Micromeritics Gemini VII 2390a, Operator'S Manual

Page: 307 / 426


Tw
V
1
I
V
1
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
 
-------------------------------------------------
=
Gemini VII Appendix C
239-42828-01 - 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 +
–
 