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FABRICATION AND PERFORMANCE OF AIR WASHER
Preparedby: Guided by:
Shyam Tank Dr. Jignesh R. Mehta
Faculty of technology and engineering
M.S. University of Vadodara
“It is due to someone’s bliss that we learn, we progress
and we succeed.”
We express our sincere gratitude to Dr. J. R. Mehta sir for
providing continues guidance and motivation towards the completionof the
project.It is very great opportunity to work under his guidance on this
At last we are sincerelythankful to Dr. D.S. Sharma (HOD) for
approving the subject of project.
“PRACTICE MAKES MAN PERFECT”
Thus, theory of any subjectis important to clear the fundamentals of
the subjects,but without practical knowledge it will become difficultfor the
degree students.A degree student cannot become aperfectengineer
without the practical understanding of the branch. Hence, this projectwork
provides goldenopportunity for all degree students.
The principle of the project is to get details about the on-line
processesand real operation tasks, projectmanagement and discipline
required in practical world.
Sr no. Title Page no.
1 Literature study 5-13
2 Components of air washer 14-23
3 Fabrication of air washer 24-28
4 Experimentation 29-35
5 Conclusion 36
In today’s world global warming is one of the biggest problems faced by human.
The maximum temperature during the summer has been increasing every year.
Different types of air conditioning systems are used in today’s world based on different
principles of thermodynamics. Air washer is one of the devices used for air conditioning.
It is based on the psychrometry. It is study of the properties of moist air.
An air washer is a device used for conditioning air. As shown in Fig, in an air
washer air comes in direct contact with a spray of water and there will be an exchange
of heat and mass (water vapour) between air and water. The outlet condition of air
depends upon the temperature of water sprayed in the air washer. Hence, by controlling
the water temperature externally, it is possible to control the outlet conditions of air,
which then can be used for air conditioning purposes.
In the air washer, the mean temperature of water droplets in contact with air
decides the direction of heat and mass transfer. As a consequence of the 2nd law, the
heat transfer between air and water droplets will be in the direction of decreasing
temperature gradient. Similarly, the mass transfer will be in the direction of decreasing
vapor pressure gradient. Here some situation are explained.
a) Cooling and dehumidification: tw < tDPT. Since the exit enthalpy of air is less than its
inlet value, from energy balance it can be shown that there is a transfer of total energy
from air to water. Hence to continue the process, water has to be externally cooled.
Here both latent and sensible heat transfers are from air to water. This is shown by
Process O-A in Fig.
[Dew-point temperature: If unsaturated moist air is cooled at constant pressure, then the
temperature at which the moisture in the air begins to condense is known as dew-point
temperature (DPT) of air.]
b) Adiabatic saturation: tw = tWBT. Here the sensible heat transfer from air to water is
exactly equal to latent heat transfer from water to air. Hence, no external cooling or
heating of water is required. That is this is a case of pure water recirculation. This is
shown process O-B in figure. This is the process that takes place in a perfectly insulated
[WBT- wet bulb temperature is defined as that temperature at which water, by
evaporating into air, can bring the air to saturation at the same temperature
c) Cooling and humidification: tDPT < tw < tWBT. Here the sensible heat transfer is from
air to water and latent heat transfer is from water to air, but the total heat transfer is from
air to water, hence, water has to be cooled externally. This is shown by Process O-C in
d) Cooling and humidification: tWBT < tw < tDBT. Here the sensible heat transfer is
from air to water and latent heat transfer is from water to air, but the total heat transfer is
from water to air, hence, water has to be heated externally. This is shown by Process
O-D in Fig. This is the process that takes place in a cooling tower. The air stream
extracts heat from the hot water coming from the condenser, and the cooled water is
sent back to the condenser.
[Dry bulb temperature (DBT) is the temperature of the moist air as measured by a
standard thermometer or other temperature measuring instruments.]
e) Heating and humidification: tw > tDBT. Here both sensible and latent heat transfers
are from water to air, hence, water has to be heated externally. This is shown by
Process O-E in Fig.
Thus, it can be seen that an air washer works as a year-round air conditioning system.
Though air washer is a and extremely useful simple device, it is not commonly used for
comfort air conditioning applications due to concerns about health resulting from
bacterial or fungal growth on the wetted surfaces. However, it can be used in industrial
1.2 Advantages over VCR refrigeration system
Introduces the fresh air. Do not circulate the air.
Refrigerant is not required.
Compressor is eliminated which consumes much power. Around 90% less
Installation is easy.
Full ventilation exhausts odors and germs.
Increased cooling capacity as outside temperature rises.
1.3 Evaporating cooling system using air washer:
Evaporative cooling has been in use for many centuries in countries such as
India for cooling water and for providing thermal comfort in hot and dry regions. This
system is based on the principle that when moist but unsaturated air comes in contact
with a wetted surface whose temperature is higher than the dew point temperature of
air, some water from the wetted surface evaporates into air. The latent heat of
evaporation is taken from water, air or both of them. In this process, the air loses
sensible heat but gains latent heat due to transfer of water vapour. Thus the air gets
cooled and humidified. The cooled and humidified air can be used for providing thermal
Classification of evaporative cooling systems:
1. Direct evaporation process
2. Indirect evaporation process
3. A combination or multi-stage systems
1. Direct evaporation process:
In direct evaporative cooling, the process or conditioned air comes in direct
contact with the wetted surface, and gets cooled and humidified. Figure shows the
schematic of an elementary direct, evaporative cooling system and the process on a
psychrometric chart. As shown in the figure, hot and dry outdoor air is first filtered and
then is brought in contact with the wetted surface or spray of water droplets in the air
washer. The air gets cooled and dehumidified due to simultaneous transfer of sensible
and latent heats between air and water (process o-s). The cooled and humidified air is
supplied to the conditioned space, where it extracts the sensible and latent heat from
the conditioned space (process s-i). Finally the air is exhausted at state i. In an ideal
case when the air washer is perfectly insulated and an infinite amount of contact area is
available between air and the wetted surface, then the cooling and humidification
process follows the constant wet bulb temperature line and the temperature at the exit
of the air washer is equal to the wet bulb temperature of the entering air (t
), i.e., the
process becomes an adiabatic saturation process. However, in an actual system the
temperature at the exit of the air washer will be higher than the inlet wet bulb
temperature due to heat leaks from the surroundings and also due to finite contact area.
2. Indirect evaporation process:
Figure shows the schematic of a basic, indirect evaporative cooling system and
the process on a psychrometric chart. As shown in the figure, in an indirect evaporative
cooling process, two streams of air - primary and secondary are used. The primary air
stream becomes cooled and humidified by coming in direct contact with the wetted
surface (o-o’), while the secondary stream which is used as supply air to the
conditioned space, decreases its temperature by exchanging only sensible heat with the
cooled and humidified air stream (o-s). Thus the moisture content of the supply air
remains constant in an indirect evaporative cooling system, while its temperature drops.
Obviously, everything else remaining constant, the temperature drop obtained in a
direct evaporative cooling system is larger compared to that obtained in an indirect
system, in addition the direct evaporative cooling system is also simpler and hence,
However, since the moisture content of supply air remains constant in an indirect
evaporation process, this may provide greater degree of comfort in regions with higher
humidity ratio. In modern day indirect evaporative coolers, the conditioned air flows
through tubes or plates made of non-corroding plastic materials such as polystyrene
(PS) or polyvinyl chloride (PVC). On the outside of the plastic tubes or plates thin film of
water is maintained. Water from the liquid film on the outside of the tubes or plates
evaporates into the air blowing over it (primary air) and cools the conditioned air flowing
through the tubes or plates sensibly. Even though the plastic materials used in these
coolers have low thermal conductivity, the high external heat transfer coefficient due to
evaporation of water more than makes up for this.
(Indirect evaporation process)
3. Multi-stage systems:
Several modifications are possible which improve efficiency of the evaporative
cooling systems significantly. One simple improvement is to sensibly cool the outdoor
air before sending it to the evaporative cooler by exchanging heat with the exhaust air
from the conditioned space. This is possible since the temperature of the outdoor air will
be much higher than the exhaust air.
It is also possible to mix outdoor and return air in some proportion so that the
temperature at the inlet to the evaporative cooler can be reduced, thereby improving the
performance. Several other schemes of increasing complexity have been suggested to
get the maximum possible benefit from the evaporative cooling systems. For example,
one can use multistage evaporative cooling systems and obtain supply air temperatures
lower than the wet bulb temperature of the outdoor air. Thus multistage systems can be
used even in locations where the humidity levels are high.
Figure shows a typical two-stage evaporative cooling system and the process on
a psychrometric chart. As shown in the figure, in the first stage the primary air cooled
and humidified (o -o’) due to direct contact with a wet surface cools the secondary air
sensibly (o -1) in a heat exchanger. In the second stage, the secondary air stream is
further cooled by a direct evaporation process (1-2). Thus in an ideal case, the final exit
temperature of the supply air (t2
) is several degrees lower than the wet bulb temperature
of the inlet air to the system (to’
1.4 Advantages and disadvantages of evaporating cooling
Compared to the conventional refrigeration based air conditioning systems, the
evaporative cooling systems offer the following advantages:
1. Lower equipment and installation costs.
2. Substantially lower operating and power costs. Energy savings can be as high as
3. Ease of fabrication and installation.
4. Lower maintenance costs.
5. Ensures very good ventilation due to the large air flow rates involved, hence, are very
good especially in 100 % outdoor air applications.
6. Better air distribution in the conditioned space due to higher flow rates.
7. The fans/blowers create positive pressures in the conditioned space, so that
infiltration of outside air is prevented.
8. Very environment friendly as no harmful chemicals are used.
Compared to the conventional systems, the evaporative cooling systems suffer from the
1. The moisture level in the conditioned space could be higher, hence, direct
evaporative coolers are not good when low humidity levels in the conditioned space is
required. However, the indirect evaporative cooler can be used without increasing
2. Since the required air flow rates are much larger, this may create draft and/or high
noise levels in the conditioned space
3. Precise control of temperature and humidity in the conditioned space is not possible
4. May lead to health problems due to micro-organisms if the water used is not clean or
the wetted surfaces are not maintained properly.
1.5 Application of air washer:
Comfort conditioning suitable for malls, hotels, garment units, engineering units,
industrial units etc.
Industrial ventilation cooling.
Pre cooling for compressor and gas turbines.
Hybrid air conditioners.
100% fresh air application.
Dust removal application.
2-Components of air washer
Air washer assembly consists of many important parts. It requires fan to draw the air
in the chamber. An insulated water tank for storage of water. Nozzle for providing fine
droplets of water. Different types of measuring equipments are also used for carrying
out the performance analysis. Different components of air washer are as below:
Pipes and fittings
All the components are explained briefly below.
Water tank is located near to the air washer. It is connected to the water pipe
from suitable source for continuous supply of the water. The central air washer
needs larger quantity of the water, which increases as the number of room to be
cooled increases. For proper performance of the air washer one has to ensure the
abundant supply of the continuously. The water in tank can be ordinary water or
chilled water. Usually ordinary water is used.
In the experiment setup we used insulated water tank so that temperature of
water remains constant for a while. Chilled water is supplied to tank by chilling plant.
So that required amount of water is supplied to the air washer continuously.
Fan is used to draw the air in the chamber so that ambient air passes through the
spray of chilled water. For carrying out the performance analysis and find out the effect
of air flow rate on process, speed of the fan changed through the regulator.
Water from the water tank is pumped to the spray nozzle via plastic or mild steel
piping. The spray nozzle sprays the water inside the air washer. The nozzle should
produce finely atomized particles so that the entire chamber is filled with the mist. In
order to break the water into fine droplets, the nozzle should have low coefficient of
discharge. The spraying nozzles are made of brass, full cone type. They are
responsible for supplying water to the equipment wash system. The pressure is
calculated so that the nozzles provide a perfect cone to cover 100% of the area of the
In experiment we used 350 mm long and 3 mm diameter aluminum tubes in
which there are fine holes produced at 10 mm distance. The purpose behind this to
cover the whole area of the chamber and produce fine droplets to get better
Pump is required for supplying water from tank to the nozzle with pressure.
Capacity of pump should be such that it can pump the water from the tank to the desire
height without pressure loss. Location of the pump is also important as per the
performance aspects. The height where the pump is located should be such that It
would provide positive head. Many types of pumps can be used according the
application. Types of pumps vary according to the flow rate of water required and
cooling capacity. For high capacity like large room and high flow rate of water,
centrifugal pump is used.
In our experiment we used a diaphragm pump as the flow rate and capacity of
setup is small. The specifications of the pumps are as below:
Volts:24 V DC
Current: 1.2 A
Open flow: 1.5LPM
Suction height: 2 m
Inlet pressure: 30 PSI
Working pressure: 74-90 PSI
Diaphragm pump works on DC supply. To convert AC to DC, an adapter is used
having capacity of 2.6 A current and 24 V voltage.
2.5Pipes and fittings:
Connections from water tank to pump and from pump to nozzles are made with
help of plastic pipes and joint. For desirable result of experiment make sure that there is
no leakage in connection so that no loss in flow rate and in pressure. For different types
of arrangement of setup different types of joints are used such as T joints, right angle
joint (elbow) etc.
Diameter of the pipe is also important factor because the flow rate of water is
depended on diameter of pipes. For high flow rates, diameter of the pipes should be
large. We used the purifier pipes and joints for the experiment setup. Connections are
made from insulated water tank to diaphragm pump and then from pump to two nozzles
provided in chamber via plastic pipes and joints.
It is passage in which the process takes place. The dimensions of the chamber
vary according to the application. It should be such that it can accommodate the fan for
drawing air. Make sure that all air passes through the chamber without leakage. It
should also provide the provision for the accommodation of the nozzles. For water exit it
should also provide provision at bottom of chamber so that water can be collected and
its temperature can be measured. The bottom portion of the chamber should be such
that it does not store the water after spray. Water should be discharged immediately
after the spray. For this a slight inclination is given in bottom portion so that it drives the
water to the exit hole.
The main requirement of chamber is to provide leak proof passages so that
desirable results can be achieved and provide provision for the nozzle and measuring
equipment used in process.
Eliminator plate is most important part of the air washer assembly. It retains the
water droplets from the wet air and sends only saturated air to exit passage. It is very
important to get desirable performance characteristics. So the basic purpose of the
eliminator plate is to remove the free particles of water from the moist air. To
satisfactorily perform this function zigzag shaped eliminator plates upon which the
moisture laden air can deposit the water are grouped in the path of the moving air.
Because these eliminator blades are prone to having solids deposited on their surfaces
as well as liquids, it is necessary to periodically clean these blades after the solids have
begun to accumulate.
This is particularly true in textile mills where lint, fly and starches are carried in
the air stream and readily joint with the water in the air stream to cover the blades with a
coating which is virtually glue. To remove this coating it is necessary to periodically
scrub the blades. This establishes the requirement that all of the surfaces of the blades
be readily accessible.
Prior art air washers have been built with some awareness of this problem.
However, in an effort to maintain structural strength and rigidity these washers have
generally been built with the eliminator blades joined to the frame members of the air
washer. The result of using such a construction is unwieldiness in separating the blades
so that a brush or the like may be passed between them to accomplish the cleaning.
Some prior constructions have utilized long rods or bolts to fasten the plates
together and retain them in slots formed in the frame members of the washer. This has
imposed the requirement of unfastening the rods or bolts before the plates could be
moved apart. Generally, such a construction has lent itself to cleaning the blades from
only one side.
Other prior construction utilizing clips of various sorts have also been limited with
respect to the access to the interior surfaces of the blades in that separation has also
best been accomplished from only one side. Further, the clips have often been used to
fasten the frame members and the blades together, making removal of the blades as
well as their separation difficult.
It is therefore apparent that each air washer has normally been assembled
almost in the status of a custom job. This is so because the frame members of the
washer were either slotted as required or had the clips fastened to them as required, for
any particular job.
This is how the spacing of the eliminator blades for each frames assembly is
established. Therefore, it has been impractical to precut the frame members until the
spacing of the blades for a particular installation has been determined.
The present invention overcomes the above-described inadequacies and permits
easy cleaning of the eliminator blades from either the front or back of the blades as they
are pivot able from either the front or the back.
In addition, the blades are held in a self-contained core which merely rests on
the frame of the air washer so that the frame members can be precut at will since the
washer can now accept any core of eliminator blades having overall outside dimensions
to fit the washer frame.
The spacing of eliminator blades in the core will have no effect on the frame
structure and further the core can be installed and removed without excessive
manipulation of fastening means.
The following shows the general schematic diagram of the eliminator plate. It is
made in zigzag pattern. Two plates are inclined at 60 degree with each other. The
passages between two plates are very narrow so that desire performance is achieved.
It is provided at end of the chamber. The purpose of this convergent portion is to
increase the exit velocity of the air. By providing this portion exit area gets fixed. So that
the flow rate of air can be measured easily.
We have used convergent portion made of 3 mm thick acrylic sheet.
2.9 Measuring equipments:
To carry out performance analysis of air washer several measuring equipments
are used in experiment. For the temperature measurement of inlet and outlet water,
thermocouple is used. For measuring the outlet velocity of the air mechanical
anemometer is used. Hydrometer is used to measure the humidity of the air.
Mechanical anemometer used is having capacity to measure velocity of 0-15
m/s. thermocouple used in experiment is having 8 channels so that we can measure up
to 8 temperature at different place simultaneously.
Any instrument capable of measuring the psychrometric state of air is called a
psychrometer. As mentioned before, in order to measure the psychrometric state of air,
it is required to measure three independent parameters. Generally two of these are the
barometric pressure and air dry-bulb temperature as they can be measured easily and
with good accuracy.
Two types of psychrometers are commonly used. Each comprises of two
thermometers with the bulb of one covered by a moist wick. The two sensing bulbs are
separated and shaded from each other so that the radiation heat transfer between them
becomes negligible. Radiation shields may have to be used over the bulbs if the
surrounding temperatures are considerably different from the air temperature.
The sling psychrometer is widely used for measurements involving room air or
other applications where the air velocity inside the room is small. The sling
psychrometer consists of two thermometers mounted side by side and fitted in a frame
with a handle for whirling the device through air. The required air circulation (≈ 3 to 5
m/s) over the sensing bulbs is obtained by whirling the psychrometer (≈ 300 RPM).
Readings are taken when both the thermometers show steady-state readings.
In the aspirated psychrometer, the thermometers remain stationary, and a small
fan, blower or syringe moves the air across the thermometer bulbs. The function of the
wick on the wet-bulb thermometer is to provide a thin film of water on the sensing bulb.
To prevent errors, there should be a continuous film of water on the wick. The wicks
made of cotton or cloth should be replaced frequently, and only distilled water should be
used for wetting it. The wick should extend beyond the bulb by 1 or 2 cm to minimize
the heat conduction effects along the stem.
Other types of psychrometric instruments:
1. Dunmore Electric Hygrometer
2. DPT meter
3. Hygrometer (Using horses or human hair)
3-FABRICATION OF AIR WASHER
We have discussed the different parts of the air washer assembly required in
previous articles. From all the parts of the air washer most are standard equipment
available in the market. Fan with the regulator, diaphragm pump with adapter, pipes and
fittings are standard parts which is easily available. Only chamber, convergent portion,
eliminator plate and the nozzles are fabricated according to the requirement. The
fabrication of each portion is explained briefly below.
3.1 Chamber with inclined bottom portion:
Chamber with inclined bottom portion is made from 5 mm thick acrylic sheet. The
chamber consists of 4 sheets. Top sheet dimension is 770 mm* 350 mm. Two left and
right side sheet having dimension 770 mm* 400 mm. Now bottom portion is made from
several acrylic sheets having different dimensions. This is due to the requirement of
providing inclination for smooth water discharge. Different sheets having different
dimensions are shown in fig. These all sheets are joined together with help of flex kwik.
Now provisions are made for the nozzle accommodation therefore two 3mm
diameter holes are drilled from the front end of the chamber. A divergent portion made
of aluminum is attached to the front portion of the chamber. At the front of this divergent
portion fan is accommodated with help of the screw and frame. In the bottom portion a
hole of 15 mm diameter is drilled with help of drill machine for water outlet.
3.2 Convergent portion:
Convergent portion is made from 3 mm thick acrylic sheet. It is the most difficult
part to fabricate in entire air washer assembly. For this fabrication of this portion, we got
3 dimensions from which one dimension is from the chamber outlet. The length and the
exit portion dimension are taken according to the requirement. The fabrication of this
portion is done by the “development of surfaces” concept of the engineering drawing.
The whole procedure is described in the fig. It consists of the front and top view of the
convergent portion drawn according to scale. Now in front view the length of inclined
edge is not true. So first we found the true length of the edge which we get by extending
the top view dimension to front view.
After obtaining the true length of the slant edge, now it becomes very easy to
complete the rest of job. Now by going from one surface to another surface whole
development is created. By this we get the actual dimension of each four parts. Now
each part is cut from the 3 mm thick acrylic sheet. These four parts are stick together
with help of flex kiwk.
Now to make the part detachable from the chamber rear, bigger side of the
portion is extended with help of acrylic sheet. Drill the hole in this four strips and
chamber back and join the convergent portion with chamber with help of nut and bolt.
Thus assembly becomes detachable.
3.3 Eliminator plates:
Eliminator plates are made in zigzag pattern so that it removes the free particles
of water droplets. One eliminator part is made of four acrylic sheet having dimension 25
mm * 38 mm. These four plates are joined with each other at 60 degree. Same 20 parts
are made identical with each other. These 20 parts are placed parallel to each other
having 15 mm distance between them. After the assembly very small passage is
created for air to pass. This helps in removal of the unwanted water particles.
Nozzles are made from the 3 mm diameter aluminum tube. These two tubes are
35 mm long. In these nozzles at 10 mm a fine hole is made by electro discharge
machining. The principle involved in the process is that the work piece and the tool
(electrode) are separated by a gap called spark gap. This gap is filled by the dielectric,
which breaks down when a proper voltage is applied between these two. The spark gap
varies from 0.005 to 0.05 mm. when a circuit voltage of 50 V to 450 V is applied,
electrons start flowing from the cathode, due to electrostatic field, and the gap is
ionized. The consequent drop in resistance and discharge of electric energy results in
an electrical breakdown. The electric spark so caused directly impinges on the surface
of the work piece. It takes only few microseconds to complete the cycle and the spark
discharges hit the anode with considerable force and velocity, resulting in the
development of a very high temperature on the spot hit by discharges. This forces the
metals to melt and a portion of it may be vaporized. The metal removal takes place due
to the erosion caused by the electric spark. It produces fine holes on the surfaces.
Now all the parts are fabricated and standard parts are available. Now all the
parts are joined and experiment setup is ready.
Now the experiment setup is ready for the performance. But before beginning the
experiment setup should test to check whether it works according to the specification.
Some precautions are made for getting desirable results.
4.1.1 Internal part of the washer:
Spraying nozzles should be centered in the chamber.
Check the pipe connection for the leakage.
4.1.2 Hydraulic network:
Check if the pump is duly installed. Check also if nuts and bolts of flanges are
Feed the water tank and inspect for dirt build-up from assembly operations.
If there is dirt, drain the tank and re-feed it.
Before actuating the pump, check if rotation is correct.
Operate the system and eliminate leaks.
4.1.3 External part of the washer:
Check seals and access doors for perfect seating to prevent leaks.
Actuate the fan (closed valve) and check if rotation direction is correct.
4.1.4 Washer starts up:
The water circulation system must be the first one to be operated.
The system must operate at full pressure to deliver nozzle spraying. Check all
nozzles for normal operation.
Make sure all access doors, passageways, ducts and other openings are closed,
locked and bolted.
Check the fan and regulator.
4.1.5 Instruction on how to stop the washer:
First turn off the fan.
After fan, disconnect the hydraulic network.
Condition of pump and fan.
Make sure there are no loose bolts in the whole set.
Check the pipe joints for leakage.
After all these steps experiment setup is ready for use.
Now in experiment we determine the effect of water flow rate and air flow rate on
the cooling effect. So we take the reading for two different water flow rates and air flow
rate with help of the fan regulator.
4.2 experiment procedure:
First check the all connection and electric supply.
Place the thermocouple at measuring points. One line to measure inlet water
temperature. One line at bottom of the chamber to measure the outlet water
Now measure the ambient temperature and relative humidity.
Keep the inlet valve full open and measure the water temperature in water tank.
Set water temperature 8* C.
Now measure the flow rate at full open valve condition.
Start the fan at full speed and turn on the pump, which supply the water from the
water tank. Water from pump is supplied to the nozzles and fine spray is
produced in the chamber.
Now measure the air velocity at exit portion with the help of the anemometer.
Measure the exit water and air temperature. Also measure the relative humidity
of exit air.
Now change the speed of the fan with help of regulator to minimum and take all
the readings as mentioned above.
After completion of the one operation change the mass flow rate with help of the
valve. Now again take all the readings for maximum and minimum fan speed.
Change the water temperature to 10*, 12*, 14* C and repeat all the procedure
and note down the readings.
After completion of the experiment turn off the fan and the pump.
Exit area: 0.0289 sqr meter
Ambient temperature: 38.5*C
Water flow rate at full open valve: 0.000025 cubic meter per sec.
Water flow rate at half open valve: 0.0000125 cubic meter per sec.
Barometer reading: 101.32 KPa.
Velocity of air leaving at maximum speed of fan: 6 meter per second.
Velocity of air leaving at minimum speed of fan: 4 meter per second.
Relative humidity of moist air(ambient) : 62%.
4.4 observation table:
Water flow rate= 0.0000125 cubic meter per second
8 14.6 33.9 51.8 6 0.1734
8 13.2 33.3 50.5 4 0.1156
10 16.6 35.4 52 6 0.1734
10 15.3 34.8 51.4 4 0.1156
12 18.3 36 52.8 6 0.1734
12 17.6 35.6 52.1 4 0.1156
14 19.7 36.5 53.6 6 0.1734
14 19.5 36.1 52.9 4 0.1156
Water flow rate= 0.000025 cubic meter per second.
8 15.4 28.7 53 6 0.1734
8 13.8 28.1 51.5 4 0.1156
10 17.2 29.6 53.9 6 0.1734
10 15.9 28.9 52.1 4 0.1156
12 18.9 30.9 54.5 6 0.1734
12 18.1 29.7 52.8 4 0.1156
14 20.5 32.5 54.9 6 0.1734
14 21.2 31.1 53.3 4 0.1156
4.6 Performance curves:
Water Flowrate = 0.0000125 cubic meter/sec
Air velocity = 6 m/s
Water Flowrate = 0.000025 cubic meter/sec
Air velocity = 6 m/s
Water Flowrate = 0.000025 cubic meter/sec
Air velocity = 4 m/s
Water Flowrate = 0.0000125 cubic meter/sec
Air velocity = 4 m/s
From result table it is clear that the as we increase the water flow rate cooling
effect increases. Also if we decrease the velocity of air, it reduces the mass flow rate
and increases the cooling effect.
Performance of air washer depends upon the air and water contact area and
time, ratio of mass of water to mass of air, velocity of air.
From the graph we can conclude that
As the water flow rate increases, the cooling effect increases as temperature
As the velocity of air decreases, mass flow rate of air decreases which increases
the cooling effect.
For constant water flow rate it is advisable to keep air mass flow rate low.
For constant air flow rate it is advisable to keep the water flow rate as high as
Also the cooling effect increases as the inlet water temperature decreases.
Better results can be obtained by providing 100 % leak proof setup and improving
the performance of nozzle by producing more atomized water spray.
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