Influência do design e das condições operacionais na aerodinâmica e no fenômeno de transferência de massa no interior de um túnel de vento portátil utilizado para estimar compostos odorantes medidos sobre superfícies líquidas passivas

Abstract

The emissions to the atmosphere by liquid passive area sources, that is, extensive liquid surfaces swept by the atmospheric flow in which occurs the emission of a certain chemical, like the tanks and lagoons in wastewater treatment plants are significative sources of odorant compounds, such as the H2S and the acetic acid. The health effects of these gaseous compounds include eye and throat irritation, and nausea. Different equipments are being used to perform a direct estimation of the emission of the odorant compound on passive surfaces. However, it is well known in the literature that the use of different equipments for the same source is conducing to different results. In general, these equipments are open-bottomed boxes in which is fluxed a clean gas in its inside that enters in contact with the gas-liquid interface and carries the odorant compound, to be posterior sampled at the equipment outlet and analyzed. Thereafter, the results provided by these equipments are straightly connected with the airflow and mass transfer phenomena on its inside. So, to properly assist the answer of the question of which equipment is more adequated to estimate the emission rate of an odorant compound in passive area sources it is first required to understand the airflow and how the mass transfer phenomena occur on its inside occurs. In this way, the present work objectives to analyze, using numerical simulations, the airflow and mass transfer phenomena inside one the of equipments used in the direct estimative of odorant compounds, namely the portable wind tunnel. The turbulent effects were incorporated using the κ−ω SST model. The finite volume method was used via the ANSYS Fluent software to numerically solve the involved equations. The analysis of the streamlines, profiles, vectors, and contours of the velocity, turbulent kinetic energy, and concentration showed that the flow inside the device is quite complex and 3D, with several recirculation zones and thus reversed flow. This feature of the flow have a direct impact on the volatilization process. Nevertheless, the results showed that the geometry configuration of the equipment has a direct impact on the airflow and thus on its mass transfer phenomena, in this way, it seems that small changes in its geometry could lead to an improvement of the flow in its inside