59,154 research outputs found
High Temperature Photochemistry in the Atmosphere of HD189733b
Recent infrared spectroscopy of hot exoplanets is beginning to reveal their
atmospheric composition. Deep with in the planetary atmosphere, the composition
is controlled by thermochemical equilibrium. Photochemistry becomes important
higher in the atmosphere, at levels above ~1 bar. These two chemistries compete
between ~1-10 bars in hot Jupiter-like atmospheres, depending on the strength
of the eddy mixing and temperature. HD189733b provides an excellent laboratory
in which to study the consequences of chemistry of hot atmospheres. The recent
spectra of HD189733b and HD209458b contain signatures of CH4, CO2, CO and H2O.
Here we identify the primary chemical pathways that govern the abundances of
CH4, CO2, CO and H2O in the cases of thermochemical equilibrium chemistry,
photochemistry, and their combination. Our results suggest that the abundance
of these species can be photochemically enhanced above or below the
thermochemical equilibrium value, so some caution must be taken when assuming
that an atmosphere is in strict thermochemical equilibrium
Thermochemical cycle analysis using linked CECS72 and HYDRGN computer programs
A combined thermochemical cycle analysis computer program was designed. Input to the combined program is the same as input to the thermochemical cycle analysis program except that the extent of the reactions need not be specified. The combined program is designed to be run interactively from a computer time-sharing terminal. This mode of operation allows correction or modification of the cycle to take place during cycle analysis. A group of 13 thermochemical cycles was used to test the combined program
Implementation and application of adaptive mesh refinement for thermochemical mantle convection studies
Numerical modeling of mantle convection is challenging. Owing to the multiscale nature of mantle
dynamics, high resolution is often required in localized regions, with coarser resolution being sufficient
elsewhere. When investigating thermochemical mantle convection, high resolution is required to resolve
sharp and often discontinuous boundaries between distinct chemical components. In this paper, we present
a 2-D finite element code with adaptive mesh refinement techniques for simulating compressible thermochemical
mantle convection. By comparing model predictions with a range of analytical and previously
published benchmark solutions, we demonstrate the accuracy of our code. By refining and coarsening
the mesh according to certain criteria and dynamically adjusting the number of particles in each element,
our code can simulate such problems efficiently, dramatically reducing the computational requirements
(in terms of memory and CPU time) when compared to a fixed, uniform mesh simulation. The resolving
capabilities of the technique are further highlighted by examining plume‐induced entrainment in a thermochemical
mantle convection simulation
The applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research
A review of the applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research during the past four decades is presented with an emphasis on chemical equilibrium models and thermochemical kinetics. Several current problems in planetary atmospheres research such as the origin of the atmospheres of the terrestrial planets, atmosphere-surface interactions on Venus and Mars, deep mixing in the atmospheres of the gas giant planets, and the origin of the atmospheres of outer planet satellites all require laboratory data on the kinetics of thermochemical reactions for their solution
3-D multiobservable probabilistic inversion for the compositional and thermal structure of the lithosphere and upper mantle: III. Thermochemical tomography in the Western-Central U.S.
Acknowledgments We are indebted to F. Darbyshire and J. von Hunen for useful comments on earlier versions of this work. This manuscript benefited from thorough and constructive reviews by W. Levandowski and an anonymous reviewer. We also thank J. Connolly, M. Sambridge, B. Kennett, S. Lebedev, B. Shan, U. Faul, and M. Qashqai for insightful discussions about, and contributions to, some of the concepts presented in this paper. The work of J.C.A. has been supported by two Australian Research Council Discovery grants (DP120102372 and DP110104145). Seismic data are from the IRIS DMS. D.L.S. acknowledges support from NSF grant EAR-135866. This is contribution 848 from the ARC Centre of Excellence for Core to Crust Fluid Systems (http://www.ccfs.mq.edu.au) and 1106 in the GEMOC Key Centre (http://www.gemoc.mq.edu.au).Peer reviewedPublisher PD
Review of Reactors with Potential Use in Thermochemical Energy Storage in Concentrated Solar Power Plants
The aim of this study is to perform a review of the state-of-the-art of the reactors available in the literature, which are used for solid-gas reactions or thermal decomposition processes around 1000 ºC that could be further implemented for thermochemical energy storage in CSP (concentrated solar power) plants, specifically for SPT (solar power tower) technology. Both direct and indirect systems can be implemented, with direct and closed systems being the most studied ones. Among direct and closed systems, the most used configuration is the stacked bed reactor, with the fixed bed reactor being the most frequent option. Out of all of the reactors studied, almost 70% are used for solid-gas chemical reactions. Few data are available regarding solar efficiency in most of the processes, and the available information indicates relatively low values. Chemical reaction efficiencies show better values, especially in the case of a fluidized bed reactor for solid-gas chemical reactions, and fixed bed and rotary reactors for thermal decompositions.The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)
and ENE2015-64117-C5-2-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for
the quality accreditation given to their research groups GREA (2017 SGR 1537) and DIOPMA (2017 SGR 118).
GREA and DIOPMA are certified agents TECNIO in the category of technology developers from the Government
of Catalonia. Dr. Aran Solé would like to thank Ministerio de Economía y Competitividad de España for Grant
Juan de la Cierva, FJCI-2015-25741
The Calcium-Looping (CaCO3/CaO) Process for Thermochemical Energy Storage in Concentrating Solar Power Plants
Articulo aceptado por la revista. * No publicado aún [28-06-2019]Energy storage based on thermochemical systems is gaining momentum as potential alternative to molten salts in Concentrating Solar Power (CSP) plants. This work is a detailed review about the promising integration of a CaCO3/CaO based system, the so-called Calcium-Looping (CaL) process, in CSP plants with tower technology. The CaL process relies on low cost, widely available and non-toxic natural materials (such as limestone or dolomite), which are necessary conditions for the commercial expansion of any energy storage technology at large scale. A comprehensive analysis of the advantages and challenges to be faced for the process to reach a commercial scale is carried out. The review includes a deep overview of reaction mechanisms and process integration schemes proposed in the recent literature. Enhancing the multicycle CaO conversion is a major challenge of the CaL process. Many lab-scale analyses carried out show that residual effective CaO conversion is highly dependent on the process conditions and CaO precursors used, reaching values as different as 0.07-0.82. The selection of the optimal operating conditions must be based on materials, process integration, technology and economics aspects. Global plant efficiencies over 45% (without considering solar-side losses) show the interest of the technology. Furthermore, the technological maturity and potential of the process is assessed. The direction towards which future works should be headed is discussed.Ministerio de Economia y Competitividad CTQ2014-52763-C2, CTQ2017- 83602-C2 (-1-R and -2-R)Unión Europea Horizon 2020 Grant agreement No 727348, project SOCRATCES
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