DOI 10.4010/2016.1002
ISSN 2321 3361 © 2016 IJESC
Research Article
Volume 6 Issue No. 4
Performance of Different Pad Materials in Advanced Desert
Coolers- A Comparative Study
Shashank Shekhar1, Santosh Suman2, Dr. H.S. Moharana3, D. Sethy4
Pre-final year student1, 2, Dean Research3, Assistant Professor4
Department of Mechanical Engineering
Gandhi Institute for Technology, Bhubaneswar, Odisha, India
Abstract:
Demand for electric power during peak periods in summer is a vital concern for many utilities in the fast-moving world. From the
demand point of view on the grid and cost to the consumer, it is quite wise to install, energy efficient evaporative coolers rather
than conventional air conditioners. Evaporative cooling has a great many advantages over other cooling processes. Due to the nonpollution creating environment, it is considered as one of the suitable ways to cool ones workplace or living place because of the
fact that it uses fresh air and replaces the air time to time, quite frequently, an hour. Due to recirculation of air, smells and allergens
are expelled. It bases on a natural process of air cooled by water, it won’t dry out the air, or irritate human skin, eyes, or other
external parts of the human body. It allows the doors to be left open for one to sustain the heat of summer. Moreover, evaporative
cooling is an inexpensive cooling option which enhances the lifestyle of people. However, evaporative cooling requires an
abundant water and is efficient when the relative humidity is low. Padding media play a major role in determining cooling
efficiency. This paper investigates the comparative performance of Desert Coolers employing six different pads in terms of cooling
efficiency, air velocity, and water consumption for a sustainable and economic application. In real practice, we use wood wool,
khus, coconut coir fiber, ceramic materials tubes, stainless steel, galvanized metal sheets as pads in desert coolers and the paper
focusses on the best of the pads used, quite suitable to the rural masses in operational and economic senses, on a wide range of
comparisons. This investigation is sorted out to bring the performance indicator of the best suited pad out of different pads used
globally.
Keywords: Evaporative cooling, wood wool, khus, coconut coir, ceramic materials, stainless steel, galvanized metal sheet pads
I.
INTRODUCTION
Evaporative cooling uses less electricity nearly one seventh
of the conventional consumption method, it is necessary that
our environment would contribute to the greenhouse gas
emission and control. The investigators have chosen six
different type of material analyzed (pads) and same have
been compared to obtain the best of the results.
were made and tested. The coconut coir pad was analyzed
and compared with those of commercial wood known as
wood wool pad. Commercial development appears feasible
for the co availability. The span of life of coconut coir pad as
compared to wood pad is more. Similarly, ceramic material
tubes, stainless steel, galvanized metal sheets are compared
and tested.
II.
Economically every pad has insignificant contributing to a
common cause (cooling of the surrounding eg building,
workplace and other places of utility where human comfort
is concern). Testing results after analysis would determine
the best material with respect to performance .Literature
reveals the manufacturing of conventional desert coolers
expecting a single entry for a modern desert cooler. The
experiment results obtained so far after analysis would
suffice parametric conditions for a modern desert cooler.
This natural evaporative cooling is otherwise known as
perspiration which secrets from body to cool itself. The heat
transfer from the body depends on the water evaporation rate
of water. This rate of evaporation of water purely depends
on the temperature humidity of the air as well as the pressure
of the particular place. Hence, sweat accumulates more on
hot humid days in which the perspiration is impossible to
evaporate.
Conventionally, evaporative cooler pads comprising of wood
wool termed as excelsior, Coconut Coir fiber are used.
Coconut coir fiber is used to fabricate coconut coir pads.
Laboratory scale of experiment and arrangement for such
International Journal of Engineering Science and Computing, April 2016
MATERIALS AND METHODS
An Evaporative cooling is a phenomenon in which
evaporation of a liquid is entertained into surrounding air.
This evaporation of liquid is taken place by absorbing latent
heat from air. To find the measurement of water evaporated
into air, the Dry Bulb and Wet Bulb temperature are needed
to measure for determining the extent for evaporative
cooling. The effect of evaporative cooling is considered as
more when the differences between the two temperatures are
more. When both temperatures remain same, then net
evaporation of water in air doesn’t occur.
Experimental Desert cooler unit comprises of a cubical box
of sheet metal containing large vertical filter pads, an
electric-motor-driven fan, a water pump, a water distribution
system, and a water sump which is at the bottom.

Wood wool, Khus, Coconut coir, Stainless steel
used as pad materials
Two small coconut coir pads of different physical
arrangements were tested using a laboratory scale of
experiment. The results derived from such experiments infer
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that cooling efficiency of the manufactured coconut coir
evaporative cooling pad was about 50% whereas that of
commercial pad was about 47%.[1]
wood wool and Khus pad materials is shown in Fig 3.
Stainless steel wire pad shows a poor cooling efficiency as
comparing to other pads but can be used where relative
humidity is higher.
The performance analysis of desert cooler was evaluated
using stainless steel wire mesh pad, coconut coir pad, khus
pad, wood wool pad, ceramic material tubes, and Galvanized
sheet pads and compared in terms of cooling efficiency,
water consumption rate and air velocity.
FIGURE 3 Speed Vs Cooling Efficiency
FIGURE I Experimental Setup for desert cooler
The experiment was conducted with varying fan speed, and
parameters like water consumptions, cooling efficiency and
air velocity. The measurement showed that the water
consumption rate for stainless steel wire mesh pad is much
lower comparing to other pads (Figure 2)[2].
FIGURE 4 Fan speed vs Air velocity
It reveals that resistance to air flow is higher at khus pad as
comparing to wood wool and coconut coir pads.
Consequently, wood wool and coconut coir pads have shown
higher air velocity providing proper air distribution in living
place or work place.
FIGURE 2 Speed vs water consumption
Maximum water consumption has been observed in wood
wool pad, coconut coir and khus pads have shown less water
consumption rate. The fan accumulates in warm outside air
through wetted medium cooling the air. The water is lifted
from the sump through distribution system over the pads and
water is trickled down back to the water sump after use.
Then the cooled air is delivered either directly through a grill
into a single room or through a duct distribution system.
Outlet comprises of DBT/WBT sensors for measurement of
outlet air conditioning. An anemometer of hot wire type is
placed at the center of the duct for measurement of air
velocity Conventional wood wool pad.
A variation of fan speed vs. cooling efficiency of various
pad materials. Maximum cooling efficiency was found in
International Journal of Engineering Science and Computing, April 2016
 Ceramic used as pad material
Ceramic materials have a crystalline structure, fully or
partially, or amorphous. The ceramics objects are pottery
made from either self or mixing with other materials and fire
hardened after proper mixing. These materials withstand
chemical erosion taking place in other materials subjected to
acidic or caustic environment and withstand to very high
temperatures even up to 1,600 °C [3].This cooler is a device
having very low initial and running cost compared to the
unitary air conditioners. The amount of heat transfer depends
on the evaporation rate of water which in turn depends on
the humidity of air and its temperature, that is why one’s
sweat accumulates more on hot and humid days.[6]
A modern application of evaporative cooling is the selfrefrigerating beverage can. A separate compartment inside
the can contain a desiccant and cooling liquid. The desiccant
comes in contact with the cooling liquid just before the
consumption, inducing evaporation. It is observed that
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electricity consumption reduces by 31% if pump is not in
action and cooler is not affected by atmospheric conditions
reducing the consumption of water to an extent of 50% less.
It is believed that water consumption increases with increase
in atmospheric temperature specific to the placement of
cooler. The average cooling efficiency was found to be 72%.
 Galvanized metal sheets used as pad material
Evaporative cooling systems using relatively expensive
cellulosic paper pads are widely used in residential,
commercial purposes. However, the minerals and dust built
up in due course of operation shorten the life of these pads.
Water drips from the top distribution bath over the pads
through small openings. Outside air is cooled by evaporating
water droplets and moisture retained at the surface of the
wetted sheets in the zigzag air pathways.
FIGURE 5 Galvanized metal sheets pads vertically aligned
Pad medium provided with top water distribution system
differ from other commercially evaporative cooling systems.
The pad is made of galvanized metal sheets (0.3 mm
thickness).In the experiment, sixty-three sheets have been
aligned vertically in series placed side by side as shown in
Fig. 5, aligned vertically in series to give a sharp crisscross
of air entering between the sheets.
The two temperature and humidity probes are employed to
measure dry-bulb temperature and relative humidity of
outside and conditioned air. It is cautioned that the sensors
are to be prevented from direct radiation and water droplets
in order to get the actual readings of temperature and
humidity. Water temperature in the reservoir was measured
through temperature probe sensors connected to a data
logger. The outside dry-bulb temperature and relative
humidity readings would determine dew point and wet-bulb
temperature from the calculation module[7] .
Pad depth (m)
Outside drybulb
temperature
(0C)
Outside wetbulb
temperature
(0C)
Outside
relative
humidity (%)
Conditioned
dry-bulb
temperature
(0C)
Conditioned
relative
humidity (%)
Reservoir
water
temperature
(0C)
Cooling
efficiency (%)
0.45
38
0.30
37.66
0.15
38.42
17.01
17.37
17.33
11.28
11.59
10.23
19.95
23.46
27.28
78.15
77.19
64.68
18.87
18.96
19.48
85.17
82.92
73.29
TABLE I
Average cooling efficiency vs. pad depths
International Journal of Engineering Science and Computing, April 2016
Clearly, it is shown that the outside dry-bulb air temperature
during the trials revealed the same pattern with very little
variations.
Analysis of Variance (ANOVA) was taken as a tool to
determine suitable pad depth which has a considerable effect
on the cooling efficiency. The difference of results in view
of cooling efficiency represent that the pad depth has a
significant
effect
on
the
cooling
efficiency.
In the experimental result, average conditioned air
temperature decreased from 23 to 21 0C and averaged
cooling efficiency increased from 73 to 85%.
III.
CONCLUSION
The ease of installation, consumption of power and
maintenance estimates the evaporative cooling at a price
nearly one-fourth of the air conditioners system. The
consistent high volumetric air flow rate reduces the
temperature of air inside the workplace. It improves the
condition of climate inside the room. Electricity
consumption is reduced and water saving is also a concern.
From the comparative account, it has been observed that the
vertically aligned galvanized metal sheets could withstand to
any temperature range in the country’s scenario and the
cooling efficiency is nearly 85% above all the performance
indicators.
In the new design, it is wiser to remove salt deposition and
dust built up on the pads surfaces which would render a
longer useful life compared to the commercially available
cellulosic pads.
IV
REFERENCES
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