Page 66 - GRIHA Manual Volume III - Introduction to National Rating System
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Building and system design optimization 59
the night when the surrounding air temperatures are lower than what it is during the day. This
ensures that the daytime ventilation requirement is reduced.
Night ventilation is suitable for buildings with periodic daily loads like offices, factories, workshops,
and so on. The basic principle of night ventilation is depicted in figure 2. Additionally, air movement
can be provided through the use of mechanical system to efficiently cool building spaces.
Figure 2 Basic principle of night ventilation
Evaporative coolers
Evaporative coolers are cooling devices based on the principle of evaporation of water in air.
Evaporative coolers are considerably cheaper to buy and operate as compared to conventional air-
conditioners. Moreover, they do not use refrigerants, which can harm the ozone layer. Evaporative
cooling is especially well suited for climates where the air is hot and dry.
Types of evaporative coolers
Direct (single stage) evaporative cooling (open circuit): This is
used to lower the temperature of air by using latent heat
of evaporation (changing water to vapour). In this process,
the ambient dry air comes in contact with water and water
droplets evaporate, thereby reducing the temperature of
the air and increasing its humidity level. The moist air, which
has dropped in temperature, flows to the occupied spaces.
The working principle of direct evaporative cooler is shown
in figure 3. The advantage of direct evaporative coolers is that Figure 3 Direct evaporative cooler
they operate at very low energy costs, and perform well in hot
and dry climates. However, the major disadvantage of these
direct evaporative coolers is that the air that is discharged is
very humid.
Indirect evaporative cooling: This is similar to direct evaporative
cooling except that in this case, the air is cooled using a heat
exchanger. The cooled moist air never comes in direct contact
with the conditioned environment. These systems have
considerably lower efficiency as compared to direct evaporative
coolers. They cannot lower the temperature to the same level as
the direct evaporative coolers. Figure 4 Indirect evaporative cooler
the night when the surrounding air temperatures are lower than what it is during the day. This
ensures that the daytime ventilation requirement is reduced.
Night ventilation is suitable for buildings with periodic daily loads like offices, factories, workshops,
and so on. The basic principle of night ventilation is depicted in figure 2. Additionally, air movement
can be provided through the use of mechanical system to efficiently cool building spaces.
Figure 2 Basic principle of night ventilation
Evaporative coolers
Evaporative coolers are cooling devices based on the principle of evaporation of water in air.
Evaporative coolers are considerably cheaper to buy and operate as compared to conventional air-
conditioners. Moreover, they do not use refrigerants, which can harm the ozone layer. Evaporative
cooling is especially well suited for climates where the air is hot and dry.
Types of evaporative coolers
Direct (single stage) evaporative cooling (open circuit): This is
used to lower the temperature of air by using latent heat
of evaporation (changing water to vapour). In this process,
the ambient dry air comes in contact with water and water
droplets evaporate, thereby reducing the temperature of
the air and increasing its humidity level. The moist air, which
has dropped in temperature, flows to the occupied spaces.
The working principle of direct evaporative cooler is shown
in figure 3. The advantage of direct evaporative coolers is that Figure 3 Direct evaporative cooler
they operate at very low energy costs, and perform well in hot
and dry climates. However, the major disadvantage of these
direct evaporative coolers is that the air that is discharged is
very humid.
Indirect evaporative cooling: This is similar to direct evaporative
cooling except that in this case, the air is cooled using a heat
exchanger. The cooled moist air never comes in direct contact
with the conditioned environment. These systems have
considerably lower efficiency as compared to direct evaporative
coolers. They cannot lower the temperature to the same level as
the direct evaporative coolers. Figure 4 Indirect evaporative cooler
