Based on the theory of distributed parameter thermodynamic system

a coupled heat transfer model for finned tube is proposed to describe the heat transfer between the two-phase fluid and the cooling air. The proposed model is applied to a 1 000 mm×94 mm×46 mm(depth×width×height) engineering oval finned tube in thermal power plant

and change rules of the temperature

heat flux

convective heat transfer coefficient

film thickness and shear inside the tube along the two-phase flow and cooling air stream are obtained. The spatial distributions of the characteristic quantities are visualized. It is found that

the heat flux inside the tube decreases sharply near the air outlet with the lateral flow of the cooling air

while the convective heat transfer coefficient grows slowly with the longitudinal development of the condensation. The pattern of two-phase fluid inside oval tube is verified as the annular flow

and the liquid film in the extreme end of the lower half ellipse shows obvious aggregation and accelerating flow. The theoretical methods and conclusions are benefit to enhancement design for heat transfer in finned tubes and safe and efficient operation of direct air-cooled condensers.