Letteratura scientifica selezionata sul tema "Thermal and ground CO2 flux"
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Articoli di riviste sul tema "Thermal and ground CO2 flux"
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Gao, Wen, Xiaoning Yang, Jing Wang, Yanqiang Bi, Boying Lin, Yonghong Shang e Xinguang Cui. "Mass Transfer Theory Based Analysis of Influencing Factors on Component Gradient of Near-surface Atmosphere on Venus". Astrophysical Journal 954, n. 1 (22 agosto 2023): 50. http://dx.doi.org/10.3847/1538-4357/ace622.
Testo completoAbstract (sommario):
Abstract The atmosphere of Venus differs completely from that of Earth despite the planets’ similarity in size and mass. At Venus's surface, the atmosphere is hot and dense, with a temperature of approximately 735 K and a pressure of approximately 92 bar. The temperature profile from the Soviet VeGa-2 probe shows high instability of the near-ground potential temperature, which, according to relevant research, can be explained by the vertical gradient of N2 mole fraction. Based on the Maxwell–Stefan mass transfer theory, we propose a theoretical model of binary gas component for a quantitative discussion of influencing factors for the N2 vertical concentration gradient, which consist of temperature, gravity, specific heat ratio, mass relative factor, thermal diffusion factor, and CO2 flux. Our model shows that the 0%–3.5% N2 concentration gradient cannot be generated without CO2 flux in the near-ground atmosphere of Venus. And the result with CO2 source indicates that the 0.000001%–3.5% N2 concentration gradient at 0–7 km atmosphere can be generated by the 2.7 × 10−6 mol m−2 s−6 CO2 flux on Venusian surface, which is in agreement of gradient reckoned by VeGa-2's data. This magnitude of CO2 flux is close to the one produced by volcanic eruptions on Earth, indicating possible existence of volcanic activities on the surface of Venus. This work has provided the community a new vision to understand the influencing factors of Venusian atmospheres composition distribution.
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Witkowski, Andrzej, Mirosław Majkut e Sebastian Rulik. "Analysis of pipeline transportation systems for carbon dioxide sequestration". Archives of Thermodynamics 35, n. 1 (1 marzo 2014): 117–40. http://dx.doi.org/10.2478/aoter-2014-0008.
Testo completoAbstract (sommario):
Abstract A commercially available ASPEN PLUS simulation using a pipe model was employed to determine the maximum safe pipeline distances to subsequent booster stations as a function of carbon dioxide (CO2) inlet pressure, ambient temperature and ground level heat flux parameters under three conditions: isothermal, adiabatic and with account of heat transfer. In the paper, the CO2 working area was assumed to be either in the liquid or in the supercritical state and results for these two states were compared. The following power station data were used: a 900 MW pulverized coal-fired power plant with 90% of CO2 recovered (156.43 kg/s) and the monothanolamine absorption method for separating CO2 from flue gases. The results show that a subcooled liquid transport maximizes energy efficiency and minimizes the cost of CO2 transport over long distances under isothermal, adiabatic and heat transfer conditions. After CO2 is compressed and boosted to above 9 MPa, its temperature is usually higher than ambient temperature. The thermal insulation layer slows down the CO2 temperature decrease process, increasing the pressure drop in the pipeline. Therefore in Poland, considering the atmospheric conditions, the thermal insulation layer should not be laid on the external surface of the pipeline.
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Witkowski, Andrzej, Andrzej Rusin, Mirosław Majkut e Katarzyna Stolecka. "The Analysis of Pipeline Transportation Process for CO2 Captured From Reference Coal-Fired 900 MW Power Plant to Sequestration Region". Chemical and Process Engineering 35, n. 4 (1 dicembre 2014): 497–514. http://dx.doi.org/10.2478/cpe-2014-0037.
Testo completoAbstract (sommario):
Abstract Three commercially available intercooled compression strategies for compressing CO2 were studied. All of the compression concepts required a final delivery pressure of 153 bar at the inlet to the pipeline. Then, simulations were used to determine the maximum safe pipeline distance to subsequent booster stations as a function of inlet pressure, environmental temperature, thickness of the thermal insulation and ground level heat flux conditions. The results show that subcooled liquid transport increases energy efficiency and minimises the cost of CO2 transport over long distances under heat transfer conditions. The study also found that the thermal insulation layer should not be laid on the external surface of the pipe in atmospheric conditions in Poland. The most important problems from the environmental protection point of view are rigorous and robust hazard identification which indirectly affects CO2 transportation. This paper analyses ways of reducing transport risk by means of safety valves.
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Demezhko, Dmitry Yu, Anastasia A. Gornostaeva, Georgy V. Tarkhanov e Oleg A. Esipko. "30,000 Years of Ground Surface Temperature and Heat Flux Changes in Karelia Reconstructed from Borehole Temperature Data". Bulletin of Geography. Physical Geography Series 6, n. 1 (1 dicembre 2013): 7–25. http://dx.doi.org/10.2478/bgeo-2013-0001.
Testo completoAbstract (sommario):
Abstract Analyses of temperature-depth profiles logged in deep boreholes (> 1 km) permit the reconstruction of ground surface temperature (GST) and surface heat flux (SHF) histories in the period of global climate change at the border of the Pleistocene and the Holocene. We reconstructed past GST and SHF histories using data obtained from the 3.5-km-deep Onega borehole (Karelia, north-west Russia). The resulting reconstructions include information on the basal thermal regime of the Scandinavian Ice Sheet, which covered the region in the Last Glacial Maximum (LGM). The surface temperature history reveals a high amplitude of Pleistocene/ Holocene warming equal to 18-20 K. The heat flux changes precede the surface temperature changes and are close to the variations of insolation at a latitude of 60°N. A comparison of the reconstructed GST and SHF histories with the records of carbon dioxide contents in Antarctic ice cores shows that CO2 changes are much closer to temperature changes than they are to heat flux changes.
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Cawse-Nicholson, Kerry, Joshua B. Fisher, Caroline A. Famiglietti, Amy Braverman, Florian M. Schwandner, Jennifer L. Lewicki, Philip A. Townsend et al. "Ecosystem responses to elevated CO<sub>2</sub> using airborne remote sensing at Mammoth Mountain, California". Biogeosciences 15, n. 24 (14 dicembre 2018): 7403–18. http://dx.doi.org/10.5194/bg-15-7403-2018.
Testo completoAbstract (sommario):
Abstract. We present an exploratory study examining the use of airborne remote-sensing observations to detect ecological responses to elevated CO2 emissions from active volcanic systems. To evaluate these ecosystem responses, existing spectroscopic, thermal, and lidar data acquired over forest ecosystems on Mammoth Mountain volcano, California, were exploited, along with in situ measurements of persistent volcanic soil CO2 fluxes. The elevated CO2 response was used to statistically model ecosystem structure, composition, and function, evaluated via data products including biomass, plant foliar traits and vegetation indices, and evapotranspiration (ET). Using regression ensemble models, we found that soil CO2 flux was a significant predictor for ecological variables, including canopy greenness (normalized vegetation difference index, NDVI), canopy nitrogen, ET, and biomass. With increasing CO2, we found a decrease in ET and an increase in canopy nitrogen, both consistent with theory, suggesting more water- and nutrient-use-efficient canopies. However, we also observed a decrease in NDVI with increasing CO2 (a mean NDVI of 0.27 at 200 g m−2 d−1 CO2 reduced to a mean NDVI of 0.10 at 800 g m−2 d−1 CO2). This is inconsistent with theory though consistent with increased efficiency of fewer leaves. We found a decrease in above-ground biomass with increasing CO2, also inconsistent with theory, but we did also find a decrease in biomass variance, pointing to a long-term homogenization of structure with elevated CO2. Additionally, the relationships between ecological variables changed with elevated CO2, suggesting a shift in coupling/decoupling among ecosystem structure, composition, and function synergies. For example, ET and biomass were significantly correlated for areas without elevated CO2 flux but decoupled with elevated CO2 flux. This study demonstrates that (a) volcanic systems show great potential as a means to study the properties of ecosystems and their responses to elevated CO2 emissions and (b) these ecosystem responses are measurable using a suite of airborne remotely sensed data.
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Cusano, Paola, Teresa Caputo, Enza De Lauro, Mariarosaria Falanga, Simona Petrosino, Fabio Sansivero e Giuseppe Vilardo. "Tracking the Endogenous Dynamics of the Solfatara Volcano (Campi Flegrei, Italy) through the Analysis of Ground Thermal Image Temperatures". Atmosphere 12, n. 8 (22 luglio 2021): 940. http://dx.doi.org/10.3390/atmos12080940.
Testo completoAbstract (sommario):
In the last decades, thermal infrared ground-based cameras have become effective tools to detect significant spatio-temporal anomalies in the hydrothermal/volcanic environment, possibly linked to impending eruptions. In this paper, we analyzed the temperature time-series recorded by the ground-based Thermal Infrared Radiometer permanent network of INGV-OV, installed inside the Solfatara-Pisciarelli area, the most active fluid emission zones of the Campi Flegrei caldera (Italy). We investigated the temperatures’ behavior in the interval 25 June 2016–29 May 2020, with the aim of tracking possible endogenous hydrothermal/volcanic sources. We performed the Independent Component Analysis, the time evolution estimation of the spectral power, the cross-correlation and the Changing Points’ detection. We compared the obtained patterns with the behavior of atmospheric temperature and pressure, of the time-series recorded by the thermal camera of Mt. Vesuvius, of the local seismicity moment rate and of the CO2 emission flux. We found an overall influence of exogenous, large scale atmospheric effect, which dominated in 2016–2017. Starting from 2018, a clear endogenous forcing overcame the atmospheric factor, and dominated strongly soil temperature variations until the end of the observations. This paper highlights the importance of monitoring and investigating the soil temperature in volcanic environments, as well as the atmospheric parameters.
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Inguaggiato, Salvatore, Fabio Vita, Iole Serena Diliberto, Agnes Mazot, Lorenzo Calderone, Andrea Mastrolia e Marco Corrao. "The Extensive Parameters as a Tool to Monitoring the Volcanic Activity: The Case Study of Vulcano Island (Italy)". Remote Sensing 14, n. 5 (5 marzo 2022): 1283. http://dx.doi.org/10.3390/rs14051283.
Testo completoAbstract (sommario):
On Vulcano Island (Italy), many geochemical crises have occurred during the last 130 years of solfataric activity. The main crises occurred in 1978–1980, 1988–1991, 1996, 2004–2007, 2009–2010 and the ongoing 2021 anomalous degassing activity. These crises have been characterized by early signals of resuming degassing activity, measurable by the increase of volatiles and energy output emitted from the summit areas of the active cone, and particularly by increases of gas/water ratios in the fumarolic area at the summit. In any case, a direct rather than linear correspondence has been observed among the observed increase in the fluid output, seismic release and ground deformation, and is still a subject of study. We present here the results obtained by the long-term monitoring (over 13 years of observations) of three extensive parameters: the SO2 flux monitored in the volcanic plume, the soil CO2 flux and the local heat flux, monitored in the mild thermal anomaly located to the east of the high-temperature fumarole. The time variations of these parameters showed cyclicity in the volcanic degassing and a general increase in the trend in the last period. In particular, we focused on the changes in the mass and energy output registered in the period of June–December 2021, to offer in near-real-time the first evaluation of the level and duration of the actual exhalative crisis affecting Vulcano Island. In this last event, a clear change in degassing style was recorded for the volatiles emitted by the magma. For example, the flux of diffused CO2 from the soils reached the maximum never-before-recorded value of 34,000 g m−2 d−1 and the flux of SO2 of the plume emitted by the fumarolic field on the summit crater area reached values higher than 200 t d−1. The interpretation of the behavior of this volcanic system, resulting from the detailed analyses of these continuous monitoring data, will complete the framework of observations and help in defining and possibly forecasting the next evolution of the actual exhaling crisis.
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Setina, Janina. "Preparation of Synthetic Cordierite by Solide-State-Reaction with Addition of Dolomite". Advances in Science and Technology 45 (ottobre 2006): 77–82. http://dx.doi.org/10.4028/www.scientific.net/ast.45.77.
Testo completoAbstract (sommario):
Cordierite was obtained from the mixture of aluminum hydroxide, sand, different magnesium compounds by a solid-state reaction method. The effect of dolomite doping on phase-transformation kinetics and microstructure has been investigated during thermal treatment by keeping a stoichiometric cordierite compound. Adding of dolomite has been used as a flux for preparation of a cordierite precursor by a coprecipitation process. Subsequently, DTA and XRD analyses were conducted to identify the phases formed in the sintered products. Morphological changes of the ground mixtures and sintered product were observed using SEM. The crystallization process of metastable quartz like μ-cordierite can be obtained at 1250…13000C. In this range of temperature form other compounds, such as spinel, quartz. Increase of sintering temperature and prolonged holding times promote the formation of only one phase – indialite or α-cordierite, the hexagonal form of cordierite. Experimental observation shows two steps in the solid-state reaction. First step – formation of volatiles compounds and pores, second – formation and growing of crystalline phases. Evolution of CO, CO2 and H2O that occurred during the thermal treatment of compositions is very important fact in the nucleation process. The intensity of crystallization depends on the gas volume and amount of pore in the sample. The experiments indicated that the intrinsic concentration of volatiles like CO, CO2, H2O influence the appearance of the cordierite phase. SEM photographs sowed that crystallization of cordierite start on the surface of pore. Growth of α-cordierite inside of pores is considerably affected by the time of thermal treatment and amount of adding of dolomite. A remarkable change in peak intensity of XRD patterns of the compositions was observed. Up to 20 wt. % addition of dolomite to the precursor allowed the fabrication of synthetic cordierite at lower temperature.
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Guo, Liang, Tiecheng Qiu, Qian Zhang, Zhanping Guo e Ming Shan. "Influences of temperature on the property of ITO/Teflon/Ag in atomic oxygen environment". Journal of Physics: Conference Series 2720, n. 1 (1 marzo 2024): 012016. http://dx.doi.org/10.1088/1742-6596/2720/1/012016.
Testo completoAbstract (sommario):
Abstract This paper uses ground simulation equipment for an atomic oxygen environment to conduct experimental research on ITO/Teflon/Ag, which is used in spacecraft using an atomic oxygen environment. The atomic oxygen integrated flux selected in the study is 9.1× 1019 atoms/cm2, with a vacuum degree of 10-2 Pa, and sample temperatures of 20°C, 70°C, and 120°C, respectively, were selected to investigate the possible impact of sample temperature on atomic oxygen environment simulation experiments. After the test, a high-precision microelectronic balance was used to test the mass loss of the sample and calculate the reaction rate of the material. The thermal emissivity and solar absorption ratio of the sample were tested using TEMP 2000A and LPSR 300, respectively. Through experiments and analysis, it was found that as the sample temperature increased, the ITO/Teflon/Ag reaction rate with atomic oxygen gradually increased but remained at 10-25. Atomic oxygen and temperature have a significant impact on the thermal physical properties of the material.
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Wang, Sheng, Monica Garcia, Andreas Ibrom e Peter Bauer-Gottwein. "Temporal interpolation of land surface fluxes derived from remote sensing – results with an unmanned aerial system". Hydrology and Earth System Sciences 24, n. 7 (22 luglio 2020): 3643–61. http://dx.doi.org/10.5194/hess-24-3643-2020.
Testo completoAbstract (sommario):
Abstract. Remote sensing imagery can provide snapshots of rapidly changing land surface variables, e.g. evapotranspiration (ET), land surface temperature (Ts), net radiation (Rn), soil moisture (θ), and gross primary productivity (GPP), for the time of sensor overpass. However, discontinuous data acquisitions limit the applicability of remote sensing for water resources and ecosystem management. Methods to interpolate between remote sensing snapshot data and to upscale them from an instantaneous to a daily timescale are needed. We developed a dynamic soil–vegetation–atmosphere transfer model to interpolate land surface state variables that change rapidly between remote sensing observations. The “Soil–Vegetation, Energy, water, and CO2 traNsfer” (SVEN) model, which combines the snapshot version of the remote sensing Priestley–Taylor Jet Propulsion Laboratory ET model and light use efficiency GPP models, now incorporates a dynamic component for the ground heat flux based on the “force-restore” method and a water balance “bucket” model to estimate θ and canopy wetness at a half-hourly time step. A case study was conducted to demonstrate the method using optical and thermal data from an unmanned aerial system at a willow plantation flux site (Risoe, Denmark). Based on model parameter calibration with the snapshots of land surface variables at the time of flight, SVEN interpolated UAS-based snapshots to continuous records of Ts, Rn, θ, ET, and GPP for the 2016 growing season with forcing from continuous climatic data and the normalized difference vegetation index (NDVI). Validation with eddy covariance and other in situ observations indicates that SVEN can estimate daily land surface fluxes between remote sensing acquisitions with normalized root mean square deviations of the simulated daily Ts, Rn, θ, LE, and GPP of 11.77 %, 6.65 %, 19.53 %, 14.77 %, and 12.97 % respectively. In this deciduous tree plantation, this study demonstrates that temporally sparse optical and thermal remote sensing observations can be used to calibrate soil and vegetation parameters of a simple land surface modelling scheme to estimate “low-persistence” or rapidly changing land surface variables with the use of few forcing variables. This approach can also be applied with remotely-sensed data from other platforms to fill temporal gaps, e.g. cloud-induced data gaps in satellite observations.
Tesi sul tema "Thermal and ground CO2 flux"
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Klein, Amelie. "Étude multi-paramètrique de l'évolution des systèmes hydrothermaux : apports à la compréhension des systèmes volcaniques en cours de réactivation". Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2024. http://theses.bu.uca.fr/nondiff/2024UCFA0125_KLEIN.pdf.
Testo completoAbstract (sommario):
L'activité hydrothermale volcanique présente des risques permanents liés à l'émission de gaz toxiques provenant à la fois du sol et des fumerolles. Cependant, des risques plus difficilement prévisibles peuvent également survenir tels que les explosions phréatiques ou l'effondrement des flancs. La présence d'un système hydrothermal a des implications importantes pour l'interprétation des signaux provenant du système magmatique. Par conséquent, la distribution spatiale et l'évolution temporelle des signaux géophysiques et géochimiques sur les volcans hydrothermaux donnent des informations cruciales pour la détection des précurseurs de l'activité éruptive.La Soufrière de Guadeloupe est actuellement dans une phase de réactivation qui a débuté en 1992 et dont l'intensité a augmenté en 2018. Afin de mieux comprendre le système hydrothermal de La Soufrière, nous avons effectué plusieurs cartographies du dégazage diffus du CO2 de la température et du Potentiel Spontané (PS) au niveau du dôme entre 2021 et 2024. Ce travail représente la première cartographie du PS depuis plus d'une décennie et la première quantification du dégazage de CO2 sur le sommet. Il fournit une image actualisée de la distribution de la circulation des fluides souterrains et les flux de chaleur et de CO2 associés. Nous proposons également une méthodologie numérique basée sur un modèle physique et des images thermiques des panaches de fumerolles permettant d'améliorer la quantification des flux des principales fumerolles de La Soufrière.En comparant nos mesures entre elles et à celles des études antérieures, nous constatons que la circulation des fluides hydrothermaux dans le secteur nord-est du sommet a augmenté de manière significative au cours de ces dernières années. Les profondeurs de condensation des fluides hydrothermaux ascendants suggèrent que ce développement peut être dû à un changement de la distribution de la perméabilité souterraine liée aux déformations du dôme. En parallèle, nous avons étudié la dynamique des flux hydrothermaux à l'aide d'une série temporelle du PS sur deux ans. Cette analyse montre des variations diurnes et semi-diurnes liées aux marées atmosphériques. Enfin, nous analysons la réponse du système hydrothermal aux précipitations, à la sismicité et à la température des fumerolles. Les résultats obtenus montrent que le secteur nord-est du sommet est fortement interconnecté et met en évidence le contrôle de la dynamique du système hydrothermal par les principales fractures du sommet.Cette thèse propose une image de la distribution actuelle et de l'évolution spatiotemporelle de la circulation des fluides hydrothermaux à La Soufrière de Guadeloupe. Nos résultats ont permis d'identifier les zones pour la surveillance future. De plus, les jeux de données acquises permettront de mieux contraindre les modèles issus d'autres méthodes géophysiques afin de déterminer l'état interne du dôme et d'évaluer les risques potentiels liés au dégazage passif, à l'altération ou à la pressurisation des fluidesVolcanic hydrothermal activity poses unpredictable hazards like phreatic explosions or flank collapse, as well as pervasive hazards such as the emission of hot, toxic gases from steaming ground and fumaroles. The presence of a hydrothermal system has important implications for interpreting signals from the magmatic system. Therefore, the spatial distribution and temporal evolution of geophysical and geochemical signals at volcanoes with long-lived hydrothermal systems provide crucial information for detecting precursors of eruptive activity.La Soufrière de Guadeloupe volcano is currently undergoing a phase of unrest, which started in 1992 and saw an increase in intensity in 2018. To advance the understanding of the shallow hydrothermal system at La Soufrière, we repeatedly mapped diffuse CO2 degassing, ground temperature and self-potential across the dome summit from 2021 to 2024. This work represents the first mapping of self-potential in over a decade and the first quantification of CO2 degassing over the entire summit. It provides an up-to-date picture of the distribution of subsurface fluid circulation and the associated ground heat and CO2 fluxes. We also outline a numerical approach to improve the quantification of the fumarole fluxes based on a physical plume model and thermal images of the fumarole plumes and use this to calculate heat and mass fluxes from La Soufrière's major fumaroles.Our multi-parameter mappings, repeated self-potential profiles, and comparisonswith previous studies show that hydrothermal fluid circulation in the northeastern summit sector has significantly increased over the last decade. Estimated condensation depths of ascending hydrothermal fluids suggest that this development may be due to a change in the distribution of subsurface permeability, which is likely related to the dome displacement field. The short-term dynamics of hydrothermal fluid circulation are investigated using a two-year self-potential time series. We observe diurnal and semidiurnal variations linked to atmospheric tides. Finally, we analyse the response of the shallow hydrothermal system to precipitation, seismicity and fumarole temperature.This shows that the northeastern summit sector is highly interconnected and highlights the strong structural control of the hydrothermal system dynamics by the main summit fractures.This work provides a picture of the current distribution and spatiotemporal evolution of shallow hydrothermal fluid circulation at La Soufrière de Guadeloupe. This helps us to identify the preferred zones for future monitoring. The datasets generated will help to constrain models from other geophysical methods to infer the internal state of the dome and assess potential hazards related to passive degassing, alteration or fluid pressurisation
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Stangier, Tobias [Verfasser]. "Atmospheric Thermal Properties of Venus and Mars - Investigation of CO2 Absorption Lines using Ground-Based Mid-Infrared Heterodyne Spectroscopy / Tobias Stangier". München : Verlag Dr. Hut, 2015. http://d-nb.info/1067708030/34.
Testo completo
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Krause, Pia [Verfasser]. "Upper Atmospheric Thermal Properties of Venus - Investigation of non-LTE CO2 Emission Lines using Ground-Based Mid-Infrared Heterodyne Spectroscopy / Pia Krause". München : Verlag Dr. Hut, 2021. http://d-nb.info/1232847267/34.
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Stangier, Tobias [Verfasser], e Lucas [Akademischer Betreuer] Labadie. "Atmospheric Thermal Properties of Venus and Mars. Investigation of CO2 Absorption Lines using Ground-Based Mid-Infrared Heterodyne Spectroscopy / Tobias Stangier. Gutachter: Lucas Labadie". Köln : Universitäts- und Stadtbibliothek Köln, 2014. http://d-nb.info/1069374229/34.
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Kandel, Hari P. "Land Use /Land Cover Driven Surface Energy Balance and Convective Rainfall Change in South Florida". FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2198.
Testo completoAbstract (sommario):
Modification of land use/land cover in South Florida has posed a major challenge in the region’s eco-hydrology by shifting the surface-atmosphere water and energy balance. Although drainage and development in South Florida took place extensively between the mid- and late- 20th century, converting half of the original Everglades into agricultural and urban areas, urban expansion still accounts for a dominant mode of surface cover change in South Florida. Changes in surface cover directly affect the radiative, thermophysical and aerodynamic parameters which determine the absorption and partitioning of radiation into different components at the Earth surface. The alteration is responsible for changing the thermal structure of the surface and surface layer atmosphere, eventually modifying surface-induced convection.
This dissertation is aimed at analyzing the extent and pattern of land cover change in South Florida and delineating the associated development of urban heat island (UHI), energy flux alteration, and convective rainfall modification using observed data, remotely sensed estimates, and modeled results.
Urban land covers in South Florida are found to have increased by 10% from 1974 to 2011. Higher Landsat-derived land surface temperatures (LST) are observed in urban areas (LSTu-r =2.8°C) with satisfactory validation statistics for eastern stations (Nash-Sutcliffe coefficient =0.70 and R2 =0.79). Time series trends, significantly negative for diurnal temperature range (DTR= -1°C, p=0.005) and positive for lifting condensation level (LCL > 20m) reveal temporal and conspicuous urban-rural differences in nocturnal temperature (ΔTu-r = 4°C) shows spatial signatures of UHI. Spatially higher (urban: 3, forest: 0.14) and temporally increasing (urban: 1.67 to 3) Bowen’s ratios, and sensible heat fluxes exceeding net radiation in medium and high-intensity developed areas in 2010 reflect the effect of urbanization on surface energy balance. Radar reflectivity-derived surface-induced convective rainfall reveals significantly positive mean differences (thunderstorm cell density: 6/1000 km2and rain rate: 0.24 mm/hr/summer, p < 0.005) between urban and entire South Florida indicating convective enhancement by urban covers.
The research fulfils its two-fold purposes: advancing the understanding of post-development hydrometeorology in South Florida and investigating the spatial and temporal impacts of land cover change on the microclimate of a subtropical city.
Capitoli di libri sul tema "Thermal and ground CO2 flux"
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Rosen, Marc A., e Seama Koohi-Fayegh. "Thermal Interactions of Vertical Ground Heat Exchangers for Varying Seasonal Heat Flux". In Progress in Sustainable Energy Technologies: Generating Renewable Energy, 575–88. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07896-0_35.
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Žižková, Nikol, Jakub Hodul e Rostislav Drochytka. "Study on the Use of Glass By-Products for Sustainable Polymer-Modified Mortars". In Springer Proceedings in Materials, 268–79. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-72955-3_27.
Testo completoAbstract (sommario):
AbstractThis investigation is focused on the observation of changes in the properties of polymer-modified cement mortars caused by the addition of recycled glass. The current requirements for reducing CO2 emissions in the production of cement composites, are also forcing the producers of polymer-modified mortars (PMMs) to use alternative materials, such as silica-rich supplementary materials. Selected types of recycled glass with pozzolanic behavior were specifically ground (particle size below 63 μm) and used as a partial cement substitute (10 wt.%, 20 wt.% and 30 wt.% substitution of Portland cement). In order to explain the obtained results and garner new knowledge of the microstructure of the mixtures being studied, the following tests were performed: scanning electron microscopy (SEM) observation, differential thermal analysis (DTA) and high-pressure mercury intrusion porosimetry. The findings show that the finely ground recycled glass has high potential to be used as an effective cement replacement for PMM materials, that are currently used in large amounts, mainly in the rehabilitation of concrete structures.
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İsmail Tosun, Yıldırım. "Microwave Carbonation of Thermal Power Plant Flue Gas/CO2 by Fly Ash/Coal Char for Soil Remediation and Ground Stabilization". In Carbon-Based Material for Environmental Protection and Remediation. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.91342.
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Jamaladdeen, Rawaa, Bruno Coudour, Fabienne Dédaldéchamp, Laurent Lemée, Jean-Pierre Garo e Hui-Ying Wang. "Influence of combined hydric and thermal stresses on Rosmarinus officinalis and Cistus albidus". In Advances in Forest Fire Research 2022, 1665–70. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_255.
Testo completoAbstract (sommario):
Wildfires are a growing threat, especially in Mediterranean climate areas during periods of drought. Wildfire research community continues to investigate propagation mechanisms on a large scale considering the thermal and fluid mechanics effects, or the main fire emissions (CO, CO2, H2O, H2, CH4). However, research on the effect of abiotic stresses on the plant emission during wildfires remains lacking, despite the fact that Mediterranean are considered important BVOC emitting and storing species. This article addresses the effect of combined hydric and thermal stresses on the volatile’s emission behaviours of two important Mediterranean shrub species; Rosmarinus officinalis and Cistus albidus that are largely consumed in wildfires. Different levels of hydric stress were applied on plants of the two species in a greenhouse of the EBI laboratories of the University of Poitiers. Thermal stress was executed by placing the water stressed plants inside a hermetic enclosure equipped with a radiant panel of maximal radiant heat flux of 84kW.m-2 and a fire-resistant glazed window for visualisation. The gaseous emissions of the plants under thermal stresses were collected and analysed by two complementary devices: an instantaneous gas analyser for CO, CO2, H2 and CH4, and adsorbent tubes by using the techniques of adsorption and desorption (by pyrolysis) for emission collection and analyses, respectively. Simultaneous Py/GC-MS experiments were realised at IC2MP on a foliar scale of the water stressed plants in order to gain more control and precision in emission analyses. The heating tests showed a good reproducibility for pyrolyses of leaf samples and interesting variations between the monoterpene emissions of stressed and unstressed plants. At plant scale, number of tests for each plant species at a given hydric stress level were insufficient to give trends and strong results because of some imposed technical problems and the constraints of public health crisis. However, these tests allowed us to adapt experimental protocols and devices for further testing such as: plant location and fixation, heat flux ramp, sampling location, use of adsorbent tubes, hydric stress duration and normalisation of measured concentrations according to the plant size.
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Palomar Aguilar, David, Carlos Miguel Iglesias Sanz e Sofia Corsini Fuhrmann. "Ground Air Temperature Control for Heat Pump Exchange. APTAE System". In Advances in Civil and Industrial Engineering, 156–75. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-7279-5.ch008.
Testo completoAbstract (sommario):
Heating and cooling consume a high amount of energy, which is today mainly provided by fossil fuels. To save fossil resources and simultaneously reduce pollutants and CO2, heating and cooling energy consumption should be reduced. Geothermal energy is a clean, inexhaustible source of energy that is available all year round because it does not depend on the weather. Nevertheless, the use of tempered subsoil air has been used as a traditional air conditioning strategy; however, nowadays, its use has been questioned by the discovery of the leaks of radon gas from the ground. The investigation searches a heat exchange system with the subsoil which prevents the introduction of radon gas into living spaces. The system that is exposed increases the performance of aerothermal heat pumps by means of thermal exchange with tempered air in the sanitary chamber. This exchange is more favorable than air at the outside temperature, increasing the COP of the machine. This system complies with the regulations for protection against radon, protecting the building from this radioactive gas.
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Hernando Aramburo Varela, Carlos, Luiz Felipe de Pinho, César Pedrajas Nieto-Márquez e Rafael Talero Morales. "Activated Clays and Their Potential in the Cement Industry". In Clay and Clay Minerals [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99461.
Testo completoAbstract (sommario):
The thermal activation of clays to produce highly reactive artificial pozzolans on a large scale is one of the most important technologies developed on an industrial scale to reduce CO2 emissions in cement manufacture. This technical document deals with the scientific basis for the thermal activation of clays to produce an extraordinarily high quality supplementary cementitious material (SCM) based on the contents of its hydraulic factors, reactive silica (SiO2r–) and reactive alumina (Al2O3r–). The production process and the optimization of its use in the new cements offers better performance, features and durability. Furthermore, its mixture with Portland cement is much more appropriate when carried out in a blending station after both components, activated clay and Portland cement, are ground separately and not jointly in a single mill.
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Gutschick, Vincent P., e Keirith A. Snyder. "Water and Energy Balances within the Jornada Basin". In Structure and Function of a Chihuahuan Desert Ecosystem. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195117769.003.0012.
Testo completoAbstract (sommario):
This chapter describes general characteristics and components of the energy and water balances in arid regions, with specific examples from the Jornada Basin. Various research efforts to characterize the energy and water balances and resultant carbon dioxide fluxes in the Jornada Basin are detailed. We provide a brief overview of how plant physiology interacts with energy and water balances in this region, and characterize general abiotic conditions and some physiological traits of plants in this arid region. The surface of a landscape may be considered as a layer with some amount of vegetation. More general descriptions divide the vegetation, like the soil, into layers, but the concern here is energy balance at the interface with the atmosphere. The net energy balance of the land surface is determined by inputs (radiant energy), outputs (reflection [i.e., albedo], emission of longwave radiation, convective heat transfer to the atmosphere [i.e., sensible heat flux], evapotranspiration of water [i.e., latent heat flux], and conduction of heat into soil), and changes in heat storage. The balance of these terms is adjusted as the surface temperature comes into steady state or nearly so. Increased solar input will drive surface temperatures higher until longwave emission and other losses come into a new balance. The net energy input, as inputs minus outputs, may be stated formally as an energy-balance equation . . . Rate of heat storage = S = Q+sw + Q+TIR − Q+TIR _ Q_E Q_H − Q_S, (8-1) . . . where the superscript + indicates an input, and − indicates an output or loss, and all terms are expressed as flux density in units of W/m2. Q+SW is the energy added to the surface layer by solar radiation from above. Q+TIR is the thermal infrared radiation emitted by gases in the atmosphere, principally water vapor and CO2, whereas Q_TIR is the thermal infrared radiation emitted from components of the Earth’s surface and lost back to the atmosphere. Q_E is the latent heat flux from the heat of vaporization of water vapors resulting from soil evaporation (E) and plant transpiration, generally measured as the composite evapotranspiration flux (ET).
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Goody, R. M., e Y. L. Yung. "Radiation Calculations in a Clear Atmosphere". In Atmospheric Radiation. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195051346.003.0008.
Testo completoAbstract (sommario):
This chapter is concerned with the requirements of numerical weather prediction and general circulation models. These numerical models always assume a stratified atmosphere and utilize a limited number of grid points in the vertical direction. Computations are repeated at many horizontal grid points and at frequent time intervals; a premium is placed on computational economy. The nested integrals involved in radiative flux and heating calculations, particularly the frequency integration, can create an unacceptable computational burden unless approximated. In this chapter we limit attention to clear-sky conditions, i.e., to absorbing constituents and a thermal source function (§2.2). For a Planck function, the formal solution, (2.86), is a definite integral involving measurable quantities, temperatures, and gaseous densities. Scattering problems, on the other hand, involve the intensity in the source function and cannot be solved by a single application of this integral. Scattering calculations will be discussed further in Chapter 8; it will be shown that scattering can be neglected if the volume scattering coefficient is not very much larger than the volume absorption coefficient. This is usually the case for aerosols in the thermal region of the spectrum. As regards boundary conditions, it is usual for clear-sky calculations to assume that the earth’s surface and the upper and lower surfaces of clouds can be treated as black surfaces in the thermal spectrum. Equations (2.86) and (2.87) are stated in terms of general boundary conditions. In the flux and heating integrals, (2.106) and (2.110), these conditions are specialized to a black surface at ground level, but they can be generalized without difficulty to include a black surface at any level or partial reflection from these surfaces, if appropriate. The equations for which efficient algorithms are required are the flux equations, (2.107) and (2.108), the heating equations, (2.110) or (2.111), and the solar flux equations, (2.115). The nested integrals are 1. the vertical integral, (2.92), for the optical depth; 2. the integral, (2.86), along the optical path; 3. the angular integral, (2.102); 4. an integral over all frequencies. We may introduce the issues by considering a restricted example, that of the intensity recorded outside the atmosphere by a downward pointing satellite spectrometer.
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Singh, Sudhansu Sekhar, Abinash Sahoo, Ramesh Chandra Nayak, Krutibash Khuntia e Prabina Pratyus Sendha. "SHIFTING OF HEAT ENERGY VIA TRANSVERSE PARALLEL SHEETS CONFIRMED WITH NATURAL CONVECTION". In Futuristic Trends in Mechanical Engineering Volume 3 Book 6, 181–91. Iterative International Publisher, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3bgme6p3ch1.
Testo completoAbstract (sommario):
Due to the progression in each and every aspect concern with energy production, utilization and harnessing of the same has been drastically optimized. The energy draws out from heat sources is one of a type among all convectional and non-convectional sources of energies. The pattern of heat energy shift through natural convection has a number of applications found in the market .The uses of this kind of energy can be listed as electrical and electronics equipments, nuclear reactors, domestic convection, dry cooling towers, thermo siphons, installed in ground and many more. On the account of functional continuity and longevity aspect the heat generates due to work execution must be radiated out of the machineries. Considering the influence concern with heat energy shift upon the untie finished pipes of upright means, it is of very trivial magnitude, As a matter of fact, the diverse field of solar and nuclear energy connecting with thermal fluid systems has also been greatly impacted by natural convection heat energy flow. Converging to the current event where heat energy shifts between two parallel flat plates excited electrically on the external region of the units to keeping steady heat flux at the boundary. The magnitude pertaining with parameters/edges like thickness, Breadth and length are 5mm, 150mm and 500 mm correspondingly. Since the exterior region maintained insulation, hence the shifting of heat energy is admitted to regulate from interior region towards the adjoined air molecules .The particular wall heat energy flux denoted by the symbol ‘q’ maintained at a magnitude of 2188W/m2.consequent to this a definite analytical as well as observational values adhering with steady state phenomena has been laid out. Keeping the heat flux status same the temp values drawn out analytically on behalf of air and wall units have successfully monitored against the particular experimental values. The outcomes concern with both the approaches match with one another yielding the heat flux magnitude of 2188W/m2.
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Saha, Saurav, Burhan Uddin Choudhury, Bappa Das e Prashant Pandey. "Dynamics of Plant Water Uptake under Modified Environment". In New Insights in Soil-Water Relationship. IntechOpen, 2024. http://dx.doi.org/10.5772/intechopen.109421.
Testo completoAbstract (sommario):
The environmental control of crop physiology increases relative sensitivity of crop water movement within the soil plant atmosphere continuum (SPAC), so as the dynamics of crop water usage under modified climate. The variable environmental conditions determine the relative direction of change. Elevated CO2 exposure depressed the water movement of transpiration flux through reduced stomatal conductance and facilitated partial stomatal closure. However, the net impact may not be ensued the significant reduction in crop water usage at the end of crop season due to modified leaf area dynamics, but with obvious rise in crop water use efficiency (WUE). Thermal stresses are often combined with drought events depressed crop WUE beyond a threshold sourced from adverse impact on total dry matter production under elevated temperature condition. The pathogenic role of O3 exposure induced stomatal sluggishness and reduction in dry matter accumulation (or yield) are sourced from reduced photosynthetic assimilation and aberration in stomatal conductance and thereby reduction in crop WUE under well-watered condition. However, the protective roles of other co-existing abiotic stress factors are subjected to more explanatory research. However, the genetic resilience toward such climate change induced abiotic stress factors and supportive field management options will provide our future facets of sustainable crop production with higher WUE crop under variable environmental conditions.
Atti di convegni sul tema "Thermal and ground CO2 flux"
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Reilly, Sean W., Ladan Amouzegar e Ivan Catton. "Comparison of Vacuum Chamber Tested Biporous Wicks With Thermal Ground Plane Testing". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22947.
Testo completoAbstract (sommario):
Investigation of bi-porous wicks has yielded an effective method for increasing surface heat transfer when the heat flux is high. It was further found that addition of a mono-porous layer on the heated surface significantly reduced the heated wall surface temperature. These bi-layer wicks were designed for use in 3″×5″ heat spreading devices called Thermal Ground Planes (TGP) in order to transfer heat from a 1 cm2 source. In this work we will investigate the performance of a biporous wick with a monoporous layer in various test set-ups to show the versatility of this heat pipe-substrate. Tests were performed at UCLA and at Advanced Cooling Technologies (ACT) to investigate the wick. Experiments at UCLA were conducted in a vacuum chamber setup to isolate the performance of the wick whereas at ACT the wick lined the evaporator side of a TGP. In order to more closely simulate the operating conditions in a TGP and characterize the vapor spacing parameter, some tests at UCLA were performed with a restrictor plate above the wick similar to the space above the wick in the TGP. The data collected using both these experiments showed similar trends of performance as a function of the spacing above the wick. The motivation of this paper is then to validate that the two testing methods provide similar results while independently addressing different parameters.
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Badache, Messaoud. "Thermal resistance of a CO2 geothermal thermosyphon with an active condenser". In International Ground Source Heat Pump Association. International Ground Source Heat Pump Association, 2024. http://dx.doi.org/10.22488/okstate.24.000038.
Testo completoAbstract (sommario):
In this study, an experimental setup was built and fully instrumented to investigate the thermal resistance of a CO2 geothermal thermosyphon (GT) with an active condenser connected to its upper section. The study explores the effects of CO2 filling ratios, cooling fluid flow rate and temperature on the thermal resistance in different zones of the experimental GT system. The results show that the total thermal resistance of the GT stands out, displaying a notably higher value, up to 12 times that of the active condenser. Furthermore, the thermal resistance of the active condenser is higher than those of the evaporator and condenser sections, being up to 3 and 7 times higher, respectively. Therefore, reducing the thermal resistance of the active condenser and between the evaporator wall and the ground represents the most effective approach to enhance the performance of the GT system. These findings offer valuable insights for the efficient design of GT systems with active condensers, identifying areas where improvements can be made to maximize GT performance.
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Zhu, Yan, e Keith Cherkauer. "Estimation of crop latent heat flux from high resolution thermal imagery". In Autonomous Air and Ground Sensing Systems for Agricultural Optimization and Phenotyping IV, a cura di J. Alex Thomasson, Mac McKee e Robert J. Moorhead. SPIE, 2019. http://dx.doi.org/10.1117/12.2519216.
Testo completo
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Xu, Shanshan, Ryan Lewis, Rongfu Wen, Ronggui Yang, Yung-Cheng Lee, Woochan Kim e Luu Nguyen. "Micromesh-Enabled Low-Cost Thermal Ground Planes for High Heat Flux Power Electronics". In 2018 IEEE 68th Electronic Components and Technology Conference (ECTC). IEEE, 2018. http://dx.doi.org/10.1109/ectc.2018.00338.
Testo completo
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Duva, Berk Can, Yen-Cheng Wang, Lauren Elizabeth Chance e Elisa Toulson. "Laminar Flame Characteristics of Sequential Two-Stage Combustion of Premixed Methane/Air Flames". In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14114.
Testo completoAbstract (sommario):
Abstract Due to their high load flexibility and air-quality benefits, axial (sequential) stage combustion systems have become more popular among ground-based power gas turbine combustors. However, inert combustion residuals passing from the initial stage onto the secondary stage affects the reactivity and stability of the flame in the second stage of the combustor. The present study investigates laminar flame characteristics of the combustion within the second stage of a sequential combustor. The method of constant pressure for spherically expanding flames was employed to obtain laminar burning velocities (LBV) and burned gas Markstein lengths (Lb) of premixed methane/air mixtures diluted using flue gas at 3 bar and 423 K. Combustion residuals were imitated using a 19.01% H2O + 9.50% CO2 + 71.49% N2 mixture by volume, while tested dilution ratios were 0%, 5%, 10%, and 15%. Experimental results showed that the LBV was decreased by 18–23%, 36–42%, and 50–52% with additions of 5%, 10%, and 15% combustion products, respectively. As the dilution and equivalence ratios increased, the Lb values increased slightly, suggesting that the stability and stretch of the CH4/air flames increased at these conditions. Numerical results were obtained from CHEMKIN using the GRI-Mech 3.0, USC Mech II, San Diego, HP-Mech, NUI Galway, and AramcoMech 1.3 mechanisms. The GRI-Mech 3.0 and HP-Mech performed best, with an average of 2% and 3% difference between numerical and experimental LBVs, respectively. The thermal-diffusion (TD), dilution (D), and the chemical (C) effects of inert post-combustion gases on the LBV were found using numerical results. The dilution effect was primarily responsible, accounting for 79–84% of the LBV reduction.
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Herner, Reed, Alexander Foutch, Kelsa Palomares, Adam Boylston e Lindsey Holmes. "Dose Impacts from Fission Products and Flux Fields for Nuclear Thermal Propulsion Ground Testing". In Nuclear and Emerging Technologies for Space (NETS 2023). Illinois: American Nuclear Society, 2023. http://dx.doi.org/10.13182/nets23-41926.
Testo completo
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DiCarlo, Anthony A., e Rickey A. Caldwell. "Gradient Based Soil Thermal Conductivity Optimization for Ground Source Heat Exchangers". In ASME 2018 12th International Conference on Energy Sustainability collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/es2018-7418.
Testo completoAbstract (sommario):
In geothermal heating and cooling, there exists an opportunity to improve the efficiency by utilizing non-uniform soil properties of a ground source heat exchanger during installation. This paper presents a gradient approach based upon finite element mathematics to determine an optimal distribution of heterogeneous soils with varying thermal conductivities. The numerically simulated case studies demonstrate the good performance of this algorithm to minimize the cross-talk of heat flux between pipes and maximize the overall efficiency.
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Mansur, Yamin, Md Ahosan Habib, Titan C. Paul e A. K. M. Monjur Morshed. "Comparative Analysis of Thermal and Hydraulic Performance of a Mini-Channel Heat Sink With Supercritical Carbon Dioxide and Water Coolants". In ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-113484.
Testo completoAbstract (sommario):
Abstract This study investigates the heat transfer performance of supercritical carbon dioxide (s-CO2) in comparison to water as a coolant within circular tubes. The study was conducted numerically using the commercially available software FLUENT. The study was conducted for the s-CO2 for the temperature range of 305 K to 316 K at 8 MPa covering the pseudocritical temperature for the CO2. The thermal and hydraulic performance, including heat transfer coefficient and pressure drop, under varying inlet temperature, mass flux, and heat flux conditions, were evaluated and compared with those of water. The study finds that for s-CO2, the heat transfer coefficient reaches its peak value at the pseudocritical temperature, which is around 307.9K at an operating pressure of 8 MPa. The bulk fluid temperature ranging from 306 K to 308 K offers better thermal and hydraulic performance for s-CO2, with a higher heat transfer coefficient and lower pressure drop than water. However, beyond this temperature range, both the heat transfer coefficient and pressure drop of s-CO2 become worse than water. Furthermore, the study observes that the heat transfer coefficient for s-CO2 increases with mass flux, similar to water. However, the slope is steeper than water, and it becomes steepest at an inlet temperature of 308K. An interesting trend for s-CO2 is noted, as the heat transfer coefficient decreases with an increase in heat flux beyond the peak temperature (the temperature at which the maximum heat flux was observed). Conversely, the reverse scenario has been observed prior to the peak temperature. Water, on the other hand, does not show any significant change in this regard. The thermophysical properties of s-CO2, including specific heat capacity, density, thermal conductivity, and viscosity, around its pseudocritical temperature at 308 K (at 8 MPa) are critical for interpreting these results. The study identifies the optimum conditions at which s-CO2 proves to be better than conventional coolants such as water.
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Zhao, Zhenxing, Jun Wu, Fan Bai, Qi Xiao, Chunhui Dai, Zhouyang Liu, Yong Liu e Mo Tao. "Numerical Investigation on Heat Transfer to Supercritical CO2 in Vertical Annular Channel". In 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-60236.
Testo completoAbstract (sommario):
The special fluid flow and heat transfer characteristics of supercritical CO2 in a vertical annular channel have been numerically investigated. The AKN k-ε model was selected to model the turbulent flow and heat transfer of supercritical fluid. The three heating types were individual outer-wall heating, simultaneous outer/inner walls heating and outer-wall heating (inner-wall cooling) separately. The local heat transfer coefficients were obtained to investigate the influence of inner-wall thermal boundary conditions, supercritical fluid mass flux, fluid temperature and flow direction on outer-wall heat transfer phenomenon. The mechanisms of abnormal heat transfer and primary influence factors were analyzed by the detailed information on the flow, turbulence and thermal fields. When the supercritical fluid is in the large-property-variation (LPV) region and flows upward, the inner-wall thermal boundary condition obviously affects the heat transfer characteristics of outer wall. When supercritical fluid flows downward, the inner-wall boundary condition hardly affects the heat transfer phenomena of outer wall. The increase of inner-wall heating heat flux will result in the larger deterioration region and heat transfer decline on outer wall when the other conditions remain unchanged. When the heat transfer deterioration also appears on the inner wall with the increase in the inner-wall heat flux, the outer-wall heat transfer no longer decreases, but the deterioration region abruptly increases. However, as inner-wall cooling heat flux increases, the heat transfer deterioration phenomenon on outer wall will weaken gradually.
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Kayaci, Nurullah, Hakan Demir, Ş. Özgür Atayılmaz e Özden Ağra. "Long Term Simulation of Horizontal Ground Heat Exchanger for Ground Source Heat Pump". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51552.
Testo completoAbstract (sommario):
The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. GHEs is commonly sized according to short time (one year or less) simulation algorithms. Variation of soil temperature in long time period is more important and, therefore, long term simulation is required to be assure the performance of the GSHP system. In this study, long time (10 years) simulation for parallel pipe GHE of a GSHP system was performed numerically with dynamical boundary conditions. In the numerical study ANSYS CFD package was used. This package uses a technique based on control volume theory to convert the governing equations to algebraic equations so they can be solved numerically. The control volume technique works by performing the integration of the governing equations about each control volume, and then generates discretization of the equations which conserve each quantity based on control volume. Thermal boundary conditions can be defined in four different types in ANSYS Fluent: Constant heat flux, constant temperature, convection-radiation and convection. In this study, periodic variation of air temperature boundary at upper surface condition is applied, the lateral and bottom surface of the solution domain are defined as adiabatic wall type boundary condition; the pipe inner surface is taken as wall with a constant heat flux. In order to provide the periodic variation of air temperature boundary at upper surface condition a User Defined Function (UDF) was written and interpreted in ANSYS Fluent. Likewise, a UDF was also written to give constant heat flux intermittently for the pipe inner surface. Constant heat flux of 10, 20, 30 W per unit length of pipe used for calculations. Effects of distance between pipes and thermal conductivity on temperature distribution in the soil were investigated. Heat transfer in the soil is time dependent three dimensional heat conduction with dynamical boundary conditions. Temperature distribution in soil were obtained and storage effect of the soil has also been investigated. An optimization methodology based on long term simulation of GHE was suggested.
Rapporti di organizzazioni sul tema "Thermal and ground CO2 flux"
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Madrzykowski, Daniel. Firefighter Equipment Operational Environment: Evaluation of Thermal Conditions. UL Firefighter Safety Research Institute, agosto 2017. http://dx.doi.org/10.54206/102376/igfm4492.
Testo completoAbstract (sommario):
The goal of this study was to review the available literature to develop a quantitative description of the thermal conditions firefighters and their equipment are exposed to in a structural fire environment. The thermal exposure from the modern fire environment was characterized through the review of fire research studies and fire-ground incidents that provided insight and data to develop a range of quantification. This information was compared with existing standards for firefighting protective equipment to generate a sense of the gap between known information and the need for improved understanding. The comparison of fire conditions with the thermal performance requirements of firefighter protective gear and equipment demonstrates that a fire in a compartment can generate conditions that can fail the equipment that a firefighter wears or uses. The review pointed out the following: 1. The accepted pairing of gas temperature ranges with a corresponding range of heat fluxes does not reflect all compartment fire conditions. There are cases in which the heat flux exceeds the hazard level of the surrounding gas temperature. 2. Thermal conditions can change within seconds. Experimental conditions and incidents were identified in which firefighters would be operating in thermal conditions that were safe for operation based on the temperature and heat flux, but then due to a change in the environment the firefighters would be exposed to conditions that could exceed the protective capabilities of their PPE. 3. Gas velocity is not explicitly considered within the thermal performance requirements. Clothing and equipment tested with a hot air circulating (convection) oven are exposed to gas velocities that measure approximately 1.5 m/s (3 mph). In contrast, the convected hot gas flows within a structure fire could range from 2.3 m/s (5 mph) to 7.0 m/s (15 mph). In cases where the firefighter or equipment would be located in the exhaust portion of a flow path, while operating above the level of the fire, the hot gas velocity could be even higher. This increased hot gas velocity would serve to increase the convective heat transfer rate to the equipment and the firefighter, thereby reducing the safe operating time within the structure. 4. Based on the limited data available, it appears currently available protective clothing enables firefighters to routinely operate in conditions above and beyond the "routine" conditions measured in the fire-ground exposure studies conducted during the 1970s. The fire service and fire standards communities could benefit from an improved understanding of: • real world fire-ground conditions, including temperatures, heat flux, pressure, and chemical exposures; • the impact of convection on the thermal resistance capabilities of firefighting PPE and equipment; and • the benefits of balancing the thermal exposures (thermal performance requirements) across different components of firefighter protective clothing and safety equipment. Because it is unlikely due to trade offs in weight, breathe-ability, usability, cost, etc., that fireproof PPE and equipment will ever be a reality, fire officers and fire chiefs need to consider the capabilities of the protection that their firefighters have when determining fire attack strategies and tactics to ensure that the PPE and equipment is kept within its design operating environment, and that the safety buffer it provides is maintained.
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Zevotek, Robin, Keith Stakes e Joseph Willi. Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival: Full-Scale Experiments. UL Firefighter Safety Research Institute, gennaio 2018. http://dx.doi.org/10.54206/102376/dnyq2164.
Testo completoAbstract (sommario):
As research continues into how fire department interventions affect fire dynamics in the modern fire environment, questions continue to arise on the impact and implications of interior versus exterior fire attack on both occupant survivability and firefighter safety. This knowledge gap and lack of previous research into the impact of fire streams has driven the need for further research into fire department interventions at structure fires with a focus on hose streams and suppression tactics. As the third report in the project “Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival”, this report expands upon the fire research conducted to date by analyzing how firefighting tactics, specifically suppression methods, affect the thermal exposure and survivability of both building occupants and firefighters in residential structures. • Part I: Water Distribution • Part II: Air Entrainment • Part III: Full-Scale Residential Fire Experiments. This report evaluates fire attack in residential structures through twenty-six full-scale structure fire experiments. Two fire attack methods, interior and transitional, were preformed at UL’s large fire lab in Northbrook, IL, in a single-story 1,600 ft2 ranch test structure utilizing three different ventilation configurations. To determine conditions within the test structure it was instrumented for temperature, pressure, gas velocity, heat flux, gas concentration, and moisture content. Ad- ditionally, to provide information on occupant burn injuries, five sets of instrumented pig skin were located in pre-determined locations in the structure. The results were analyzed to determine consistent themes in the data. These themes were evaluated in conjunction with a panel of fire service experts to develop 18 tactical considerations for fire ground operations. As you review the following tactical considerations it is important to utilize both these research results and your per- sonal experience to develop your department’s polices and implement these considerations during structural firefighting.