Thermal aspects of conventional and alternative fuels

Peiman, Wargha; Pioro, Igor; Gabriel, Kamiel; Hosseiny, Mohammad

doi:10.1016/b978-0-08-100149-3.00018-5

Cited by 6 publications

(4 citation statements)

References 39 publications

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“…Currently, upper limits of pressures and temperatures used in the thermal-power industry are about 30-38 MPa and 600-625°C, respectively (see Table 1). A new direction in SCW application in the power industry has been the development of SCWR concepts (see Table 2), as part of the Generation-IV International Forum (GIF) [27] initiative (for details, see [6,[9][10][11][12][13][28][29][30] [17]) [18].…”

Section: Specifics Of Forced-convection Heat Transfer At Supercriticamentioning

confidence: 99%

Supercritical-Fluids Thermophysical Properties and Heat Transfer in Power-Engineering Applications

Pioro¹

2020

Advanced Supercritical Fluids Technologies

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Researches on specifics of thermophysical properties and heat transfer at supercritical pressures (SCPs) started as early as the 1930s with the study on free-convection heat transfer to fluids at a near-critical point. In the 1950s, the concept of using SC "steam" to increase thermal efficiency of coal-fired thermal power plants became an attractive option. Germany, USA, the former USSR, and some other countries extensively studied heat transfer to SC fluids (SCFs) during the 1950s till the 1980s. This research was primarily focused on bare circular tubes cooled with SC water (SCW). However, some studies were performed with modeling fluids such as SC carbon dioxide and refrigerants instead of SCW. Currently, the use of SC "steam" in coal-fired thermal power plants is the largest industrial application of fluids at SCPs. Near the end of the 1950s and at the beginning of the 1960s, several studies were conducted to investigate a possibility of using SCW as a coolant in nuclear reactors with the objective to increase thermal efficiency of nuclear power plants (NPPs) equipped with water-cooled reactors. However, these research activities were abandoned for some time and regained momentum in the 1990s. In support of the development of SCW-cooled nuclearpower reactor (SCWR) concepts, first experiments have been started in annular and various bundle flow geometries. At the same time, more numerical and CFD studies have been performed in support of our limited knowledge on specifics of heat transfer at SCPs in various flow geometries. As the first step in this process, heat transfer to SCW in vertical bare tubes can be investigated as a conservative approach (in general, heat transfer in fuel bundles will be enhanced with various types of appendages, that is, grids, end plates, spacers, bearing pads, fins, ribs, etc.). New experiments in the 1990-2000s were triggered by several reasons: (1) thermophysical properties of SCW and other SCFs have been updated from the 1950s-1970s, for example, a peak in thermal conductivity in the critical/ pseudocritical points was "officially" introduced in 1990s; (2) experimental techniques have been improved; (3) in SCWRs, various bundle flow geometries will be used instead of bare-tube geometry; (4) in SC "steam" generators of thermal power plants, larger diameter tubes/pipes (20-40 mm) are used, however in SCWRs hydraulic-equivalent diameters of proposed bundles will be within 5-12 mm; (5) with Research and Development (R&D) of next-generation or Generation-IV nuclear-power-reactor concepts, new areas of application for SCFs have appearedfor example, SCP helium was proposed to be used as a reactor coolant, SCP Brayton 1 and Rankine cycles with SC carbon dioxide as a working fluid are being developed, etc. A comparison of thermophysical properties of SCFs with those of subcriticalpressure fluids showed that SCFs as single-phase fluids have unique properties, which are close to "liquid-like" behavior below critical or pseudocritical points and are quite similar to the behavior of "gas-li...

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Section: Specifics Of Forced-convection Heat Transfer At Supercriticamentioning

confidence: 99%

Supercritical-Fluids Thermophysical Properties and Heat Transfer in Power-Engineering Applications

Pioro¹

2020

Advanced Supercritical Fluids Technologies

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“…Atomistic calculation approaches for materials modeling can be used as an independent route to aid in new materials synthesis 1 , characterizing mixtures for use as fuel 2,3 , or quantifying rates for chemical decomposition of organic materials 4 . These types of studies generally rely on quantum mechanical approaches such as Kohn-Sham Density Functional Theory (DFT) in order to aid in experimental interpretation and/or new materials design.…”

Section: Introductionmentioning

confidence: 99%

Enhancing the Accuracy of Density Functional Tight Binding Models Through ChIMES Many-body Interaction Potentials

Goldman¹,

Fried²,

Lindsey³

et al. 2023

Preprint

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Semi-empirical quantum models such as Density Functional Tight Binding (DFTB) are attractive methods for obtaining quantum simulation data at longer time and length scales than possible with standard approaches. However, application of these models can require lengthy effort due to the lack of a systematic approach for their development. In this work, we discuss use of the Chebyshev Interaction Model for Efficient Simulation (ChIMES) to create rapidly parameterized DFTB models which exhibit strong transferability due to the inclusion of many-body interactions that might otherwise be underestimated. We apply our modeling approach to silicon polymorphs and review previous work on titanium hydride. We also review creation of a general purpose DFTB/ChIMES model for organic molecules and compounds that approaches hybrid functional and coupled cluster accuracy with two orders of magnitude fewer parameters than similar neural network approaches. In all cases, DFTB/ChIMES yields similar accuracy to the underlying quantum method with orders of magnitude improvement in computational cost. Our developments provide a way to create computationally efficient and highly accurate simulations over varying extreme thermodynamic conditions, where physical and chemical properties can be difficult to interrogate directly and there is historically a significant reliance on theoretical approaches for interpretation and validation of experimental results.

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“…Plutonium oxide (PuO 2 ) is a stable ceramic that forms spontaneously from the metal in the presence of atmospheric oxygen or water [1]. PuO 2 has a number of industrial uses, including as a component in mixed oxide fuels for nuclear power reactors [2] and as a fuel source for deep-space spacecrafts [3]. Similar to many transition metals, the oxide layer on plutonium-based materials acts as a protection against corrosion due to atmospheric gases [4].…”

Section: Introductionmentioning

confidence: 99%

Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO2

et al. 2022

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We detail the estimation of activation energies and quantum nuclear vibrational tunneling effects for hydrogen diffusion in PuO2 based on Density Functional Theory calculations and a quantum double well approximation. We find that results are relatively insensitive to choice of exchange correlation functional. In addition, the representation of spin in the system and use of an extended Hubbard U correction has only a small effect on hydrogen point defect formation energies when the PuO2 lattice is held fixed at the experimental density. We then compute approximate activation energies for transitions between hydrogen interstitial sites seeded by a semi-empirical quantum model and determine the quantum tunneling enhancement relative to classical kinetic rates. Our model indicates that diffusion rates in H/PuO2 systems could be enhanced by more than one order of magnitude at ambient conditions and that these effects persist at high temperature. The method we propose here can be used as a fast screening tool for assessing possible quantum nuclear vibrational effects in any number of condensed phase materials and surfaces, where hydrogen hopping tends to follow well defined minimum energy pathways.

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Thermal aspects of conventional and alternative fuels

Cited by 6 publications

References 39 publications

Supercritical-Fluids Thermophysical Properties and Heat Transfer in Power-Engineering Applications

Supercritical-Fluids Thermophysical Properties and Heat Transfer in Power-Engineering Applications

Enhancing the Accuracy of Density Functional Tight Binding Models Through ChIMES Many-body Interaction Potentials

Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO2

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