International Journal of Heat and Mass Transfer, Vol.42, No.13, 2419-2426, 1999
Pressure gradient and variable wall temperature effects during filmwise condensation from downward flowing vapors onto a horizontal tube
A simple model is developed to study the process of combined forced and natural convection film condensation from downward flowing vapors onto a horizontal tube with variable wall temperature, including effects of the pressure gradient and vapor shear stress. In the present work, the result of mean heat transfer shows that: for forced-convection film condensation, as the wall temperature variation amplitude, A, increases, the value of <(Nu)over bar> Re-1/2, with inclusion of the pressure gradient effect, goes down appreciably. However; the value of <(Nu)over bar> Re-1/2 when ignoring the pressure gradient effect will increase with A at a smaller pace. As for natural-convection film condensation, the mean heat transfer coefficients remain almost uniform for varying A, which are in goad agreement with the previous work.