Effects of water vapor condensation on the convection heat transfer of wetflue gas in a vertical tube

The annular thin film condensation of water vapor in wet flue gas flowing t hrough a vertical tube was studied theoretically and experimentally. Especi ally discussions were conducted on the effects induced by condensation of s mall amount of water vapor (10 = 20% fraction) on convection heat transfer in a vertical tube. The convection heat transfer was enhanced by the conden sation of the condensable gas (water vapor) existing in the wet flue gas. T he experiments also indicate that the wall temperature was an important fac tor affecting the condensing rate and the fog formation in the wet Rue gas. The fog formation in the wet flue gas has a significant influence on the c ondensing rate and associated heat transfer. The proportion of the sensible and latent heat contribution to total heat transfer would change with the Re number. When the wall temperature is much lower than the saturation temp erature of the inlet wet flue gas, the effect of the superheat could be neg lected. But when the fog forms in the bulk flow, the temperature and concen tration profile would be altered. (C) 2001 Elsevier Science Ltd. All rights reserved.