2. 1.0 Brief Story about the
Beginning of Air-
conditioning by Willis de
Havilland Carrier
2
3. 2.0 Some Important Definitions
2.1 Air-Conditioning –
the control of temperature, humidity,
cleanliness and motion of air
in an enclosed space
•For the comfort of the occupants of the space
•For the treatment of diseases
3
4. •For the very exacting control of temperature and
relative humidity, other than for comfort, in
many manufacturing processes such as in
pharmaceuticals, electronics and
semiconductors, and many others
•For preserving important documents, valuable
paintings, and other valuable treasures against
the ravages of environmental pollution and
vagaries of the weather
•For many, many other purposes
4
10. 2.3 Refrigerant –
a chemical substance
that has the characteristics
of absorbing heat at a low
pressure and temperature,
and discharging that heat
at a high pressure
and temperature.
10
12. 2.4 Psychrometrics –
a branch of physics that is
defined as the science of
moist air properties and
processes which is used to
illustrate and analyze air-
conditioning cycles
12
13. The composition of dry air by volume is:
79.08% Nitrogen (N)
20.95% Oxygen (O)
0.93% Argon (Ar)
0.03% Carbon Dioxide (CO2)
0.01% Other Gases
Dry air has the capacity of absorbing water vapor in
amounts depending on the temperature of the air.
Since the air around us is not really dry but is moist
or it contains some water vapor, technically
speaking, the air we breathe contains superheated
steam.
13
15. 3.0 Sources of Air-Conditioning
Loads or Heat Loads
3.1 Sensible Heat
•Direct sunlight or solar heat
•Transmitted heat due to temperature difference
of the air between outside and inside across
walls, glass windows, roofs and ceiling, and
partitions
•People, the sensible component of the heat they
produce
15
16. •Lighting
•Appliances such as computers, printers, motors,
etc.
•Outside air for ventilation, its sensible heat
component due to its elevated temperature
above room air
•Air infiltration from the outside, its sensible
component
16
17. 3.2 Latent Heat
• People, the latent heat component of the heat they produce
• Exposed water in the space
• Steam
• Air infiltration from the outside, its latent component
17
18. 3.3 Average Air Conditioning Loads of Various Spaces
APPLICATION SQUARE METER PER TON
1. Residences:
Living / Dining 20 – 22
Bedrooms 22 – 25
2. Offices:
General Offices 20 – 22
Conference Room 12 – 14
3. Banking Areas 16 – 18
4. Theaters, Auditoriums 0.10 – 0.12 (ton/seat)
18
19. 5. Eateries:
Fast Foods 8 – 10
Ordinary restaurant, Coffee shop, Canteen 10 – 12
Fine Dining 12 – 14
6. Classrooms, Training rooms 16 – 17
7. Shopping Centers; Dept. Stores
Main Floors 16 – 18
Upper Floors 20 – 22
Grocery Store 20 – 22
19
21. 10. Manufacturing:
Semi – conductors 8 – 10
Pharmaceuticals 8 – 10
Assembly areas & Light Manufacturing 8 – 12
11. Call Centers:
Main Production Areas 15 – 16
Server room / LAN room 4 – 10
UPS room 8 – 10
Training room 16 – 17
21
22. 4.0 Types of Systems
Two types of systems
are in use:
the direct expansion
or the DX type
and the
chilled water type.
22
23. 4.1 DX System
In the DX system, the refrigerant in the
evaporator tubes cools directly the air flowing
across the tubes. They are mostly used in small
installations where the compressor, together
with its condenser, is connected directly to an
air handling unit or fan coil unit working
together on a one-on-one basis. This has been
the traditional DX system configuration. The
room air-conditioner and the popularly known
split type unit are DX type units.
23
25. More recently, however, due to advancements in the art and
manufacturing technology, the so-called Variable Refrigerant
Volume (VRV) or Variable Refrigerant Flow (VRF) units were
introduced into the market and there are now several
installations of this type worldwide including here locally. In this
variation of the DX System, one compressor and condenser
combination (or condensing unit) can be connected to several
fan coil units.
25
27. 4.2 Chilled Water System
In the chilled water system, the refrigerant cools the water first
and in turn, the water is circulated through several air handling
units to cool the air. It is sometimes called “indirect system”.
This type of system is found in large installations such as
buildings, shopping centers, manufacturing plants, hospitals,
schools, etc.
27
29. 5.0 Equipment
5.1 Compressors
They are manufactured in either open type or
hermetic construction. In the open type, the
compressor and the drive motor are in
separate enclosures and they are mechanically
linked together through a flexible coupling. In
the hermetic type, the compressor and the
drive motor are in one single enclosure and
they are linked together through a common
shaft.
29
30. The common types are as follows:
5.1.1 Reciprocating Type
It comes in either open or hermetic construction. It is
manufactured from the smallest to about 150 tons capacities. In
up to 10 tons capacities, they operate up to 3500 rpm. Larger
sizes are designed to operate at 1750 rpm. They are used in
either DX or Chilled Water Systems.
30
32. 5.1.2 Rotary Type
This is a small compressor used mostly in
refrigerators, room type air-conditioners, and
car air-conditioners. It comes either in open or
hermetic type construction.
32
33. 5.1.3 Centrifugal Type
It comes in either open or hermetic construction.
It has very few moving parts and it operates at
high speeds, even up to 12000 rpm.
In both cases, it comes factory-assembled
together with its matching condenser and water
chiller. Centrifugal chillers are manufactured in
single sizes up to 1500 tons capacity for the
hermetic unit and up to 10000 tons for the open
type. They are used only in centralized chilled
water systems.
33
37. 5.1.4 Rotary Screw Compression
This type of compressor has also positive
displacement, just like the reciprocating type.
On the other hand, just like the centrifugal type,
it also has few moving parts. However, it
operates only at 3500 rpm. It is manufactured in
single sizes at up to 500 tons capacity. It can be
used for either DX or Chilled Water Systems. It
also comes in open or hermetic enclosures. It is
the latter that is used more in air-conditioning
applications. On the other hand, the open type
is mostly used in low temperature refrigeration.
37
39. 5.1.5 Scroll Compressor
This compressor is the latest development in compressor
technology. It is also of the positive displacement type and has
been found to be reliable. It comes only in hermetic
construction. It can be used in DX or Chilled Water Applications.
39
41. 5.2 Condensers
These usually come in two kinds, water-cooled and air-
cooled.
5.2.1 Water-Cooled Condensers
A water-cooled condenser consists of a bundle of tubes
(usually copper) enclosed in a cylindrical steel shell with
cast steel condenser heads at each end. Water flows
inside the tubes and the hot refrigerant gas to be
condensed is outside the tubes. Cooling water is
recirculated through a cooling tower where the air-
conditioning heat and heat of compression is finally
rejected to the atmosphere.
41
43. 5.2.2 Air-Cooled Condensers
An air-cooled condenser is constructed of copper
tubes with aluminum fins to enhance heat
transfer and increase the condensing surface.
The tubes are arranged in rows and are
assembled into a galvanized or corrosion-
protected steel casing. Within the casing is a fan
or a number of fans, depending upon the
condenser size. The condenser assembly may be
arranged for horizontal installation with the fans
discharging air upward or for vertical installation
with the fans discharging air horizontally.
43
45. 5.2.3 Cooling Towers
Cooling towers are mechanical draft, where
atmospheric air is forced through the tower fill
surface with fans, usually of the propeller type.
The fill or heat transfer surface, thru which the
water drips down, is made of wood slats or
plastic material.
Cooling towers are either of the counter flow
type or cross-flow type.
45
46. In the counter flow type, the cooling air enters at
the bottom of the fill and flows upward thru it in
strict counter flow against the water that drips
down.
In the cross-flow type, the cooling air enters at
the sides horizontally and flows at right angle
with the dripping down water.
In most cases, the towers are induced draft,
meaning, the fans are installed at the top of the
tower structure sucking the cooling air thru the
fill.
46
47. In the forced draft tower, the fans are installed at
the lower side of the tower to force the cooling
air thru the fill. Forced draft fans can only be
adapted in counter flow towers.
The configuration of the cooling towers may
either be rectangular or circular.
Fans are either driven thru gear reducers or belts
and pulley combination.
47
49. 5.2.4 Fluid Coolers or Chillers
They are constructed
almost similarly as
water cooled condensers,
shell and tube.
There are two types
of fluid coolers:
the dry expansion type
and the flooded type.
49
50. a. Dry Expansion Type
The evaporating refrigerant in the dry expansion type is inside the
tubes and the liquid to be cooled is outside the tubes. A
thermostatic expansion valve with several small distributor tubes
distributes the expanding refrigerant to the tube bundle of the
cooler. This type of cooler is common to small chiller packages.
50
52. b. Flooded Type
The tubes in the shell in the flooded type are submerged in a
liquid refrigerant and cooling is affected with the evaporation
of the refrigerant that is subjected to the suction of the
compressor. The liquid refrigerant level inside the shell is
controlled by a float valve. The fluid or water to be cooled
flows inside the tubes. This type of cooler is standard in large
chiller packages.
52
54. 5.3 Equipment Selection
In air conditioning and refrigeration systems there are two
modes of condensing; air cooled and water cooled.
Both modes have their own advantages and
disadvantages.
A. Reciprocating and Scroll Compressors
1. Air cooled condensing is usually employed in small
installations like window type units and packaged
units of sizes up to 30 tons capacity in single model.
For air conditioning levels, the specific compressor
input is 1.60 kw/ton. These type of unit lend itself to
totally independent energy metering and its is
popular with condominium developers and owners.
For high rise buildings, however, with very limited
machine spaces, the air cooled condensers pose some
serious problems on unit locations to prevent
condenser air short circuiting.
54
55. 2. Water cooled condensing has the principal advantage of
better efficiency resulting lower average specific energy
input of the compressor at about, 0.90 kw/ton. These
units are used mostly in central type installations.
Both air cooled and water cooled units can be employed in
either direct expansion and chilled water systems.
55
56. B. Centrifugal Units
These are the most efficient units with an average power input of
0.55 kw/ton at air conditioning levels. They come in single
sizes from 150 to 10,000 tons capacity. They can only be
used in chilled water systems. The centrifugal compressor
has excellent capacity unloading characteristics.
56
57. C. Screw Type Units
This is a relatively new type of compressor. It is a
cross between the reciprocating and
centrifugal compressor. It has positive
displacement like the reciprocating and has
good capacity modulation like the centrifugal
machine. It can be air cooled or water cooled
and it can be used for either direct expansion
or chilled water systems. It comes in sizes
from 40 tons to 750 tons capacity. Its power
input is about 0.75kw/ton at air conditioning
levels.
57
58. D. Absorption Type
This is a type of equipment that uses steam or high temperature
water as motive power and it is, therefore, used mostly where
these media are available. It is applicable for chilled water
systems only. It comes in single sizes from 90 to 1500 tons
capacity. Per ton of nominal cooling capacity its steam
consumption is about 10 pounds per hour at 115 psi pressure for
double stage models and about 18 pounds per hour at 20 psi
pressure for single stage models.
58
59. 6.0 Air Distribution
Air distribution in the
air-conditioned space is
accomplished through
constant volume air supply
or through
variable air volume (VAV)
boxes.
59
60. 6.1 Constant Air Volume Method
In the constant air volume method, which is still
much employed today, the rate of air flow into
the space is kept the same no matter what the
cooling demand is in a particular room or zone.
The result is that sometimes rooms are too warm
or too cold depending on the occupancy or
where the sun exposure is at any particular
time.
60
61. 6.2 Variable Air Volume Distribution System
To improve on the above system, the variable air
volume (VAV) distribution system was
introduced, and this is now in use in high-end
office buildings. In this method, an automated
volume damper is provided upstream of a supply
outlet to a room or supply duct branch to a
zone. The damper actuator is controlled by a
room temperature sensor. The damper is
modulated to open or to throttle down to supply
more air or less air into a room or zone to keep
the temperature almost constant no matter
what the occupancy or sun exposure the room or
zone has.
61
64. 6.3 Air Duct Design
There are two (2) generally used methods in air duct design:
6.3.1 Equal – friction: The principle of this method is to make
pressure loss per unit of duct length the same for the entire
system.
64
65. 6.3.2 Static – regain method: This is a design
procedure in which the reduction in air velocity
after each branch take-off that results in a gain
in static pressure is made used of. This regain in
static pressure is taken advantage of to offset
the pressure loss in the succeeding duct section.
This method is employed mostly in large systems
where high duct velocities are adopted. It
results in lower fan horsepower.
65
66. 6.3.3 Because it is simpler and easier to apply, the equal friction
method is more widely used.
Enclosed herewith is an equal-friction chart used for sizing air
ducts.
Also enclosed is a table for recommended and maximum velocities
for air ducts and other components of conventional systems.
66
70. 7.0 Chilled Water Distribution
Sometime in the near past it has been discovered
that economy in chilled water pumping energy
can be realized by varying the speed or RPM of
the pump with the use of a variable frequency
drive motor controller based on cooling demand.
This method neatly makes use of one of the
affinity laws for pumps, namely:
BHP1 = GPM1
3
BHP2 GPM2
70
71. Very seldom is a chilled water plant 100% loaded. Most of the
time, the load is only about 70% (or even less) of design capacity
and therefore, only 70% of the design chilled water flow rate
need to be supplied to the system. Following the above
equation, if the flow is reduced down to 70%, the pump power
will be reduced down to the cube of 70% or down to 34.3% of the
original power, which is very significant.
71
73. 8.0 Indoor Air Quality
8.1 Definition by ASHRAE
ASHRAE defines acceptable Indoor Air Quality as
“air in which there are no known contaminants
at harmful concentrations as determined by
cognizant authorities and with which a majority
(80% or more) of the people exposed do not
express dissatisfaction.” The absence of it may
result into the so-called sick building syndrome
or SBS.
73
74. 8.2 Sources of Contaminants
•Those generated within the space
•Those that come with the fresh air supply such
as dusts, vehicular exhaust fumes, pollens, etc.
•Miscellaneous organisms that breed within the
space due to high humidity – molds, mildew, and
fungi. They are the most harmful contaminants.
They can even be pathogenic or can cause
disease.
74
75. 8.3 Amount of Outside Air (OA) to be introduced
to the space
•Before, it was only 10 CFM per person
•Now, this was increased to 20 CFM per person
•Recommended rates are meant to limit CO2
concentration in the space to 700 ppm above the
outside air CO2 level. Generally, outdoor air CO2
level ranges from 300 to 500 ppm, which means
that the CO2 level in the space must be between
1000 to 1200 ppm.
75
76. •But the outside air is very expensive to
refrigerate down to the room dew point
temperature. For comfort conditioning at 75oF
and 50% RH, it takes about 100 Btu per hour to
refrigerate 1 CFM of OA. Example, in a space of
75 square meters, with 10 people needing 200
CFM of OA, 20,000 Btu per hour or 1.67 tons of
refrigeration is needed.
•If investment would permit, an energy-saving
device such as an air-to-air Heat Exchanger may
be used. With an effectiveness of 60%, this load
could be reduced down to 12,000 Btu per hour.
76
77. 9.0 Refrigerants, Ozone
depletion, Global Warming
9.1
In 1974, scientists theorized that CFC’s
(chlorofluorocarbons) posed a threat to the
ozone layer. This was verified by measurements.
9.2
In 1986, it was concluded that CFC’s and global
warming and climate change are connected.
77
78. 9.3
In 1987, the Montreal protocol was convened by
the industrialized countries, and the participants
decided to restrict the use of CFC’s, such as CFC
– 11, 12, 113, 114 and 115.
9.4
In the year 2000, the production of CFC’s was
halted. Two (2) new refrigerants were invented
and these are:
78
79. 9.4.1
HFC – 134a (tetrafluroethane). This is a
replacement for CFC – 12
9.4.2
HCFC – 123 (dichlorotrifluroethane). This is a
replacement for CFC – 11, 113, and 114. These
refrigerants are used in centrifugal chillers.
9.4.3
An existing refrigerant, R – 22, or HCFC – 22
(chlorodifluromethane) is still widely used today.
79
80. However, because of their
ozone depleting potential,
both HCFC – 22 and 123
will no longer be used
on new equipment manufactured
after January 1, 2010
in industrial countries.
It is safe to assume that
Third World Countries would be forced
to follow suit not very long
after that date.
80
81. 10.0 Thermal Energy Storage
System (TESS)
10.1
Reasons for adapting TESS
10.1.1
Where there is an incentive like lower electric energy cost to shift
high electrical demand form on-peak hours to off-peak hours to
reduce strain on the electric power plants.
81
82. 10.1.2
There is a need to handle short duration but high-
cooling load requirements, such as churches,
auditoriums, etc.
10.1.3
Need to provide cooling for small after-office
hours loads such as restaurants, individual
offices and computer rooms.
82
83. 10.2
Generally, there are two (2) types of TESS:
10.2.1
Liquid storage, primarily chilled water in
stratified type storage tanks.
10.2.2
Phase change, primarily ice. Ice is frozen during
off-peak hours and then melted for use during
the air-conditioning hours.
83
84. 10.3
Because of smaller chiller plant size as compared to
the conventional system, TESS has the following
advantages:
10.3.1 On the part of the user:
• The lower electric power demand would result in his
paying less transmission charge and distribution
charge.
• Lower investment cost on electrical power feeders,
transformer and switch gear.
• Smaller emergency Genset if 100% standby power is
desired.
84
85. 10.3.2
On the part of the electric power providers, there
will be less strain on their power plants. Their
load factor would be high and they would have
better operating efficiency. Because of this, they
could even postpone adding new plant
capacities.
10.3.3
On the part of the country as a whole, the
improved operating efficiency will result in
reduced oil importation.
85
86. 10.4
On the other hand, the disadvantages that have
to be shouldered by the user are the following:
- Higher investment cost
- May need additional operating
personnel due to longer operating
hours of the TESS.
86
88. 11.0 Cogeneration
11.1
Cogeneration is defined as the sequential production
of electricity and useful thermal energy from a
single fuel source.
11.2
The thermal energy that is otherwise dissipated into
the atmosphere through the engine exhaust and
jacket cooling water is trapped to generate steam
and/or high temperature water.
88
92. 11.3
Normally, on straight electricity production, a
diesel-generating set has a thermal efficiency of
about 33%. In cogeneration for air-conditioning
purposes, the efficiency is increased to about
42%.
11.4
On the other hand, based on straight electric
energy production, a gas turbine driven
generating set has a thermal efficiency of only
about 20%. With cogeneration for air-
conditioning, the efficiency is increased to about
34%.
92
93. 12.0 Some Energy-Saving Devices
in Air-Conditioning Systems
12.1
The air-to-air heat exchanger is constructed of
thin aluminum sheets coated with solid desicant
material corrugated to form a multitude of
narrow flutes through which streams of exhaust
air and outside air pass from opposite direction.
In the process, the cool exhaust air from the air-
conditioned spaces pre-cool the warm and humid
outside air.
93
95. This device, depending upon the ratio of outside
air intake to that of the exhaust air could save
about 50% of the energy required to cool the
required outside air required to the room dew
point condition.
This saving is very significant. For high density
occupancies such as in casinos, theaters,
auditoriums, restaurants or even offices where
outside air intake and exhaust can be
centralized, it is advisable that this device be
adapted.
95
96. 12.2
Heat reclaim from a refrigerant hot gas
desuperheater. The discharge gas from a
compressor is very hot. The available heat
energy from it, which would otherwise be
dissipated into the atmosphere, can be trapped
through a desuperheater to produce hot water of
around 130oF
In many instances, the available heat can fill the
entire hot water requirements of hotels, motels,
and hospitals. In most instances, it is also
sufficient to supply the reheat requirements of
the air-conditioning systems of some
manufacturing processes.
96
