Laminar Flow Condensation Heat Transfer Characteristics in Vertical Tube under Natural Circulation Condition

Considering the effect of vapor velocity,the Nusselt theoretical formula for laminar film condensation is modified.By using the Nusselt formula and the modified model,the laminar flow condensation heat transfer characteristics inside a vertical tube are studied in a natural circulation system.The result shows that the effect of vapor velocity can not be neglected.The vapor shear decreases the liquid-film thickness and results in a increasing of condensation heat transfer compared to that calculated from Nusselt formula.The modified model considers the interface shear stress appropriately,so the calculated values agree well with the experiment results.