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PROJECT REPORT

FABRICATION AND PERFORMANCE OF AIR WASHER TEST RIG

Prepared by: Guided by:

Shyam Tank Dr. Jignesh R. Mehta

Mechanical department

Faculty of technology and engineering

M.S. University of Vadodara

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ACKNOWLEDGMENT

“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 completion of the project. It is very great opportunity to work under his guidance on this project.

At last we are sincerely thankful to Dr. D.S. Sharma (HOD) for approving the subject of project.

PREFACE

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“PRACTICE MAKES MAN PERFECT”

Thus, theory of any subject is important to clear the fundamentals of the subjects, but without practical knowledge it will become difficult for the degree students. A degree student cannot become a perfect engineer without the practical understanding of the branch. Hence, this project work provides golden opportunity for all degree students.

The principle of the project is to get details about the on-line processes and real operation tasks, project management and discipline required in practical world.

INDEX

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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

1-Literature study1.1 Introduction:

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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.

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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 evaporative cooler.

[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 adiabatically.]

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 Fig.

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

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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 applications.

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

operating cost. 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 comfort.Classification of evaporative cooling systems:

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1. Direct evaporation process 2. Indirect evaporation process3. 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 (towbt), 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.

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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, relatively inexpensive.

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.

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(Indirect evaporation process)

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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’).

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1.4 Advantages and disadvantages of evaporating cooling systems: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 75%.

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.

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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 following disadvantages:

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 humidity

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.

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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:

Water tank

Fan

Nozzles

Pump

Pipes and fittings

Chamber

Eliminator plate

Convergent portion

Measuring equipments

All the components are explained briefly below.

2.1Water tank:

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.

2.2Fan:

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.

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2.3Nozzles:

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 chamber.

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 performance characteristics.

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2.4 Pump:

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

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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.

2.6Chamber:

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.

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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.

2.7Eliminator plate:

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.

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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.

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2.8Convergent portion:

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.

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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.

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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

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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)

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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.

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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.

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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.

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3.4 Nozzles:

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.

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4- EXPERIMENTATION

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 Testing:

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 duly set.

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.

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4.1.5 Instruction on how to stop the washer:

First turn off the fan.

After fan, disconnect the hydraulic network.

4.1.6 Precautions:

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.

[Experiment setup]

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[Experiment setup]

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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 temperature.

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.

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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.

4.3 Observations:

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%.

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4.4 observation table:

Water flow rate= 0.0000125 cubic meter per second

Water inlet temp *C

water outlet temp *C

Air outlet temp *C

Outlet air relative humidity %

Velocity of air m/s

DischargeCubic meter per sec

8 14.6 33.9 51.8 6 0.17348 13.2 33.3 50.5 4 0.115610 16.6 35.4 52 6 0.173410 15.3 34.8 51.4 4 0.115612 18.3 36 52.8 6 0.173412 17.6 35.6 52.1 4 0.115614 19.7 36.5 53.6 6 0.173414 19.5 36.1 52.9 4 0.1156

Water flow rate= 0.000025 cubic meter per second.

Water inlet temp *C

water outlet temp *C

Air outlet temp *C

Outlet air relative humidity %

Velocity of air m/s

DischargeCubic meter per sec

8 15.4 28.7 53 6 0.17348 13.8 28.1 51.5 4 0.115610 17.2 29.6 53.9 6 0.173410 15.9 28.9 52.1 4 0.115612 18.9 30.9 54.5 6 0.173412 18.1 29.7 52.8 4 0.115614 20.5 32.5 54.9 6 0.173414 21.2 31.1 53.3 4 0.1156

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4.6 Performance curves:

Water Flowrate = 0.0000125 cubic meter/sec

Air velocity = 6 m/s

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Water Flowrate = 0.000025 cubic meter/sec

Air velocity = 6 m/s

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Water Flowrate = 0.000025 cubic meter/sec

Air velocity = 4 m/s

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Water Flowrate = 0.0000125 cubic meter/sec

Air velocity = 4 m/s

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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.

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5- ConclusionFrom the graph we can conclude that

As the water flow rate increases, the cooling effect increases as temperature drop increases.

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 possible.

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.