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THERMODYNAMICS IIANALYSIS OF AIR-CONDITIONING

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1.0Title

MEC 554-THERMALFLUIDS LAB

THERMODYNAMICS II LAB

ANALYSIS OF AIR-CONDITIONING

LECTURER: NOR AMALINA BTE RESALI


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Table of Contents

1.0 Title............................................................................................................................................. 1

2.0 Abstract...................................................................................................................................... 3

List of Symbols........................................................................................................................................ 4

List of figure......................................................................................................................................... 5

3.0 Introduction And Applications................................................................................................... 6

4.0 Objectives.................................................................................................................................... 7

5.0 Theory......................................................................................................................................... 8

6.0 Experimental Procedures..................................................................................................... 12

6.1 Apparatus/Experimental Setup............................................................................................... 12

6.2 Procedure .................................................................................................................................... 15

7.0 Data and calculations............................................................................................................... 16

7.2 Sample calculations: ................................................................................................................... 16

7.2 Data: ............................................................................................................................................ 19

8.0 Discussion................................................................................................................................. 20

9.0 Conclusion................................................................................................................................ 20

10.0 References................................................................................................................................ 21

11.0 Appendices .................................................................................................................... 22


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2.0Abstract

We knew that the air properties is changes based on what types of process that we

running it. Each types of process which is the simple heating, steam humudification, simple

cooling and dehudification have their own result and reason why it is occur like that. With

that data and result we can study throughout about the air-conditioning. But still an error must

be avoided in order to get the precise data.


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List of Symbols

A Area over which force (F) acts (m2)

E Elastic modulus (GPa)

F Force (N)

() Initial dimension in direction i (mm)

T Specimen thickness (m)

Rate of chart displacement (mm/min)

Rate of sample displacement (mm/min)

w Specimen width (m)

Displacement of chart (mm)

Displacement of sample (mm)

Strain

=0 Predicted strain at zero stress

Normal strain in direction i

E Error in the predicted elastic modulus (GPa)

F Error in the force (N)

Change in dimension in direction i (mm)

t Error in the specimen thickness (m)

w Error in the width (m)

=0 Error in the predicted strain at zero stress

Error in the predicted intercept of stress-stain data (MPa)

Error in the stress (MPa)

Predicted intercept of stress-strain data (MPa)

Engineering stress (MPa)

Yield point (MPa)

Ultimate strength (MPa)


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List of figureFigure 1: Air-Conditioner(Home or office usage) .................................................................................... 6

Figure 2: Heating coil mechanism ........................................................................................................... 9

Figure 3: Schematic diagram for condensation process ......................................................................... 9Figure 4: Shematic diagram for humidifying section ............................................................................ 10

Figure 5: The flow of air through insulator and mixing section ............................................................ 11

Figure 6: Computer Linked Air Conditioning Laboratory Unit ( P.A. Hilton) ......................................... 12

Figure 7: Computerized Data Display System ...................................................................................... 13

Figure 8: Control Panel.......................................................................................................................... 13

Figure 9: System Schematic Diagram .................................................................................................... 14
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3.0 Introduction And Applications

Air conditioning system is a process of treating the air to establish and maintainrequired standard of the occupants in the conditioned space. Air conditioning system consists

of a group of equipment connected in series to control the environmental parameters. It is a

direct application of the refrigeration cycle. The properties of air can be altered by

experiencing certain thermodynamics process. The most basic of processes involved in an air

conditioning system are simple heating, steam humidification, simple cooling and

dehumidification.

Air-conditioning is useful to maintain the surrounding environment of temperature

and ambient to satisfy the the temperature of human comfort, which is between 20C to 25C.

Conventional air-condition is use to cool and to heat the surrounding environment, but in

some country, air-condition may use both heating and cooling, with or without humidifing

air. Also the industrial usage of air-condition is to reduce temperature of thermal produce

machine.

Nowadays, we can see the the usage of the air-conditioning is increasing day by day

wheather is on house or at the office. It shows to us that most people desire a good

surrounding for their comfortable life. For that, air conditioning is a solution for that and it is

important for us to study how it works. Theoretically, analysis of air conditioning processes is

required for maintaining proper temperature and humidity in living space such as residential,

commercial, and industrial facilities.

Figure 1: Air-Conditioner(Home or office usage)


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4.0 Objectives

The purpose of this experiment is to:

1. To study and understand the changes in air properties as it is treated in a basic air-

conditioning unit system.

2. To develop knowledge of refrigeration cycle and air conditioning system.

3. To experiencing the air conditioning system in practical.

4. to experiencing the usage of Computer Linked Air Conditioning Laboratory Unit ( P.A.

Hilton)


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5.0 Theory

The type of air conditioning process :

simple heating (raising the temperature) simple cooling (lowering the temperature)

humidifying (adding moisture)

dehumidifying (removing moisture)

Air conditioning process are modeled as steady flow processes with general mass and energy

balance.

Mass balance

dry air

wet air or

Energy Balance

=

Simple Heating and Cooling

- value of is constant

- sensible heating by means of a electric resistance heater, a hot water coil, heat pump and

etc.

- In simple heating, specific humidity remained constant but the relative humidity decreases

- In simple cooling, the cooling coil is in place. Therefore the humidity remained constant but

the relative humidity increases.


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Figure 2: Heating coil mechanism

Dry air : ma1= ma2 = ma

Water/ Vapour :ma1=ma2

1= 2

Energy : Qin + mah1=mah2

Qin= ma(h2- h1)

Cooling with Dehumidification

- When the relative humidity is too high, some moisture is removed from the air to

dehumidify it.

- When the air is cooled below its dew point temperature, condensation will start to form.

- Water vapor is removed from the cooled air and the relative humidity is lowered.

Figure 3: Schematic diagram for condensation process


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Adiabatic Mixing of Airstreams

- Air-Conditioning appilcation may require mixing of airstreams.

- The turn air is mixed with a small fraction of fresh outside air before it is routed into the

living space.

- When hot humid air is mixed with cold air the result may be fog.

- The mixing point is below the saturation line, and the moisture in the air condensates as

small droplets floating in the air.

- If the mixing point is below the saturation line, water is condensated as droplets and fog is

created.

Figure 5: The flow of air through insulator and mixing section

Dry air mass balance : ma1+ ma2= ma3

Water mass balance : ma11+ ma22 = ma33

Energy balance : ma1h1 + ma2h2 = ma3h3


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6.0 Experimental Procedures

6.1 Apparatus/Experimental Setup

Computer Linked Air Conditioning Laboratory Unit ( P.A. Hilton)

Figure 6: Computer Linked Air Conditioning Laboratory Unit ( P.A. Hilton)

Control

Panel

Fan

Stop

Watch Container

Cooling

Area


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Figure 7: Computerized Data Display System

Figure 8: Control Panel

Computer

Display

CPU

Printer


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Figure 9: System Schematic Diagram


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6.2 Procedure

Start the unit by having the suction fan running and the screen displaying the master menu.

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

programme 2 displays the properties of the treated air on the psychrometric chart. There are

for condition for this experiment.

1) No Process- the data and psychrometric chart are print to read the initial

properties of the air as it enters the air-conditioning unit.

2) Sensible heating

a)

1kW pre-heater is switch on and allow 5 minute. The data and psychrometric

chart are print.

b)

Then, 05kW re-heater is switch on and allow 5 minute. The data and

psychrometric chart are print

c) For this process, the temperature rise of the air is calculate at the exit.

3)

Steam humidification all water heater is switch on to boil the water. When steam

is produces, only 3 kW if heat is switch to maintain the steam and allow 5 minute.

The data and psychrometric chart are print. Then the amount of steam introduced,the change in relative humidity and corresponding rise of temperature are

calculate.

4) Colling and Dehumidification- the compressor of the refrigeration system is

switch on. The air is cool until 18oCto 20oC (stable temperature), allow 5 minute

when the temperature is stable. The heat rate and amount of moisture removed

from the air are calculate. During experiment the time and the rate of condensation

(100ml) are measure from the beginning of the cooling process (stable

temperature). Compare with analysis


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7.0

Data and calculations

7.2 Sample calculations:

1. SENSIBLE HEATING

Pre-heater

Tdryout = 37.4 C Twetout = 26.8 C

Tdryin = 27.6 C Twetin = 23.1 C

Temperature rises at the exit = Tdry = Tdryout - Tdryin

= 37.4 C - 27.6 C

= 9.8 C

Twet= Twetout - Twetin

= 26.8 C - 23.1 C

= 3.7 C

Re-heater

Temperature rises at the exit = Tdry = Tdryout - Tdryin

= 48.7 C - 27.1 C

= 21.6 C

Twet= Twetout - Twetin

=29.0 C - 22.4 C

= 6.6 C


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2. STEAM HUMIDIFACTION

Ma= 0.0533 kg/s

From the Psychrometric chart

1 = 67 % 2 = 96 %

1 = 0.016 kgv/kga 1 = 0.030 kgv/kga

Amount of steam induced

mw = ma(2- 1)

= 0.0533 (0.030 - 0.016 )

= 7.462 x 10-4kg/s

Change in relative humidity

= 2- 1= 96 % - 67 %

= 29 %

Temperature rises at the exit

Tdry = 37.2C27.6C = 9.6 C

Twet = 36.3C 23.3C = 13.0 C

3. COOLING AND DEHUMIDIFICATION

Ma= 0.2079 kg/s

From the Psychrometric chart

1 = 62 % 2 = 96 %

1 = 0.009 kgv/kga 1 = 0.0155 kgv/kga

h1 = 35.8 kJ/kg h2 =69.0 kJ/kg

Amount of steam induced

mw = ma(2- 1)

= 0.2079 (0.0155 - 0.009 )

= 1.35135 x 10-3kg/s


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Change in relative humidity

= 2- 1= 96 % - 62 %

= 34 %

Temperature rises at the exit

Tdry = 29.2C13.1C = 16.1 C

Twet = 23.3C 13.0C = 10.3 C

Amount of heat transfer

hw= hf@ T8= 14.1 from table A-4, therefore hw= ?

=

hw= 59.2092 kJ/kg

Qout = ma (h2h1)- mwhw

= 0.2079 (69.0 -35.8 )- 7.462 x 10-4 (59.2092 )

= 6.858 kJ/s

hf(kJ/kG) Temperature(C)

42.022 10

hw 14.1

62.982 15


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7.2 Data:

ExperimentNO PROCESS SENSIBLE HEATING STEAM HUMIDIFICATION

COOLING

AND DEHUMIDIFICATION

Reading

T1 (TAd)

(oC)27.5 27.6 27.1 27.6 28.9 27.2

T2 (TAw)

(oC)

23.1 23.1 22.4 23.3 23.3 23.3

T3(TBd)

(oC)

28.2 42.3 44.6 36.5 29.2 29.3

T4(TBw)

(oC)24.1 30.0 30.3 37.8 24.4 24.1

T5(TCd)

(oC)

27.6 39.4 44.0 36.4 13.4 12.5

T6(TCw)(

oC)

22.9 27.0 27.9 36.9 13.1 12.2

T7(TDd)

(oC)27.5 37.4 48.7 36.3 14.1 13.1

T8 (TDw)

(oC)

23.3 26.8 29.0 37.2 14.1 13.0

T9(T1)

(oC)

- - - 6.0 6.4

T10(T2)

(oC)

- - - 69.0 78.7

T11(T3)

(oC)- - - 42.4 43.1

T12(T4)

(oC)

- - - 2.7 2.7

Qp

(W)- 1019.9 1005.5 - -

Qr

(W)- 0 534.7 - -

Qb

(W)- - 2806.2 -

Pevap (P1)

(kN/m2)- - - 168.1 169.8

Pcond (P3)(kN/m2)

- - - 1043.5 1067.9

ma

(g/s)205.6 199.0 55.3 53.3 207.9 120.0

mr

(g/s)- - - 10.4 10.0

TIME

(s)- - - 5 minutes 21 minutes

DRAIN

WATER(ml)- - - 100 100

Table 1: Data recorded


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8.0

Discussion

This part of report is individually hand written. The result of each member is attached

with this report.

9.0

Conclusion

This part of report is individually hand written. The result of each member is attached

with this report.


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10.0 References

Webside:

1) http://en.wikipedia.org/wiki/HVAC [Accessed 27/09/14]

2)

http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-

system-components-for-hvac/ [Accessed 27/09/14]

Books:

3) Yunus A. Cengel , AfshinJ. Ghajar,2007, Heat and Mass Transfer (fundamentals and

applications),Fourth edition in SI units,McGrawHill,Singapore

4) Yunus A. Cengel, Michael A. Boles,2006, Thermodynamics: An Engineering

Approach 5th Edition, McGraw Hill.

5)

Yunus A. Vengeland Micheal A. Boles, Thermodynamics An Engineering

Approach,7thedition in SI units, 2011 , The McGraw-Hill Companies.

.
http://en.wikipedia.org/wiki/HVAChttp://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://www.brighthubengineering.com/hvac/125581-design-principles-and-major-system-components-for-hvac/http://en.wikipedia.org/wiki/HVAC


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11.0 Appendices


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