclear fuel assembly, electronic packaging, municipal solid waste, and others. The work described in this paper is devoted to the numerical verification assessment of the thermal behavior of porous materials obtained from thermal modeling and simulation. Two-dimensional, steady state analyses were conducted on unit cell nano-porous media models using the finite element method (FEM). The effective thermal conductivity of the structures was examined, encompassing a range of porosity. The geometries of the models were generated based on ordered cylindrical pores in six different porosities. The dimensionless effective thermal conductivity was compared in all simulated cases. In this investigation, the method of manufactured solutions (MMS) was used to perform code verification, and the grid convergence index (GCI) is employed to estimate discretization uncertainty (solution verification). The system response quantity (SRQ) under investigation is the dimensionless effective thermal conductivity across the unit cell. Code verification concludes an approximately second order accurate solver. It was found that the introduction of porosity to the material reduces effective thermal conductivity, as anticipated. This approach can be readily generalized to study a wide variety of porous solids from nano-structured materials to geological structures.
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