Study Of Heat Transfer For Wet Mixture Gas Flowing Over A Finned Tube

The recovery of waste heat is important for conserving the energy and protecting environment. A complicated physical process including heat and mass transfer and phase change takes place in the condensation heat exchanger when waste heat is recovered from wet flue gas. The mechanism of convective condensation heat transfer for mixture gas flowing over a finned horizontal tube is studied theoretically and experimentally in this paper. Several parameters influcting the condensation are studied especially, including the fin. And also the thickness distribution of film is analyzed theoretically.The experimental system is rebuilt and the feasibility test on the non-finned tube is put up. Some vapor and air are taken into the system to change the velocity of the flow and the mass friction of the vapor in the experiments. The effects of flue gas velocity, flue gas temperature, entry temperature of cooling water and non-condensable gas content on convective condensation heat transfer are studied experimentally. The effect of fin on condensation is studied in the experiments.The condensation heat transfer is divided into two parts: the condensation on the sidewall of the fin and on the tube surface between the fins. A mathematical model describing convective condensation heat transfer is established. The temperature distribution in the finned tube is studied by numerical simulation. In the sidewall of the fin, the interaction of film is considered. The distribution of the film thickness on the sidewall of the fin is obtained. The heat and mass transfer of mixture gas is analyzed theoretically. The quality of the condensate is calculated by using Matlab and Mathematica. Theoretical results and experimental results are in good agreement, so the mathematical model is reasonable. The thickness of liquid film on the sidewall of fin is between 10^-8 and 10^-7m for the mixture gas with mass content in range of 10%-27%, which is so thin that the liquid film conductive heat resistance can be ignored in the whole heat transfer process.