There are three general types of wheels
being used today.
They are sensible, enthalpy and regenerative. Many
times
they are referred to as “desiccant” wheels,
but this only confuses rather than clarifies since
only two of these types have desiccant as part of
their designs. The actual definitions are:
SENSIBLE WHEEL -
This wheel is not coated with a desiccant
and therefore transfers only sensible energy. The
wheel can
be constructed of almost any material (paper, metal
or plastic) and transfers energy between two air streams
as the mass of the material gains or loses heat to
the opposite air
stream. The wheel rotates at a speed of 25 to 50 revolutions
per minute.
ENTHALPY WHEEL -
It is similar to the sensible wheel except that a
desiccant
media is added to the wheel’s surface. As
the wheel rotates, it now can transfer sensible energy
and humidity.
This wheel also rotates at 25 to 50 revolutions per
minute.
REGENERATION WHEEL
- This wheel is used when low dew-point conditions
(<45°F) are required, such as industrial applications.
It achieves low dewpoints by slowing the wheel
to a speed of between 0.25 and 1 revolution per minute
and by using an air stream heated
to
250°F or more to drive off moisture and regenerate
the wheel.
This heated air stream is typically focused on only
1/4 of the wheel’s area thereby allowing 3/4
of
the area to be available for the process side.
