GE Moisture Image 1 Series, Руководство по обслуживанию, Страница: 85 / 107

Application of the Hygrometer (900-901D1) A-23
June 2003
Henry’s Law Type Analysis (cont.)
Also, the value of K is determined from the known water saturation
concentration of the organic liquid at the measurement temperature:
(b)
For a mixture of organic liquids, an average saturation value can be
calculated from the weight fractions and saturation values of the pure
components as follows:
(c)
where, X
i
is the weight fraction of the i
th
component, (C
S
)
i
is the
saturation concentration (PPM
W
) of the i
th
component, and n is the
total number of components.
In conclusion, the Henry’s Law constant (K) is a constant of
proportionality between the saturation concentration (C
S
) and the
saturation vapor pressure (P
S
) of water, at the measurement
temperature. In the General Case , the Henry’s Law constant varies
with the measurement temperature, but there is a Special Case in
which the Henry’s Law constant does not vary appreciably with the
measurement temperature. This special case applies to saturated,
straight-chain hydrocarbons such as pentane, hexane, heptane, etc.
A: General Case
Determination of Moisture Content if C
S
is Known:
The nomograph for liquids in Figure A-2 on page A-32 can be used to
determine the moisture content in an organic liquid, if the following
values are known:
•
the temperature of the liquid at the time of measurement
•
the saturation water concentration at the measurement temperature
•
the dew point, as measured with the GE Panametrics hygrometer
K
Saturation PPM
W
P
S
-------------------------------------------- =
Ave. C
S
X
i
C
S
( )
i
i 1 =
n
∑
=