Page 181 - Industrial Ventilation Design Guidebook

4.3 HEAT AND MASS TRANSFER I 43

with reference to Eq. (4.251),

or Eq. (4.320).
The logarithmic function in Eq. (4.320) can be written as

s
s
When (pA( )-pA(y))/(P-pA( )) < 1, a logarithmic function to a series
(ln(l + x) = x-x /$+••• ) can be developed, and using the first term gives
the approximation

In this approximation /^(s) in the denominator is replaced by p^(T, u\
We use the following notations:

Using approximation (4.319) in Eq. (4.318) and Eq. (4.317) in Eq. (4.320)
leads to the steam flow formula

Eliminating PA(S) gives

The total conductance is determined from

' f
The total vaporization on both sides of the web is determined by Eq.
(4.324) multiplied by 2. If the radiation power absorbed in the web is
<2"(W rrf ~), the energy balance can be written as

where l(T, u) is the vaporization heat of water and C" is the heat capacity of
the web ( J m~~K~ ). This can be calculated from

2
where m" is the square mass of the dry substance of the paper web (kg m ), c pl
is the specific heat of the dry substance, and c p2 is the specific heat of water.