Design of Air conditioning System

OZONE SCIENCEOZONE SCIENCE
Philippine Society of MechanicalPhilippine Society of Mechanical
EngineersEngineers

Outline of PresentationOutline of Presentation
 WHAT IS OZONE?WHAT IS OZONE?
 WHAT IS THE OZONE LAYER?WHAT IS THE OZONE LAYER?
 HOW IS OZONE CREATED AND DESTROYED?HOW IS OZONE CREATED AND DESTROYED?
 WHAT IS THE OZONE HOLE?WHAT IS THE OZONE HOLE?
 WHAT ARE THE EFFECTS OF OZONEWHAT ARE THE EFFECTS OF OZONE
DEPLETION?DEPLETION?
 WHAT ARE THE CAUSES OF OZONEWHAT ARE THE CAUSES OF OZONE
DEPLETION?DEPLETION?
 HOW CAN THE OZONE LAYER BE SAVED?HOW CAN THE OZONE LAYER BE SAVED?

WHAT IS OZONE?
 Is a gas that is naturally present inIs a gas that is naturally present in
the atmospherethe atmosphere
 Chemical symbol – OChemical symbol – O33
 Derived from Greek wordDerived from Greek word OZEINOZEIN
 Ozone molecules have relatively lowOzone molecules have relatively low
abundanceabundance

The sun
gives this
earth light
and life,
but is also
the main
source of
ultraviolet
radiation.
THE SUN

The Ozone Layer is a thin,The Ozone Layer is a thin,
fragile shield that envelopsfragile shield that envelops
the entire earth whichthe entire earth which
efficiently and effectivelyefficiently and effectively
filters and screens almostfilters and screens almost
all of the harmful ultravioletall of the harmful ultraviolet
raysrays

There are three
categories of UV:
•UV-A: Most UV-A is able to reach theUV-A: Most UV-A is able to reach the
earth’s surface. Generally not dangerousearth’s surface. Generally not dangerous
•UV-B: 90% of UV-B is blocked off by theUV-B: 90% of UV-B is blocked off by the
ozone layer. Harmfulozone layer. Harmful
•UV-C: 100% of UV-C is blocked off by theUV-C: 100% of UV-C is blocked off by the
ozone layer. Lethalozone layer. Lethal

What filters the
dangerous radiation
from the sun that
could practically
burn all life on earth
is the OZONE
LAYER.

Ozone molecules are created and destroyed high
above the surface of the earth, about 20-40 km
above ground.
How is ozone created and destroyed?How is ozone created and destroyed?

The depletion or the
loss of the blocking
effect of the ozone
layer against
ultraviolet rays is what
we call the OZONE
HOLE

The largest
ozone hole is
the size of
North America
Although the ozone
hole is found in the
Antarctica, the
global ozone level
throughout the
stratosphere has
also decreased by
3% every decade.

The largest ozone hole
is found in Antarctica
because:
- ODS are present throughout the
atmosphere regardless of where they are
released
- The symmetry of the land of Antarctica
affects the very cold climate
- The temperature leads to chemical
changes that promote the production of
chemically active chlorine and bromine
from ODS

WHAT ARE
THE EFFECTS
OF OZONE
DEPLETION?

Ozone
Depletion
harms and
endangers
all living
forms.

Effects of increased UV-B
radiation
• More skin cancers
• More eye cataracts
• Weakened immune systems
• Reduced plant yields
• Damage to ocean eco-systems and
reduce fishing yields
• Adverse effects on animals
• More damage to plastics and other
building materials
Ozone depletion allows the entry of UV-B radiation

ManMan will find hiswill find his
immune systemimmune system
deteriorating makingdeteriorating making
him prone to skinhim prone to skin
cancer, eye cataractscancer, eye cataracts
blindness rapid agingblindness rapid aging
and other seriousand other serious
diseases. UV-Bdiseases. UV-B
arrests the growth ofarrests the growth of
plants and trees andplants and trees and
phytoplanktonsphytoplanktons..
UV-B also results inUV-B also results in
degradation ofdegradation of
building materials.building materials.

Causes of Ozone
Depletion
• CERTAIN CHEMICALS UPSET THE OZONE BALANCE,
>>> CALLED OZONE-DEPLETING SUBSTANCES
• OZONE-DEPLETING SUBSTANCES (ODS) ARE CHEMICAL
SUBSTANCES THAT HAVE THE POTENTIAL TO REACT
WITH OZONE MOLECULES IN THE STRATOSPHERE.
• THE ABILITY TO DEPLETE THE OZONE LAYER IS
REFERRED TO AS THE OZONE- DEPLETING POTENTIAL
(ODP)

OZONE DEPLETING SUBSTANCESOZONE DEPLETING SUBSTANCES
(ODS) AND THEIR USES(ODS) AND THEIR USES
•CFCs are used inCFCs are used in
refrigerators, air-refrigerators, air-
conditioners, sprayconditioners, spray
cans, solvents,cans, solvents,
foams, otherfoams, other
applicationapplication
HALO-CARBONSHALO-CARBONS
(CHLOROFLUOROCARBONS or CFCs and(CHLOROFLUOROCARBONS or CFCs and
HALONS)HALONS)
•Halons areHalons are
primarily used inprimarily used in

CFC AND ITS MOST COMMONCFC AND ITS MOST COMMON
USESUSES

•HYDROBROMOFLUOROCARBONSHYDROBROMOFLUOROCARBONS
(HBFCs) are used in fire(HBFCs) are used in fire
extinguishersextinguishers
•CARBON TETRACHLORIDE andCARBON TETRACHLORIDE and
METHYL CHLOROFORM are used asMETHYL CHLOROFORM are used as
solventssolvents
•HYDROCHLOROFLUOROCARBONSHYDROCHLOROFLUOROCARBONS
(HCFCs) were developed as the(HCFCs) were developed as the
first major CFC replacementfirst major CFC replacement

•METHYLMETHYL
BROMIDE (CHBROMIDE (CH33 Br)Br)
is used as ais used as a
fumigant and infumigant and in
quarantinequarantine
treatmenttreatment
•BROMOCHLOROMETHANEBROMOCHLOROMETHANE
(BCM) is used as fire(BCM) is used as fire
extinguishing agent andextinguishing agent and

HOW CAN
THE OZONE
LAYER BE
SAVED?

THE OZONE LAYER CAN BE
SAVED ONLY BY PHASING
OUT THE USE OF CFCs,
HALONS AND OTHER OZONE
DEPLETING SUBSTANCES

HOW CAN WE HELP
PROTECT AND
PRESERVE THE
OZONE LAYER?

Five ThingsFive Things
ConsumersConsumers
must remember to helpmust remember to help
save the Ozone Layersave the Ozone Layer

1. Check the1. Check the
labels oflabels of
consumerconsumer
goods andgoods and
patronizepatronize
ODSODS
alternatives.alternatives.

Most aerosols and brand newMost aerosols and brand new
refrigerators and air-refrigerators and air-
conditioners do not utilizeconditioners do not utilize
CFCs anymore. However,CFCs anymore. However,
some second-hand refs andsome second-hand refs and
aircons available in theaircons available in the
market still use the ozone-market still use the ozone-
depleting CFCs. Consumersdepleting CFCs. Consumers
are advised not to patronizeare advised not to patronize
these.these.

2. Consumers are encouraged2. Consumers are encouraged
to patronize tear gas andto patronize tear gas and
metered-dose inhalers (usedmetered-dose inhalers (used
by asthma patients) that do notby asthma patients) that do not
contain CFCs.contain CFCs.

3. Consumers are3. Consumers are
advised to supportadvised to support
service shops that areservice shops that are
accredited by the DTI toaccredited by the DTI to
ensure that theirensure that their
technicians are capabletechnicians are capable
of handling refrigerantsof handling refrigerants
and are not rechargingand are not recharging
their aircons or refs withtheir aircons or refs with
incompatibleincompatible
refrigerants.refrigerants.

4. Owners of cars with R-134a as4. Owners of cars with R-134a as
refrigerant in their aircon shouldrefrigerant in their aircon should
not back-convert or change theirnot back-convert or change their
system into CFC-12 or R-12system into CFC-12 or R-12
because car models 1999 up tobecause car models 1999 up to
present that use R-12 will nopresent that use R-12 will no
longer be registered at the Landlonger be registered at the Land
Transportation Office startingTransportation Office starting
January 2006.January 2006.

5. Owners of cars with R-125. Owners of cars with R-12
manufactured 1998 and belowmanufactured 1998 and below
are advised to retrofit orare advised to retrofit or
change their aircon system tochange their aircon system to
an alternative system (R-134aan alternative system (R-134a
or HC).or HC).

 OZONE and the OZONE LAYEROZONE and the OZONE LAYER
 Creation and destruction of OZONECreation and destruction of OZONE
 The OZONE HOLEThe OZONE HOLE
 The effects of ozone depletionThe effects of ozone depletion
 The causes of ozone depletionThe causes of ozone depletion
 Ways to help save the ozone layerWays to help save the ozone layer
Wrap-UpWrap-Up

Save OSave O33 ur Sky:ur Sky:
Ozone-Ozone-
FriendlyFriendly
Planet,Planet,

The most common refrigerants are the fluorinated
hydrocarbons, but numerous other substances also
function well as refrigerants, including many
inorganic compounds and hydrocarbons.
TYPES OF REFRIGERANTS USED IN AIR-CONDITIONING

Haolocarbon compoundsHaolocarbon compounds
The halocarbon group includes refrigerants which contain one or more
of the three halogens chlorine, fluorine, and bromine. The numerical
designation, the chemical name, and the chemical formula of some of the
commercially available members of this group are shown in the Table.
The numbering system in the halocarbon group follows this pattern: the first
digit on the right is the number of fluorine atoms in the compound; the
second digit from the right is one more than the number of hydrogen atoms
inthe compund; and the
third digit from the right is one less than the numver ofcarbon atoms. When
the thrid digit is zero, it is omitted.

Numerical
designation
Chemical name
Chemical
formula
11 Trichloromonofluoromethane CCl3F
12 Dichlorodifluoromethane CCl2F2
13 Monochlorotrifluoromethane CClF3
22 Monochlorodifluoromethane CHCLF2
40 Methyl chloride CH3Cl
113 Trichlorotrifluoroethane CCl2FCClF2
114 Dichlorotetrafluoroethane CClF2CClF2
Some halocarbon refrigerants

AzeotropesAzeotropes
An azeotropic mixture of two substances is one which
cannot be separated into its components by distillation. An
azeotrope evaporates and condenses as a single substance
with properties that are different from those of either
constituent. The most popular azeotrope is refrigerant 502,
which is a mixture of 48.8 percent refrigerant 22 and 51.2
percent refrigerant 115.

Numerical
designation †
Chemical name
Chemical
formula
717 Ammonia NH3
718 Water H2O
729 Air
744 Carbon dioxide CO2
764 Sulfur dioxide SO2
Some Inorganic refrigerants
† The last two digits are the molecular weight.

Hydrocarbon refrigerants
† Follows same principle as the halocarbon scheme.
Numerical
designation †
Chemical name Chemical formula
50 Methane CH4
170 Ethane C2H6
190 Propane C3H8

Refrige
rant
Evaporat
ing
pressure,
kPa
Condens
ing
pressure,
Kpa
Pressure
ratio
Refrigera
ting
effect
KJ/kg
Suction
vapor flow
per kW of
refrigeration
COP
11 20.4 125.5 6.15 155.4 4.90 5.03
12 182.7 744.6 4.08 116.3 0.782 4.70
22 295.8 1192.1 4.03 162.8 0.476 4.66
502 349.6 1308.6 3.74 106.2 0.484 4.37
717 236.5 1166.6 4.93 1103.4 0.462 4.76
Thermodynamic characteristics of several refrigerants
Operation on a standard vapor-compression cycle with an evaporating
temperature of -15°C and a condensing temperature of 30°C

Air Conditioning System Heat Load Determination
General Method
Show how to compute the total heat load for an
air condition building fitted with windows, internal
heat from people and machines and heat
transmission grains from wall, roof and floor.

Step 1. Determine the design outdoor and indoor conditions.
Inside condition 75 °F RH °60% enthalpy – 30BTU/lb
Outside condition Tdry = 98°F Twet = 80 °F enthalpy 45BTU/lb
Step 2. Calculate required BTU/hr to control space temperature to
be cooled.
assumed air changed per hour in a room = 2.5
Inside condition outside condition
temp 75°F temp 98°F dry bulb
RH 60% temp 80°F wet bulb
enthalpy 30 BTU/lb enthalpy 45BTU/lb
Space to be cooled = sensible heat + latent heat
Sensible heat = floor area (ft²) x (8’ ht) x 2.5 air change/hr x 0.076x
0.24 x (98°-75°)
= floor area (ft²) x 8.45

Latent heat = floor area (ft²) x (8’ ht) x 2.5 air change/hr x 0.076 x
(h2 – h1)
= floor area (ft²) x 8 x 2.5 x 0.076 x (45-30)
= floor area x 22.80
Space to be cooled BTU/hr = Area (ft²) x (8.45 + 22.8)
BTU/hr = Area (ft²) x (31.25)

Step 3. Compute heat loss thru glass, roof and walls
Heat loss thru a building surface
HL = U area ▲t
HL = Heat loss in BTU/Hr
U = coefficient of heat transmission for the material
▲t = Temperature difference (Outside Temp. - Inside temp.)
Typical area and heat transfer coefficient
Building surface Type U BTU/sqft. Hr °F
Walls 8” thick brick 0.5
Residential wall 0.25
Commercial wall 0.33
Roof 2” concrete 0.82
Residential roof & ceiling 0.31
Commercial roof & ceiling 0.40
Windows Ordinary glass 1.13
Storm window 0.45
Double window 0.65

3.A Heat less than Roof
BTU / hr = .82 x Area of roof ( sq. ft ( ∆t )
3.B Heat less than Walls
BTU / hr = 0.5 x Area of wall ( sq. ft ) ( ∆t )
3.C Heat less than Windows
BTU = 1.13 x Area of windows ( sq. ft ) ( ∆t )

Step Four
Calculate the heat generated by occupants, allow 600 BTU per person.
Occupant BTU/Hr = number of people x 600
Step Five
Calculate the heat generated by each item of machinery - copiers,
computers, ovens etc. Find the power in watts for each item, add
them together and multiply by 3.4
Equipment BTU/Hr = total equipment watts x 3.4
Step Six
Calculate the heat generated by lighting. Find the total wattage for all
lighting and multiply by 4.25
Lighting BTU/Hr = total lighting watts x 4.25

Step Seven
Add the above together to find the total heat load.
Total heat load BTU/hr = Area BTU/hr + Total Window,
walls & roof BTU/hr + Occupant BTU/hr + Equipment
BTU/hr + Lighting BTU/hr
Step Eight
Aircon capacity in tons = total heat load BTU / hr
12 000 BTU / hr

GIVEN:
AREA TO BE AIR-CONDITIONED

18m
36 m
1. Get the total area to be air-conditioned. (m2
)
A = L x W
PROPOSED HANDYMAN (Hardware Store)

18m
36 m
1. Get the total area to be air-conditioned. (m2
)
A = A = 648 m2
PROPOSED HANDYMAN (Hardware Store)
18 x 36

DESIGNATION A/C SYSTEM FLR AREA/ TR REQ’D
(m2
/TR)
A. Common Mall Areas
B. Rentable areas
1. Fine Dining/ Fast Food
8. Amusement Center
6. Department Stores
7. Supermarket
2. Food Court
3. Retail Stores (dry)
4. Hardware (Handyman)
5. Stores/ Anchor Stores CENTRALWATER-
COOLEDCHILLED
WATERSYSTEM
20
12
18
18
18
12
18
18
18
2. Get the floor area/ton of refrigeration required from chart. (m2
/TR)

DESIGNATION A/C SYSTEM FLR AREA/ TR REQ’D
(m2
/TR)
A. Common Mall Areas
B. Rentable areas
1. Fine Dining/ Fast Food
8. Amusement Center
6. Department Stores
7. Supermarket
2. Food Court
3. Retail Stores (dry)
4. Hardware (Handyman)
5. Stores/ Anchor Stores CENTRALWATER-
COOLEDCHILLED
WATERSYSTEM
20
12
18
18
18
12
18
18
18
2. Get the floor area/ton of refrigeration required from chart. (m2
/TR)
Use 18 m2
/TR for Hardware

3. Calculate Tons of Refrigeration (TR)
TR =
Total Area
Floor Area/ TR
=
648 m2
18 m2
/TR
TR = 36 TR
Use 40 TR

4. Divide the area to be air-conditioned equally spaced 6m x 6m.
6m
6m

5. Calculate TR per 6m x 6m.
6m
6m
Aper square = 36 m2
TRper square =
36 m2
18 m2
/TR
= 2 TRper square

6. Calculate CFM/nozzle:
2 TR
= 2 TRper square
x 400 cfm/TR

7. Make proposed Air Distribution Layout:
branch 1
branch 2
branch 3
diffuser
Total number of diffusers = 18
40 TR
AHU

8. Calculate Air Distribution and Duct sizing:
Total CFM = 40 TR x 400 cfm per TR
16,000 cfm=
Total number of diffusers = 18
CFM/diffuser = 16,000
18
= 880 cfm per diffuser

To get CFM for each branch:
Note: branch 1 = branch 2 = branch 3
CFMper branch = 6 x 880 = 5,280 cfmper branch
For one branch:
880 cfm 880 cfm 880 cfm 880 cfm 880 cfm 880 cfm
To compute sizing of branch:

5280 cfm
Note: for 3 consecutive diffusers use
only one size of duct for economical use
Q = AV
Use 2000 fpm for Velocity
A =
5280
2000
= 2.64 ft2
Acircle = πD2
/4
D =
4 x 2.64
π

5280 cfm
Note: for 3 consecutive diffusers use
only one size of duct for economical use
Q = AV
A =
5280
2000
= 2.64 ft2
Acircle = πD2
/4
D = 1.83 ft x 12 in/ft
= 22 inches ø

2640 cfm
Do the same procedure for the next
three diffusers
Q = AV
A =
2640
2000
= 1.32 ft2
Acircle = πD2
/4
D =
4 x 1.32
π

2640 cfm
Do the same procedure for the next
three diffusers
Q = AV
A =
2640
2000
= 1.32 ft2
Acircle = πD2
/4
D = 1.2 ft x 12 in/ft
= 15 inches ø

9. Draw the final layout including duct size
40 TR
AHU
22” ø 15” ø

- END OF LECTURE -
THANK YOU FOR LISTENING!

Design of Air conditioning System

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