In the present study, the effect of twisted tape insert on the wet flue gas condensation in a horizontal tube, as a widely used application of condensation in the presence of non-condensable gas are examined experimentally and numerically. Four different tapes were evaluated under various range of combustion excess air. Several parameters of heat and mass transfer, such as convection/total heat transfer coefficient, friction factor, condensation ratio, latent heat proportion and total performance were investigated. As shown in the results, any kind of the tape insert causes the heat transfer enhancement and this improvement is not uniform for investigated range of excess air (5–30%). A wall film condensation model is used to simulate the vapor condensation. To validate the numerical model, the experiments of ambient air at same inlet Reynolds number is used to ensure that the trend of numerical data is acceptable. The numerical data demonstrates friction factor has two different trends before and after a complete combustion process (excess air = 10%). But the variation of friction factor is not more tangible under investigated range of inlet mass flow. The increase of condensation ratio is more considerable for lower values of excess air. Meanwhile, the greatest effect of twisted tape on latent heat proportion was achieved at excess air = 30%. The best improvement of condensation ratio and latent heat proportion were 24 and 25%, respectively. The calculation of total performance shows that, under investigated range of excess air, the higher twist ratio is preferred. Finally, the correlation of condensation ratio was reported and compared with experimental results.

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