Experimental and Numerical Study on Vapor Condensation of Wet Flue Gas in Chimney Nijaz Delalić 1, a , Ejub Džaferović 2, b and Ejup Ganić 3,c 1 Mechanical Engineering Faculty of University in Sarajevo, Vilsonovo setaliste 9, 71000 Sarajevo, Bosnia and Herzegovina a delalic@mef.unsa.ba, b dzaferovic@mef.unsa.ba, c ejup_ganic@hotmail.com Keywords: chimney, vapor-gas mixture, condensation, finite-volume CFD, diffusion layer. Abstract. Increase of the emission of CO 2 , which is mostly the result of the combusted fossil fuels into the atmosphere, exponentially increases. Through increased energy efficiency there is lower CO 2 emission. There is a tendency to reduce exhaust gases temperatures down from their original value referred to as “acid dew point”, 115-160°C. A result is vapor condensation of wet flue in chimney. Condensation occurs when the surface temperature is below the dew point of the vapor-gas mixture. Therefore, Vapor-Liquid Equilibrium models are required in order to determine the dew point of the mixture. Wet flue gas is simulated with vapor-air mixture. A numerical model was presented to calculate the velocity and thermal field of turbulent vapor-air mixture flow trough a chimney. The momentum and temperature field were calculated via a finite-volume CFD code, using the k – e turbulence model. The validation of this calculation was conducted employing an experimental set for heat and mass transfer in vertical upward vapor-air mixture. Measurements were done using a stainless steel tube of 13.2 mm I.D. (internal diameter) and 70 I.D. lengths. Flow rates of steam and air were varied as the experimental parameters. The experiment involves two-phase, two-component, heat and mass transfer. Comparisons of wall temperature and condensate rate were made and the model was shown to give an acceptable results. Introduction Increase of the emission of CO 2 , which is mostly the result of the combusted fossil fuels into the atmosphere, exponentially increases. This trend of increase of CO 2 presents immense danger for the planet. Emission of CO 2 in certain countries or group of countries is very different and is mostly connected with the size and economic development of certain countries or region. Economic development of the countries that have such increase of emission of CO 2 is not acceptable for mankind. For this reason the organized part of the world must resist this trend of the increase of emission. Some measures to stop increase of the emission of CO 2 must be undertaken, and then measures to reduce emission of CO 2 into the atmosphere should follow. One of the very important ways to decrease the emission of CO 2 is to increase energy efficiency. The development of new techniques for heating buildings systems, like high performance generator, burners with modulated functioning, allow design henceforth installation with high thermal efficiency. Such installations require all energy recuperation and consequently lower temperatures of exhaust flue gases. This causes vapor condensation of flue gases. Use of latent heat of the vapor condensation from exhaust gases as well as the measure for increasing the energy efficiency is very suitable regarding the combustion of the gaseous fuels. But, problem is very complex, because as it involves more coupled phenomena: two-phase flow, multi component flow, turbulence, condensation, liquid film, diffusion vapor of water from centerline to the wall of the chimney conduit. There are not many papers in this topic. Some researchers had experimental approach, some numerical. Researchers, Junker [3] and Pitschak [4] provided numerical and experimental work for prediction thermal field flows, the heat transfer of the flue gases and diffusion vapor across the wall of the chimney. Maref and coworkers [5] employed numerical method of finite volume for prediction of thermal field flows, the heat transfer of the flue gases in the simple chimney. Some researchers from GWI-Germany [2] had experiment with condensation vapor in domestic chimney. The aim of this work is experimental and numerical prediction of the thermal