Services II AC system

8/7/2019 Services II AC system

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BE 2202 Services II Course Work Design of Air Conditioning System

Department of Building Economics i

Acknowledgement

We are having a long list of individuals to whom we should convey our acknowledgement. We express

our indebtedness to each individual for giving us a great support to finish our course work successfully

and specially Mr. Wickramasooriya for helping us in many ways to find information.

It is our foremost duty to pay our gratitude to the Department of Building Economics, University of

Moratuwa, and all the lecturers in the department of Building economics and the staff. Special thank goes

to our Services II Lecturer Mr. Patrick Weerasinghe, Project Work Lecturers, Ms. Nilupa Udawatta and

Ms. Nilushi Abesinghe for their valuable advices and guidance towards the successful completion of our

course work. In addition, our special thanks go to the staff of laboratory of Department of Building

Economics and staff of Library of University of Moratuwa.


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Department of Building Economics iii

Table of Figures

Figure 2.1: Classifications of AC Systems ................................ ................................ ............................... 3Figure 2.2: Central Air Conditioning Systems ................................ ................................ .......................... 3Figure 2.5: Window Air Conditioner ................................ ................................ ................................ ........ 4Figure 2.4: Split Air Conditioner ................................ ................................ ................................ .............. 4Figure 2.3: Packaged Air Conditioner ................................ ................................ ................................ ...... 4Figure 2.6: Fan Coil Units ................................ ................................ ................................ ........................ 4Figure 3.1: Selected Building ................................ ................................ ................................ ................... 6


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Department of Building Economics 1

1.0 Introduction

Air conditioning means the full mechanical control of the internal environment to maintain the specified

and required condition of a building. The objectives of the air conditioning are to provide a thermally

comfortable temperature, humidity, air cleanliness and freshness for the uses of the building. The air

conditioning differs from mechanical ventilation, which includes the moving air by means of fans, air

filtration, heating, humidification, by the incorporation of refrigeration. However, air conditioning

requires six main functions, cooling, heating, air circulation, air cleaning, humidification and

dehumidification. So air conditioning can be defined as the simultaneous control of temperature, humidity

and air motion. Temperature, relative humidity, air motion, air filtration, indoor air quality and noise are

the main parameters controlled and maintained by an air conditioning system.

The air conditioning system basically has four interconnected components: compressor, condenser,

thermostatic expansion valve and evaporator. Compressor is known as the heart of the refrigeration

system which takes the refrigerant vapour at a low temperature and low pressure from the evaporator,

raises it to a higher temperature and pressure and forces it into the condenser. Condenser liquidifies the

refrigerant vapour while thermostatic expansion valve throttles the high pressure liquid to the evaporator.

Then the refrigerant in the evaporator absorbs heat from the conditioned space and sends back to

compressor.

Nowadays as the population rises, the number of buildings for residential, commercial, industrial and

other needs is increasing making the limited land available scarce. Though the high rise buildings are one

of the best solutions to provide more area for the population, prevailing wind pressure may preclude the

opening of the windows to provide the necessary ventilation and occupied areas cannot be satisfactorily

supplied with enough fresh air by natural ventilation. Also heat gains occurring within the building, from

people, lights, electrical, catering and mechanical equipment, external air pollution, the need to air seal

the buildings in order to limit noise penetration and close control of internal atmosphere required to

manufacturing of pharmaceuticals, electronics, paper and cotton products have emphasized the need and

requirement of a proper air conditioning system to buildings.

There are various types of air conditioning systems like central air conditioning system, room air

conditioning system and fan coil units which are briefly discussed in next chapter. So when designing a

suitable air conditioning system, factors like available space, sound level, friction loss, installation cost

and life cycle cost, heat and leakage loss and gain, requirement of the client, aesthetic appearance, size of

the internal space in which the temperature should be controlled, function or the purpose of the building,

number of occupants and the degree of changing the amount of occupants of the building, availability,

existing resources and technology, amount of vibration, environmental conditions and weather conditions,

electrical appliances and computers, expected life of the system should be thoroughly considered to select

the most appropriate and cost effective system for the selected building.


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In this report, chapter one provides a brief and comprehensive details about the main types of air

conditioning system. The chapter two of the report discusses about the project details and client

requirements. The cooling load calculation, which is used to determine the appropriate air conditioning

system to the building, is focused in chapter three. Then the options available for air conditioning the

building are considered in chapter four. The justification and valid arguments for the selection ispresented in chapter five finally the report provides an estimate for the proposed air conditioning system

and the layout plans as annexes.


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2.0Types of A/C Systems

Figure 2.1: Classifications of AC Systems

2.1 Central air conditioning system

The central air conditioning system is mostly used for cooling high rise buildings, offices, entire hotels,

gyms, movie theatres, where it is very expensive initially as well in the long run to provide individualunits to each room for the whole building is to be air conditioned. The central air conditioning system is

comprises of cooling towers, chillers, Air handling units, and air ducts to provide pathway to distributed

cool air throughout the building. (Figure 2.2)

Figure 2.2: Central Air Conditioning Systems

Air ConditioningSystem

Central A/CSystem

oom A/CSystem

WindowSystem

Split System

ackageSystem

Fan Coilnit


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3.0 Project Details and Client Requirements

The two storied building situated in No. 29, Wipulasena Mawatha, Deans Road, Colombo 10 was selected

to design an Air Conditioning system which has not been air conditioned yet. At the design stage, the

owner, Wickramasooriya Opticians Ltd, has planned to use the total building for his company. But due to

various reasons, after construction he wishes to use this first floor of the building as their main branch to

provide better service to the customer and to lease the second floor to a Dental Centre for two years. The

floor plans of the two storied building (Annexe 1 & 2) shows the internal partition work that has been put

up by the owner in the first floor and second floor.

After the discussing with the building owner, the following basic requirements for the air conditioning

system were identified.

y As the two stories have to function separately as two buildings, the client requires an airconditioning system which can be controlled at one place to provide constant temperature in the

whole building.

y As both Wickramasooriya Opticians Ltd and Dental Centre provide services to the customers inthe day time, client wish to have all the occupied areas with air conditioning service for day time

use.

y The selected air conditioning system should have the ability to automatically reduce the powerconsumption when the building is totally cooled down as the number of occupants of this building

is not a fixed amount.

y The owner initially leases out the second floor for two year period but wishes to have a durable airconditioning system that may generally meets the needs of Wickramasooriya Opticians Ltd or any

other commercial organization that may occupy the second floor in the future.

y However the owner has permanently put up timber partitions since he has first decided to use bothfloor to Wickramasooriya Opticians Ltd and wishes to have a constant temperature in the total

building. So the tenants have to compensate their operational requirements with the building

structure.

y The owner wishes to have an added value to the building with an attractive and reliable airconditioning system.

y The client requires having an air conditioning system which needs less space from the operationalspace of the building other than the ceiling void and roof top.

y The system shall meet the above basic requirement with least capital cost and operational cost.


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5.0 Selected air-conditioning system

After considering the clients requirements and the options available to meet those requirements, it was

decided that water cooling package air conditioning system would be appropriate. The following reasons

are considered when selecting the package system as the ideal air-conditioning system to this building.

y In the package air conditioning system all the major components like compressor, evaporator andother items are in one single box except the cooling tower, and it does not require separate large

plant room to install all those items. Because of this reason the floor space for operation of the

function of the building can be utilized well.

y The package unit and the cooling tower will emit a large amount of sound compared to other airconditioning systems. But since both these equipments can be located in the roof top of the

building, the disturbance by noise is minimised.

y This has a unique feature to control the functioning of the system. Here as cooling zones in thebuilding cool down, air flow control dampers are closed, evaporator blowers are slowed down,

and compressors is staged off and un-loaded. These features improve efficiency and reduce the

power consumption of the unit.

y Unlike the split systems and window systems, packaged system provides ability to maintain aconstant temperature in the whole building with the minimum use of energy. Though even the

central air conditioning system can fulfil this requirement, that system is costlier and package

system can provide same requirement with much lower installation and maintenance cost.

y Though the owner has already built up timber partitions in the both floor, he has the ability toremove them when he needs to go for a different design. At this situation the package system has

the flexibility, so that the owner gets the chance to adjust this system to the new design.

The above reasons justify the selection of Packaged Air conditioning System as the most suitable A/C

system for this building.

When designing the installation of the packaged system to this building the following factors and analysis

were taken into consideration.

As the entrances to main occupied areas in both floor is somewhat near the middle of the width of the

building, with two glazed windows in the either side of the main entrance it was decided to have two ductways dividing the floor in to two zones in both floors as shown in layout plans, to preserve the symmetry

of the layout and to reduce the cross section of the air duct. In this way the wastage of cool air can be

minimized.

The ducts are designed to distribute throughout the building through the ceiling void which is not used for

any other purpose. Supply air diffusers and return air diffusers would be located one from each in a room

or more if the size of room is large or the required cooling load is high. As the cost would increase


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immensely when the length of ducts increase, it was decided to use air ducts only for the supply air and

for return air the normal ceiling void would be used without ducts.

The Package Unit, which is the most important component of package air conditioning system, can be

installed on the concrete slab of the roof of the building since it has a flat roof as shown in Figure 3.1.

Also the cooling tower too can be installed on the roof slab since it has adequate space. However it

creates cost of piping and pumping although it saves valuable land space which is allocated for vehicleparking.


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6.0 Cooling Load Calculations

6.1 Assumptions

Item Exposure FactorWindow North 27

East 52

West 64

South 32

Walls North 03

East 06

West 07

South 03

Partitions 06

Roof 11

Ceiling 04

Floor 05

Electrical & Appliances 3.4

People 465

Computer 250

y Artificial lighting inside the building is about 1.4W per ft 2.y The office provides approximate 20ft2 of working space per person.y Floor to floor height is 11.5fty The total building has the same constant temperature of 240C.y Assume that walls and windows have similar heat transfer.y As the whole building is under one constant temperature, the partitions were neglected.

Sizes of Doors and Windows

Type Size

D1 5.00 x 7.00

W1 21.17 x 9.00

W2 28.50 x 9.00

W3 30.67 x 9.00

W4 55.08 x 9.00


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6.2 First floor

Floor area = 282ft x 184ft = 51888ft2

Ceiling area = 282ft x 184ft = 51888ft2

Nr of Occupancy = 250

Electrical Appliances = 51888ft2

x 1.4 = 72.64kW

Nr of computers = 22

West External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 184.00 11.50 2116.00

Glass Area 2 21.17 9.00 381.06

Net Wall Area

North External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 282.00 11.50 3243.00

Glass Area 2 28.50 9.00 513.00

Net Wall Area

East External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 184.00 11.50 2116.00

Glass Area2

1

21.17

30.67

9.00

9.00 657.09

Net Wall Area

South External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 343.34 11.50 3948.41

Glass Area

2

1

1

50.08

36.58

22.90

9.00

9.00

9.00 1436.70

Net Wall Area


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Item Exposure Quantity Factor BTU/hr

Solar Gain Glass North 513.00 ft2 7.5 3847.50

East 657.09 ft2

16 10513.44

West 381.06 ft2

23 8764.38

South 1436.70 ft2

7.5 10775.25

Transmission - Glass North 513.00 ft2

27 13851.00

East 657.09 ft2 52 34168.68

West 381.06 ft2 64 24387.87

South 1436.70 ft2

32 45974.40

Transmission - Walls

North 2730.00 ft2

03 8190.00

East 1458.91 ft2

06 8753.46

West 1734.94 ft2 07 12144.58

South 2511.74 ft2 03 7535.22

Partitions - - ft2

06 -

Ceiling 51888.00 ft2

04 97552.00

Floor 51888.00 ft2

05 59440.00

Electrical & Appliances 7264.00 W 3.4 24697.60

People 250 Nr 465 11250

Computer 12 W 250 3000

GrandT

otal Heat 213040.43

Total heat load of the First floor=213040.43 BTU/hr

= (213040.43 x3.517)/12000

= 62.48kW

= 65kW


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6.3 Second floor

Floor area = 282ft x 184ft = 51888ft2

Ceiling area = 282ft x 184ft = 51888ft2

Nr of occupancy = 250

Electrical Appliances = 51888ft2

x 1.4 = 72.64kW

Nr of computers = 22

West External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 184 11.5 2116

Glass Area 2 21.17 9 381.06

Net Wall Area

North External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 282 11.5 3243

Glass Area 2 28.5 9 513

Net Wall Area

East External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 184 11.5 2116

Glass Area2

1

21.17

30.67

9

9 657.09

Net Wall Area

South External Wall Qty Length(ft) Height(ft) Area(sq. ft.)

Wall Area 1 343.34 11.5 3948.41

Glass Area

2

1

1

1

55.08

36.58

22.90

34.41

9

9

9

9 1836.54 Net Wall Area


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Item Exposure Quantity Factor BTU/hr

Solar Gain Glass North 513.00 ft2 7.5 3847.50

East 657.09 ft2

16 10513.44

West 381.06 ft2

23 8764.38

South 1436.70 ft2

7.5 10775.25

Transmission - Glass North 513.00 ft2

27 13851.00

East 657.09 ft2 52 34168.68

West 381.06 ft2 64 24387.87

South 1436.70 ft2

32 45974.40

Transmission - Walls

North 2730.00 ft2

03 8190.00

East 1458.91 ft2

06 8753.46

West 1734.94 ft2 07 12144.58

South 2511.74 ft2 03 7535.22

Partitions - - ft2

06 -

Ceiling 51888.00 ft2

04 97552.00

Floor 51888.00 ft2

05 59440.00

Electrical & Appliances 72640.00 W 3.4 24697.60

People 2594 Nr 465 11250

Computer 12 W 250 3000

GrandT

otal Heat 213040.43

Total heat load of the Second floor =213040.43 BTU/hr

= (213040.43 x3.517)/12000

= 62.48kW

= 65kW

Total cooling load of the building = 2 x 213040.43 BTU/hr

= 426080BTU/hr


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7.0 Estimate for the proposed system

No DESCRIPTION UNIT QTY RATE AMOUNT

01

02

Air Conditioning System

Packaged Air Conditioning Units

Supply, position and connection of water cooled

packaged air conditioning units as specified and

comply with the specifications. Rate shall

include for all necessary flexible connections,

fresh air supply connections and condenser water

piping connections interlocking arrangement

between flow switches and complete with globe

valves, gate valves, flow switches, pressure

gauges, thermometer tapping, flow control

devices, condensate drain connections, airdistribution ducting connections, all necessary

power and control cabling and wiring required

for complete installation.

MWCP70A Packaged UnitCooling capacity 480,000 Btu/h

Air Flow Rate 10,800 m3/h

Carried to summary on page 5

Cooling Towers

Supply, position and Connection of water

cooling towers having a capacity to match the

total heat rejection of the condensers connected

to the cooling tower condenser, water flow rate

of 22.1 l/s. temperature entering 37oC , leaving

33oC connected and rated temperature shall be as

specified in specifications. Power supply shall be

4000 V / 3 phase / 50 Hz. Rate shall include

gate values, flexible coupling, and for all

necessary cut off devices connections to gate

valves necessary interconnections of water pipes

where required and shall be to working order.


Nr

Nr

1

1

250,000.00

125,000.00

250,000.00

250,000.00

125,000.00

125,000.00

Page 1


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No DESCRIPTION UNI

T

QTY RATE AMOUNT

03

04

05

06

07

Air Condition Diffusers

12 x 12 neck size Supply air diffusers


Air Condition Duct Work

All air conditioning and ventilation duct work to befabricated with GI sheets and fabrication and

installation should fully confirm to ASHEREstandards.

All supply and return duct work shall be fully

insulated with fibre glass insulation 25 mm thick 32kg/cum density. The thermal conductivity less than

0.4 W/moC and the thickness of the Aluminium foil

vapour barrier shall avoid any condensation.

Rate of duct work shall include bends, tees, flexible

connection, and sound attenuators, anti vibration

mounts, air sealant, connecting flanges, turning

vanes, splitters, supporters, access panels, and fire

barriers.

All duct supports shall be galvanized.

Supply Air Duct

50 x 12

25 x 12

20 x 12

12 x 10


Nr

ft.

ft.

ft.

ft.

45

450.00

120.00

80.00

332.50

2,500.00

1,550.00

860.00

700.00

600.00

112,500.00

112,500.00

697500.00

103200.00

56000.00

199500.00

1,056,200.00

Page 2


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Page 3

No DESCRIPTION UNIT QTY RATE AMOUNT

16

17

18

19

20

21

Condenser Water Supply Pipes

Condenser water supply pipes from Makeup tankto cooling tower

1 dia. (provisional Qty)

Condenser water supply pipes from cooling

tower to Condenser Water pumps

5 dia. Supply pipe (provisional Qty)

Condenser water supply pipes to AC units

3 dia. pipe

2 dia. pipe

Condenser water return pipes from AC units

3 dia. pipe

2 dia. pipe


ft.

ft.

ft.

ft.

ft.

ft.

20

120

100

100

100

100

180.00

1,520.00

665.00

400.00

665.00

400.00

3,600.00

182,400.00

66,500.00

40,000.00

66,500.00

40,000.00

399,000.00


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Page 4

DESCRIPTION AMOUNT

A

B

C

D

E

Summary

Packaged Air Conditioning Units

Cooling Towers

Air Condition Diffusers

Air Condition Duct Work

Condenser Water Supply Pipes

Total

250,000.00

125,000.00

112,500.00

1,056,200.00

399,000.00

1,830,000.00


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8.0 Conclusion

With the development of the technology, people are in search of new methods to make their lives more

and more comfortable. Commonly used one such advanced technological method is controlling the

temperature of a building. This is accomplished by Heating, Ventilating and Air Conditioning (HVAC)

system which consists of a group of components or equipment connected in series to control the

environmental parameters.

The process of Air Conditioning can be simply defined as the process of controlling the air temperature,

relative humidity, ventilation, air movement and air cleanliness of a given space in order to provide the

occupants with a comfortable indoor temperature. There are various types of air conditioning system like

central system, room systems and fan coil units etc. These systems are installed in various buildings

considering the requirements.

The amount of heat generated in the building from various sources is one of the key factors that should be

considered in designing the appropriate air conditioning system. In a tropical country like Sri Lanka, heat

gained by the walls, roof and partitions, windows, people, electrical appliances is high due to the solar

radiation. To maintain the comfort conditions inside the room the total heat generated inside the room per

hour should be removed completely. For this other than the heat gain, factors like space, sound level,

friction loss, installation cost and life cycle cost, requirement of the client, aesthetic appearance, size of

the internal space in which the temperature should be controlled, function or the purpose of the building,

number of occupants and the degree of changing the amount of occupants of the building should also be

considered.

There are alternative methods of cooling buildings other than full comfort air conditioning. These include

night-time cooling, evaporative cooling, chilled beams and ceilings, hollow floor slabs with air and

cooling air by subsoil or water. Some of these will use significantly less energy than conventional air

conditioning.

As well as providing comfortable condition in buildings, several problems associated with air

conditioning systems are identified by the HVAC engineers. Most commons ones are Legionnaires

Disease, Humidifier Fever and Sick Building Syndrome. In Legionnaires Disease, the bacteria thrive

naturally in warm moist conditions found in swamps and get adapted to the artificial climate of air

conditioned buildings. Abolition of cooling towers, replacement with air cooled condenser units or a strict

maintenance routine would be the solutions for this disease. In Humidifier Fever, an allergy causes

temporary discomfort with symptoms similar to influenza. For this problem biocidal treatment to the

spray water is one solution while replacement with a steam injection humidifier would be another. Sick

Building Syndrome reveals itself in a number, or combination of symptoms including headaches,

lethargy, skin irritations, dry or running eyes, runny nose, throat inflammation and loss of concentration.


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9.0 References

2001.Building services component life manual. London: Blackwell Publishing Limited.

Brumbaugh, J. E., 1986. Heating, ventilating and air conditioning library volume I. New York:

Macmillan Publishing Company.

Charles, H.B., 1959.Residential and commercial air conditioning. 2nd Ed. New York: McGraw Hill Book

Company.

Derek, J.C. and Brian, M.R., 1981.Air conditioning and ventilation of buildings . 2nd

ed. London: William

Clowes Limited.

Jones, W.P., 1980.Air Conditioning Applications and Design. London: Edward Arnold (Publishers) Ltd.

Jordan, R.C., 1956.Refrigeration and Air Conditioning. U.S.A :Prentice-Hall.

Raymond, K.S., 1976.HVAC control systems. Canada: John Wiley & sons Limited.


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10.0 Annexes

In the layout plans, indicates Diffuser, indicates 20 x 12 ducts and

reprsents 12 x 10 ducts.

Documents

Services II AC system