Perma Pure Baldwin-Series MP5400 - Manual (Page 5)

Section C: Principle of Operation 5
C: P
RINCIPLE OF
O
PERATION
Thank you for purchasing a Baldwin eCOOL™ Mini Digital Portable Gas Sample
Conditioning System.
All Baldwin coolers use thermo-electric elements (Peltiers) to cool the sample gas to
the desired dew point temperature. A thermo-electric cooler is best illustrated as a
small heat pump with no
moving parts. The Peltiers
operate 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.
Baldwin Thermo-Electric Coolers remove the moisture from the sample gas by
cooling the gas 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
Figure 1: Thermo-electric element (Peltier)