GE MG-101, Руководство пользователя

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MG-101 User’s Manual 17
Appendix A. Supplemental Information
Appendix A. Supplemental Information
A.1 Formulas
The moisture content generated by the MG-101, as determined by the water vapor pressure, is calculated with the
following equation:
(1)
where:
P
w
= the generated vapor pressure of water
P
s
= the saturation vapor pressure of water as determined by the water temperature of the saturator
P
d
= the vapor pressure of water in the dry nitrogen stream
F
w
= the flow rate of the wet gas diluted stream
F
w1
= the flow rate of the wet gas stream
F
d
= the flow rate of the dry gas second dilution stream
F
d1
= the flow rate of the dry gas first dilution stream
In general, P
d
F
d
<< P
s
F
w
and P
d1
F
d1
<< P
s
F
w1
. Thus, Equation 1 above simplifies to:
(2)
The value of P
s
and the dew point (from the calculated value p
w
) are determined from a chart of vapor pressure of water
as a function of temperature (see Table 1 on page 19 ). Equation 1 above produces an error of less than 2°C (3.6°F)
dew/frost point temperature at the lowest generated dew/frost point temperatures, and virtually no error at higher
dew/frost point temperatures. The advantage of
Equation 2 above is that a precise determination of the dew/frost point
temperature of the gas supply is not necessary. It is good practice, however, to use the hygrometer to determine an
approximate dew/frost point temperature of the dry gas supply. To obtain the lowest dew/frost point temperatures
within the specified accuracy, the dry gas supply should not exceed 3% of the desired mixture concentration.
P
w
F
w
P
s
F
w1
P
d1
F
d1
+
F
w1
F
d1
+
---------------------------------------
 
 
 
P
d
F
d
×
+
F
w
F
d
+
-----------------------------------------------------------------------------
=
P
w
F
w
F
w
F
d
+
-------------------
 
 
  F
w1
F
w1
F
d1
+
-------------------------
 
 
 
P
s
=