Evaporative cooling , roof pond , water spraying , indirect evaporative cooling , climate where it is used

1. EVAPORATIVE COOLING
Neha Singhi
Aditi Saha

2. • Evaporative cooling is reduction in temperature resulting
from the evaporation of a liquid, which removes latent heat
from the surface from which evaporation takes place. This
process is employed in industrial and domestic cooling
systems, and is also the physical basis of sweating.
• Historically, water has been used in the form of fountains and
cascades to improve the thermal comfort of buildings.
• Evaporation of water helps to passively cool buildings,
reducing the energy needed for air conditioning. When
combined with other passive design techniques, adequate
thermal comfort might be achieved without air conditioning.

4. OBJECTIVES AND BENEFITS
• To attain comfort zone by modification in present existing
system.
• To develop a new module of energy conserver.
• As Air conditioner consumes more power( approx. 15-20KW)
Emits harmful gases such as CFC and much costly.
• By using application of passive down drought evaporative
cooling tower in desert cooler , and could be better substitute
of A.C.
• Thus this project solves this problems and is efficient as well
as economical and tends to provide comfort zone.

6. INDIRECT EVAPORATIVE COOLING
• When evaporative processes are used to cool an element of
the building, which then acts as a heat sink, this is known as
indirect evaporative cooling.
• Cooling is provided whilst keeping the evaporative process
outside, which avoids elevating the indoor humidity level.
Direct evaporative cooling cools outside air through
evaporation, and brings this air into the building.
• The drawback of this method is that indoor humidity levels
are increased.

7. ROOF POND
• In the simplest form, this involves placing a pond on the
building roof. As water evaporates from the pond, heat is
consumed. This cools the roof, which acts as a heat sink and
absorbs heat from the interior of the building.
• A more refined method involves insulating the pond during
the daytime, to prevent solar gain. During the day water in the
pond absorbs heat, cooling the ceiling below. At night, water
is circulated over the insulation. Heat is then removed by
means of evaporation, convection and radiation (to the black
body night sky). Such systems have been successfully trialled
in the hot, humid climate
• Roof ponds require additional structural support and there
may be public health concerns associated with standing water
(mosquitoes etc.).

9. WATER SPRAYING
• Water spraying is a simple and inexpensive way of reducing
the solar heat gain of buildings in the tropics.
• Water is typically sprayed onto roofs for 40 seconds every five
minutes. A small amount of external power is required to
pump the water up to the roof, but the energy required for
this is minimal compared with the additional cooling that is
attained
• While roof spraying has some potential for cooling in hot
humid climates, the effect is relatively small – a reduction of
indoor air temperature of 1-4 deg C has been reported.
• Studies show that roof spraying is a less effective cooling
method under cloudy conditions

11. CLIMATE WERE IT IS USED
• Evaporative cooling systems are suitable in any dry climate,
especially cool and dry climates. For example, it can be used
in high altitude regions. A dry environment is needed for
evaporative cooling due to higher evaporation rates. The
evaporation process would absorb heat and create coolness in
the surrounding.
• Areas with cooler temperatures are also preferred, as the gap
between the environmental ambient temperature and human
comfort range is smaller as compared to a hot and dry
environment. This would translate into energy saved due to a
lower cooling load.

13. APPLICATION AND COST
• Evaporative cooling systems are suitable for residential,
industrial and commercial buildings; especially in areas with
big open spaces that encourages air circulation. Integration of
evaporative cooling systems with other active systems are
dependent on site conditions. Filters to purify polluted air,
humidifiers to maintain the humidity or other active systems
can be installed in tandem with evaporative cooling.
• Initial building cost is generally higher, as there is a need to
construct addition structure and the equipment needed is
usually more costly as compared to the conventional cooling
systems. However, the advantages are that it reduces
operational cost significantly.