Filter
Top Products
71
Section Three - Part A
THEORY OF OPERATION
THEORY OF DRYING
To understand how a dryer can dry laundry, it is necessary to understand how the process of drying,
or evaporation, can be accelerated.
The goal of drying is to remove the water that has saturated the laundry during washing. During the
SPIN CYCLE of the washer, much of the water is extracted while it is still in its liquid form. To remove
the remaining water, it is necessary to convert the liquid water into water vapor. This process of
changing a liquid to a vapor is called evaporation. Under normal conditions, the process of evapora-
tion is very slow.
As an example, water in a glass set on a table at room temperature will take days to completely evapo-
rate. A damp towel from a shower, balled up and placed in a clothes hamper will probably still be damp
several days later when it is removed.
However, by controlling the conditions during the evaporation process, the rate of evaporation can be
accelerated.
BY APPLYING HEAT
The process of evaporation can be accelerated by
applying heat. As shown in
Figure 3-1
, when a pan
of water is heated on a stove top, the water rapidly
boils (evaporates from liquid to vapor.)
BY MOVING THE SURROUNDING AIR
The process of evaporation can be accelerated by
moving the surrounding air. During evaporation,
the air immediately surrounding the surface of
the liquid water can become saturated with water
vapor. At this point the air cannot accept any more
evaporating water. Moving the saturated air away
from the surface of the liquid water and replacing
it with air that can still accept water vapor can ac-
celerate the rate of evaporation.
As an example, clothing hung out to dry on a
clothes line will dry faster when there is a breeze,
and you will feel cooler (a sign of evaporation) when
you stand in front of a fan on a hot day.
(Fig. 3-2)
BY INCREASING THE SURFACE AREA OF THE LIQUID
The process of evaporation can be accelerated by
increasing the surface area of the liquid. As show
in Figure 3-3, the water in a glass can be poured
out onto the floor. Spread out in a puddle, the water
will likely evaporate in just a short amount of time.
Fig. 3-1
Fig. 3-2
Fig. 3-3