PERMA PURE LLC
Model 5210 User’s Manual
Doc. #561: Revision: 000
Page 4 of 21
General description
Sampling combustion product stack gas or exhaust from internal combustion engines requires a
method to remove the moisture from the sample, without removing the gas compounds of interest.
The Baldwin-Series Classic TE Cooler is an ideal way to decrease the dew point of combustion
gases to a repeatable, stable, constant low dew point. The Classic cooler prevents water
condensation in sample pre-filters, pumps, and analyzers. For gas analyzers where water vapor is
an interferent, a stable, repeatable dew point becomes a part of the gas analyzer performance
specification. Classic coolers provide this constant low water concentration, resulting in an accurate
gas measurement.
All Classic coolers use thermo-electric
elements (Peltiers) to cool the sample gas
to the desired dew point temperature. A
Classic Thermo-Electric (TE) Cooler is best
illustrated as a small heat pump with no
moving parts. The Peltier operates on direct
current and may be used for heating or
cooling by reversing the direction of current
flow. This is achieved by moving heat from
one side of the module to the other with
current flow and the laws of
thermodynamics. A typical single stage
Peltier (Figure 1) consists of two ceramic
plates with p- and n-type semiconductor
material (bismuth telluride) between the
plates. The elements of semiconductor
material are connected electrically in series
and thermally in parallel.
When a positive DC voltage is applied to the n-type thermo-electric element, electrons pass from
the p- to the n-type thermo-electric element and the cold side temperature will decrease as heat is
absorbed. The heat absorption (cooling) is proportional to the current and the number of thermo-
electric couples. This heat is transferred to the hot side of the Peltier element where it is dissipated
into the heat sink and surrounding environment.
The Classic Cooler removes the moisture from the sample gas by cooling it as it passes through a
laminar impinger (heat exchanger). A diagram showing the gas flow path through an impinger is
shown in the Appendix. The heat exchanger, made of 316L stainless steel, Durinert® (a corrosion-
resistant inert coating over 316L stainless steel), PVDF (Kynar), or glass, is mounted within a
thermally insulated heat transfer block bored to receive the heat exchanger without a mechanical
lock. This assembly allows the easy removal of any heat exchanger simply by slipping it out of the
cooling block by hand. The heat transfer block cools the heat exchanger through the heat pumping
action of the Peltier element. The heat transfer block is on the cold side of the thermo-electric
element and the heat sink is on the hot side of the thermo-electric element. The heat from the heat
transfer block is pumped to the heat sink where it is then dissipated into the air by the heat sink
fan. See Figure 2. The desired temperature is maintained by a closed loop control system, which is
implemented through an analog proportional controller. The controller uses a type K thermocouple
in the heat transfer block located very close to the cold side of the peltier element as the input
sensor.
Figure 1: Thermo-electric element (Peltier)
