Análise dos métodos de cálculo de golpe de ariete em tubulações

This work studies the most commonly used methods and make comparisons and discussions of the findings made by each of them and the results provided by them. The objective of this research was to show that the method of characteristics is currently the most efficient method to perform these simulations because of its broad scope low simplifications, requirement allowing to consider every detail of the pipe and fluid. Manual calculations are performed and also a software capable of calculating this phenomenon for various situations, such as water pump, elevated tanks, valves and quick maneuver was developed. The software is based on the method of characteristics that is currently recommended by ABNT. These methods, and the results are obtained numerically and graphically are adopted pipes and amount of downstream conditions and in which will be applied. The conclusions reached showed that the Allievi method is widely used yet because of its efficiency and quick calculation for simple pipes. The method of characteristics, although a lot of work to be calculated due to the calculation is iterative process and requires a program to use it, is the only one that allows the calculation with all amount to the conditions situations and downstream of all the pipe possibilities found

Study on the initial stages of water corrosion of fluorozirconate glasses

The surface corrosion process associated with the hydrolysis of fluorozirconate glass, ZBLAN (53ZrF(4), 20BaF(2), 20NaF, 4LaF(2), 3AlF(3)) was investigated using X-ray photoelectron spectroscopy (XPS), grazing-incidence small angle X-ray scattering (GISAXS), X-ray reflectivity (XRR) and scanning electron microscopy (SEM). After a short exposure period (25 min) of the glass surface to deionized water the XPS data indicate an increase of the oxygen content accompanied by a decrease of fluorine concentration. The analysis of the chemical bonding structure identified the predominant surface reaction products as zirconium hydroxyfluoride and oxyfluoride species. The second most abundant glass component, bariumfluoride, remains almost unaffected by oxygen, while sodium fluoride is completely removed from the attacked surface region. The detected structural and compositional changes are related to the selective dissolution of the glass components leading to the formation of a new surface phase. This process is accompanied by a visible surface roughening caused by reprecipitated species, observed by SEM. The modification of the glass surface is responsible for an increase of the GISAXS intensity. The scattering was attributed to nanovoids formed at the surface region of the glass with an average size of 2.4 +/- 0.05 nm. (C) 2004 Elsevier B.V. All rights reserved.

XPS study on water corrosion of fluorzirconate glasses and their protection by a layer of surface modified tin dioxide nanoparticles

The surface corrosion process associated with the hydrolysis of fluorozirconate glass, Z-BLAN (53ZrF(4), 20BaF(2), 20NaF, 4LaF(2), 3AlF(3)), and the corrosion protection efficiency of a nanocrystalline transparent SnO2 layer were investigated by X-ray photoelectron spectroscopy. The tin oxide film was deposited by the sol-gel dip-coating process in the presence of Tiron(R) as particle surface modifier agent. The chemical bonding structure and composition of the surface region of coated and non-coated ZBLAN were studied before water contact and after different immersion periods (5-30 min). In contrast to the effects occurring for non-coated glass, where the surface undergoes a rapid selective dissolution of the most soluble species inducing the formation of a new surface phase consisting of stable zirconium oxyfluoride, barium fluoride and lanthanum fluoride species, the results for the SnO2-coated glass showed that the hydrolytic attack induces a filling of the film nanopores by dissolved glass material and the formation of tin oxylluoride and zirconium oxyfluoride species. This process results in a modified film, which acts as a hermetic diffusion barrier protecting efficiently the glass surface. (C) 2006 Elsevier B.V. All rights reserved.