The exact expressions of concentration and local or average Sherwood number

Sh or Sh for non-Newtonian power law fluids when the flow index n takes any positive rational value

have been obtained by solving the differential equation of diffusion together with the velocity distribution in the falling film. The use of Fourth-order Runge-Kutta method and Wegstiens iteration method in the computer yields results which are a series of values of dimen-sionless concentration 0 local and average Sherwood number for n equal to 1/4

1/3

1/2

1/1.4

1/1.2

1

1.25

2.5

and GO. When the flow index n=1

i. e. for Newtonian fluids

the result agrees well with the data from the literature. In the above equations

if we substitute thermal diffusivity a for the diffusivity D

local and average Nusselt number Nu

Nu for Sh

Sh

dimens-ionless temperature T=(Ts-T)/(Ts-T1) for

then

they may be used to evaluate the problem of heat transfer in film flow. All the results of calculation may be used for engineering design

but they must be applied within the limits of laminar flow or non-wavy film flow.