Condensation Heat Transfer on Tubes in Actual Flue Gas (Parametric Study for Condensation Behavior)

摘要

In order to improve a boiler efficiency, latent heat recovery from the flue gas is very important concept. Condensation heat transfer on horizontal tubes was investigated experimentally by using an actual flue gas from a natural gas boiler. The parametric studies concerning the effects of tubes stages, gas velocities,-SO_2 in the flue gas and Teflon lining on tubes were conducted at a wide range of tube surface temperature. The heat transfer was enhanced at the second stage due to the wake turbulence of the first stage. No significant decrease of the condensation on the second stage due to the condensate falling from the first stage could be observed. Even at the high gas velocity condition, the condensation pattern was similar to that observed in the previous low gas velocity experiments. The effect of SO_2 in the flue gas on the condensation behavior could not be observed. The heat and mass transfer behaviors on the stainless steel and Teflon lining surface were well predicted with the analogy correlation. The above results suggested that the heat and mass transfer were dominated with the convection and diffusion process in the gas side.