Dissertations / Theses on the topic 'Rewetting'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 47 dissertations / theses for your research on the topic 'Rewetting.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Ilyas, Muhammad. "Rewetting processes during PWR reflood." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6378.
Full textMao, Chris Qun. "Local rewetting and distortion of paper." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62919.pdf.
Full textPereira, Paulo Manuel Sendim Aires. "Heat transfer in rewetting of hot surfaces." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/7284.
Full textEngelhardt, Ilonka. "Impact of changing precipitation patterns on the plant-microbial response to rewetting." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK017/document.
Full textWater availability governs terrestrial nutrient cycles by impacting the functioning of both plants and of soil microorganisms. The predicted changes in precipitation patterns (i.e. the magnitude and frequency of precipitation events) associated with climate change, will thus likely have important consequences on ecosystem functioning. Dry and seasonally dry ecosystems are particularly vulnerable to changes in precipitation patterns, as they are already constrained to a large extent by water availability. However, more mesic systems may also experience dry periods that may impact plant-soil functions. In this thesis, experiments in soil-only systems and plant-soil systems were used to gain insight into how the legacy effects of several weeks of exposure to contrasted precipitation patterns set the scene for the rewetting response of the system. First, in an experiment using soil-only mesocosms, we evaluated the effects of contrasting precipitation regimes on the actively growing as well as the inactive bacterial and fungal communities 2 and 5 days after rewetting, using an 18O-SIP (stable isotope probing) approach by applying H218O followed by metagenomics targeting soil bacteria and fungi. Second, we performed two separate and complementary experiments using plant-soil mesocosms with wheat plant cover. The first plant-soil experiment focused on soil depth. It determined the effects of contrasting precipitation patterns on the flux of C from plants to microbes and the microbial response to rewetting at different soil depths, using a heavy isotope tracer approach (13C-CO2) and 18O-SIP with metagenomics respectively. The second plant-soil experiment evaluated the effects of a history of contrasting precipitation patterns on the dynamics of the rewetting response of the plant-soil system over time (over 29 hours post-rewetting). In addition, two levels of N inputs allowed to determine how N availability modulated plant-soil responses. The response of the potentially active soil bacterial and fungal communities to rewetting was assessed using targeted metagenomics. The responses of biogeochemical cycles were evaluated using heavy isotope tracers (13C-CO2 and 15N-NO3-) to quantify C flux from plants to soil microorganisms and plant-microbial competition for N over time post-rewetting.We found that precipitation patterns shaped plant morphology and physiology, microbial community composition as well as soil N cycling in our systems, which set contrasting scenes for the rewetting responses in our systems. In particular, infrequent precipitation patterns (cycles of longer dry periods followed by larger magnitude rain events) resulted in increased microbial N transformation potentials and smaller inorganic N pools. The rewetting responses were determined by evaluating C dynamics (plant-microbial coupling and soil CO2 efflux rate), N dynamics (plant-microbial competition for N and soil N2O efflux rate) and microbial dynamics (composition of active and potentially active bacterial and fungal communities after rewetting). First, we found that plant-microbial coupling (i.e the microbial assimilation of C from fresh photosynthate) may be reduced under more infrequent precipitation patterns, especially near the soil surface, and under conditions of low N availability. Our findings also suggest that whilst in soil-only systems, dead microbial cells appear to be a major source fuelling soil CO2 efflux pulse upon rewetting, in plant-soil systems root respiration plays an important role in the magnitude of the CO2 efflux upon rewetting. Second, concerning soil N dynamics, we found, in concurrence with previous studies, that soil microorganisms were the stronger competitor for N over short time scales, likely due to their overall fast response rates and high affinity for substrate, whilst plants outcompeted soil microbes for soil N assimilation, over longer time scales likely taking advantage of the fast microbial turnover (...)
Lee, Sung-Ching. "Annual greenhouse gas budget for a bog ecosystem undergoing restoration by rewetting." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58985.
Full textArts, Faculty of
Geography, Department of
Graduate
Silva, Ana Beatriz de Albuquerque Morais. "Phosphorous cycling in dry and rewet incubated soils subjected to different fertilization histories." Master's thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/3919.
Full textPhosphorus continuous application in fertilizers, in quantities superior to those required by plants causes a P buildup in soils, potentially increasing nutrient losses and compromising water quality by eutrophication process. This work was aimed at assessing the effect of DRW cycles, in two soils with different fertilization histories subjected to organic and mineral fertilization, over P availability. Soils were collected from a long-term fertilizer management platform (NW Italy) divided in two plots experiencing since 1996 different fertilization management (one plot fertilized with low N and K levels and no P and another with fertilization high on N and P levels), and each was divided in 3 subplots treated with mineral, compost and without fertilization, since 2010. The soils were subjected, under laboratory conditions, to four DRW cycles and compared with another set at constant moisture. Weekly the soils were sampled and analyzed for some of their P forms. Soluble P increased in compost fertilized soil, especially after the third dry and rewet cycle, following microbial decay. Yet, this was more pronounced in the overfertilized soils. From these findings it is possible to conclude that the availability of P may be further enhanced by water content variations as by compost addition.
Henstra, Steven W. "Vegetation responses to ecological restoration (rewetting) of abandoned block-cut peatlands in eastern Québec." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/40829.
Full textSjöstrand, Björn. "Dewatering aspects at the forming section of the paper machine : Rewetting and forming fabric structure." Licentiate thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-47640.
Full textThis thesis quantifies aspects of dewatering such as rewetting and the influence of the forming fabric. Understanding these dewatering aspects further provides for the potential enhancement of energy efficiency in the forming section, and thereby the entire papermaking process. The forming fabric can play an important role in improving energy efficiency: rewetting after the high vacuum suction boxes occurs more rapidly than was previously known, so its design might be the only possible way of impeding it. The forming fabric can also improve the rate of dewatering: it is therefore likely that its design will be important in the next stage of developing energy efficiency and thereby play a part in achieving a more sustainable future.
Dinh, Mai-Van [Verfasser], and Egbert [Akademischer Betreuer] Matzner. "Soluble phosphorus in forest soil : Effects of drying and rewetting / Mai-Van Dinh ; Betreuer: Egbert Matzner." Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/1143009843/34.
Full textGordon, Helen. "Drying and rewetting effects on microbial community composition and nutrient leaching form soils of contrasting management." Thesis, Lancaster University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533122.
Full textPeacock, Michael Anthony. "The effect of peatland rewetting on gaseous and fluvial carbon losses from a Welsh blanket bog." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/the-effect-of-peatland-rewetting-on-gaseous-and-fluvial-carbon-losses-from-a-welsh-blanket-bog(648921f3-152a-43e8-9d13-29f56fb4b965).html.
Full textPettersson, Emelie. "A study in how rewetting can be reduced in the paper machine with focus on the forming section." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-10827.
Full textKwari, J. D. "Effects of straw burning and drying-rewetting cycles on the fertility of some soils of North-East Nigeria." Thesis, University of Aberdeen, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379809.
Full textMamalis, Dimitrios. "Phase change and complex phenomena in drops and bubbles of pure and binary fluids." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25477.
Full textHarrison-Kirk, T. "The effects of drying and rewetting cycles on carbon and nitrogen dynamics in soils of differing textures and organic matter contents." Lincoln University, 2008. http://hdl.handle.net/10182/656.
Full textMälson, Kalle. "Plant responses after drainage and restoration in rich fens." Doctoral thesis, Uppsala University, Department of Ecology and Evolution, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8882.
Full textRich fens are an important, but threatened, habitat type in the boreal landscape. In this thesis I have examined responses of rich fen vascular plants and bryophytes after drainage and restoration.
The effects of drainage on the rich fen flora were observed in a long time study and the responses were rapid and drastic. During an initial stage a rapid loss of brown mosses was observed, followed by increases of sedges and early successional bryophytes, and later by an expansion of dominants. Initial effects of hydrological restoration showed that rewetting can promote re-establishment of an ecologically functional rich fen flora, but has to be combined with other treatments, such as mowing or surface disturbance.
After restoration, re-establishment of locally extinct species may be hampered by dispersal limitations. To test if reintroductions could help to overcome dispersal limitations I performed transplantation studies with four common rich fens bryophytes to a rewetted site. The results showed that the species were able to establish, and that survival and growth were promoted by desiccation protection and liming.
I further examined competition among three of the most common bryophytes in natural boreal rich fens that usually occur mixed in a mosaic pattern but show small but important microtopographical niche separation. The results indicate similar competitive abilities among the species, and no case of competitative exclusion occurred. The results help to explain the coexistence of these species under natural conditions with microtopographic variation and repeated small scale natural disturbances.
Restoring a functional flora in drained rich fens is a complex task, which requires understanding of underlying causes of substrate degradation in combination with suitable restoration measures. The thesis suggests how the results can be used in practical restoration work, and also stresses the need for monitoring of restoration experiments over longer time.
Marques, Adriana. "Estudo do efeito da adição de diésteres em fluidos industriais de origem vegetal e suas propriedades." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-06052012-155617/.
Full textVegetable oils have been studied in the replacement of mineral oils in many industrial applications particularly on the quenching steel in the heat treatment process. This work presents studies conducted to vegetable oils in terms of viscosity characteristics and cooling behavior. Such studies incorporate also formulations on vegetable oil based by diesters additions [Bis (2-etylhexyl) Adipate - DOA, Bis (2-etylhexyl) Sebacate DOS, Diiso Trydecil Adipate DITA] in the proportions of 2.5 and 5.0 % (m/m). Oxidation stability was evaluated by NMR performed in the vegetable oil without diesters additions. This evaluation was based in the satured and insatured compounds presented in the vegetable oil chain. Similar evaluations were also performed for formulations based on the soybean oil, before and after the accelerated oxidation tests. Results indicated coconut oil as the most stable in terms of oxidation. Peanut oil and soybean oil shown minor alterations on the viscosity values when the raise of temperature, since they presented lower Walther coefficient (B). Comparing the formulations soybean oil based in the not oxidized condition, the addition of 2,5% DOS was that shown greater maximum cooling rates (CRmax) and less stable vapour phase. After accelerated oxidation tests (48 hours), formulation with 5% DOA (soybean oil based) was that presented minor variations in terms of cooling parameters compared with not oxidized condition.
Åslund, Peter. "On Suction Box Dewatering Mechanisms." Doctoral thesis, KTH, Fiber- och polymerteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4780.
Full textQC 20100924
Schwieger, Sarah [Verfasser], Jürgen [Akademischer Betreuer] Kreyling, Gesche [Akademischer Betreuer] Blume-Werry, Jürgen [Gutachter] Kreyling, Vicky [Gutachter] Temperton, and Scott [Gutachter] Wilson. "Invisible to the eye - Root dynamics in temperate minerotrophic peatlands under drainage and rewetting / Sarah Schwieger ; Gutachter: Jürgen Kreyling, Vicky Temperton, Scott Wilson ; Jürgen Kreyling, Gesche Blume-Werry." Greifswald : Universität Greifswald, 2021. http://d-nb.info/123669368X/34.
Full textMaigrat, Guillaume. "Caractérisation expérimentale du remouillage des aciers." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0098/document.
Full textOn a run out table of a hot rolling mill, the cooling of steel strips is mainly provided by ramps of water jets falling down that will directly impact the upper surface of the strip. The temperature of the strip starts between 800 and 900 °C and it is intended to cool at temperatures much lower than the start but still accurate before its winding, the temperature ranges from ambient temperature to 700 °C depending on the required properties for the steel product. This water-based process ensures a transient cooling at an uneven rate depending on the nature of the boiling regime. The rewetting point is defined by the temperature at which the stable film boiling regime ends. In general, the cooling fluxes show a significant increase at this particular transition. In this thesis, we sought to characterize rewetting by vapor thickness measurements and analysis using optical probes. The optical sensors inform us whether their sensitive area is mainly in the gas or in the liquid and are generally used to make void fraction measurements. The use that is made here, namely a precise measurement of the position of the interface, required a precise experimental calibration in order to know the exact position of the interface on the sensitive area. In order to have a working tool, we also modeled the response of the probes by using a ray tracing method and taking into account the formation of the meniscus on the tipoff the probe. Finally, the calibration and model were compared with experimental measurements in the case of the cooling of a hemispherical area initially at high temperature that provides a stable film boiling regime when it is partially immersed
Tzevelecos, Wassilis. "Contribution to Heat and Mass Transfer for Space Experiments." Doctoral thesis, Universite Libre de Bruxelles, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/269864/6/contratWT.pdf.
Full textDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Velty, Silke. "Einfluss von Wiedervernässungsmaßnahmen auf den Stoffhaushalt degradierter Niedermoore." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2008. http://dx.doi.org/10.18452/15752.
Full textA formerly drained, and since 1996 rewetted, 10 ha fen site within the Randow-Welse-Bruch fen area in northeastern Brandenurg (Germany) has been investigated for several years to evaluate the impacts of rewetting on nutrient dynamics of the degraded fen. Modifications of nutrient cycles were attributed to changes in redox conditions after rewetting. Although phosphorus which causes eutrophication is not directly influenced by a change from aerobic to anaerobic conditions following rewetting its availability increased due to the dissolution of reactive iron (hydr)oxides where phosphorus was fixed before.With prolonged water-logging phosphorus was released from Fe(III) (hydr)oxides. A lysimeter study was carried out to promote the reuse of purified municipal wastewater as an alternative solution for water supply required during rewetting of fens. Fen soil lysimeters were irrigated with wastewater of the secondary treatment of a municipal wastewater treatment plant over the growing seasons. The objective of this study was to assess how restoration of a degraded fen by means of wastewater usage affects input/output nutrient mass balances. Furthermore, we assessed the effect on trace gas emissions and discussed potential changes in the greenhouse potential. No adverse impact of wastewater utilisation for rewetting the fen soil lysimeters on soil and water quality was found over the period of study with regard to the investigated nutrients and heavy metals. Gaseous fluxes during alternative rewetting were estimated for a consideration within nutrient balances and to evaluate the global warming and cooling, respectively. Besides nitrous oxide dinitrogen was formed and released under anaerobic conditions following rewetting. A potential increase of the nitrate concentration in wastewater would be harmless because a high denitrification of the fen soil would cause a major share of dinitrogen emissions of the total gaseous nitrogen loss.
LIMA, RITA de C. F. de. "Comportamento termoidraulico de vareta aquecida eletricamente durante transitorio de fluxo critico de calor." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10640.
Full textMade available in DSpace on 2014-10-09T13:57:16Z (GMT). No. of bitstreams: 1 05031.pdf: 4962096 bytes, checksum: 39c12c06c0063abb20c1c82005ecef33 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Bejarano, Roberto Villa. "An Investigation Into| I) Active Flow Control for Cold-Start Performance Enhancement of a Pump-Assisted, Capillary-Driven, Two-Phase Cooling Loop II) Surface Tension of n-Pentanol + Water, a Self-Rewetting Working Fluid, From 25 ?C to 85 ?C." Thesis, University of Nevada, Reno, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1565813.
Full textCold-start performance enhancement of a pump-assisted, capillary-driven, two-phase cooling loop was attained using proportional integral and fuzzy logic controls to manage the boiling condition inside the evaporator. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting fluid, was also investigated for enhancing heat transfer performance of capillary driven (passive) thermal devices was also studied. A proportional-integral control algorithm was used to regulate the boiling condition (from pool boiling to thin-film boiling) and backpressure in the evaporator during cold-start and low heat input conditions. Active flow control improved the thermal resistance at low heat inputs by 50% compared to the baseline (constant flow rate) case, while realizing a total pumping power savings of 56%. Temperature overshoot at start-up was mitigated combining fuzzy-logic with a proportional-integral controller. A constant evaporator surface temperature of 60°C with a variation of ±8°C during start-up was attained with evaporator thermal resistances as low as 0.10 cm2–K/W. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting working fluid, as a function of concentration and temperature were also investigated. Self-rewetting working fluids are promising in two-phase heat transfer applications because they have the ability to passively drive additional working fluid towards the heated surface; thereby increasing the dryout limitations of the thermal device. Very little data is available in literature regarding the surface tension of these fluids due to the complexity involved in fluid handling, heating, and experimentation. Careful experiments were performed to investigate the surface tension of n-Pentanol + water. The concentration and temperature range investigated were from 0.25%wt. to1.8%wt and 25°C to 85°C, respectively.
Rebhann, Marco Frank. "Bewirtschaftung von Niedermooren in der gemäßigten Klimazone: Treibhausgasemissionen und Rentabilität." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19334.
Full textFens are sites influenced by the groundwater where peat is formed in or located in the upper soil layer. They emit greenhouse gases (GHG) through microbiological processes in which the main influencing factor is the groundwater level. The lowering of the groundwater level increases carbon dioxide and dinitrogen monoxide emissions, while higher groundwater levels lead to methane emissions. It is assumed that fens cause 5% of global anthropogenic GHG emissions. In order to save peat and reduce GHG emissions, rewetting fens has been discussed and applied. This leads to low profitable land use due to limited trafficability and cultivation options. There is a lack of comparison of management systems in different land use systems regarding GHG emissions and profitability on fenlands in the temperate climate zone. The soil-borne GHG emissions for the land use systems were identified with a meta-analysis of published measurements of GHG emissions on fenlands in the temperate climate zone. The GHG emissions due to cultivation and possible land use changes were identified and summarized as the overall emissions. Costs and revenues were calculated for comparability purposes of profitability of management systems. GHG abatement costs were estimated too. Results indicated that overall GHG emissions increase with higher land use intensity and deeper groundwater level. Management induced GHG emissions are negligible compared to the soil-borne emissions. Fenlands should be extensified to save peats and reduce GHG emissions. The comparison of profitability showed that management systems of intensive land use systems, in contrast to extensive land use systems, with the low groundwater level are broadly profitable without subsidies. Subsidies and grants are indispensable to promote peat-saving and climate-friendly practices. This thesis provides a systematic overview of overall GHG emissions and profitability of common management systems of fenlands.
Gu, Sen. "Release of dissolved and colloidal phosphorus from riparian wetlands : a field and laboratory assessment of the mechanisms and controlling factors." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S063/document.
Full textPhosphorus (P) is a key nutrient in controlling surface water eutrophication. Because of the decrease of urban and industrial P emissions, most of the P nowadays causing surface water eutrophication in western countries consists of P transferred from agricultural soils, explaining why current eutrophication research focused on understanding the mechanisms by which P is released from soils. In this thesis, we studied these release mechanisms for dissolved P (DP) – i.e. the most bioavailable P component for algae - using an approach combining field monitoring of soil and stream water compositions in a small, headwater catchment typical of western countries agricultural catchments (the Kervidy-Naizn catchment, France), and laboratory experimental simulations. Field monitoring data revealed that riparian wetlands (RW) are the main zones of DP release and DP production in the studied catchment, through essentially two mechanisms triggered by groundwater table fluctuations, namely i) rewetting of dry soils (DRW), and ii) reductive dissolution of soil Fe (hydr)oxides during anaerobic periods. Field monitoring data also revealed the presence of strong spatial variations in the chemical nature (inorganic vs. organic/colloidal) of the released DP, which was in relation to differences in soil properties and local topography. Seasonal and inter-annual hydroclimate variations, combined with variations in local topography were found to control the frequency of soil DRW events and duration of anaerobic periods, resulting in strong seasonal and inter-annual variations of DP release dynamics. As shown in a conceptual model, topography is likely to be the key driver of the observed spatial and temporal variations, because of its combined control on i) the transfer of P from upland fields to RW zones, ii) the mineralization rates of soil organic P and iii) the triggering of the above two release mechanisms. Laboratory leaching experiments on the same soils confirmed the role of DRW events as a major process causing DP release pulses in RWs. The data demonstrated that the released DP consisted not only of true dissolved inorganic and organic P but also of colloidal P, the latter phase being the most reactive to DRW events. The data also revealed that the different P forms came from different P sources in the soil (soil macro/mesopores for colloidal P and organic DP; soil micropores for inorganic DP) and that the amount of released colloidal P correlated positively with the organic matter contents and soil microbial biomass size of the soil. Anaerobic incubation experiments, on their hand, confirmed the role of anoxic conditions as conditions favoring the release of DP in RW. Reductive dissolution of soil Fe-oxyhydroxide was, however, not the sole process involved in that release, another process being the rise in pH caused by reduction reactions. Experimental data showed that the pH rise controlled the DP release in organic-rich soils, this release being on the contrary mainly controlled by soil Fe-oxyhydroxides reductive dissolution in organic-poor soils. Experimental data also showed that the input of soil sediments from upland fields enhanced the release of DP in RW, most likely due to the enhanced dissolution of sediment Fe-oxyhydroxides by RW Fe-reducing bacteria. Overall, this thesis allowed new constraints to be placed on the release mechanisms of DP in headwater agricultural catchments. One very practical output is that great care should be taken of hydroclimate variability, local topography, and soil property when designing and implementing management options to reduce DP release and transfer in agricultural catchments
Zaaroura, Ibrahim. "Amélioration du transfert de chaleur et de masse à l'aide de nanofluides auto-réhumidifiants." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0024.
Full textThermal management is currently a major issue in many sectors of industry. Heat transfer devices (like Heat Pipes, Heat exchangers…) are integrated systems that use transfer modes by convection, evaporation and condensation. The efficiency of heat exchange can be improved by using a new nanotechnology method known as nanofluids. Nanofluids are suspensions of nano-size particles (from 2 to 100nm) in the fluids. This improvement is due to the significant increase in the effective conductivity in the range 10-50% as well as their convective heat transfer coefficients. However, limitations related to the phenomena of nanoparticle, sedimentation and aggregation appear during different phases. In this project, in order to optimize the performance and stability of nanofluids, two different methods were used: an optical one coupled to an infrared thermography method and a high frequency acoustic method. The selection of nanoparticles was based on their thermal performance during evaporation of sessile droplets using a Kruss system, under same conditions and at different concentrations. Thus, high frequency acoustic waves, at the surface, make it possible to analyze the stabilities of nanoparticles during its evaporation where these particles are in suspension with base fluids such as ionized water, self-rewetting binary mixture (To improve the circulation of fluids inside heat pipes thanks to their physical properties like thermal Marangoni, concentration Marangoni, capillary...). The selected nanofluids will be used later to analyze experimentally their performance on two-phase capillary fluid loop heat transfer devices and in micro-channel heat exchangers by finding and calculating the thermal resistance of the system, convection heat transfer coefficient and wall temperature
Kheir, Maya. "Fonctionnement des sols méditerranéens sous changement climatique : effet de la préexposition au stress, de la mixité des litières et de l'identité de l'espèce végétale." Thesis, Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/200710_KHEIR_495pzb687n410mxugdf923oaivtm_TH.pdf.
Full textThis work takes place in the context of climate change. We aimed to explore plant litter microbial communities' functioning depending on climate contrasts Northern/Southern Mediterranean but also according to inland/coastal context, and to assess their response to aridification stresses, considering the effect i) of the type of litter (plant species identity and mixture) and ii) of the preexposure to stress intrinsic of coastal environments. Aridity stress was applied in the laboratory (drying /rewetting cycles) and in natura via "litter bags" transfer from France to Algeria. Results show that microbial biomass and basal respiration depend on litter chemical traits (C/N and lignin/N): when these ratios increase, microbial biomass decreases, while the effect on respiration depends on the climate contrasts. The effect of binary litter mixtures on microbes depends on the climate context and the mixture composition: some mixtures seem to limit carbon release through heterotrophic respiration in Algerian arid context. In addition, a particular microbial functioning of coastal environments was highlighted: i) preexposure to coastal constraints limited the effect of stress applied in the laboratory on microbial catabolic structures ii) the in natura experiment showed that microbial responses to stress depend on the context (coastal/inland) but also on litter type, highlighting litter influence even at large spatial scales
Nguyen, Ngoc diep. "Characterization and contribution of colloidal fraction in the mobility and bioavailability of sedimentary phosphorus." Thesis, Limoges, 2020. http://aurore.unilim.fr/theses/nxfile/default/9f8fcb76-5d28-468c-8289-23bd366f1bb7/blobholder:0/2020LIMO0078.pdf.
Full textThe mobilization of phosphorus (P) from sediment is a persistent internal nutrient source sustaining eutrophication, especially in reservoir. Current knowledge about sedimentary P release does not consider colloidal form, although it is well-known for its efficiency as P-carrier, its high mobility and potentially bioavailability. This thesis provides new constraints to place sedimentary colloids and sedimentary colloidal P into light concerning their important stock and release potential in the reservoir. Colloids are shown to be an intrinsic component of reservoir sediment, and their recovery under sediment resuspension indicated the contribution of water mobilizable colloids up to 2.3 % of the sediment mass in Champsanglard dam reservoir (Creuse, France). The amount of P associated with colloids was up to 6 % of total sedimentary P and 80 % of water-mobilizable P. After the application of different protocols for colloid extraction, separation and for sediment storage, a framework for selecting appropriated method for colloid recovering from a sediment is proposed. The recommendation for colloid recovery is to work with wet sediment, avoid using high-power extraction protocol (i.e. sonication), using filtration with pre-separation step instead of successive centrifugation to avoid under or overestimation in quantity and quality of recovered colloids. The quantity and quality of sedimentary colloids and associated P varied spatially in the reservoir according to sediment size grain distribution and the influence of flow hydrodynamics, the presence of tributaries and fluctuations in the water-level. The highest content of water mobilizable colloids and especially large colloids (0.2 - 1 μm) were found in lacustrine bottom sediments, downstream of the tributary confluence. Bank sediments impacted by water-level fluctuations released P in bioavailable forms (dissolved P and small/nano P-colloids). Under anoxic condition, the potential of sediment to mobilize colloidal P was significantly higher than truly dissolved P and represented up to 40 % of total sedimentary P. When condition became oxic subsequently, major portion of released P remained in suspension under small/intermediate size (300 kDa - 0.45 μm). In redox changing conditions, the closely linked biogeochemical cycles of iron and organic matter could be the key parameters involved in mobility of colloidal P. This thesis highlights the need to consider colloids and their contribution in the P mobility at the boundary of sediment-water and associated bioavailability to aquatic plankton, particularly in dam reservoir context
Scheiff, Valentin. "Etude expérimentale et modélisation du transfert de chaleur de l'ébullition transitoire." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0145/document.
Full textThe study of rapid transient boiling is an important issue in the nuclear safety. Such a phenomenon may occur in the case of a RIA (Reactivity Initiated Accident) in the core of a nuclear reactor powerplant, where a power excursion can trigger the formation of a vapour film around the fuel rod, leading to an important rise of the rod temperature and a risk of failure. Some studies in reactor conditions provided transient boiling curves but the modeling lacks of reliability. In collaboration with the IRSN (Institut de Radioprotection et de Sûreté Nucléaire), an experiment model was built at the Institute of Fluid Mechanics of Toulouse. It generates the flow of a refrigerant, HFE7000, in a semi-annular section channel, whose inner wall is made of a metal foil rapidly heated by Joule effect, simulating the heating of a fuel rod. Infrared thermography is used to measure the temperature of the metal foil, painted with a black paint to increase its emissivity, causing also an increase of the wall thermal resistance. The measurement accuracy of the interest temperature has been optimized according to the paint thickness and a correction on the energy balance takes account this parameter. These measurements are coupled with a high-speed camera that allows visualizing the boiling regimes and get bubble sizes using image processing algorithms. On a flux-temperature diagram, the heat transfers are represented both for steady and transient regimes. Each boiling regime is then reviewed : convection, onset of nucleate boiling, nucleate boiling, boiling crisis, film boiling and rewetting. Steady regimes are correctly modeled by usual correlations. Transient convection is characterized over the whole wall and its evolution is closed to the quasi-steady solution. It is shown that heat transfer during the transition to nucleate boiling are strongly related to the formation of a large vapor phase that spreads on the wall. A local study of this propagation is then necessary. In order to simulate and control transient temperature during nucleate boiling, a P.I.D. is implemented to impose a steady or ramps temperature (from 5 to 500 K.s 1 ). The results in nucleate boiling make it possible to recover the results of the literature in both steady and transient conditions. The experiment allows to study the heat transfer when a vapor film is formed and insulates the wall. The film boiling regime during heating or the cooling of the wall can thus be stabilized for several seconds with this system. The conditions for triggering of film boiling are thus characterized, as its spread dynamic and its transfers once established. Finally, the implementation of the physical characteristics of our experience in IRSN’s SCANAIR code allows us to begin to calculate and compare our experimental results with numerical simulations. Unsteady conduction calculations are applied to the measured temperature to analyze our results during the convection regime and after the onset of boiling
Meyer, Ann-Carolin. "Physiologische Untersuchungen am Stamm und im Kronenraum eines Fichtenaltbestandes nach experimenteller Manipulation des Wasser- und Ionenhaushaltes (Dachprojekt Solling)." Doctoral thesis, [S.l. : s.n.], 2001. http://webdoc.sub.gwdg.de/diss/2002/meyer/meyer.pdf.
Full textShatadal, Pankaj. "Thin-layer rewetting rates of canola (Brassica campestris L.)." 2009. http://hdl.handle.net/1993/3603.
Full textLin, Wei-Jhih, and 林威志. "The Application of Self-Rewetting Fluids on Loop Heat Pipe." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95945667975312908438.
Full text國立臺灣大學
機械工程學研究所
101
The objective of this study is the application of self-rewetting fluid as the working fluid on loop heat pipe (LHP), with sintered copper as the chosen capillary structure material; this study also investigates the effect of using different components and concentrations of self-rewetting fluid as well as compares their heat transfer performances with that of water. Previous studies have show that using self-rewetting fluid as working fluid can enhance the heat transfer mechanisms of pool boiling,traditional heat pipe, and wickless heat pipe. Compared with using pure substance as working fluid, where the surface tension decreases linearly with increasing temperature, self-rewetting fluid’s surface tension has a non-linear relationship with temperature changes; therefore, at a certain temperature, the self-rewetting fluid’s surface tension increases with increasing temperature, resulting in the Marangoni effect, and the condensed liquid can be transported to the heating surface, delaying the occurrence of dryout and thus increasing the critical heat load. Concerning the effect of varying the concentration of butanol aqueous solution on heat transfer performance of LHP, concentrations ranging from 2% to 8% is investigated. Experimental results show that 6% butanol aqueous solution results in the the best heat transfer performance of LHP; compared with that of water, the critical heat load is increased by 130% and the total thermal resistance is decreased on average by 50%. Concerning the effect of changing the components of self-rewetting working fluid, the fluids considered are butanol, pentanol, hexanol, and heptanol, with the concentration of each as the maximum solubility concentration in water under standard conditions. Experimental results show that, compared with using water as working fluid, using self-rewetting fluid can allow the total thermal resistance of LHP system to decrease, increasing the critical heat load. Concerning the heat transfer performance of different self-rewetting fluids, under operating temperature of 90°C or lower, hexanol aqueous solution achieves the largest heat load of 250W and lowest total thermal resistance of 0.33°C/W; at operating temperatures higher than 90°C, hexanol aqueous solution has already reach the critical heat load, causing the system to be unstable, but butanol aqueous solution achieves the best results, with maximum critical heat load of 350W and minimum total thermal resistance of 0.32°C/W. Therefore, after analysis of the heat transfer performance of various self-rewetting fluids, butanol water solution has the largest operating temperature range, highest critical heat load, and lowest total thermal resistance, indicating that butanol water solution is most effective on heat transfer performance of LHP.
Xie, Stella Xiao Min. "Roughening due to inkjet rewetting: Effect of paper treatment and composition." 2006. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=442004&T=F.
Full textChu, Mao-Long, and 朱茂榕. "Heat Transfer Enhancement of Loop Heat Pipe with Self-Rewetting fluid." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/62422980327924299494.
Full text國立臺灣大學
機械工程學研究所
102
The objective of this study is the application of self-rewetting fluid as the working fluid on loop heat pipe (LHP), with sintered copper as the chosen capillary structure material; this study also investigates the effect of using different contents and concentrations of self-rewetting fluid on heat transfer performances of LHP as well as compares the results with those from using water as working fluid. Previous studies have shown that using self-rewetting fluid as working fluid can enhance the heat transfer mechanisms of pool boiling, traditional heat pipes, and wickless heat pipes. Compared to using pure substance as working fluid, where the surface tension decreases linearly with increasing temperature, self-rewetting fluid’s surface tension has a non-linear relationship with temperature changes; therefore, at a certain temperature, the self-rewetting fluid’s surface tension increases with increasing temperature, resulting in the Marangoni effect, and the condensed liquid can be transported to the heating surface, delaying the occurrence of dry out and thus increasing the critical heat load. Concerning the effect of varying the concentration of butanol and petanol aqueous solutions on heat transfer performance of LHP, butanol concentrations ranging from 2% to 8% is investigated, and pentanol concentrations ranging from 1% to 3% is investigated. Experimental results show that 6% butanol aqueous solution results in the best heat transfer performance of LHP; compared with that of water, the critical heat load is increased by 100% and the total thermal resistance is decreased on average by 30%. Concerning the effect of changing the components of self-rewetting working fluid, the fluids considered are butanol, pentanol, hexanol, with the concentration of each being the maximum solubility concentration in water under standard conditions. Experimental results show that, compared with those from using water as working fluid, using self-rewetting fluid can allow the total thermal resistance of LHP system to decrease, increasing the critical heat load. Concerning the heat transfer performance of different self-rewetting fluids, under operating temperature of 90°C or lower, hexanol aqueous solution achieves the largest heat load of 200W and lowest total thermal resistance of 0.33°C/W; at operating temperatures higher than 90°C, hexanol aqueous solution has already reach the critical heat load, causing the system to be unstable, but butanol aqueous solution achieves the best results, with maximum critical heat load of 500W and minimum total thermal resistance of 0.26°C/W. Therefore, after analysis of the heat transfer performance of various self-rewetting fluids, butanol water solution has the largest operating temperature range, highest critical heat load, and lowest total thermal resistance, indicating that butanol aqueous solution is the most effective in enhancing the heat transfer performance of LHP.
Lin, Wei-Jhih, and 林煒智. "Study of Self-Rewetting Fluid Applied to PTFE Wick of Loop Heat Pipe." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/23665625930080743052.
Full text中華科技大學
航空機械系飛機系統工程碩士班
103
This study applied butanol aqueous solution to form self-rewetting fluid to LHP with a PTFE wick. Porous PTFE structure advantages including low sintering temperature and resistant to oxidation; however, due to PTFE’s hydrophobic nature, with water as working fluid, for example, it has been observed that PTFE cannot effectively pump the working fluid by capillary action. In this paper, self-rewetting fluid (butanol aqueous solution) was used to address the hydrophobic nature of PTFE, allowing the working fluid to successfully flow through the PTFE wick by capillary forces. 0 ~ 7wt% butanol aqueous solutions and 1~2.75mm wick thickness were tested for effectiveness and ease in allowing the working fluid to flow through the wick and LHP heat transfer performance test. Experimental results showed that, with 6wt% butanol aqueous solution and 2mm wick thickness, heat transfer performance is 550W, the minimal total thermal resistance is approximately 0.273℃/W, and the heat flux is 28W/cm2. Dimensionless performance figure of loop heat pipe, and can be used as reference for future wick designs.
Butterly, Clayton Robert. "Drying/rewetting cycles in southern Australian agricultural soils: effects on turnover of soil phosphorus, carbon and the microbial biomass." 2008. http://hdl.handle.net/2440/48167.
Full texthttp://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1321018
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008
Asota, Celestine Ngozi. "Effects of repeated rewetting and drying on breakage and moisture desorption characteristics of soybeans." 1987. http://catalog.hathitrust.org/api/volumes/oclc/17860661.html.
Full textTypescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 220-245).
Chia-Hsuan, Lin, and 林家璿. "On the performance analysis of using self-rewetting fluid in intermittent spray cooling system." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/kygu89.
Full text國立臺灣大學
機械工程學研究所
106
In this study, we utilize the self-rewetting fluid in an intermittent spray system and study the effects of pulsed duration and duty cycle on the heat transfer mechanism and the cooling capacity. Compared to water, using the self-rewetting fluid can successfully induced inverse Marangoni convection and proven to prolong the cooling time within a cycle. This leads to a lower fluid consumption because comparable heat transfer rate can be delivered by spraying the self-rewetting fluid at much lower frequency. For a given duty cycle, increasing the pulsed duration leads to a higher heat transfer rate per period. The working fluid left on the heated surface is so abundant that the inverse Marangoni convection is sustained. However, longer spray pulse decreases the spray frequency and is unfavorable when a given time span is consider. Although a shorter pulsed duration only shows moderate cooling capacity per cycle, the time-averaged heat transfer rate is improved by the increase in spray frequency. On the other hand, reducing the duty cycle also augments the heat transfer rate per period when the pulsed duration is fixed. As the spray frequency decreases, the surface temperature increases, so that a stronger inverse Marangoni convection is induced. Nevertheless, dry-out may occur if the duty cycle becomes too small. As a result, we find that a pulsed duration of 1.5 s with a 7.5% duty cycle produces the best cooling effect and with the highest spray cooling efficiency and the lowest fluid consumption.
Hour, Bor Kae, and 侯博凱. "A Study on the Thermal-Fluid Phenomenoa of Rewetting along a F uel Rod." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/31438893204012959644.
Full textChou, Ta-Li, and 周大立. "Heat Transfer Enhancement of Loop Heat Pipe with Metal and Polymer Capillary Structure using Self-Rewetting Fluid." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/23095570107961268676.
Full text國立臺灣大學
機械工程學研究所
104
The objective of this study is the application of self-rewetting fluid as the working fluid on loop heat pipe (LHP), with nickel and teflon(PTFE) as the capillary structure materials respectively. Self-rewetting fluids, generally the dilute aqueous solutions of high carbon alcohols(number of carbon atoms ≥ 4), shows not only better wettability compared with pure water but also a special thermophysical effect that the surface tension increases with increasing temperature. Since the Marangoni effect induces a flow from liquid with lower surface tension to the liquid with higher surface tension, which results a liquid flow to hotter interface, it is advantageous to use self-rewetting fluid as working fluid on heat-transfer devices. In this study, we measure the surface tension of different self-rewetting fluids at different concentration in the temperature range 25~70 oC, and the working fluids of 1-butanol, 1-pentanol, 1-hexanol and 2-butanol(isomer of 1-butanol) are choosed. The result shows that self-rewetting fluids possess higher positive surface tension gradient("σ" _"T" ) at saturation. Furthermore, the 1-butanol (6%) and 2-butanol (20%) show higher "σ" _"T" than others, which are 0.27 mN/moC and 0.30 mN/moC respectively. These two self-rewetting fluids are then applied to the LHP with nickel capillary structure. The maximum heat load are 500W and 600W relatively when the working fluid is 1-butanol (6%) and 2-butanol (20%) , which was increased by 50 % and 70 % compared with using water as working fluid, and the total thermal resistence decreased from 0.31 oC/W to 0.22 oC/W. Due to the hydrophobicity of PTFE, water can’t be used on PTFE capillary structure. This study applied the self-rewetting fluids, which possess better wettability than water, on LHP with PTFE capillary structure. The results show that when the working fluid is 2-butanol (20%), the LHP system successfully work and the maximun heat load can reach 250W with total thermal resistence 0.54 oC/W, and the maximum heat flux is 12.9 W/cm2. Compared with results in other literatures, the maximum heat flux in this study is higher by 3 to 5 times other reference.
YEN, SHIH-HSUAN, and 顏士軒. "Study of Self-Rewetting Fluid Applied to PTFE Wick structure of Loop Heat Pipe with flat evaporator." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/00634478782462936917.
Full text中華科技大學
飛機系統工程研究所
104
This study investigated the application of self-rewetting fluid to Nickel and PTFE wick structure of Loop Heat Pipe with flat evaporators (FLHP) and its effect on the heat transfer performance of FLHP. PTFE wick structure can prevent FLHP heat leakage problem, however, PTFE material with strong hydrophobic nature, cannot use the water as the working fluid. Therefore, this study attempts to use Self-rewetting fluid's good wettability to overcome the PTFE wick's hydrophobicity. At a certain temperature, a self-rewetting fluid, contrary to common newtonian fluids, has the ability to reverse its surface tension's trend, inducing colder fluid to flow to the heated surface and delaying the occurrence of dry-out in FLHP during operation. Thus, this study focused on a few self-rewetting fluids; the surface tensions of these fluids were measured, and then it was applied to FLHP as working fluid to investigate its effect on the heat transfer performance. Heat transfer performance test results shows that DI water and 1-Butanol;1-Heptanol aqueous solution in nickel wick’s FLHP, the maximum heat load can be up to 280W,Compared to DI water's 140W can improve heat transfer performance about 70 to 100% . DI water and 1-Butanol;1-Heptanol aqueous solution in PTFE wick's FLHP, the maximum heat load can be up to 240W,Compared to DI water's 40W can improve heat transfer performance about 300 to 500% .
Hung, Chia-Yin, and 洪嘉吟. "Exploring the cooling capability of self-rewetting fluid deposited on the cold end of a copper strip with horizontal temperature gradient." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9xmnz8.
Full text國立臺灣大學
機械工程學研究所
107
This study aims at applying the inverse Marangoni convection to cooling augmentation of a super-hydrophilic copper strip with a horizontal temperature gradient. The self-rewetting fluid used herein is the 0.2%wt 1-heptanol dilute aqueous solution and there are two different supplied quantity: 1 ml and 1.5 ml. The horizontal temperature gradient is varied by adjusting the inlet temperature of coolant and the initial temperature of the hot end. We find that the inverse Marangoni convection is able to cool the hot end effectively and result in higher accumulated cooling amount comparing to water. For a given initial temperature of the copper strip in the hot end, warmer coolant at the results in lower inlet temperature gradient and therefore weaker inverse Marangoni convection. When temperature gradient exceeds 3°C cm-1 on the other hand, applying less working fluid produces a higher temperature gradient, therefore, the stronger inverse Marangoni convection and the higher accumulated cooling amount. However, a temperature gradient less than 3°C cm-1 leads to very weak inverse Marangoni convection, and the low temperature of copper strip in the hot end makes the change in sensible heat of fluid dominate the heat transfer mechanism. As the result, 1.5 ml of working fluid produces a higher accumulated cooling amount comparing to that of 1 ml. In addition, dryout can be effectively delayed by strong inverse Marangoni convection when 1 ml of the self-rewetting fluid is applied with a large temperature gradient in horizontal direction.
Ketcheson, Scott James. "An evaluation of the water balance and moisture dynamics within Sphagnum mosses following the restoration (rewetting) of an abandoned block-cut bog." Thesis, 2011. http://hdl.handle.net/10012/6328.
Full textMalloy, Shannon. "Fen restoration on a bog cut down to sedge peat: A hydrological assessment of rewetting and the impact of a subsurface gyttja layer." Thesis, 2013. http://hdl.handle.net/10012/7355.
Full textKozub, Łukasz. "Wpływ restytucji torfowiska niskiego metodą usuwania warstwy murszu na warunki siedliskowe, produktywność i bilans gazów cieplarnianych." Doctoral thesis, 2016. https://depotuw.ceon.pl/handle/item/1819.
Full textKnorr, Klaus-Holger [Verfasser]. "Dynamics of soil processes under extreme meteorological boundary conditions : response of below-ground carbon, sulfur, and iron cycling in fen soils ; effects of experimental drought and subsequent rewetting on internal carbon, sulfur, iron, and arsenic turnover in a soil from a northern temperate fen / vorgelegt von Klaus-Holger Knorr." 2009. http://d-nb.info/992484421/34.
Full text