Modelagem mecanicista da transferência de calor no escoamento bifásico líquido-gás em golfadas considerando o efeito Joule-Thomson

Abstract

The gas-liquid two-phase slug flow is largely found in the industry, especially in oil and gas production operations. The major part of the Brazilian oil production is offshore, where the cooling process of the oil-gas mixture is done through the pipe wall due to the external marine environment. The temperature decrease influences the properties of the mixture and also generates a change in the volume flow of the phases, especially the gas. Based on this context, the following research aims at developing a mechanistic model for the heat transfer in slug flows at high-pressure scenarios. In these scenarios, the gas must be treated as real and its density cannot be neglected in comparison to the liquid phase one, as it has usually been done in such type of models. The heat exchange between the gas and the pipeline wall and the temperature variation resulting from the pressure drop - known as the JouleThomson effect - are phenomena to be taken into account in the present work. The mathematical modeling encompasses the heat exchange of the phases with the pipe wall and the heat exchange between two unit cells - known as thermal scooping phenomenon. Moreover, a heat generation term is included in the energy balance so as to represent the Joule-Thomson effect. Results for the methane and water flows varying the inlet pressures from 100 to 250 bar will be shown for a 1,5 km-length pipeline. The inlet pressure effects - related mainly to the higher gas density - will be shown considering the hydrodynamics (velocity and pressure) and heat transfer (temperature and heat transfer coefficient) of the slug flow, as well as the geometry of the unit cell (lengths and phase fractions).