GE Moisture Image 1 Series, Руководство по обслуживанию, Страница: 87 / 107

Application of the Hygrometer (900-901D1) A-25
June 2003
B: Special Case
As mentioned earlier, saturated straight-chain hydrocarbons represent
a special case, where the Henry’s Law constant does not vary
appreciably with temperature. In such cases, use the nomograph for
liquids in Figure A-2 on page A-32 to complete the analysis.
Determination of moisture content if the Henry’s Law constant (K) is
known.
1. Using a straightedge, connect the known K value on the center
scale with the dew/frost point, as measured with the GE
Panametrics hygrometer.
2. Read moisture content (PPM
W
) where the straightedge crosses the
scale on the left.
Typical Problems
1. Find the moisture content in benzene, at an ambient temperature
of 30°C, if a dew point of 0°C is measured with the GE
Panametrics hygrometer.
a. From the literature, it is found that C
S
for benzene at a
temperature of 30°C is 870 PPM
W
.
b. Using a straightedge on Figure A-2 on page A-32, connect the
870 PPM
W
saturation concentration with the 30°C ambient
temperature and read the Henry’s Law Constant of 27.4 on the
center scale.
c. Using the straightedge, connect the above K value of 27.4 with
the measured dew point of 0°C, and read the correct moisture
content of
125 PPM
W
where the straightedge crosses the
moisture content scale.
2. Find the moisture content in heptane, at an ambient temperature of
50°C, if a dew point of 3°C is measured with the GE Panametrics
hygrometer.
a. From the literature, it is found that C
S
for heptane at a
temperature of 50°C is 480 PPM
W
.
b. Using a straightedge on Figure A-2 on page A-32, connect the
480 PPM
W
saturation concentration with the 50°C ambient
temperature and read the Henry’s Law Constant of 5.2 on the
center scale.
c. Using the straightedge, connect the above K value of 5.2 with
the measured dew point of 3°C, and read the correct moisture
content of
29 PPM
W
where the straightedge crosses the
moisture content scale.