EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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4 resultados
Resultados da Pesquisa
Item Computer simulation of moisture transfer in walls : impacts on the thermal performance of buildings.(2021) Araújo, Mariana Tonini de; Souza, Henor Artur de; Gomes, Adriano PintoIn order to reduce electricity consumption in buildings, it is imperative to improve their thermal performance. Due to the many variables involved in thermal processes computer simulation is a consolidated method for thermal analysis. However, in many energy efficiency analyses calculus of heat conduction through the dwelling envelope does not consider moisture transportation and storage. The objective of this work was to evaluate the impacts of moisture transfer in walls on the thermal performance of naturally ventilated and artificially conditioned buildings using EnergyPlus computer simulation. This research contributed to the literature by showing the difference in thermal zone air humidity, temperature and annual energy demand (i.e. electricity consumption) when moisture effects are considered in walls. Buildings were composed of masonry and solid concrete envelopes and three numerical models were simulated: Conduction Transfer Function Model (CTF), Effective Moisture Penetration Depth Model (EMPD) and Combined Heat and Moisture Transfer Model (HAMT). The CTF model does not consider moisture effects. Results found a higher relative air humidity for the studied thermal zone by applying the HAMT model in the numerical simulation, and the envelope porosity was proven to affect HAMT humidity results. Comparing the HAMT and EMPD models with the CTF model, the annual energy demanded for cooling presented a 21% reduction for the EMPD model in the masonry and 9% increase for the HAMT model in the solid concrete. This article shows the importance of an accurate EnergyPlus heat transfer model for simulating a whole building to check edification attendance of minimum comfort parameters and select envelope materials aiming the reduction of electricity consumption.Item A novel two degrees of freedom system for measuring iron ore water content on a conveyor belt.(2021) Pinto, Érica Silva; Santos, Gabriel Almeida; Magalhães, Paulo Henrique Vieira; Rêgo Segundo, Alan KardekWater content or moisture of materials is a parameter widely used in the industry. In mining, it is an important variable to control in iron ore production. High moistures may cause instability of iron ore piles and may make transport by ship unfeasible. Therefore, this paper presents the development of a system for measuring iron ore moisture on a conveyor belt (laboratory-scale). The structure that supports the sensor has two degrees of freedom, which allow perpendicular and parallel movements. The parallel movement makes the relative velocity between the measurement cell and the ore almost zero. The vertical movement allows the sensor to be placed at different depths in the ore. These sets enable real-time and in situ measurements. The system uses the capacitive method to determine the dielectric constant of the iron ore located between the sensor electrodes and, consequently, the moisture. This system has a measuring range of 0 to 14% on a dry basis and presents an uncertainty up to 0.07 percentage points for a 2-standard-deviation confidence level. In the validation process, the absolute error was less than 0.34 percentage point in the mining interest range of 6 to 14%. The founded results achieve a significant advance in the development of real-time equipment for measuring ore moisture since there is no device capable of doing it with the necessary level of accuracy and precision. For mining, this kind of system represents a big step to take corrective and preventive decisions around iron ore moisture control.Item Electrical profiling of vibration-induced dewatering of sand.(2021) Reis, Jonathan Leandro Martins; Luz, José Aurélio Medeiros da; Vardanega, FábioElectrorresistive profiling of moisture inside a quartz sand bed on a pilot-scale vibrating screen was treated here. As electrode or probe configuration for resistivity measurement is concerned, the classical Wenner α array was used, requiring equal electrode spacing, and correct penetration depth and alignment. Here, the influence of small variations in penetration depth and lack of probe collinearity on the moisture readings, using a digital earth resistance tester and copper wires as probes, was evaluated. The penetration depths studied were 50 mm and 55 mm. In turn, the electrode misalignment tested was 10 mm. The only factor that has caused statistically significant effect in measurements was probe penetration depth, at least under the range tested here.Item Effects of hematite surface characteristics on filtration process.(2016) Graça, Leonardo Martins; Lagoeiro, Leonardo Evangelista; Galery, Roberto; Peres, Antônio Eduardo ClarkIn iron ore pelletizing plants a range of process parameters such as particle size distribution, specific surface area, and moisture, must be controlled to achieve opti¬mized operation conditions. Particle size distribution and specific surface area are con¬trolled during the grinding operations. Moisture, however, is controlled during filtra¬tion of the ground products. This work investigates the relationship between particle morphology, filter cake moisture and filter capacity. The samples were taken during the filtration tests and referred to three different blends presenting distinct mineralogical features and similar chemical compositions in order to investigate the effects of only the hematite surface characteristics. Six types of morphology are distinguished: granu¬lar hematite, tabular hematite, martitic hematite, polycrystalline hematite, hematite-goethite aggregates and goethite. For each filtration test, the filter cloth product was characterised. The characterisation analysis revealed that blends containing martitic hematite concentration above 11.45 percent increased substantially the filter capacity. However, it had also caused an increasing in final moisture content that reached values around 10.0 % compared with industrial moisture specification that can vary on the range of 8.5 to 9.5 %.