Figure 6-9. Semi-Permeable Membrane Drying Process; Figure 6-10. Sample Dryer - Teledyne T200 User Manual

The process by which the water vapor molecules are collected and transported through
Nafion ® material is called per-evaporation and is driven by the humidity gradient between
the inner and outer tubes as well as the flow rates and pressure difference between inner
and outer tubing. Unlike micro-porous membrane permeation, which transfers water
through a relatively slow diffusion process, per-evaporation is a simple kinetic reaction.
Therefore, the drying process occurs quickly, typically within milliseconds.
Because this chemical reaction is based on hydrogen bonds between the water molecule
and the Nafion
unaffected. Specifically, the gases of interest, NO and NO
the dryer unaltered.
On the other hand, other small polar gases that are capable of hydrogen bonds such as
ammonia (NH
NH can cause interference for the measurement of NO
3
083730200A DCN7962

Figure 6-9. Semi-Permeable Membrane Drying Process

® material most other chemical components of the gas to be dried are usually
) can be absorbed this way, too. This is an advantage since gases such as
3

Figure 6-10. Sample Dryer

Teledyne API T200 NO/NO
, do not get absorbed and pass
2
, NO and NO
x
/NO Analyzer with NumaView™ Software
2 x
(see Table 6-1).
2
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