Page 67 - GRIHA Manual Volume III - Introduction to National Rating System
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60 GRIHA Manual: Volume 3
Two-stage evaporative cooling or indirect–
direct: Humidity levels produced by two-
stage evaporative coolers are not as high as
that produced by traditional single-stage
evaporative coolers, but they cost more than
direct coolers and operate at a lower efficiency.
In the first stage of a two-stage cooler, warm
air is pre-cooled indirectly without adding
humidity. In the direct stage, the pre-cooled air
passes through a water-soaked pad and picks
up humidity as it cools. As the air supplied to Figure 5 Indirect–direct evaporative cooler
the second stage evaporator is pre-cooled, less
humidity is added to the air.
Earth air tunnel system
Earth air tunnel (EAT) system comprises a metal, plastic or concrete pipe buried at a depth of about
4 m below the ground. At a depth of 4 m from the earth’s surface, temperature remains constant
throughout the year. Ambient air sucked from one end is passed through the tunnel. Depending on
the ambient temperature, air gets cooled in summer and heated in winter. This cooled/heated air
is then supplied to the various areas for space cooling/heating and provide recommended thermal
comfort to the building’s occupants. The earth air tunnel consists of four parts. The first part is fresh-
air intake column. This consists of a masonry structure like a manhole. Hot air is sucked from the top
and is taken up to the depth of 4 m. The second part is a straight tunnel made of hume pipe laid
at a depth of 4 m below the ground level. The diameter of the tunnel varies from 0.3m–0.7 m and
Figure 6 Schematic diagram of earth air tunnel system
Two-stage evaporative cooling or indirect–
direct: Humidity levels produced by two-
stage evaporative coolers are not as high as
that produced by traditional single-stage
evaporative coolers, but they cost more than
direct coolers and operate at a lower efficiency.
In the first stage of a two-stage cooler, warm
air is pre-cooled indirectly without adding
humidity. In the direct stage, the pre-cooled air
passes through a water-soaked pad and picks
up humidity as it cools. As the air supplied to Figure 5 Indirect–direct evaporative cooler
the second stage evaporator is pre-cooled, less
humidity is added to the air.
Earth air tunnel system
Earth air tunnel (EAT) system comprises a metal, plastic or concrete pipe buried at a depth of about
4 m below the ground. At a depth of 4 m from the earth’s surface, temperature remains constant
throughout the year. Ambient air sucked from one end is passed through the tunnel. Depending on
the ambient temperature, air gets cooled in summer and heated in winter. This cooled/heated air
is then supplied to the various areas for space cooling/heating and provide recommended thermal
comfort to the building’s occupants. The earth air tunnel consists of four parts. The first part is fresh-
air intake column. This consists of a masonry structure like a manhole. Hot air is sucked from the top
and is taken up to the depth of 4 m. The second part is a straight tunnel made of hume pipe laid
at a depth of 4 m below the ground level. The diameter of the tunnel varies from 0.3m–0.7 m and
Figure 6 Schematic diagram of earth air tunnel system
