Simulação computacional de escoamentos verticais ascendentes gás-líquido no padrão disperso com transferência de calor

Abstract

In this work a study was carried out on gas-liquid vertical upwards two-phase flows, considering the homogeneous flow hypothesis on dispersed bubble pattern. The primary objective is to verify the influence that an external heat source produces on the flow. In this way, a numerical model for solving the energy conservation equation by the Runge-Kutta method, executed in a computer code written in MATLAB®, is proposed. However, to solve this model, it is also necessary to solve the hydrodynamic model by the conservation equations of mass and momentum. Thus, a simplified model for solving the homogeneous flow, also numerically, is presented first. The results of this model are represented in terms of the pressure gradient and then compared with data in the literature. Then the resolution of the heat transfer model is coupled to the hydrodynamic, and the results are obtained for four heat flux values: 10 kW/m², 100 kW/m², 250 kW/m², and 400 kW/m². In this analysis, the pressures and fractions of the phases are compared with each other, as well as with the hydrodynamic isothermal model. It has been found that the phase fraction is more affected by the temperature difference than the pressure. Finally, the mixing and wall temperatures were analyzed, showing how and when the two-phase flow differs from the single phase.