dryers are used to remove most of the water vapor from
compressed air.
The Navy uses two basic types of air dehydrators
and a combination of the two. These air dehydrators are
classified as follows:
1. Type I-refrigeration
2. Type II–heater, desiccant
3. Type III-refrigeration, desiccant
Each of these types meets the specified require-
ments for the quality of the compressed air used in
pneumatic control systems or for clean, dry air used for
shipboard electronic systems. Usually, specific
requirements involve operating pressure, flow rate, dew
point, and purity (percent of aerosols and size of
particles). We will briefly discuss each of the types of
air dehydrators.
REFRIGERATION AIR DEHYDRATOR
(TYPE I)
Refrigeration is one method of removing moisture
from compressed air. The dehydrator shown in figure
10-29 is a REFRIGERATION DEHYDRATOR or
REFRIGERATED AIR DRYER. This unit removes
water vapor entrained in the stream of compressed air
by condensing the water into a liquid that is heavier than
air. Air flowing from the separator/holding tank first
passes through the air-to-air heat exchanger, where
some of the heat of compression is removed from the
airstream. The air then moves through the evaporator
section of the dehydrator, where the air is chilled by
circulating refrigerant. In this unit, the airstream is
cooled to a temperature that is below the dew point. This
will cause the water vapor in the air to condense so the
condensate drain system can remove it. After leaving the
evaporator section, the dehydrated air moves upward
through the cold air side of the air-to-air heat exchanger.
Figure 10-29.—Dehydrator (type I).
10-32
