This work describes a methodology that allows an accurate correlation for natural gas compressibility factor to be obtained. This methodology was applied to the Parana State natural gas distribution network in Southern Brazil, whose operating conditions were characterized by more than 14,000 pairs of pressure-temperature readings, measured along eight months. Compressibility factors calculated following Peng-Robinson, Patel-Teja-Valderrama, Shell Oil Company, Soave-Redlich-Kwong, and Van der Waals were compared to those given by the American Gas Association equation, which is used by most natural gas companies. Finally, an alternative correlation was proposed, which is highly accurate within the network operating range.Keywords: COMPAGAS natural gas Brazilian network, compressibility factor of natural gas, equation of state for natural gas, natural gas thermodynamic properties
Para garantir que, mesmo sob solicitações mecânicas repetitivas, não ocorram falhas em um sistema de implante dentário, é imprescindível compreender a influência dos parâmetros geométricos na resistência mecânica. Neste trabalho foi avaliado a influência da altura de transmucoso e do diâmetro de componentes protéticos retos na resistência mecânica em quatro grupos, considerando os extremos de cada parâmetro, em configuração de acordo com a norma ISO 14801. A avaliação se deu por simulações estáticas não lineares pelo método de elementos finitos, através do software comercial FEMAP. Os resultados mostraram que, de acordo com o que é apresentado em literatura, a porção entre a cervical e os três primeiros filetes da rosca externa do implante foi a que apresentou a maior solicitação mecânica e, portanto, a mais suscetível à falha. O diâmetro foi o parâmetro de maior influência, possuindo influência positiva (diminuição da tensão) com o aumento do mesmo. A altura de transmucoso teve um efeito positivo somente nos componentes de maior diâmetro e pouco impacto nos componentes protéticos de menor diâmetro. Concluiu-se ainda que o grupo com componente protético de menor diâmetro e maior altura foi o que obteve maiores tensões, sendo, portanto, o caso crítico para o ensaio mecânico.
During the preliminary phases of typical operations in the petroleum industry, particularly those involving distribution networks and/or natural gas transmission projects, when complete information is not available, it is sometimes necessary to estimate some thermodynamic properties of natural gas. The behavior of natural gas is affected directly by its chemical composition. It comprises a mixture of volatile hydrocarbons, nitrogen, oxygen, carbon dioxide, and traces of other components. This knowledge is crucial to engineers involved in the areas of equipment design, processing and transportation of such fluids. The design of these systems uses conventional flow equations for both stationary and transient systems, which also include various natural gas fluid properties such as density, gas constant, specific heat, critical temperature and pressure, compressibility factor, and dynamic viscosity, among others. In view of this, a proposition is given to determine the main properties of natural gas from its average chemical composition and related operational conditions (pressure and temperature). This proposal, developed in Matlab, allows the determination of some of the key properties of natural gas, giving users the option to choose the most representative equation of state among the available models, namely, Peng-Robinson, Patel-Teja-Valderrama, Shell Oil Company, Soave-Redlich-Kwong, and van-der-Waals, to determine the compressibility factor of the samples. The results of a particular simulation were compared with actual data from the distribution network COMPAGAS, which is the company responsible for the distribution of piped natural gas in the state of Paraná (Brazil), demonstrating a good convergence between the values obtained and encouraging their use in future.
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