Conjugate heat transfer effects on gas turbine film cooling : including thermal fields, thermal barrier coating, and contaminant deposition

textThe efficiency of natural gas turbines is directly linked to the turbine inlet temperature, or the combustor exit temperature. Further increasing the turbine inlet temperature damages the turbine components and limits their durability. Advances in turbine vane cooling schemes protect the turbine components. This thesis studies the conjugate effects of internal cooling, film cooling and thermal barrier coatings (TBC) on turbine vane metal temperatures. Two-dimensional thermal profiles were experimentally measured downstream of a single row of film cooling holes on both an adiabatic and a matched Biot number model turbine vane. The measurements were taken as a comparison to computational simulations of the same model and flow conditions. To improve computational models of the evolution of a film cooling jet as it propagates downstream, the thermal field above the vane, not just the footprint on the vane surface must be analyzed. This study expands these data to include 2-D thermal fields above the vane at 0, 5 and 10 hole diameters downstream of the film cooling holes. In each case the computational jets remained colder than the experimental jets because they did not disperse into the mainstream as quickly. Finally, in comparing results above adiabatic and matched Biot number models, these thermal field measurements allow for an accurate analysis of whether or not the adiabatic wall temperature was a reasonable estimate of the driving temperature for heat transfer. In some cases the adiabatic wall temperature did give a good indication of the driving temperature for heat transfer while in other cases it did not. Previous tests simulating the effects of TBC on an internally and film cooled model turbine vane showed that the insulating effects of TBC dominate over variations in film cooling geometry and blowing ratio. In this study overall and external effectiveness were measured using a matched Biot number model vane simulating a TBC of thickness 0.6d, where d is the film cooing hole diameter. This new model was a 35% reduction in thermal resistance from previous tests. Overall effectiveness measurements were taken for an internal cooling only configuration, as well as for three rows of showerhead holes with a single row of holes on the pressure side of the vane. This pressure side row of holes was tested both as round holes and as round holes embedded in a realistic trench with a depth of 0.6 hole diameters. Even in the case of this thinner TBC, the insulating effects dominate over film cooling. In addition, using measurements of the convective heat transfer coefficient above the vane surface, and the thermal conductivities of the vane wall and simulated TBC material, a prediction technique of the overall effectiveness with TBC was evaluated.Mechanical Engineerin

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Behavioral responses of terrestrial mammals to COVID-19 lockdowns

DATA AND MATERIALS AVAILABILITY : The full dataset used in the final analyses (33) and associated code (34) are available at Dryad. A subset of the spatial coordinate datasets is available at Zenodo (35). Certain datasets of spatial coordinates will be available only through requests made to the authors due to conservation and Indigenous sovereignty concerns (see table S1 for more information on data use restrictions and contact information for data requests). These sensitive data will be made available upon request to qualified researchers for research purposes, provided that the data use will not threaten the study populations, such as by distribution or publication of the coordinates or detailed maps. Some datasets, such as those overseen by government agencies, have additional legal restrictions on data sharing, and researchers may need to formally apply for data access. Collaborations with data holders are generally encouraged, and in cases where data are held by Indigenous groups or institutions from regions that are under-represented in the global science community, collaboration may be required to ensure inclusion.COVID-19 lockdowns in early 2020 reduced human mobility, providing an opportunity to disentangle its effects on animals from those of landscape modifications. Using GPS data, we compared movements and road avoidance of 2300 terrestrial mammals (43 species) during the lockdowns to the same period in 2019. Individual responses were variable with no change in average movements or road avoidance behavior, likely due to variable lockdown conditions. However, under strict lockdowns 10-day 95th percentile displacements increased by 73%, suggesting increased landscape permeability. Animals’ 1-hour 95th percentile displacements declined by 12% and animals were 36% closer to roads in areas of high human footprint, indicating reduced avoidance during lockdowns. Overall, lockdowns rapidly altered some spatial behaviors, highlighting variable but substantial impacts of human mobility on wildlife worldwide.The Radboud Excellence Initiative, the German Federal Ministry of Education and Research, the National Science Foundation, Serbian Ministry of Education, Science and Technological Development, Dutch Research Council NWO program “Advanced Instrumentation for Wildlife Protection”, Fondation Segré, RZSS, IPE, Greensboro Science Center, Houston Zoo, Jacksonville Zoo and Gardens, Nashville Zoo, Naples Zoo, Reid Park Zoo, Miller Park, WWF, ZCOG, Zoo Miami, Zoo Miami Foundation, Beauval Nature, Greenville Zoo, Riverbanks zoo and garden, SAC Zoo, La Passarelle Conservation, Parc Animalier d’Auvergne, Disney Conservation Fund, Fresno Chaffee zoo, Play for nature, North Florida Wildlife Center, Abilene Zoo, a Liber Ero Fellowship, the Fish and Wildlife Compensation Program, Habitat Conservation Trust Foundation, Teck Coal, and the Grand Teton Association. The collection of Norwegian moose data was funded by the Norwegian Environment Agency, the German Ministry of Education and Research via the SPACES II project ORYCS, the Wyoming Game and Fish Department, Wyoming Game and Fish Commission, Bureau of Land Management, Muley Fanatic Foundation (including Southwest, Kemmerer, Upper Green, and Blue Ridge Chapters), Boone and Crockett Club, Wyoming Wildlife and Natural Resources Trust, Knobloch Family Foundation, Wyoming Animal Damage Management Board, Wyoming Governor’s Big Game License Coalition, Bowhunters of Wyoming, Wyoming Outfitters and Guides Association, Pope and Young Club, US Forest Service, US Fish and Wildlife Service, the Rocky Mountain Elk Foundation, Wyoming Wild Sheep Foundation, Wild Sheep Foundation, Wyoming Wildlife/Livestock Disease Research Partnership, the US National Science Foundation [IOS-1656642 and IOS-1656527, the Spanish Ministry of Economy, Industry and Competitiveness, and by a GRUPIN research grant from the Regional Government of Asturias, Sigrid Rausing Trust, Batubay Özkan, Barbara Watkins, NSERC Discovery Grant, the Federal Aid in Wildlife Restoration act under Pittman-Robertson project, the State University of New York, College of Environmental Science and Forestry, the Ministry of Education, Youth and Sport of the Czech Republic, the Ministry of Agriculture of the Czech Republic, Rufford Foundation, an American Society of Mammalogists African Graduate Student Research Fund, the German Science Foundation, the Israeli Science Foundation, the BSF-NSF, the Ministry of Agriculture, Forestry and Food and Slovenian Research Agency (CRP V1-1626), the Aage V. Jensen Naturfond (project: Kronvildt - viden, værdier og værktøjer), the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy, National Centre for Research and Development in Poland, the Slovenian Research Agency, the David Shepherd Wildlife Foundation, Disney Conservation Fund, Whitley Fund for Nature, Acton Family Giving, Zoo Basel, Columbus, Bioparc de Doué-la-Fontaine, Zoo Dresden, Zoo Idaho, Kolmården Zoo, Korkeasaari Zoo, La Passarelle, Zoo New England, Tierpark Berlin, Tulsa Zoo, the Ministry of Environment and Tourism, Government of Mongolia, the Mongolian Academy of Sciences, the Federal Aid in Wildlife Restoration act and the Illinois Department of Natural Resources, the National Science Foundation, Parks Canada, Natural Sciences and Engineering Research Council, Alberta Environment and Parks, Rocky Mountain Elk Foundation, Safari Club International and Alberta Conservation Association, the Consejo Nacional de Ciencias y Tecnología (CONACYT) of Paraguay, the Norwegian Environment Agency and the Swedish Environmental Protection Agency, EU funded Interreg SI-HR 410 Carnivora Dinarica project, Paklenica and Plitvice Lakes National Parks, UK Wolf Conservation Trust, EURONATUR and Bernd Thies Foundation, the Messerli Foundation in Switzerland and WWF Germany, the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Actions, NASA Ecological Forecasting Program, the Ecotone Telemetry company, the French National Research Agency, LANDTHIRST, grant REPOS awarded by the i-Site MUSE thanks to the “Investissements d’avenir” program, the ANR Mov-It project, the USDA Hatch Act Formula Funding, the Fondation Segre and North American and European Zoos listed at http://www.giantanteater.org/, the Utah Division of Wildlife Resources, the Yellowstone Forever and the National Park Service, Missouri Department of Conservation, Federal Aid in Wildlife Restoration Grant, and State University of New York, various donors to the Botswana Predator Conservation Program, data from collared caribou in the Northwest Territories were made available through funds from the Department of Environment and Natural Resources, Government of the Northwest Territories. The European Research Council Horizon2020, the British Ecological Society, the Paul Jones Family Trust, and the Lord Kelvin Adam Smith fund, the Tanzania Wildlife Research Institute and Tanzania National Parks. The Eastern Shoshone and Northern Arapahoe Fish and Game Department and the Wyoming State Veterinary Laboratory, the Alaska Department of Fish and Game, Kodiak Brown Bear Trust, Rocky Mountain Elk Foundation, Koniag Native Corporation, Old Harbor Native Corporation, Afognak Native Corporation, Ouzinkie Native Corporation, Natives of Kodiak Native Corporation and the State University of New York, College of Environmental Science and Forestry, and the Slovenia Hunters Association and Slovenia Forest Service. F.C. was partly supported by the Resident Visiting Researcher Fellowship, IMéRA/Aix-Marseille Université, Marseille. This work was partially funded by the Center of Advanced Systems Understanding (CASUS), which is financed by Germany’s Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament. This article is a contribution of the COVID-19 Bio-Logging Initiative, which is funded in part by the Gordon and Betty Moore Foundation (GBMF9881) and the National Geographic Society.https://www.science.org/journal/sciencehj2023Mammal Research InstituteZoology and Entomolog

Heat Transfer Analysis of a Conceptual Horizontally-Oriented High Temperature Gas-Cooled Reactor

Abstract High temperature gas-cooled reactors (HTGRs) have been constructed around the world since the 1960s. Compared to light water reactors, HTGRs feature a low core power density, which ultimately results in the need for larger components and structures. The successful widespread deployment of HTGRs will likely require a significant reduction in reactor building size per kW, to compete with other sources of carbon-free energy. The Modular Integrated Gas-cooled High Temperature Reactor (MIGHT-R) has been recently proposed to leverage inherent safety characteristics of HTGRs and its proven technology, while increasing its reactor building power density by 4 to 5 times. Contrarily to the vertical side-by-side orientation of the reactor core and steam generator of the typical HTGR design, the MIGHTR primary system components are laid horizontally, inline with one another. In this paper, a design embodiment of MIGHT-R concept is presented and preliminary heat transfer analysis under normal operating conditions is performed adopting a simplified porous representation of the flow behavior inside the reactor core and steam generator. The predicted mass flow rates in the fuel region, inner reflectors and outer reflectors agree with analytical estimations. A set of sensitivity tests for components variations are presented to provide insights on the influence of design parameters. A preliminary design reactor cavity cooling system (RCCS) is presented which is basically a 100 °C “water shell” surrounding the reactor vessel and it only covers the reactor core regions. Comparison of the same design with different orientations is also made and indicates that the mass flow and temperature distribution inside the reactor core have low dependence on orientation. Based on the computational results, the stratification of the coolant in the horizontal configuration for normal operation is deemed negligible. The presented work supports the normal operation feasibility of a horizontally-oriented HTGR concept with its potential to significantly reduce HTGR capital cost.</jats:p

The archaeogenetics of Europe

A new timescale has recently been established for human mitochondrial DNA (mtDNA) lineages, making mtDNA at present the most informative genetic marker system for studying European prehistory. Here, we review the new chronology and compare mtDNA with Y-chromosome patterns, in order to summarize what we have learnt from archaeogenetics concerning five episodes over the past 50,000 years which significantly contributed to the settlement history of Europe: the pioneer colonisation of the Upper Palaeolithic, the Late Glacial re-colonisation of the continent from southern refugia after the Last Glacial Maximum, the postglacial re-colonization of deserted areas after the Younger Dryas cold snap, the arrival of Near Easterners with an incipient Neolithic package, and the small-scale migrations along continent-wide economic exchange networks beginning with the Copper Age. The available data from uniparental genetic systems have already transformed our view of the prehistory of Europe, but our knowledge of these processes remains limited. Nevertheless, their legacy remains as sedimentary layers in the gene pool of modern Europeans, and our understanding of them will improve substantially when more mtDNAs are completely sequenced, the Y chromosome more thoroughly analysed, and haplotype blocks of the autosomal genome become amenable to phylogeographic studies