Air-conditioning Process 1

8/7/2019 Air-conditioning Process 1

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Contents

List of Figures ................................ ................................ ................................ ................................ ..... 2

Title ................................ ................................ ................................ ................................ ................... 3

Objective ................................ ................................ ................................ ................................ ........... 3

Introduction ................................ ................................ ................................ ................................ ....... 3

Theory ................................ ................................ ................................ ................................ ............... 4

Specific humidity, relative humidity, and percentage saturation ................................ ..................... 4

Psychometric chart................................ ................................ ................................ ......................... 4

Equipment ................................ ................................ ................................ ................................ ......... 7

Procedures ................................ ................................ ................................ ................................ ......... 8

Result................................ ................................ ................................ ................................ ................. 9

Discussion (Individual), Conclusion(Individual), References(individual) ................................ ............. 10

Appendixes................................................................................................................... ........................ 21



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List of Figures

Figure 1............................................................................................................................ ...................... . 5

Figure 2................................................................................................. .................................................. 7

Figure 3..................................................................................................................... .............................. 7

Figure 4..................................... .............................................................................................................. 7

Figure 5..................................................................................................................... .................. ............ 7

Figure 6..................................................................................................................... .............................. 7

Figure 7........................................................................... ........................................................................ 7

Figure 8..................................................................................................................... .............................. 7

Figure 9............................................................................................................................................ ....... 7

List of Tables

Table 1.................................................................................................. ................................................. 6

Table 2...................................................................................................................... ............................. 9



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Title

Analysis Of Air-conditioning P rocesses

Object iveTo observe and understand the changes in air properties as it is treated in a basic air -

conditioning unit.

Int roduct ion

Did you ever put an alchohol in your palm and see it disapear and your hand feel cold at the

same time? This fenomena is the basic air-conditioning system. Air conditioning and

refrigeration are provided through the removal of heat. The idea of creating air-conditioningfirst introduce in the 2nd century. A Chinese inventor named Ding Huane of the Han Dynasty

invent a rotary fan with seven wheels for cooling purpose. Then, in the Tang Dynasty Cool

Hall was built in the imperial place which have water powered fan wheel for air -conditioning.

In 1820, an inventor named Michael Faraday found that the compressing and liquifying

ammonia could chill air. In 1902, the first electrical air -conditioning was invented by Willis

Haviland Carrier in Buffalo, New York. Then in 1906, Stuart W. Cramer of Charlotte, North

Carolina found a way to add moisture to his fabric fact ory. The idea to improve the efficiency

of air-conditioning continue untill now. Air-conditioning application is broadly devided into

two types which are:

y Comfort applications Provide indoor buiding environment that remains costant in

range

preffered by humans.

y Process applications Provide a suitable condition for the process being carried out.

There are various type of air-conditioner in the market, such as:

y Window air-conditioner

y Split air-conditioner

y Package air-conditioner

y Central air conditioning system



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Theory

Specif ic humidit y, relat ive humidit y, and percentage sat urat ion

Specific humidity is the ratio of mass of water vapour to the mass of dry air. Denoted by,

Specific humidity ,

The relative humidity is the ratio of actual mass of water vapour in a given volume to that,

which it would have if it were saturated at the same temperature.

Relative humidity ,

Relative humidity is usually expressed as a percentage. Another altelnative way to find the

relative humidity is by knowing the wet and dry bulb. With the aid of table 1, the relative

humidity can directly be found.

The percentage saturation is define as the ratio of specific humidity of a mixture to thespecific humidity of the mixture when saturated at the same temperature.

P ercentage saturation,

Psychomet ric chart

The specific humidity and percentage saturation can be obtaine in the psychometric chart .

An ordinate is erected at the known dry bulb temperature and the point of intersection

between it and the diagonal line representing the known wet bulb temperature is found. The

percentage saturetion is then found from the curve of constant percentage of

saturationwhich passes through this point. The specific humidity is read off the ordinate

scale in kilograms of vapour per kilogram of dry air. The enthalpy of the mixture in kilojouls

per kilograms kilograms of dry air can be read off the diagonal scale of specific enthalpy. The

zero specific enthalpy for the vapour is always taken at 0°C. For the dry air the zero for

specific enthalpy is also taken at 0°C.



5 |

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Figure 1: Example of Psychometric Chart



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Tabl

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Tabl

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Figure 2: Blowing Fan Figure 3: Control Panel

Figure 5: Compressor

Condenser Unit

Figure 9: E 4 aporator

Figure 8: Electronic Interface

Figure 7: Condensate

Measurement

Figure 6: Water 5 eaters

Figure 4: Air Flow Exit



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Procedures

The unit is started and the blower is running and the computer screen displaying the master

menu. Programme 1 show the process data displayed on a schematic layout of the system.

Programme 2 displayed the properties of the treated air on the psychometric chart.

a) No processy The data and the psychometric chart of the initial properties of the air as it

enter the air-conditioning unit is printed.

b) Sensible heating

y The pre-heat and re-heat switch is switched on and the data and the

psychometric chart is then printed. Then, both of the switch is switched off.

c) Steam Humidification

y All heaters switched on to boil the waters. After steam produced, the upper

heater is switched off and the data and the psychometric chart is then

printed. After d ata printed, all heaters are switched off.

d) Cooling and Dehumidification

y Compressor is switched on and the temperature is allowed to cooled until

18°C to 20°C range. Time started to record when the drain water is start to

pour out. Time stopped recorded as the drain water reach 100ml. Then, the

data and the psychometric chart is printed.



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Result

Experiment

Reading

No Process Sensible

Heating

Steam

Humidification

Cooling and

Dehumidification

T1 ( TA d ) 26.6 26.5 27.7 28.9

T2 ( TA w ) 22.1 22.2 23.3 22.8

T3 ( TB d ) 26.6 34.1 30.4 29.1T4 ( TB w ) 21.9 24.6 29.6 22.9

T5 ( TC d ) 26.3 33.3 29.6 19.0

T6 ( TC w ) 21.9 24.2 29.0 18.0

T7 ( TD d ) 26.4 36.0 29.9 19.1

T8 ( TD w ) 21.9 24.9 29.3 18.4

T9 ( T 1) X X X 10.9

T10 ( T 2 ) X X X 77.0

T11 ( T 3 ) X X X 45.3

T12 ( T 4 ) X X X 6.8

Qp X 1012.2 X X

Qr X 538.3 X XQb X X 2785.0 X

Pevp ( P 1 ) X X X 216.7

Pcond ( P 3 ) X X X 1135.7

ma 130.8 127.1 125.9 125.7

mr X X X 12.7

Time X X X 16.52

Drain Water (ml) X X X 100

Tabl6

2: R6

sult7 8

o9 @

xp6 8

i9 6

nt

Units:

All Temperatures, T = °CQp, Qr, Qb = W

Pevp , Pcond = kN/m2

ma , mr = g/s

Time = minutes . sec

Drain Water = ml



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Discussion

No process

The dry air enters the air-conditioning unit at 26.6°C and leave at 26.4°C. This show that the

air temperature has slightly decrease. This probably cause by the blower. The air get cooled

as it pass through the air-conditioning unit. The percentage saturation at this period is about75%, while the moisture contents is about 0.016 kg/kgdry air of dry air. At this point, there is

no energy in terms of heats coming in or going out in the process.

Sensible Heat ing

After heat introduced the initial air is raise to 36°C. The initial temperature raised by 9.5°C

for the dry temperature and 2.7°C for the wet bulb temperature. Heat energy at this point is

1012.2 W at the pre-heat section and 538.3 W at re -heat section. The percentage saturation

has decrease to 38% from 75%. The moisture content shows a signif icant decreament from

0.016 kg/kgdry air to 0.014 kg/kgdry air.

Steam Humidif icat ion

At this point, the air introduced with the steam to humidify the air. The moisture content has

increase to 0.26 kg/kgdry air. The steam provide the moisture for the air. This fenomena same

with the fan that has water jet. The water jet provide moisture in the air while the fan

blowing. Thus the humidity of the air can be added to provide the desired condition. If more

steam present in this air-conditioning unit, the moisture content in the air will increase . The

exit teperature is 29.9°C. That shows an increasing of 2.2°C. Because of the steam that carryheat with it, the air will pick up the heat and thus the exit temperature is higher than inlet

temperature.

Difference between dry bulb and wet bulb at inlet, = 4.3°C

From table,

Difference between dry bulb and wet bulb at exit, = 0.6°C

From the relative humidity table,

From this data, the relative humidity has increase.



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Air Condit ioner device

A basic device shoud have in an air-conditioning syste�

are�

y Compressor

y Condenser

y Expension Valve

y Evaporator

y Fan

y Piping system

A schematic diagram of air-conditioner has shown in the figure 10�

Figure 10: Schematic Diagram For

Air-Conditioner



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The used of each device are discribed in the below table�

De�

ice Function

Compressor The use of compressor is to compress the

refrigerant.

Condenser Used to liquif y the high presure refrigerant

from the compressor.

Expension Valve Used to lower the refrigerant pressure

before it enter the compressor.

Evaporator Absorbe heat from the air.

Fan Used to suc�

and blow the air.

Piping System Enable refrigerant to flow and also for

condensate water to flow.

Air Condit ionin� in Car

A typical air conditioning in car shown in the figure 11.

The device in the car air-conditioner are fan, condenser, compressor, expension valve, drier,evaporater and blower. The air enters the system through the fan and flow trough the

condenser. At the condenser, the heat carried by therefrigerant are dump to the

surrounding. The air then flow through an evaporator. The refrigerant in the evaporator pic�

up the heat in the air as the air flow throgh it. The refrigerant keep flowing to expension

valve and compressor and lastly the refrigerant remove the heat that its carried at the

Figure 11: Schematic Diagram of Car Air-Conditioner



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condenser. The copressor, fan and blower are powered by the car engine through belting.

The condenser is usualy placed in front of the car hud and the evaporator placed at the back

of the car front hud. The compressor is placed nearly to the engine to reduce the power loss

in the belting. Today modern car has used R134a as the refrigerant because this refrigerant

has less toxict that can harm the environment.

Conclusion

In this experiment, the purpose of this experiment is to investigate the air that have been

treated in 4 type of process. The comfort condition of air is abot 20°C and 60% of humidity.

Different condition of air -conditioning may be needed for different type of purpose. For an

example, the bird nest building need a higher humidity about 75%. At the hospital storage

required below absolute zero temperature to avoid b acteria. For a conclusion, the

temperature and humidity is very important to our life. If there is no air -conditioning, the

nowdays life will not be able to achieved. However the current air -conditioner has effected

our environment. Researchers all around the world still findings the solution to avoid

pollution to the environment.

References

http://en.wikipedia.org/wiki/Relative_humidity

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html

http://www.gorhamschaffler.com/humidity_formulas.htm

Houghton Mifflin Company

Monograph on Thermal Engineering



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Discussion 1:

1. When there is no pr ocess, we can see that the temper ature in the air conditioning

ventilation is inside the r ange of 21.9 C to 26.6 C. The temper ature was in this

r ange because it is equal to the r oom temper ature. The temper ature occur s at T1, T3,

T5 and T7 are higher because there are at dry condition and the temper ature occur s at

T2, T4, T6 and T8 are smaller because there are at wet condition. The value of mass

flow r ate, ma was 130.8 g/s.

2. When it is under go the sensible heating, the pre-heater 1 k W and 0.5k W was on. The

temper ature r ise up in T2 to T8 but decreased at T1. The maximum temper ature occur s

in T3, T5 and T7 which are at pre-heater . The value of mass flow r ate, ma was 127.1

g/s and shown decreasing. Heat occur s, Qp and Qr in this pr ocess. This pr ocess use

heat exchanger that increase or decreased the air temper ature. Usually may use steam,

hot water or electr ic as the heating medium.

3. When the air conditioning tur ns to the steam humidification pr ocess, the 3 water

heater was on. The temper ature at T1, T2, T4, T6 and T8 r ise a bit fur ther compared

with temper ature at sensible heating pr ocess but temper ature in T3, T5 and T7 are

decreasing. The value of mass flow r ate, ma was 125.9 g/s and shown decreasing. Heat

occur s dur ing this pr ocess which is Qb is 2785.0 watt. Humidifier is used to increase

the moisture content of the air . Such as, water may be spr ayed directly into the air ,

may be evapor ated f r om the moist sur face, or steam may be injected into the air .4. When it is under goes the Cooling and Dehumidification the temper ature in T1 was

increased and T2 until T8 decreased because the heater s had been tur ned off because

we don¶t need heater dur ing the cooling and dehumidification pr ocesses. In this

pr ocess compressor was on, and T9 until T12 occur s in this pr ocess. The value of mass

flow r ate, ma was 125.7 g/s and shown decreasing and mr was 12.7g/s. Pressure occur s

dur ing this pr ocess at evapor ate and condenser . Dehumidifier is used to reduce the

moisture content of the air . It is usually achieved by cooling the air below its dew

point so that sur plus moisture is precipitated.

5. Cooling and Dehumidification pr ocess pr oduced 100 ml dr ain water in 16 minutes 52

second.



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Discussion 2:

1. A air conditioning or heat pump compressor which compresses low pressure

ref r iger ant gas into a high pressure, high temper ature gas. Usually the compressor is in

the outdoor por tion of an air conditioning or heat pump system. The compressor is

basically a high pressure pump dr iven by an electr ic motor . The air conditioning

compressor is usually packaged in the outdoor compressor /condenser unit illustr ated

by our page top dr awing.



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2. A condenser or condensing unit: typically a condensing coil inside which high

temper ature high pressure ref r iger ant gas flows, and over which a fan blows air to cool

the ref r iger ant gas back to a liquid state (thus tr ansf err ing heat f r om the ref r iger ant gas

to the air being blown by the fan). The condenser unit is basically a coil of finned

tubing and a fan to blow air acr oss the coil. Usually the condenser unit is in the

outdoor por tion of an air conditioning system, often packaged along with the

compressor motor discussed above. See COMPRESSOR CONDENSER and see our

page top sk etch too. The change of state of the ref r iger ant, f r om hot high pressure gas

to a liquid releases heat, including heat collected inside the building) to the outdoor s.

3. A metering device which dispenses liquid ref r iger ant into an evapor ator coil. The

meter ing device may be simply a thin section of tubing (a capillary or "cap" tube) or it

may be a bit more sophisticated thermostatic expansion valve (TEV) which includes atemper ature sensing contr ol that can open and shut the device against ref r iger ant flow.

4. An evaporator coil or cooling coil: typically the cooling coil is a section of finned

tubing (it looks a lot lik e a car r adiator ) into which liquid ref r iger ant is metered and

permitted to evaporate f r om liquid to gas state inside the coil. This state change of the

ref r iger ant, f r om liquid to gas, absor bs heat, cooling the evapor ator coil sur face and

thus cooling indoor air blown acr oss the cooling coil. Usually the cooling coil is

located inside the air handler . See AIR HANDLER / BLOWER UNITS and ar ticles

lik e DIRTY COOLING COIL.

5. An air handler and blower unit which pr ovides a fan to blow building air acr oss or

thr ough the evapor ator coil. The air handler blower fan unit moves building air acr oss

the evapor ator coil sur face in or der to condition building air by cooling it (and thus

also by removing moisture f r om the cooled air ).

6. A duct system which distr ibutes conditioned air f r om the air handler in to the

occupied space (supply ducts), and which tak es air f r om the occupied space and

retur ns it to the cooling system air handler .

7. Air conditioner controls and features, which include a r oom thermostat, electr ical

switches, fuses or cir cuit break er s, condensate handling system, and air filter s.



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Discussion 3:

1. Vehicles are found to have pr imar ily three diff erent types of air conditioning systems.

While each of the three types diff er , the concept and design are very similar to one

another . The most common components which mak e up these automotive systems are

the following:

COMPRESSOR , CONDENSER , EVAPORATOR , ORIFICE TUBE, THERMAL

EXPANSION VALVE , RECEIVER -DRIER ,ACCUMULATOR .

Note: if your car has an Orifice tube, it will not have a Thermal Expansion Valve

as these two devices serve the same purpose. Also, you will either have a

Receiver-Dryer or an Accumulator,

but not both

2. Your vehicles heating and air conditioning system can be very confusing and involve

complicated diagnostics and repair pr ocedures. To help in your repair mak e sure you

have a quality repair manual lik e those off ered online.Without the heating and air

conditioning systems in today¶s moder n vehicles, we would all be miser able dr iving to



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our destinations. We tak e for gr anted the heat that k eeps us warm in the winter

months, and the cool air that ref reshes in the summer time. Let¶s tak e a look at how

both systems wor k to k eep us comfor table all year r ound.

The heater in your car is basically a smaller ver sion of your cooling systems

r adiator . Hot engine coolant is cir culated thr ough a small r adiator , often times called a

heater core. A fan is positioned in f r ont of the heater core to blow cold outside air over

the fins. As this air tr avels over the heater core, it heats up and becomes the hot air

which blows out your heater vents.

Lik e your engines cooling system r adiator , the heater core can suff er some of the

same issues. If the heater core becomes clogged with r ust or sludge, you will no longer

have heat. Also leaks can cause a cabin full of white steam and really mess up your

windows. If you smell the sweet ar oma of coolant when your heater is on, chances are,

you have a small leak in the heater core. Often times the heater core is bur ied under

the dashboar d, and replacing it, is a major job.

The air conditioning system in your car is compr ised of a compressor , condenser ,

expansion valve and evapor ator . If you have ever used a can of compressed air to

clean computer components, you will know that the bottle gets very cold in a shor t

amount of time. This is due to the r apid expansion of the compressed gas. The same

thing happens in your car ¶s air conditioning system. R ef r iger ant (AKA Freon) is

compressed in the compressor and tur ns into a hot gas. In the condenser , this hot gas is

cooled to a liquid state and tr avels to the expansion valve. As the Freon goes thr ough

the expansion valve it retur ns to a low-pressure gas and r apidly cools in the

evapor ator . A fan blows over the evapor ator and cools the air that eventually blows

out your vents.



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Fr om this exper iment, we can conclude that the objectives have been achieve which is toobser ved and under stand the changes in air pr oper ties as it is treated in a basic air-

conditioning unit. In the air conditioning, we need sever al main components such as

condenser , compressor and heater to overr un the air conditioning system. Nowadays, we have

air treatment in air conditioning to treat the air for comfor t air cir culation. The air conditioner

may aff ect by some thermodynamic pr ocesses. In air conditioner , we can have some basic

pr ocess such heating, pre-heating, reheating, dehumidification and cooling.

The err or of this exper iment and how to over come this pr oblem are in table below.

err or precaution

The time we tak e dur ing the

exper iment is not accur ate even the

mistak e is small such as a f ew

second; this will cause the other

value become incorrect.

We must repeat the time tak en for

sever al times to get the very high

accur ate result.

Par allax err or due to the obser ver . Mak e sure the eye level of the

obser ver is at the same level with

the scale reading.

Too many obser ver Only one obser ver must done the

obser vation pr ocess to avoid taking

the value with diff erent way



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1. http://en.wikipedia.or g/wiki/Air_ conditioning

2. http://www.familycar .com/classr oom/ac1.htm

3. http://www.automotive-res.com/automotive-air-conditioning-diagr am/

4. Heat Tr ansf er Labor atory Sheet f r om Heat Tr ansf er Labor atory

5. Cengel, Y. A. (2003). Heat Tr ansf er A Pr actical Appr oach, Second Edition. In Y. A.

Cengel, Heat Tr ansf er A Pr actical Appr oach, Second Edition (pp. 17-23). New Yor k:

McGr aw-Hill.



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Appendixes

Air-conditioning Process 1

Documents

Transcript of Air-conditioning Process 1