Approche micromécanique est utilisée pour étudier le transport et la congélation dans les milieux poreux non saturés. Dans les milieux poreux non saturés, film d'eau ainsi que la pression de disjonction sont introduits dans le transport et les problèmes de gel. Dans la modélisation, il est constaté que, couche capillaire avec l'eau interstitielle dominent le transport au degré de saturation élevé (Sr> 10%). Cependant, le film d'eau jouera un rôle important dans le transport à degré de saturation basse (Sr <10%), et le coefficient de diffusion sera faible que 3 à 4 ordres de grandeur à celle à degré de saturation élevé. Un modèle micromécanique de gel dans les milieux poreux non saturés est établi. Modèle micromécanique de congélation est plus physique basée dans la nature. En effet, différent du modèle poromécanique du milieu de congélation, dans lequel la pression de cristaux de glace est introduit, la pression de disjonction du film d'eau non gelée à la place de la pression de cristaux de glace est introduite dans le modèle micromécanique de congélation / Micromechanical approach is employed to investigate the transport and freezing within unsaturated porous media. In unsaturated porous media, water film as well as disjoining pressure are introduced in the transport and freezing problems. In the modeling, it is found that, capillary layer along with pore water dominate the transport at high saturation degree (Sr>10%). However, water film will play a significant role in transport at low saturation degree (Sr<10%), and the diffusion coefficient will be lower than 3 to 4 orders of magnitude than that at higher saturation degree. A micromechanical model of freezing in unsaturated porous media is established. Micromechanical model of freezing is more physical based in nature. That is because different from poromechanical model of freezing media in which ice crystal pressure is introduced, the disjoining pressure of unfrozen water film instead of ice crystal pressure is introduced in the micromechanical model of freezing

Orientador : Elias Basile Tambourgi / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T01:56:06Z (GMT). No. of bitstreams: 1 Veloso_MariaAuxiliadoraFortini_D.pdf: 6659840 bytes, checksum: 9158a84e3db6fe7278b8e1cc55b8277e (MD5) Previous issue date: 2004 / Resumo: O programa computacional STHIRP-1 (Simulação Termo-Hidráulica de Reatores de Pesquisa), cujos fundamentos são descritos neste trabalho, utiliza os princípios da técnica de subcanais e tem a capacidade de simular, em condições estacionárias e transitórias, os fenômenos térmicos e hidráulicos que ocorrem no núcleo de um reator de pesquisa refrigerado a água sob regime de convecção natural. Os modelos e correlações empíricos necessários para descrição das grandezas do escoamento que não podem ser descritos por relações teóricas foram selecionados de acordo com as características de operação do reator. Apesar de o objetivo primeiro ser o cálculo de reatores de pesquisa, a formulação utilizada para descrever o escoamento do fluido e a condução térmica nos elementos aquecedores é suficientemente geral para estender o uso do programa a aplicações em reatores de potência e a outros sistemas térmicos que tenham as características representadas pelas equações do programa. Para demonstrar a capacidade analítica de STHIRP-1, foram feitas comparações entre resultados calculados e medidos no reator de pesquisa TRIGA IPR-R1 do CDTN/CNEN. Os resultados indicam que o programa reproduz com boa precisão dados experimentais de temperaturas de saída de subcanais. No entanto, resultados experimentais mais consistentes deverão ser usados no futuro para corroborar a validação do programa / Abstract: The STHIRP-1 computer program, which fundamentals are described in this work, uses the principles of the subchannels analysis and has the capacity to simulate, under steady state and transient conditions, the thermal and hydraulic phenomena which occur inside the core of a water-refrigerated research reactor under a natural convection regime. The models and empirical correlations necessary to describe the flow phenomena which can not be described by theoretical relations were selected according to the characteristics of the reactor operation. Although the primary objective is the calculation of research reactors, the formulation used to describe the fluid flow and the thermal conduction in the heater elements is sufficiently generalized to extend the use of the program for applications in power reactors and other thermal systems with the same features represented by the program formulations. To demonstrate the analytical capacity of STHIRP-1, there were made comparisons between the results calculated and measured in the research reactor TRIGA IPR-R1 of CDTN/CNEN. The comparisons indicate that the program reproduces the experimental data with good precision. Nevertheless, in the future there must be used more consistent experimental data to corroborate the validation of the program / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Clouds and aerosols impact the Earth’s thermostat and precipitation. There is increasing evi- dence that dust aerosol frequently controls cloud glaciation, modifying clouds’ radiative eect and response to global warming. For realistic climate change projections, it is crucial to improve the simulated pathway between dust immersion freezing and cloud glaciation. However, current freezing schemes, which extrapolate laboratory results to larger atmospheric scales, are poorly constrained. Based on spaceborne observations of cloud-phase and aerosols, we explore whether dust-driven immersion freezing can be improved in a climate model so that the climate impact of dust ice-nuclei can be estimated more accurately. Combining an aerosol model reanalysis with spaceborne retrievals of cloud phase, we estimated the global co-variability between mineral dust aerosol and cloud glaciation. Relying on a spaceborne lidar, a lidar-radar synergy, and a radiometer-polarimeter synergy, we also locate and quantify the hemispheric and seasonal con- trast in cloud-phase. Finally, we use these estimations to refine the dust-driven droplet freezing in a climate model. Our results show that observations of cloud-top phase contrasts may be used to evaluate dust-driven droplet freezing in climate models. In the extratropics, the average frequency of ice cloud increases by +5% to +10% for higher mineral dust mixing-ratios on a day-to-day basis. For similar mixing-ratios of mineral dust, we found that the ice frequency can still vary between latitudes, especially between Hemispheres and between mid- and high-latitudes. By using only retrievals for which satellite products agree on cloud-phase, we find that the cloud-phase transition from liquid to ice occurs within a narrower temperature range. This suggests that individual products tend to classify too many clouds as liquid for temperatures below -30°C and too many as ice for temperatures above -10°C. At -30°C, the hemispheric and seasonal contrasts — relative to the Southern Hemisphere and boreal spring, respectively — lie between +21% to +39% for individual cloud- phase products and between +52% to +75% for a combination of products. We use these contrasts to tune the dust ice-nuclei eciency in the model, limiting their eect during clean conditions. Consequently, the model agrees better with the estimated cloud-top-phase contrasts and a dust-driven glaciation eect of 0.14 ± 0.13 W m^2 in the Northern Hemisphere, which is lower than previously assumed. These changes are associated with a decrease in the cloud liquid water path and a weak enhancement of the stratiform precipitation at the expense of convective precipitation. Our results show that observations of cloud-top phase contrasts may be used as a constraint for dust-driven droplet freezing in climate models. Thus, our constraining approach may help to achieve more accurate climate predictions and direct future climate model development. / Wolken und Aerosole beeinflussen den Energiehaushalt und den Wasserkreislauf der Erde. Es gibt zunehmend Hinweise darauf, dass Staubaerosol die Vereisung von Wolken, ihren Strahlungsef- fekt und ihre Antwort auf die globale Erwärmung beeinflusst. Um den Klimawandel genauer zu projizieren, ist es daher wichtig, den Weg von staubinduzierten Gefrierprozessen zur Vereisung der Wolken besser zu simulieren. Gegenwärtige Gefrierschemen, die von Laborergebnissen auf gröbere atmosphärische Skalen extrapolieren, sind jedoch limitiert in ihrer Anwendbarkeit. Basierend auf Satelliten-Beobachtungen von Wolkenphasen und Aerosolen wird in dieser Ar- beit untersucht, wie das staubbedingte Gefrieren in Klimamodellen verbessert werden kann, um Klimaeekte von Staubeiskeimen genauer abschätzen zu können. Zu diesem Zweck wer- den Reanalyse-Daten eines Aerosolmodells mit dem Satelliten-Beobachtungen von Wolkenphase kombiniert und die globale Kovariabilität zwischen Mineralstaubaerosol und Wolkenvereisung abgeschätzt. Basierend auf einem weltraumgestützten Lidar, einer Lidar-Radar Kombination und einer Radiometer-Polarimeter Kombination werden hemisphärische und saisonalen Kon- traste in der Wolkenphase lokalisiert und quantifiziert. Schließlich werden diese Schätzungen verwendet, um den Einfluss des Mineralstaubes auf das Gefrieren von Wolkentröpfchen in einem Klimamodell einzugrenzen. Die vorgelegten Ergebnisse zeigen, dass Beobachtungen des Kon- trastes in der Wolkenphase dafür verwendet werden können, das staubgetriebene Gefrieren von Wolkentröpfchen in Klimamodellen zu optimieren. In den Extratropen steigt die durchschnittliche Häufigkeit von Eiswolken für höhere Mineralstaub- Mischungsverhältnisse um +5% bis +10%. Bei ähnlichen Mischungsverhältnissen von Min- eralstaub kann die Häufigkeit von Eiswolken für verschiedene Breiten immer noch variieren. Einzelne Wolkenphasen-Produkte neigen dazu, zu viele Wolken als flüssig für Temperaturen unter -30°C und zu viele als Eis für Temperaturen über 10°C zu klassifizieren. Bei -30°C liegen die hemisphärischen und die saisonalen Kontraste — relativ zur südlichen Hemisphäre bzw. zum borealen Frühjahr — zwischen +21% und +39% für einzelne Produkte in der Wolken- phase und zwischen +52% und +75% für eine Kombination der Produkte. Diese Kontraste wurden verwendet, um die Ezienz der Staubeiskeime im Modell zu optimieren. Nach er- folgter Optimierung stimmt das Modell besser mit den aus Beobachtungen der geschätzten Kontraste in der Wolkenphase überein und zeigt einen staubbedingten nordhemisphärischen Netto-Strahlungseekt von 0.14 ± 0.13 W m^2 durch die Vereisung, der niedriger ist als bisher angenommen. Diese Änderungen sind mit einer Abnahme der Gesamtwassermenge in den Wolken und einer Verstärkung des stratiformen Niederschlags auf Kosten des konvektiven Niederschlags verbunden.

This work deals with the assessment of the influence of low-temperature treatment on the structure and properties of casehardened surface layer of parts. The objective was to assess whether low-temperature treatment is sufficient, insufficient, or unnecessary for the given purpose. Gears which form a part of Zetor tractors gear boxes were used as samples. Thirteen pairs of frozen and non-frozen samples were used; they were taken from production batches throughout 2007, their hardness was assessed and furthermore, the experiment itself, freezing casehardened and hardened samples to different temperatures reaching as low as -196°C, was carried out. A moderate increase in hardness was registered with the majority of the frozen samples, which proved the effectiveness of the low-temperature treatment.

This thesis summarizes our latest findings on liquid-solid equilibria for fluids in confined spaces. In the first part of the thesis we introduce a microscopic lattice model which we have developed for the exploration of the freezing and melting phenomena in mesoporous solids with arbitrary geometries of the pore spaces. By applying this model to materials with well-ordered pore structures we (i) establish the mechanisms of the freezing and melting transitions and identify the equilibrium and metastable transition branches for different boundary conditions, (ii) illuminate the role of thermodynamic fluctuations, and (iii) find rigorous equations governing the transition temperatures for the lattice model considered. In the second part of the thesis the results obtained with the ordered pore systems are used for an in-depth analysis of the transitions occurring in geometrically disordered porous solids. First, by considering the ink-bottle pore geometry the efficacies of the different phase transition mechanisms established in the first part are elucidated. As a particularly important result, it is shown that thermodynamic fluctuations may alter the transition mechanisms. In the light of these findings the freezing and melting behaviors in statistically disordered porous materials are discussed. In the third part of the thesis several experimentally-relevant topics are considered and the potentials of the microscopic model for evaluation of the experimental data are demonstrated.

Textile wastewater contains very high concentration of color, COD, suspended solids and other pollutants. Methods such as reverse osmosis, nano-filtration and ultrafiltration are known to be effective to remove some pollutants but these methods are very expensive. A new treatment approach which is the combination of freezing technology and Microbial Fuel Cell technology has been studied in this thesis work and seems to have great potential to remove color and COD from textile wastewater. Freezing splits a diluted stream into two different streams; one stream in which water is transferred into ice with a low pollutant concentration leaving a concentrated stream with pollutants. Microbial fuel cell uses the concentrated stream to convert biochemical energy into electrical energy. Three different types of substrates, KMnO4 solution, municipal wastewater and orange juice, were studied. Freezing technology can produce high quality water by neutralizing pH-value; close to 7.0, removal of COD is more than 95% and separating color by almost 100%. Similarly MFC can remove color, and COD by 88.8% and 73.6% respectively. The maximum generation of electrical power by MFC was estimated to 1.03 mW/m2 of electrode area. The findings suggest that this new approach of textile wastewater treatment can be a costeffective way to remove pollutants from textile wastewater while generating some electricity.

A water droplet that impacts on a cold surface will start to freeze and in time ice will accumulate. To exemplify, effects of ice accretion is important in areas such as power generation e.g. wind power and vehicles located in a cold climate e.g. aircraft, cars, and boats. The common denominator for these examples is that ice accumulation can lead to a loss of efficiency and in some cases danger. Most studies have so far focused on investigating freezing water droplets visually in experiments or numerically in regards to how the freezing process behaves in terms of shape or freezing time for either a sessile or impacting droplet. It has been observed that the surface material and structures of the substrate is of importance. One part of the freezing process that has been less investigated is the internal flow and how it affects the freezing process. In this thesis, the internal flow in a freezing water droplet has been investigated experimentally. The internal flow inside a droplet is calculated by using Particle Image Velocimetry. A metal plate with a groove filled with ice was used to generate an area for the nucleation to start and to be able to control the shape of the droplet.  Previous work indicate that the substrate is of importance for the freezing process. The influence of the substrate material on the internal flow for similar shaped droplets is therefore investigated in Paper A, for a substrate temperature of -8°C. The results show that the substrate material, here in terms of metals such as aluminum, copper and steel, affect the magnitude of the internal velocity. In paper B it is investigated how the contact angle influence the internal flow. The vector field is examined at 9% of the total freezing time for water droplets at five different contact angles. A droplet with a higher contact angle will have a higher internal velocity in the center. A lower contact angle will barely show any movement in the center, however a higher velocity magnitude is observed close to the free surface compared to a droplet with a higher contact angle. Paper C studies the time until the directional change of the internal flow in a water droplet. Experiments at -8°C as in Paper B are used as well as experiments at -12°C for the five different contact angles. The time until the directional change is similar in time for both -8°C and -12°C while the total freezing time and also the time of the directional change varies with contact angles. A droplet with a lower contact angle will have a shorter time until the directional change occure while an increase in contact angle prolongs both freezing time and the time until the directional change.

Municipal wastewater treatment has a long history of local handling with recovery of toilet wastes for use in agriculture and to some extent energy recovery from biogas by use of local handling. This may be seen as ―the first way‖ further developed by septic tanks and infiltration and recovery as in Ecological Sanitation and use of urine separation toilets. However, problems related to water borne diseases and odor problems successively gave rise to ―the second way‖ with central wastewater systems with large investments in water and sewer nets and increasingly better technologies for water treatment and wastewater treatment. This technology may treat municipal wastewater to a drinking water quality and recover part of energy and nutrients contents for eco-cycling. The problems noted and which are quite obvious are affordability in poor countries and the need for much energy supply and with negative effects of emission of greenhouse gases. Ways should be better evaluated to obtain both an effluent wastewater of drinking water quality and at the same time be self-sufficient with energy, obtain products with a commercial value and comply with methods to reduce the amounts of released greenhouse gases. It is suggested that an intermediate dehydration step should be used by dividing the main stream into two streams, one to which water has been transferred by methods as forward osmosis or freezing and one remaining concentrated stream that could be treated more efficiently. New technologies should be considered for electricity production as use of fuel cell technology and forward osmosis. Methods to diminish greenhouse gas emissions include avoidance of such redox potentials and process conditions that lead to greenhouse gas emissions and binding of carbon dioxide in algae and plants and in clatharates.

This thesis evaluated the role of Serine/Arginine-rich proteins, also known as SR proteins, in addition to LAMMER kinases in the cold acclimation response using Brassica napus and Arabidopsis thaliana. Transcription profile analyses of SR and LAMMER kinase genes in Brassica napus and BnCBF overexpressor lines showed that exposure to low temperatures led to increased transcript levels for nine SR genes and two kinases. BnCBF overexpression was found to exacerbate this response. This was associated with increases in SR protein abundance and phosphorylation status, suggesting that SR proteins play an essential role in cold acclimation. These findings prompted further studies to assess the role of SR proteins and kinases in the cold acclimation induced adjustment of photosynthesis, the acquisition of freezing tolerance and the transcriptional profile of CBF, SPS and COR genes, which play an important role in the transcriptional cascade allowing plants to undergo cold acclimation. Using Arabidopsis loss-of-function mutants of SR proteins and AME3 LAMMER kinase, it was shown that At-RSZ22 and At-SR45 are indispensable in the regulation of photosynthesis under non-acclimated and cold acclimation conditions. At-RSZ22a, At-SCL30 and At-RS41 were then proposed to play a crucial role in the cold acclimation induced adjustment of photosynthetic performance. Moreover, the deletion of At-AME3 kinase not only jeopardized the cold acclimation induced adjustment of photosynthetic performance, but also the acquisition of freezing tolerance. This was associated with attenuation of the transcription profile of key cold responsive genes and protein abundance of COR15 A/B and dehydrins. These findings prompted further physiological characterization of ame3 mutants, and the elucidation of Serine/Arginine-rich proteins capable of interacting with this LAMMER kinase of interest. Under cold stress and acclimation conditions, the deletion of At-AME3 LAMMER kinase impeded Photosystem I physiology and state-1 state-2 transitions. These findings were associated with decreases in Photosystem II and Photosystem I protein abundance. Yeast 2-hybrid assays showed that six SR proteins are capable of physically interacting with AME3. Taken together, the results of this study demonstrate that At-RSZ22 and At-SR45 are essential in the photosynthetic performance of Arabidopsis, that At-RSZ22a, At-SCL30 and At-RS41 play an essential role in the cold acclimation induced recovery of photosynthetic performance, and that At-AME3 plays an essential role in the cold acclimation response.

Soil is the most widely used material in the construction of various civil infrastructure. Various types of soils are extensively used in its natural or compacted form in the construction of dams, canals, road and railway subgrades, and waste containment structures such as soil covers and liners. These infrastructure and foundation soils are exposed to the influence of environmental factors. In the permafrost and seasonally frozen regions, soils can be in different states (e.g., saturated or unsaturated, frozen or thawed, or combinations of them) due to the variations in moisture content and temperature. The soil-water characteristic curve (SWCC), which is the relationship between soil water content and suction, is used in the interpretation and prediction of unsaturated soils behavior. Similarly, the soil-freezing characteristic curve (SFCC), which is the relationship between unfrozen water content and subzero temperature, is used in the prediction and interpretation of frozen soils behavior. In this thesis, the SWCC and SFCC of two Canadian soils (i.e. Toronto silty clay (TSC) and Toronto lean clay (TLC)) were extensively investigated for better understanding the fundamental relationship between SWCC and SFCC. The soil resilient modulus (MR) is a key material property used in the rational design of pavements. Experimental investigations were undertaken to determine the MR of five Canadian soils (i.e., TSC, TLC, Kincardine lean clay (KLC), Ottawa Leda clay (OLC), and Indian Head till (IHT)), considering the influence of moisture and temperature, with the aid of an advanced triaxial testing equipment. Two simple models were proposed for estimating the MR of frozen soils, in this thesis. In addition, an artificial neural network (ANN) model was developed for estimating the MR of the five Canadian soils considering various influencing factors. The conclusions from the various studies in this thesis are succinctly summarized below. (1) Four expressions (i.e. power relationship, exponential relationship, van Genuchten equation, and Fredlund and Xing equation) that are widely used for representing the SFCC were selected for providing comparisons between the measured and fitted SFCCs for different soils. The results suggest that the exponential relationship and van Genuchten equation are suitable for sandy soils. The power relationship reasonably fits the SFCC for soils with different particle sizes, but not for saline silts. The Fredlund and Xing equation is flexible and provides good fits for all the soils. (2) The SFCC and SWCC of TSC and TLC were experimentally determined, analyzed, and compared. Many factors influence the reliable measurement of SFCC, which include sensors’ resolution and stability, sensor calibration for each soil, and thermodynamic equilibrium condition. The hysteresis of SFCC for the two soils is mainly attributed to the supercooling of pore water. The quantitative dissimilarity in the measured SFCC and SWCC may be attributed to specimen structure variations during compaction and saturation, and during freezing / thawing processes, and cracks formation due to sensors insertion. In addition, some fundamental differences may exist between the drying / wetting and freezing / thawing processes, resulting in dissimilarity. (3) Two novel models were proposed for the estimation of MR of frozen soils. The semi-empirical model extends the mechanics of unsaturated soils and employs SFCC for prediction. Several coarse- and fine-grained saturated soils were used to validate this model. The empirical hyperbolic model was proposed considering that the frozen MR versus subzero temperature relationship resembles hyperbola. This model was validated on coarse- and fine-grained soils under saturated / unsaturated conditions. The hyperbolic model has wider application since it can be used for both saturated and unsaturated frozen soils. Both the models are simple and promising. (4) The MR of five Canadian soils subjected to wetting and freezing was determined by using the GDS ELDyn triaxial testing system. A freezing system was established for controlling the desired testing temperatures within the soil specimens. The results suggest: (i) The effect of subzero temperature on the MR is significant. (ii) For TLC, KLC, OLC, and IHT, the frozen MR versus subzero temperature relationship of the saturated specimen typically has steeper slope than specimen at the optimum water content, for the temperature range from 0 to -5 °C. (iii) The effect of stress levels on the frozen MR depends on soil type, water content, and subzero temperature. Lastly, (iv) Loading frequency does not show a significant influence on the frozen MR. (5) The MR of the five Canadian soils was determined considering wetting and freeze-thaw (F-T) conditions. The results suggest: (i) The F-T cycles result in weak soil structure due to reduction in suction, particles movement, loss of cohesion, and formation of cracks / channels. (ii) The critical numbers of F-T cycles were determined as 1, 1, 2, and 1 for TLC, KLC, OLC, and IHT at the optimum water content, respectively. (iii) The percentage of reduction in MR after the critical number of F-T cycles was strongly related to the plasticity index for specimens tested at the optimum water content. (iv) The wetting process results in the decrease in suction and enlargement of soil pores. Consequently, relatively low MR values were measured at high water contents, and the effect of F-T cycles becomes insignificant. Finally, (v) The effect of stress levels on the MR was dependent on the initial water content of the specimen and soil type.