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- ItemTribologia e Temperatura de Contato do Peek Deslizando Contra Latão, Peek e Alumina(Universidade Federal do Espírito Santo, 2024-01-30) Camporez, Rubson Mação; Scandian, Cherlio; https://orcid.org/0000-0002-4393-719X; http://lattes.cnpq.br/8466752738430250; https://orcid.org/0000-0003-2378-025X; http://lattes.cnpq.br/2417559348617413; Mello, Valdicleide Silva e; https://orcid.org/0000-0001-6413-6650; http://lattes.cnpq.br/4147387781308845; Strey, Nathan Fantecelle; https://orcid.org/0000-0002-2568-116X; http://lattes.cnpq.br/3613706957012460; Silva, Carlos Henrique da; https://orcid.org/0000-0002-2897-4347; http://lattes.cnpq.br/6218847264452522; Souza, Roberto Martins de; https://orcid.org/0000-0002-7384-1914; http://lattes.cnpq.br/4586350967708284The increase in contact temperature resulting from friction during sliding between bodies influences tribological behavior, leading to changes in the microstructure and properties of materials. This thermal increase can induce softening and melting of the bodies, phenomena particularly impactful in polymers due to their low glass transition and melting temperatures. Therefore, studying and predicting the contact temperature for polymeric materials is of paramount importance to maximize their tribological application. The calculation of the contact temperature can be performed by numerical methods or through mathematical models developed for problems of lesser geometric complexity and boundary conditions. Despite the relevance and presence of methodologies for determining the contact temperature, this challenge persists in contexts involving polymeric pairs. The obstacle arises from simplifications and from not considering changes in material properties as a function of temperature. A case that occurs with polymers is the alteration of thermal conductivity, which is sensitive to the molecular ordering of polymer chains, as well as to temperature and contact pressure. The literature has gaps to be filled regarding the contact temperature of polymers, especially polymer-polymer pairs. In this context, an investigation of the contact temperature of spheres and cylindrical pins (geometry) of two different diameters (dimension) of polyetheretherketone (PEEK), an ultra-high-performance polymer, sliding against brass, PEEK, and alumina discs was conducted, varying the normal load (13 different loads) and sliding velocity (0.5 and 1 m/s). Additionally, the surface temperature of the disc was measured during the test using an infrared thermal camera. Overall, it was observed that sliding velocity, geometry, dimension, and nature of the discs influenced the parameters used in calculating the contact temperature, such as heat partition and the Peclet number. In contrast, regarding the increase in flash temperature, nominal temperature, and maximum contact temperature, sliding velocity did not influence, while the geometry, dimension, and nature of the discs did. Errors between the temperature measured with the thermal camera and one of the components of the contact temperature were observed, and to improve the accuracy of the mathematical model, the use of correction factors called γ1 and γ2 was proposed, which multiply the thermal conductivities of the pin/sphere and disc, respectively. With their use, errors were reduced to zero under some conditions, increasing the applicability of the mathematical model of contact temperature.
- ItemEstimation Problems In Advective-Diffusivereactive Phenomena Using Meshless Numerical Methods Combined With Bayesian Inference(Universidade Federal do Espírito Santo, 2024-03-22) Dalla, Carlos Eduardo Rambalducci; Dutra, Júlio Cesar Sampaio ; https://orcid.org/0000-0001-6784-4150; http://lattes.cnpq.br/5331990513570911; Colaço, Marcelo José; https://orcid.org/0000-0002-8020-6222; http://lattes.cnpq.br/4953372732452626; Silva, Wellington Betencurte da ; https://orcid.org/0000-0003-2242-7825; http://lattes.cnpq.br/6900925458823632; https://orcid.org/0000-0002-8078-6554; http://lattes.cnpq.br/2522314513419213; Neto, Carlos Friedrich Loeffler; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; Lara, Luciano de Oliveira Castro ; https://orcid.org/0000-0003-1329-2957; http://lattes.cnpq.br/1675675424615229; Lamien, Bernand; https://orcid.org/0000-0003-1665-26-20; http://lattes.cnpq.br/3496682177555473; Costa, José Mir Justino da ; https://orcid.org/0000-0001-5719-4377; http://lattes.cnpq.br/2396817509327075The mathematical modeling of advective-diffusive-reactive phenomena finds numerous applications in various scientific fields, such as the transport of pollutants and adsorption columns. Mesh reduction techniques have proven efficient and have been gaining prominence in the literature. However, despite all the progress observed, some things could be improved in dealing with complex partial differential equations. With these limitations, variations of these methods emerged and sought to deal with complex systems. The present thesis proposal involves the development of a numerical method that combines the Eulerian-Lagrangian Method (ELM) with the Method of Fundamental Solutions (MFS) to solve a series of examples modeled by the transport equation. In addition, Bayesian inference methodologies, such as particle filters, which allow the estimation of states and model parameters, will be considered, providing an inverse approach to the problem. The results contemplated the solution of benchmark cases, which have an analytical solution for evaluating the proposed method, showing accurate and stable results when tested against different Peclet numbers between 0.5-200. The method sensitivity to parameters, such as node number and positioning, was also investigated. Its performance was evaluated against metrics such as root mean squared error and absolute error. We also performed manipulations to original models to address the reaction term and extend the cases to high-dimensionalities and complex geometries using the proposed methodology.
- ItemTribological behavior of ZnO@GO core-shell nanoparticles as water-based lubricants additive and in composite cobalt-based coatings prepared via cathode plasma electrolysis deposition(Universidade Federal do Espírito Santo, 2023-06-22) Romero, Manuelle Curbani; Scandian, Cherlio; https://orcid.org/8466752738430250; http://lattes.cnpq.br/8466752738430250; https://orcid.org/0000-0002-3578-8577; http://lattes.cnpq.br/2213541475559069; Tschiptschin, André Paulo; https://orcid.org/0000-0002-1806-2010; http://lattes.cnpq.br/2163698776105146; Mello, Valdicleide Silva e; https://orcid.org/0000-0001-6413-6650; http://lattes.cnpq.br/4147387781308845; Vieira, Lucia; Murray, Henara Lillian Costa; Strey, Nathan FantecelleCore-shell nanoparticles are hybrid nanostructure. This thesis addresses the electrostatic self-assembly of core-shell nanoparticles with hardcore of ZnO and soft graphene oxide (GO) shells. The assembled structures (ZnO@GO) were used as additive in water-based lubricants and in cobalt-based coatings. In the second chapter, the GO nanoparticles were synthesized and assembled with ZnO using a surface modifier, forming a ZnO@GO core-shell nanostructures. ZnO@GO, GO and ZnO were used as additives in water nanofluids which were wear tested in a ball-on-plate configuration using AISI 52100 as the ball and AISI 304 as the plate. ZnO@GO were efficient in reducing wear by the formation of a GO-rich protective tribolayer. The third chapter regards the production of cobalt coatings by cathodic plasma electrolytic deposition (CPED). The deposition mechanism and the effect of polyethylene glycol (PEG) on it are discussed. CPED was efficient in forming nanocrystalline and wear-resistant coatings. PEG decreased the current needed for deposition and affected the thickness and morphology of coatings, while not altering wear or friction. In the fourth chapter, the ZnO@GO nanoparticles were added to the electrolytic bath forming a composite cobalt-based coating. Coatings were tested against an AISI 52100 ball in sliding wear tests. Nanoparticles increased coatings hardness and decreased surface roughness. Composite coatings had a superior tribological performance when compared to pure Co-coatings due to the entrapment of exfoliated GO nanoparticles on the wear track, protecting the surface.
- ItemModelagem termoeconômica generalizada e sistemática para o tratamento de resíduos e internalização de encargos ambientais em sistemas térmicos(Universidade Federal do Espírito Santo, 2023-07-10) Faria, Pedro Rosseto de; Santos, José Joaquim Conceição Soares; https://orcid.org/0000-0003-3695-2014; http://lattes.cnpq.br/6666040476009642; https://orcid.org/0000000261503248; http://lattes.cnpq.br/5236112337927566; Reis Junior, Neyval Costa; https://orcid.org/0000000261594063; http://lattes.cnpq.br/4944106074149720; Palacio, José Carlos Escobar; https://orcid.org/0000-0001-8691-2737; http://lattes.cnpq.br/1472037977658347; Orozco, Dimas José Rúa; https://orcid.org/0000-0001-8153-989X; http://lattes.cnpq.br/3457569194994816; Ramos, Rogério; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139Thermoeconomics originally combines Thermodynamics with Economics. Nevertheless, environmental issues can be incorporated. Despite the thermoeconomic modelling improvement and the quantity of methodologies available, topics such as waste cost allocation are still subject to criticism and can be considered important challenges to be solved for the rational and systematic inclusion of environmental charges. In many of the proposed methodologies there are subjective, incomplete, inconsistent or particular allocation criteria, which makes it difficult to define the waste cost formation process. Therefore, a generalized and systematic thermoeconomic methodology capable of treating waste and taking into account environmental issues in analyses of multiproduct systems is required. The main objective of this work is to consolidate the systematization of a methodology that is directly associated with the integration of a device that represents the environment with thermoeconomic diagrams. Models that already use this device have never been applied in thermal systems with more than one source of combustion to demonstrate the need for generalization and systematization. Still concerning the device that represents the environment, this work shows for the first time: i) how it is considered in closed-cycle thermal systems, such as steam cycles; ii) how it can be introduced in models that originally do not consider it explicitly, as in the E Model that uses exergy flows to define the thermoeconomic diagram; iii) the fundamental role it plays in the internalization of environmental charges, such as carbon credits and mitigation and environmental control devices cost; and iv) how it behaves and affects a thermoeconomic diagnosis assessment. The internalization of environmental cost exactly in the environment device systematically redistributes the costs to the other components of the system and the final products. Case studies, considering gas and steam cogeneration systems, show that the environmental device has a fundamental role in the generalized and systematic internalization of environmental charges, for instance, pollutant emissions, acquisition costs of mitigation and environmental control devices, and carbon pricing, among others. Through this internalization, it becomes feasible to assess the financial and environmental implications of emissions, foster the mitigation of greenhouse gases (GHG), and enhance the design and operation of systems.
- ItemToward a safe and circular thermochemical process to sanitize human feces in resource-poor environments(Universidade Federal do Espírito Santo, 2023-04-28) Bittencourt, Flavio Lopes Francisco; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/0000000182624762; http://lattes.cnpq.br/5146106444604968; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; Errera, Marcelo Risso; https://orcid.org/0000-0002-9394-2712; http://lattes.cnpq.br/1262935578021391; Magri, Maria Elisa; https://orcid.org/0000-0002-5911-4390; http://lattes.cnpq.br/2200887225218302; Pan, RumingDefecating in precarious facilities or even in the open environment is an undeniable reality in low-income countries. Despite the efforts made in recent years, unimproved facilities and the practice of open defecation are still generating around 70 wt% of the worldwide fecal matter. Smoldering combustion can be a fast, viable, and efficient mechanism to mitigate the impacts of fecal matter on the surrounding environment, using the energy potential of feces to transform them into solid and gaseous products without pathogens. Nevertheless, using human waste as a feedstock brings many challenges, especially regarding its hazardous aspect, rheologic properties, naturally moist state, and very-low permeability. In this thesis, a latrine-like device is conceptualized, constructed, and operated. The end products are safe for reuse from the perspective of circular economy and sustainability. A novel smoldering configuration driven by vacuum-induced airflow is studied to understand a series of thermal events that changes the aspects of propagating a combustion front in a smoldering reactor: the combination of a reactive porous bed shrinking with time and an open inlet increases the effects of free convection. Negligible free convection effects are observed when the shrinkage is meager; however, from the moment the thermal plume starts to grow, the boundary layer is squeezed into the reactor wall, gradually quenching the combustion front. A Nusselt number correlation expresses the energy available at the fluid-porous interface that can be recovered for secondary processes. After understanding and dominating the combustion process using the novel smoldering configuration, we present and launch the FeD-Latrine, reproducing in a laboratory-scale, real defecation scenarios to destroy fresh feces with an average dropping rate of 120 g/h. For the first time, fresh feces are destroyed in a smoldering reactor without decreasing their moisture content. To accomplish it, the arrangement of the FeD-Latrine uses out-of-bed heat to transform fecal matter into fecal chars and ashes. Even though the FeDLatrine emits pollutants at a controlled rate, reducing the global CO2-eq can make it even more sustainable. In such context, we present an integrated process for CO2 reduction and capture, using a gas looping to oxidize combustible gases and create favorable conditions to capture CO2 in bed. CaO used as a sorbent captures up to 8 mmol of CO2 per gram. Compared to kinetic-dominant processes for CO2 capture, we obtain an efficiency of around 52 %. Our findings show that using the FeD-Latrine to replace typical pit latrines reduces 60% of the CO2-eq emissions. Finally, a field trip to an Amazon community reveals that thermochemical processes are already part of the community member's routine, providing evidence of the potential application of thermochemical units for sanitation in resource-poor environments.