An analytical model of heat and mass transfer processes in a flue gas condensing heat exchanger system was developed to predict the heat transferred from flue gas to cooling water and the condensation rate of water vapor in the flue gas. Flue gas exit temperature, cooling water outlet temperature, water vapor mole fraction, and condensation rate of water vapor were computed using the analytic model. A pilot-scale heat exchanger was used to validate the analytical model. The experimental results show a very good agreement with analytical model results. The performance of the heat exchanger system was evaluated as functions of the ratio of the mass flow rate of cooling water to the mass flow rate of inlet flue gas, the inlet cooling water temperature and the ratio of flue gas flow rate to total heat transfer surface area. (C) 2010 Elsevier Ltd. All rights reserved.