Appendix A. Supplemental Information; Formulas - GE MG-101 User Manual

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:
where:
P = the generated vapor pressure of water
w
P = the saturation vapor pressure of water as determined by the water temperature of the saturator
s
P = the vapor pressure of water in the dry nitrogen stream
d
F = the flow rate of the wet gas diluted stream
w
F = the flow rate of the wet gas stream
w1
F = the flow rate of the dry gas second dilution stream
d
F = the flow rate of the dry gas first dilution stream
d1
In general, P F << P F
d d s w
The value of P and the dew point (from the calculated value p
s
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.
MG-101 User's Manual

P
---------------------------------------
F 
w

P -----------------------------------------------------------------------------
=
w
and P F << P F . Thus, Equation 1 above simplifies to:
d1 d1 s w1

 ------------------ -
P
=
w
F


F P F
+
s w1 d1 d1
×
 P
+
d
F F
+ 
w1 d1
F F
+
w d
F   F 
w w1
  ------------------------ - 
P
s
F F F
+   + 
w d w1 d1
) are determined from a chart of vapor pressure of water
w
Appendix A. Supplemental Information
F
d
(1)
(2)
17