ISSN Online: 2377-424X
ISBN Print: 0-89116-299-2
International Heat Transfer Conference 7
HEAT TRANSFER IN THE THERMAL ENTRANCE REGION OF A TURBULENT FALLING LIQUID FILM UNDERGOING HEATING OR EVAPORATION
要約
A new analytical solution is presented for
heating or evaporation in the thermal entrance
and fully developed regions of a turbulent falling
liquid film with the boundary condition of constant
wall heat flux or constant wall temperature. A
modified van Driest model, which incorporates a
damping factor f and the effect of variable shear,
is found to predict the average film thickness and
local heat transfer coefficient accurately and in
good agreement with previous experimental data and
a finite difference numerical solution in the range
of 1600≤Re≤17500 and 1.77≤Pr≤210. The calculations show that the thermal entrance length for evaporation is longer than that for heating and the length decreases with increasing Re or Pr, or both. The
entrance effect is particularly important for a
turbulent film with small Re and Pr when the
heating or evaporation length is short.