project report on evaporative cooler,

1. A
Project report
On
Entitled
“EVAPORATIVE COOLER”
Submitted in partial fulfilment for theaward of degree of
Bachelor of Technology
In
Department of mechanical engineering
Jagan Nath University
Jaipur
Submitted by: Submitted to:
Amit Prasad MahendraPratap Singh
(H.O.D)
(Mechanicalengineering)

2. CANDIDATE’S DECLARATION
I hereby declare that the work which is being presented in this dissertation titled
“EVAPORATIVE COOLER” Towards partial fulfillment of requirements for the award of
the degree of “Bachelor of Technology in Mechanical Engineering” submitted in the
department of mechanical engineering Jagannath University, Jaipur in the supervision of
Mr. Mahendra Pratap Singh H.O.D of Mechanical Engineering Department, Jagannath
University, Jaipur
Date:
Place:Jaipur

3. CERTIFICATE
This is to verify that the above statement made by the student is correct to the
best of my knowledge.
(Mahendra Pratap Singh)
H.O.D
Dept. of mechanical engineering
Jagannath University

4. ABSTRACT
An evaporative cooler (also swamp cooler, desert cooler and wet air cooler) is a device that
cools air through the evaporation of water. Evaporative cooling differs from typical air
conditioning systems which use vapour-compression or absorption refrigeration cycles.
Evaporative cooling works by employing water's large enthalpy of vaporization. The
temperature of dry air can be dropped significantly through the phase transition of liquid
water to water vapour (evaporation), which can cool air using much less energy
than refrigeration. In extremely dry climates, evaporative cooling of air has the added
benefit of conditioning the air with more moisture for the comfort of building occupants.
The cooling potential for evaporative cooling is dependent on the wet bulb depression, the
difference between dry-bulb temperature and wet-bulb temperature. In arid climates,
evaporative cooling can reduce energy consumption and total equipment for conditioning
as an alternative to compressor-based cooling. In climates not considered arid, indirect
evaporative cooling can still take advantage of the evaporative cooling process without
increasing humidity. Passive evaporative cooling strategies offer the same benefits of
mechanical evaporative cooling systems without the complexity of equipment and
ductwork.
.

5. WORKING PRINCIPLE
Evaporative coolers lower the temperature of air using the principle of evaporative cooling,
unlike typical air conditioning systems which use vapour-compression refrigeration or
absorption. Evaporative cooling is the addition of water vapour into air, which causes a
lowering of the temperature of the air. The energy needed to evaporate the water is taken
from the air in the form of sensible heat, which affects the temperature of the air, and
converted into latent heat, the energy present in the water vapour component of the air,
whilst the air remains at a constant enthalpy value. This conversion of sensible heat to
latent heat is known as an adiabatic process because it occurs at a constant enthalpy value.
Evaporative cooling therefore causes a drop in the temperature of air proportional to the
sensible heat drop and an increase in humidity proportional to the latent heat gain.
Evaporative cooling can be visualized using a psychrometric chart by finding the initial air
condition and moving along a line of constant enthalpy toward a state of higher humidity.

6. THEORY
As water is evaporated, energy is lost from the air, reducing the temperature. Two
temperatures are important when dealing with evaporative cooling systems.
Dry Bulb Temperature
This is the temperature that we usually think of as air temperature, measured by a regular
thermometer exposed to the air stream.
Wet Bulb Temperature
This is the lowest temperature that can be reached by the evaporation of water only.
When considering water evaporating into air, the wet-bulb temperature, as compared to
the air's dry-bulb temperature is a measure of the potential for evaporative cooling. The dry
and wet bulb temperature can be used to calculate the relative humidity.
Evaporation will take place when the humidity is below 100% and the air begins to absorb
water. Any given volume of air can hold a certain amount of water vapour and the degree of
absorption will depend on the amount it is already holding.
The term humidity describes how much water is already in the air; relative to the amount it
is capable of holding. Air is saturated when it cannot hold any more water. Imagine it as a
sponge, if the sponge held half as much water as it was capable of holding, it would be 50%
saturated. In the case of air, we would describe the Relative Humidity as being 50%.
Energy is required to change water from liquid to vapour. This energy is obtained in an
adiabatic process from the air itself. Air entering an evaporative air cooler gives up heat
energy to evaporate water. During this process, the dry bulb temperature of the air passing
through the cooler is lowered
What is an evaporative cooler?
An evaporative cooler is a box-shaped appliance with one or more porous surfaces that
enable air to pass through. A fan inside the unit pulls outside air through the sides and into
the house. To produce cool air, each porous side is fitted with a pad of water-absorbing
material. Water is stored in a pan at the bottom of the cooler and a small pump lifts the
water to the top of each side.
To effectively cool your home, each pad needs to remain damp, but not soaked. Dampness
creates the most evaporation and, therefore, the most cooling. The amount of water the
pump moves may need to be adjusted from time to time to properly dampen the pads.

7. Adjusting the air flow
Climate control inside a home with an evaporative cooler depends on proper air balance. To
limit humidity, you need to make sure that the same volume of air flows out of your home
as is pumped in.
You can attain balanced air flow by installing ducts in each room or opening windows when
the cooler is in use. A window should be open just enough to allow air pressure inside a
room to slowly and quietly close the door to that room. If the door closes forcefully, there is
too little exhaust and the window should be opened wider. However, the window is open
too far if the door doesn't move at all.
A simple example of natural evaporative cooling is perspiration, or sweat, secreted by the
body, evaporation of which cools the body. The amount of heat transfer depends on the
evaporation rate, however for each kilogram of water vaporized 2,257 kJ of energy (about
890 BTU per pound of pure water, at 95 °F) are transferred. The evaporation rate depends
on the temperature and humidity of the air, which is why sweat accumulates more on hot,
humid days, as it does not evaporate fast enough.
Vapour-compression refrigeration uses evaporative cooling, but the evaporated vapor is
within a sealed system, and is then compressed ready to evaporate again, using energy to
do so. Simple evaporative coolers water is evaporated into the environment, and not
recovered. In an interior space cooling unit, the evaporated water is introduced into the
space along with the now-cooled air; in an evaporative tower the evaporated water is
carried off in the airflow exhaust.
A closely related process, sublimation cooling differs from evaporative cooling in that a
phase transition from solid to vapour, rather than liquid to vapour occurs.
Sublimation cooling has been observed to operate on a planetary scale on the
planetoid Pluto, where it has been called an anti-greenhouse effect. Another application of
a phase change to cooling is the "self-refrigerating" beverage can. A separate compartment
inside the can contains a desiccant and a liquid. Just before drinking, a tab is pulled so that
the desiccant comes into contact with the liquid and dissolves. As it does so it absorbs an
amount of heat energy called the latent heat of fusion. Evaporative cooling works with the
phase change of liquid into vapour and the latent heat of vaporization, but the self-cooling
can uses a change from solid to liquid, and the latent heat of fusion to achieve the same
result.

8. Evaporative air conditioning uses evaporation to cool the air. In an evaporative cooler, a
pump circulates water from the reservoir on to a cooling pad, which in turn becomes very
wet. A fan draws air from outside the unit through the moistened pad. As it passes through
the pad the air is cooled by evaporation. The key to effective evaporative cooling is ensuring
that each of the cooling pads are completely saturated at all times during operation and
that the systems fan & motor are sized and designed to deliver the appropriate airflow for
the home.
.
Fig.1.1 Schematic Diag. Of Evaporative Cooler
Evaporative coolers, often called "swamp coolers", are cooling systems that use only water
And a blower to circulate air. When warm, dry (unsaturated) air is pulled through a water-
soaked pad, water is evaporated and is absorbed as water vapour into the air. The air is
cooled in the process and the humidity is increased.
The evaporator cooling technology is an energy-efficient alternative to compressor-based
Cooling. In dry and arid regions, evaporative cooling can meet most or all building cooling
loads using one-fourth the energy of conventional equipment. It can also be applied cost-
effectively when integrated with conventional chiller systems, which can greatly improve a
facility's load profile. Unfortunately, evaporative cooling requires an abundant water source
and is only effective when the relative humidity is low, restricting its efficient use to dry
climates (most of the south-western USA and other dry-climate areas worldwide).

9. Psychrometric chart’s Terminology
Dry-bulb temperature(DBT)
The dry-bulb temperature is the temperature indicated by a thermometer exposed to the
air in a place sheltered from direct solar radiation. The term dry-bulb is customarily added
to temperature to distinguish it from wet-bulb and dew point temperature. In meteorology
and psychrometrics the word temperature by itself without a prefix usually means dry-bulb
temperature. Technically, the temperature registered by the dry-bulb thermometer of a
psychrometer.
Wet-bulb temperature(WBT)
The thermodynamic wet-bulb temperature is a thermodynamic property of a mixture of air
and water vapour. The value indicated by a wet-bulb thermometer often provides an
adequate approximation of the thermodynamic wet-bulb temperature.
The accuracy of a simple wet-bulb thermometer depends on how fast air passes over the
bulb and how well the thermometer is shielded from the radiant temperature of its
surroundings. Speeds up to 5,000 ft/min (~60 mph) are best but it may be dangerous to
move a thermometer at that speed. Errors up to 15% can occur if the air movement is too
slow or if there is too much radiant heat present (from sunlight, for example).
A wet bulb temperature taken with air moving at about 1–2 m/s is referred to as a screen
temperature, whereas a temperature taken with air moving about 3.5 m/s or more is
referred to as sling temperature.
A psychrometer is a device that includes both a dry-bulb and a wet-bulb thermometer.
A sling psychrometer requires manual operation to create the airflow over the bulbs, but
a powered psychrometer includes a fan for this function. Knowing both the dry-bulb
temperature (DBT) and wet-bulb temperature (WBT), one can determine the relative
humidity (RH) from the psychometric chart appropriate to the air pressure.
Relative humidity
The ratio of the vapour pressure of moisture in the sample to the saturation pressure at the
dry bulb temperature of the sample.
Dew point temperature
The saturation temperature of the moisture present in the sample of air, it can also be
defined as the temperature at which the vapour changes into liquid (condensation). Usually
the level at which water vapour changes into liquid marks the base of the cloud in the
atmosphere hence called condensation level. So the temperature value that allows this
process (condensation) to take place is called the 'dew point temperature'. A simplified
definition is the temperature at which the water vapour turns into "dew"

10. Humidity & Specific Humidity
Specific humidity is defined as the proportion of the mass of water vapour per unit mass of
the moist air sample (dry air plus the water vapour); it is closely related to humidity ratio
and always lower in value.
Absolute humidity
The mass of water vapour per unit volume of air containing the water vapour. This quantity
is also known as the water vapour density.[
Humid heat
Humid heat is the constant-pressure specific heat of moist air, per unit mass of dry air
Locating parameters onchart
* Dry bulb temperature: These lines are drawn straight, not always parallel to each other,
and slightly inclined from the vertical position. This is the t–axis, the abscissa (horizontal)
axis. Each line represents a constant temperature.
* Dew point temperature: From the state point follow the horizontal line of constant
humidity ratio to the intercept of 100% RH, also known as the saturation curve. The dew
point temperature is equal to the fully saturated dry bulb or wet bulb temperatures.
* Wet bulb temperature: These lines are oblique lines that differ slightly from the enthalpy
lines. They are identically straight but are not exactly parallel to each other. These intersect
the saturation curve at DBT point.
* Relative humidity: These hyperbolic lines are shown in intervals of 10%. The saturation
curve is at 100% RH, while dry air is at 0% RH.
* Humidity ratio: These are the horizontal lines on the chart. Humidity ratio is usually
expressed as mass of moisture per mass of dry air (pounds or kilograms of moisture per
pound or kilogram of dry air, respectively). The range is from 0 for dry air up to 0.03
(lbmw/lbma) on the right hand ω-axis, the ordinate or vertical axis of the chart.
* Specific enthalpy: These are oblique lines drawn diagonally downward from left to right
across the chart that are parallel to each other. These are not parallel to wet bulb
temperature lines.
Specific volume: These are a family of equally spaced straight lines that are nearly parallel.
The region above the saturation curve is a two-phase region that represents a mixture of
saturated moist air and liquid water, in thermal equilibrium.
The protractor on the upper left of the chart has two scales. The inner scale represents
sensible-total heat ratio (SHF). The outer scale gives the ratio of enthalpy difference to
humidity difference. This is used to establish the slope of a condition line between two
processes.

11. Psychrometric Processes:
In the domestic and industrial air conditioning applications some psychrometric processes
have to be performed on the air to change the psychrometric properties of air so as to
obtain certain values of temperature and humidity of air within the enclosed space. Some of
the common psychrometric processes carried out on air are: sensible heating and cooling of
air, humidification and dehumidification of air, mixing of various streams of air, or there may
be combinations of the various processes.
Illustrating and analyzing the psychrometric properties and psychrometric processes by
using the psychrometric chart is very easy, convenient and time saving. In the next few
paragraphs we shall see some of the most commonly employed psychrometric processes in
the field of HVAC and how they are represented on the psychrometric chart.
Fig.1.2 psychrometric process

12. SensibleCooling of the Air
Cooling of the air is one of the most common psychrometric processes in the air
conditioning systems. The basic function of the air-conditioners is to cool the air absorbed
from the room or the atmosphere, which is at higher temperatures. The sensible cooling of
air is the process in which only the sensible heat of the air is removed so as to reduce its
temperature, and there is no change in the moisture content (kg/kg of dry air) of the air.
During sensible cooling process the dry bulb (DB) temperature and wet bulb (WB)
temperature of the air reduces, while the latent heat of the air and the dew point (DP)
temperature of the air remains constant.
There is overall reduction in the enthalpy of the air. The ordinary window or the split air
conditioner the cooling of air is carried out by passing it over the evaporator coil, also called
as the cooling coil. The room air or the atmospheric air passes over this coil carrying the
refrigerant at extremely low temperatures, and gets cooled and passes to the space which is
to be maintained at the comfort conditions.
In general the sensible cooling process is carried out by passing the air over the coil. In the
unitary air conditioners these coils are cooled by the refrigerant passing through them and
are called also called evaporator coils. In central air conditioners these coils are cooled by
the chilled water, which is chilled by its passage through the evaporator of the large air
conditioning system. In certain cases the coil is also cooled by the some gas passing inside it.
The sensible cooling process is represented by a straight horizontal line on
the psychrometric chart. The line starts from the initial DB temperature of the air and ends
at the final DB temperature of the air extending towards the left side from high temperature
to the low temperature (see the figure below). The sensible cooling line is also the constant
DP temperature line since the moisture content of the air remains constant. The initial and
final points on the psychrometric chart give all the properties of the air.

13. Fig 1.3 sensible cooling
Sensible Heating of the Air
Sensible heating process is opposite to sensible cooling process. In sensible heating process
the temperature of air is increased without changing its moisture content. During this
process the sensible heat, DB and WB temperature of the air increases while latent of air,
and the DP point temperature of the air remains constant.
Sensible heating of the air is important when the air conditioner is used as the heat pump to
heat the air. In the heat pump the air is heated by passing it over the condenser coil or the
heating coil that carry the high temperature refrigerant. In some cases the heating of air is
also done to suit different industrial and comfort air-conditioning applications where large
air conditioning systems are used.
In general the sensible heating process is carried out by passing the air over the heating coil.
This coil may be heated by passing the refrigerant, the hot water, the steam or by electric
resistance heating coil. The hot water and steamare used for the industrial applications.
Like the sensible cooling, the sensible heating process is also represented by a straight
horizontal line on the psychometric chart. The line starts from the initial DB temperature of
air and ends at the final temperature extending towards the right (see the figure). The
sensible heating line is also the constant DP temperature line.

14. Fig 1.4 sensible heating
What is Humidification Process?
The process in which the moisture or water vapour or humidity is added to the air without
changing its dry bulb (DB) temperature is called as humidification process. This process is
represented by a straight vertical line on the psychrometric chart starting from the initial
value of relative humidity, extending upwards and ending at the final value of the relative
humidity. In actual practice the pure humidification process is not possible, since the
humidification is always accompanied by cooling or heating of the air. Humidification
process along with cooling or heating is used in number of air conditioning applications. Let
us see how these processes are obtained and how they are represented on the
psychrometric chart.
This article describes psychrometric processes like humidification, cooling and
humidification, and heating and humidification. The article describes how these processes
are achieved and how they are represented on the psychrometric chart.

15. Cooling and Humidification Process
Cooling and humidification process is one of the most commonly used air conditioning
application for the cooling purposes. In this process the moisture is added to the air by
passing it over the stream or spray of water which is at temperature lower than the dry bulb
temperature of the air. When the ordinary air passes over the stream of water, the particles
of water present within the stream tend to get evaporated by giving up the heat to the
stream. The evaporated water is absorbed by the air so its moisture content, thus the
humidity increases. At the same time, since the temperature of the absorbed moisture is
less than the DB bulb temperature of the air, there is reduction in the overall temperature
of the air. Since the heat is released in the stream or spray of water, its temperature
increases.
One of the most popular applications of cooling and humidification is the evaporative
cooler, also called as the desert cooler. The evaporative cooler is the sort of big box inside
which is a small water tank, small water pump and the fan. The water from the tank is
circulated by the pump and is also sprayed inside the box. The fan blows strong currents of
air over the water sprays, thus cooling the air and humidifying it simultaneously. The
evaporative cooler is highly effective cooling devise having very low initial and running cost
compared to the unitary air conditioners. For cooling purposes, the cooling and
humidification process can be used only in dry and hot climates like desert areas, countries
like India, China, Africa etc. This cooling process cannot be used in hot and high humidity
climates.
The cooling and humidification process is also used in various industries like textile, where
certain level of temperature and moisture content has to be maintained. In such cases large
quantity of water is sprayed, and large blowers are used to blow the air over the spray of
water.
During the cooling and humidification process the dry bulb of the air reduces, its wet bulb
and the dew point temperature increases, while its moisture content and thus the relative
humidity also increases. Also, the sensible heat of the air reduces, while the latent heat of
the air increases resulting in the overall increase in the enthalpy of the air.
Cooling and humidification process is represented by an angular line on the psychrometric
chart starting from the given value of the dry bulb temperature and the relative humidity
and extending upwards toward left.

16. Fig 1.5 cooling and humidification
Heating and Humidification Process
In heating and humidification psychrometric process of the air, the dry bulb temperature as
well as the humidity of the air increases. The heating and humidification process is carried
out by passing the air over spray of water, which is maintained at temperature higher than
the dry bulb temperature of air or by mixing air and the steam.
When the ordinary air is passed over the spray of water maintained at temperature higher
than the dry bulb temperature of the air, the moisture particles from the spray tend to get
evaporated and get absorbed in the air due to which the moisture content of the air
increase. At the same time, since the temperature of the moisture is greater than the dry
bulb temperature of the air, there is overall increase in its temperature.
During heating and humidification process the dry bulb, wet bulb, and dew point
temperature of the air increases along with its relative humidity. The heating and
humidification process is represented on the psychrometric chart by an angular line that

17. starts from the given value of the dry bulb temperature and extends upwards towards right
(see the figure below).
Fig 1.6 heating and humidification
Whatis Dehumidification?
The process in which the moisture or water vapour or the humidity is removed from the air
keeping its dry bulb (DB) temperature constant is called as the dehumidification process.
This process is represented by a straight vertical line on the chart starting from the initial
value of relative humidity, extending downwards and ending at the final value of the relative
humidity. Like the pure humidification process, in actual practice the pure dehumidification
process is not possible, since the dehumidification is always accompanied by cooling or
heating of the air. Dehumidification process along with cooling or heating is used in number
of air conditioning applications. Let us see how these processes are obtained and how they
are represented on the psychrometric chart.

18. This article describes psychrometric processes like dehumidification, cooling and
dehumidification, and heating and dehumidification. The article describes how these
processes are achieved and how they are represented on the psychrometric chart.
Cooling and Dehumidification Process
The process in which the air is cooled sensibly and at the same time the moisture is
removed from it is called as cooling and dehumidification process. Cooling and
dehumidification process is obtained when the air at the given dry bulb and dew point (DP)
temperature is cooled below the dew point temperature.
Let us understand the cooling and dehumidification process in more details. When the air
comes in contact with the cooling coil that is maintained at the temperature below its dew
point temperature, its DB temperature starts reducing. The process of cooling continues and
at some point it reaches the value of dew point temperature of the air. At this point the
water vapour within the air starts getting converted into the dew particles due to which the
dew is formed on the surface of the cooling and the moisture content of the air reduces
thereby reducing its humidity level. Thus when the air is cooled below its dew point
temperature, there is cooling as well as dehumidification of air.
The cooling and dehumidification process is most widely used air conditioning application. It
is used in all types of window, split, packaged and central air conditioning systems for
producing the comfort conditions inside the space to be cooled. In the window and split air
conditioners the evaporator coil or cooling coil is maintained at temperature lower than the
dew point temperature of the room air or the atmospheric air by the cool refrigerant
passing through it. When the room air passes over this coil its DB temperature reduces and
at the same time moisture is also removed since the air is cooled below its DP temperature.
The dew formed on the cooling coil is removed out by small tubing. In the central air
conditioning systems the cooling coil is cooled by the refrigerant or the chilled water. When
the room air passes over this coil, it gets cooled and dehumidified.
In the general the cooling and dehumidification process is obtained by passing the air over
coil through which the cool refrigerant, chilled water or cooled gas is passed.
During the cooling and dehumidification process the dry bulb, wet bulb and the dew point
temperature of air reduces. Similarly, the sensible heat and the latent heat of the air also
reduce leading to overall reduction in the enthalpy of the air. The cooling and
dehumidification process is represented by a straight angular line on the psychrometric
chart. The line starts from the given value of the DB temperature and extends downwards
towards left.

19. Fig 1.7 cooling and dehumidification
Heating and Dehumidification Process
The process in which the air is heated and at the same time moisture is removed from it is
called as heating and dehumidification process. This process is obtained by passing the air
over certain chemicals like alumina and molecular sieves. These elements have inherent
properties due to which they keep on releasing the heat and also have the tendency to
absorb the moisture. These are called as the hygroscopic chemicals.
In actual practice the hygroscopic elements are enclosed in the large vessel and the high
pressure air is passed inside the vessel through one opening. When the air comes in contact
with the chemicals the moisture from the air is absorbed and since the chemicals emit heat,
the DB temperature of the air increases. The hot and dehumidified air comes out from the

20. vessel through other opening in the vessel. The inlet and outlet openings of the vessel are
controlled by the valve.
The heating and humidification process is commonly used for reducing the dew point
temperature of air. There are number of automatic valves in the chemical plants that are
operated by the compressed air at high pressure. If the dew point temperature of this air is
high, there are chances of formation of dew inside the valves which can lead to their
corrosion and also faulty their operation. Thus it is very important that the air passing to
such automatic valves have very low dew point temperature. The heating and
dehumidification process by using hygroscopic materials is used often in the air drying units.
During the heating and dehumidification process dry bulb temperature of the air increases
while its dew point and wet bulb temperature reduces. On the psychrometric chart, this
process is represented by a straight angular line starting from the given DB temperature
conditions and extending downwards towards right to the final DB temperature conditions.
fig 1.8 heating and dehumidification

21. Advantages of Evaporative Cooling Systems
 They are energy efficient. Evaporative coolers use up to 75 percent less electricity
than a standard air conditioner. This can result in significant savings, especially in hot
desert climates.
 They are environmentally friendly. They do not use refrigerants like CFCs and HCFCs
for the cooling process, so there are no greenhouse gases emitted.
 They don’t need much repair. The technology for evaporative coolers is very simple,
and there are fewer working parts, which means maintenance and repair costs are
low.
 They use common household current. Evaporative coolers do not require high
amperage circuits — they operate on 120-volt electricity, which is less than a
standard air conditioner uses. That means evaporative coolers can be plugged into
any household outlet.
 They filter the air effectively. Evaporative cooling systems use moist pads as part of
the cooling process, and these pads are very good air filters, effectively trapping dust
and pollen. They are also very inexpensive to replace, compared to air conditioner
filters.
 They add moisture to the house. These coolers naturally add moisture to a house,
which keeps wood furniture and fabrics from drying out.
 They do not require ductwork. Because they fit in a window, you do not need
ductwork to distribute the air. Smaller units can be placed on the window with very
little installation.
Disadvantages of Evaporative Cooling Systems
 They do not work as well in humid climates. Evaporative cooling works best in dry
climates. Too much moisture in the outside air makes the system work inefficiently.
Moisture can build up, causing condensation and corrosion.
 They need some attention. The moisture pads in an evaporative cooler must be kept
moist with water. If they dry out the cooler will not work well. This can be a problem
in desert areas where the dry air will take a toll on the pads.
Evaporative cooling systems use a time-tested technique for temperature control. If you live
in a dry climate, they are a viable option to explore.

22. Bibliography
 Air conditioning & refrigeration by R.S.Khurmi
 R&AC by R K Rajput
 http://en.wikipedia.org/wiki/Evaporative_cooler
 http://www.ijergs.org/
 http://www.brighthubengineering.com/