Thermoelectric Cooler

The thermoelectrically cooled condensation trap, better known as "Peltier Drier" is an optional accessory device for the Model 500 and Model 700 combustion-emissions analyzers. Its purpose is to replace the standard condensation trap for those critical applications that demand higher accuracy for the measurement of nitrogen dioxide (NO₂) and sulfur dioxide (SO₂).

NO₂ and SO₂ are gases that are highly soluble in water. The exhaust sample contains typically between 5% and 20% of water vapor, most of which will condense in the probe and sample line.

To prevent significant loss of NO₂ and SO₂ during transport of the sample from the probe to the analyzer, the following conditions must be satisfied:

• Rapid sample transport. This is accomplished by maintaining a high flow rate using a relatively small diameter sampling line.
• Use of a sample line made from a highly hydrophobic material. A Teflon sample line limited to 15 ft. long is used.
• Minimum contact of the gas sample with the water collection mechanism and also no additional condensation occurring following the Peltier drier. This is accomplished by using a specially designed Peltier cooled manifold to separate the gas from the water.

The Peltier drier will maintain the sample at a certain temperature below ambient temperature to ensure no further condensation inside the analyzer. You can control this temperature differential by adjusting the "COOLER DUTY CYCLE", if necessary. The following table shows the approximate relation between duty cycle and temperature differential:

DUTY CYCLE	SAMPLE TEMP - AMBIENT TEMP (F.)*	ENERAC 500 BATTERY LIFE
50%	- 9	2.5 hours
75%	-13	2.0 hours
100%	-16	1.5 hours

*At 75 degrees F. ambient.

This temperature differential between sample temperature and ambient temperature is set at the factory to 75%. The condensation trap will fill with water after 2 to 4 hours depending on the fuel used. To empty the condensation trap simply unscrew it from the manifold. When replacing it, be careful to seat the O-ring properly.

PELTIER DRIER OUTLINE

The sample consisting of gas and partially condensed water vapor enters the drier through the "SAMPLE INLET". It flows through multiple narrow thermoelectrically cooled passages, where total separation of gas and vapor occurs. The dried sample makes a 180 degree turn, flowing upwards and goes through a membrane filter exiting through the "SAMPLE OUTLET". The purpose of the membrane filter is to remove any particles and also to prevent flow of condensate into the analyzer by accidentally tilting the unit downwards. The membrane filter is disposable and can be easily replaced by unscrewing the plastic white bushing.