Micromeritics TriStar II 3020 - Page 321

Tw
V1
I
V1
I 1+
–10
8
A/cm
SAw
I
-----------------------------------------------------------------
=
Vc
I
VI
I
VI
I 1+
–Vd
I
–=
Rc
K 1+
A–
1 F+Pr
I 1+
ln
-------------------------------------------------
=
TriStar II 3020 Appendix C
302-42828-01 - Dec 2012 C-13
The total volume of gas desorbed from walls of previously opened pores is calculated:
for all previously opened pores
where LP
J
= length of previously opened pores as calculated in Step b(2).
b.) The physical processes occurring for this pressure interval are determined as follows:
(1.) If Vd
I
is greater than the current increment of volume desorbed (Vl
I
- Vl
I+1
), 
desorption from walls only is occurring. Total surface of walls exposed thus far (cm
2
/
g) is calculated as follows:
for all previously opened pores
where
D
avgJ
= weighted average pore diameter calculated below in Step b(2).
A new layer thickness (Tw) that will not overcompensate for the actual volume
desorbed in this interval is calculated:
Since no cores are evaporated in this pressure interval, no new pores are revealed.
Thus no ending Kelvin radius and average pore diameter are calculated for this inter-
val. Note that this means the report may have fewer tabulated intervals on the
collected data report than experimental pressure intervals.
(2.) If Vd
I
is less than the volume increment desorbed during this interval , the
remaining volume is due to new pores with core evaporation taking place in this inter-
val. K, the number of intervals with new pores exposed, is increased by 1. (For the
interval from the lowest Pr
1
to zero relative pressure, no new pore volume is calculated
and the rest of Step b is skipped.)
The volume desorbed from newly opened pores in this interval is calculated as
follows:
The Kelvin radius for the end of the
interval is calculated as follows:
All new pores opened in this interval are represented by one pore having a length-
Vd
I
Lp
J
CSAa
J


=
SA
W
 LP
J
D
avg
J
10
8–
cm/A

=
Vl
1
Vl
l 1+
–