In order to study the effects of tube type on vapor-gas condensation heat transfer and strengthen vapor-gas condensation heat transfer

the present paper establishes the integrated model of gas liquid film thickness and heat transfer coefficient along the wall when vapor-gas mixed fluid crosses vertically both circular tube and drop-shaped tube and condensation occurred. Through the finite difference method

the calculation and comparison are carried out with flue gas from natural gas combustion as an example. In the circumstance that the effective heat transfer area is same

compared with circular tube

diameter is smaller on upper half of drop-shaped tube and pressure gradient is greater

which is helpful for drainage; surface curvature is larger on lower half of drop-shaped tube

which is also helpful for drainage. Gas film on surface of drop-shaped tube is thinner

and liquid film is also thinner; drop-wise condensation area is larger and droplet size is smaller

so condensation heat transfer coefficient is greater. Besides

drop-shaped tube also has certain enhancement to sensible heat transfer. The calculation results are compared and verified by experiment

and this model is also suitable for oval tube and other kinds of vapor-gas mixed fluid.