b,, =- cdg(n-) eqn 2.17
1-g
The variables (c, g, b, and d) are given in Table 2-6.
Table 2-6 Expressions for the variables (c, g, b, and d ) used in eqns. 2.16 and 2.17.
All variables are expressed in terms of the forward or reverse adsorption coefficient
(a1, a,) and the removal ratio (2).
c 2a,(1-a,)+a, 2(1-e-"P )e -P' +(i -e-vp')
g (1-af)(1-a,)A22 e- ve-P, A2
b af (1- a,)+ a, Al I-e-ve ) e-"Pt +(1- e-P"')
d A(1-a,.) Ae-_1
The adsorption fractions can be expressed in a Langmuir form similar to the previous
model section as given by eqns 2.18 and 2.19 for the forward and reverse cases,
respectively.
a =I e-P' eqn 2.18
a,. = 1 e" eqn 2.19
The adsorption fractions are a function of the deposition constant (v), the partial
pressure of the gas (P), and the exposure time in the forward or reverse directions
(tf,t,). The only difference between the forward and reverse adsorption coefficients
concerns the exposure time in the direction of travel t and t,. Each position along the
track has a unique value for tf and t,r. Only at the midpoint of the track does t, equal t,.
The coefficients v and P are constants for a gaseous environment that is
compositionally and thermally steady. Eqns 2.20 and 2.21 give the closed-form