A numerical analysis was carried out on the heat and mass transfer, and pressure drop characteristics of the modular tube bundle heat exchanger. The finite volume method with a $k-varepsilon$ turbulence model was used for the analysis. Due to condensation, the total heat transfer rate is observed about $4~8\%$ higher than that on dry surfaces. Total heat transfer rate increases with increase in the velocity, temperature and relative humidity of incoming air. It also increases with decreasing the aspect ratio of heat exchanger tube. The inlet velocity of cooling water has little effect on the total heat transfer when the other conditions are fixed.