TABLE 7.6. Formulae for calculating conductances (mol rnV2 s-') for diffusion, convection, and turbulent transport in air.
Process
Heat lkansfer
Vapor Transfer
Other Mass Transfer
conduction or diffusion
(molecular processes)
Forced convection (fluid
moved past surface by
external force)
Free convection (fluid flow
generated from temperature
gradients)
Eddy diffision or turbulent
transport (wind over fields)
Plane gH = a
Plane g, =
BDj
A2
Plane gj =
Sphere g~ =
Sphere g, =
Sphere gj = - bDj
&(I- z )
&(I- 5 )
& ( I - 5 )
Cylinder gH = a
Cylinder g - -@kb ~ .
z,In 2
- rrin
Cylinder g j = 2 zs In 2
g ~ ,
= 0.135fi
g,, = 0.147fl
g , , = 0.110fl
go, = 0.130fi
g ~ ,
= 0.050 ( 9 )
114
g,, = 0.055 (
)IJ4
gca = 0.038 ( 9 )'I4
go, = 0.048 ( 9 )
114