This document provides an introduction to HVAC systems, including: - The primary function of HVAC systems is to provide healthy and comfortable interior conditions for occupants while minimizing energy usage and emissions. - HVAC system types include air systems, hydronic and steam systems, and unitary systems. Common components are fans, pumps, ducts, diffusers, filters, heating/cooling coils and controls. - Proper HVAC design considers indoor air quality, energy efficiency, and reducing heating/cooling loads through building design.

1. HVAC Systems – Understanding
HVAC Systems – Understanding
the basis
the basis
Table of Contents
Table of Contents
1.
1. Introduction to HVAC Systems
Introduction to HVAC Systems
2.
2. HVAC System Types
HVAC System Types
3.
3. HVAC Piping System
HVAC Piping System
4.
4. HVAC Air Distribution Equipments
HVAC Air Distribution Equipments
5.
5. Fans and Pumps
Fans and Pumps
6.
6. HVAC Instrumentation and Control
HVAC Instrumentation and Control
7.
7. HVAC System Commissioning
HVAC System Commissioning

2. Introduction to HVAC Systems
Introduction to HVAC Systems
 This article introduces the heating, ventilating and air-conditioning
This article introduces the heating, ventilating and air-conditioning
(HVAC) systems. The primary function of HVAC systems is to provide
(HVAC) systems. The primary function of HVAC systems is to provide
healthy and comfortable interior conditions for occupants; well-
healthy and comfortable interior conditions for occupants; well-
designed, efficient systems do this with minimal non-renewable
designed, efficient systems do this with minimal non-renewable
energy and air, and water pollutant emissions.
energy and air, and water pollutant emissions.

3. Introduction to HVAC Systems
Introduction to HVAC Systems
 The purpose of
The purpose of HVAC design
HVAC design is both high indoor air quality and energy
is both high indoor air quality and energy
efficiency. These dual considerations require an integrated design
efficiency. These dual considerations require an integrated design
approach. Rigs heating,
approach. Rigs heating,
ventilation, and air conditioning
ventilation, and air conditioning
system (HVAC) creates a climate
system (HVAC) creates a climate
that allows for maximum comfort by
that allows for maximum comfort by
compensating for changing climatic
compensating for changing climatic
conditions.
conditions.
 Though more costly to install and more complicated to operate, a chiller plant
Though more costly to install and more complicated to operate, a chiller plant
offers a number of benefits over a large number of individual packaged
offers a number of benefits over a large number of individual packaged
cooling units, including greater energy efficiency, better controllability,
cooling units, including greater energy efficiency, better controllability,
cheaper overall maintenance, and longer life. Using a comprehensive
cheaper overall maintenance, and longer life. Using a comprehensive
approach to building design, designers around the world have succeeded at
approach to building design, designers around the world have succeeded at
creating highly efficient air-conditioning systems that provide excellent
creating highly efficient air-conditioning systems that provide excellent
comfort at significant savings.
comfort at significant savings.

4. Introduction to HVAC Systems
Introduction to HVAC Systems
 Heating, ventilating and air-
Heating, ventilating and air-
conditioning (HVAC) systems
conditioning (HVAC) systems
reduce the environmental
reduce the environmental
impact of rigs/buildings in several
impact of rigs/buildings in several
key ways. The most important
key ways. The most important
function of a HVAC systems is
function of a HVAC systems is
to provide the rig/buildings occupants
to provide the rig/buildings occupants
with healthy and comfortable interior
with healthy and comfortable interior
conditions. A carefully designed, efficient
conditions. A carefully designed, efficient
system can do this with minimal non-
system can do this with minimal non-
renewable energy and air and water pollutant emissions to minimize the
renewable energy and air and water pollutant emissions to minimize the
environmental impact.
environmental impact.
Cooling equipment that avoids chlorofluorocarbons and hydro-
Cooling equipment that avoids chlorofluorocarbons and hydro-
chlorofluorocarbons (CFCs and HCFCs) eliminates a major cause of
chlorofluorocarbons (CFCs and HCFCs) eliminates a major cause of
damage to the ozone layer.
damage to the ozone layer.

5. Introduction to HVAC Systems
Introduction to HVAC Systems
 Even the best HVAC equipment and systems cannot compensate for a
Even the best HVAC equipment and systems cannot compensate for a
faulty rig design. Problems of this type cause inherently high cooling and
faulty rig design. Problems of this type cause inherently high cooling and
heating needs and consume unnecessary resources and should be
heating needs and consume unnecessary resources and should be
corrected if possible. Conservation of non-renewable energy through an
corrected if possible. Conservation of non-renewable energy through an
intelligent architectural design offers the greatest opportunity for savings.
intelligent architectural design offers the greatest opportunity for savings.
The most important factors in these designs are careful control of solar gain,
The most important factors in these designs are careful control of solar gain,
while taking advantage of passive heating, daylighting, natural ventilation
while taking advantage of passive heating, daylighting, natural ventilation
and cooling. The critical factors in mechanical systems' energy consumption
and cooling. The critical factors in mechanical systems' energy consumption
- and capital cost - are reducing the cooling and heating loads they must
- and capital cost - are reducing the cooling and heating loads they must
handle.
handle.

6. HVAC System Types
HVAC System Types
 Types of System Designs - There are several major heating, ventilating, and air
Types of System Designs - There are several major heating, ventilating, and air
conditioning system types in wide spread use today. These are air systems, hydronic
conditioning system types in wide spread use today. These are air systems, hydronic
and steam systems, and unitary type systems. Most systems in use today fall into one of
and steam systems, and unitary type systems. Most systems in use today fall into one of
these categories, or are a combination or variation of them. Each type of system has
these categories, or are a combination or variation of them. Each type of system has
advantages and disadvantages.
advantages and disadvantages.
 Air cooled
Air cooled
-
- Air cooled
Air cooled Chillers
Chillers

10.  Air Cooled Chiller Advantages
Air Cooled Chiller Advantages
• Lower installed cost
Lower installed cost
• Quicker availability
Quicker availability
• No cooling tower or condenser pump required
No cooling tower or condenser pump required
• Less maintenance
Less maintenance
• No mechanical room required
No mechanical room required

11.  Water Cooled
Water Cooled
- Sea Water cooled Chillers
- Sea Water cooled Chillers
- Fresh Water cooled Chillers
- Fresh Water cooled Chillers

13.  Water-Cooled Chiller advantages
Water-Cooled Chiller advantages
• Higher efficiency
Higher efficiency
• Custom selection in larger sizes
Custom selection in larger sizes
• Large tonnage capabilities
Large tonnage capabilities
• Indoor Chiller location
Indoor Chiller location
• Longer life
Longer life

14. Purpose of an air handling system
Purpose of an air handling system
Air Handling
System
Room
With
Defined
Requirements
Supply
Air
Outlet
Air
Air Handling Systems

15. Objectives
In the following slides, we will study the components of
air handling systems in order to:
1. Become familiar with the components
2. Know their functions
3. Become aware of possible problems

16. +
Room/Cabin
Exhaust air treatment
Central air handling unit
Terminal air treatment
at production room level
Fresh air treatment
(make-up air)
Main subsystems

17. Filter
Silence
r
Terminal filter
Weather louvre Control damper
Fan
Flow rate controller
Humidifier
Heating
coil
Cooling
coil
with
droplet
separator
Production Room
Overview components
+
Prefilter
Exhaust Air Grille
Heater
Secondary Filter
Re-circulated
air

18.  Weather
Weather
louvre
louvre
 Silencer
Silencer
 Flow rate
Flow rate
controller
controller
 Control
Control
damper
damper
 To prevent insects, leaves,
To prevent insects, leaves,
dirt
dirt and rain
and rain from entering
from entering
 To reduce noise caused by air
To reduce noise caused by air
circulation
circulation
 Automated adjustment of
Automated adjustment of
volume of air (night and day,
volume of air (night and day,
pressure control)
pressure control)
 Fixed adjustment of volume
Fixed adjustment of volume
of air
of air
Components (1)

19.  Heating unit
Heating unit
Cooling unit
Cooling unit
/dehumidifier
/dehumidifier
Humidifier
Humidifier
Filters
Filters
Ducts
Ducts
 To
To heat
heat the air to the proper
the air to the proper
temperature
temperature
 To
To cool
cool the air to the
the air to the required
required
temperature
temperature or to remove moisture
or to remove moisture
from the air
from the air
 To bring the air to the proper
To bring the air to the proper
humidity, if too low
humidity, if too low
 To eliminate particles of pre-
To eliminate particles of pre-
determined dimensions and/or
determined dimensions and/or
micro-organisms
micro-organisms
 To transport the air
To transport the air
Components (2)

20. +
Production Room
Exhaust
air
Return air
(re-circulated)
Fresh air
(make-up air)
Supply
air
Air types

21. Filter classes
Filter classes
Dust filters
Standard Aerosol
Fine
Coarse ULPA
HEPA
10 µ m > Dp > 1 µ m
Dp > 10 µ m Dp < 1 µ m
F5 - F9
G1 - G4 U 14- 17
H 11 - 13
EN 1822 Standard
EN 779 Standard

22. Primary panel
Primary panel
filter
filter
Secondary
Secondary
filter
filter
HEPA or tertiaary filter

23. Duct heaters
Duct heaters Room Heters
Room Heters
Silensers
Silensers

24. Volume control damper
Volume control damper
De-humidification
Filter Pressure
Gauges
AHU with fan
Variable Speed
Controller
Humid room air
Air heater
Regeneration air
Humid room air
Adsorber wheel Dry air
Fire
Fire Dampers
Dampers

25. Annex 1, 17.26
Regulation of room pressure
Regulation of room pressure – pressure
– pressure
differentials concept
differentials concept
Room pressure
gauges
Room pressure indication panel

26. Pressure cascade injectables
Pressure cascade injectables
P
Protection from micro-organisms and
rotection from micro-organisms and
particles
particles
N o te : D ir e c t io n o f d o o r o p e n in g r e la t iv e to r o o m p r e s s u r e
1 5 P a
0 P a
A ir
L o c k
3 0 P a P a s s a g e
D
C
A
B
D
L F
A ir L o c k
A ir L o c k
4 5 P a
R o o m 3
R o o m 2
R o o m 1
4 5 P a
6 0 P a
3 0 P a

27. Pressure cascade solids
Protection from cross-contamination
Note:Directionofdooropeningrelativetoroompressure 15Pa
15Pa
15P aE
30PaPassage 0PaAirLock
Room3
Room2Room115Pa
AirLockAirLock
N o t e : D i r e c t i o n o f d o o r o p e n i n g r e l a t i v e t o r o o m p r e s s u r e
1 5 Pa
1 5 Pa
1 5 Pa
E
3 0 Pa
P a s s a g e
0 Pa
A ir
L o c k
R o o m 3
R o o m 2
R o o m 1
1 5 Pa
A ir L o c k
A ir L o c k

32. Fan Coil Unit
Fan Coil Unit

33. Self Contain Unit
Self Contain Unit

34. HVAC Air Distribution Equipments
HVAC Air Distribution Equipments
 Diffusers
Diffusers
4 Way Diffusers
4 Way Diffusers Two Way Diffusers One Way Diffuser
Two Way Diffusers One Way Diffuser
Round Diffusers
Round Diffusers

35. Cabin Units
Cabin Units

36.  Return / Exhaust Grilles
Return / Exhaust Grilles

37. Contents
Contents
 Fan Design
Fan Design
 Fan Performance
Fan Performance
 Fan-duct Systems
Fan-duct Systems
 Duct Construction
Duct Construction
 Air Duct Design
Air Duct Design
Fans and Pumps

38. Fan Design
Fan Design
 Common types of fans
Common types of fans

Centrifugal fans
Centrifugal fans: radial, forward curved, air
: radial, forward curved, air
foil (backward curved), backward inclined,
foil (backward curved), backward inclined,
tubular, roof ventilator
tubular, roof ventilator

Axial fans
Axial fans: propeller, tube-axial, vane-axial
: propeller, tube-axial, vane-axial
 Fan arrangements
Fan arrangements

Motor location, air discharge orientation, drive
Motor location, air discharge orientation, drive
train type (direct drive or pulley drive)
train type (direct drive or pulley drive)

Centrifugal: single width single inlet (SWSI),
Centrifugal: single width single inlet (SWSI),
double width double inlet (DWDI)
double width double inlet (DWDI)

39. Centrifugal and axial fan components
AXIAL FANS
CENTRIFUGAL FANS

40. Propeller Tube-axial
Tube-vane
AXIAL FANS

41. Tubular centrifugal fan Centrifugal roof ventilator
CENTRIFUGAL FANS
(* Note the airflow paths and impeller design.)

42. Drive arrangements and motor positions

43. Single- and double-width centrifugal fans

44. Fan Performance
Fan Performance
 Major parameters
Major parameters
 Fan volume flow rate (m
Fan volume flow rate (m3
3
/s or l/s),
/s or l/s), V
Vf
f
 Fan total pressure
Fan total pressure Δ
Δp
ptf
tf, fan velocity pressure
, fan velocity pressure
p
pvf
vf & fan static pressure
& fan static pressure Δ
Δp
psf
sf (Pa)
(Pa)

Fan power & efficiency
Fan power & efficiency
• Fan power or air power (W) =
Fan power or air power (W) = Δ
Δp
ptf
tf x
x V
Vf
f
• Fan power input on the fan shaft (brake
Fan power input on the fan shaft (brake
horsepower),
horsepower), P
Pf
f
• Fan total efficiency:
Fan total efficiency: η
ηt
t =
= Δ
Δp
ptf
tf x
x V
Vf
f /
/ P
Pf
f

Combined aerodynamic, volumetric & mechanical
Combined aerodynamic, volumetric & mechanical
efficiencies
efficiencies
• Fan static efficiency:
Fan static efficiency: η
ηs
s =
= Δ
Δp
psf
sf x
x V
Vf
f /
/ P
Pf
f
• Air temp. increase through fan,
Air temp. increase through fan, Δ
ΔT
T =
= Δ
Δp
p /(
/(ρ
ρc
c η
η)
)

45. Fan performance curves
Total pressure
Static pressure
Fan total efficiency
Fan static efficiency
Fan power input
Velocity pressure
Volume flow rate

46. Typical fan performance curve

47. Fan Performance
Fan Performance
 Fan Laws
Fan Laws

Speed (
Speed (n
n)
)

Volume flow (
Volume flow (V
V)
)

Total pressure loss
Total pressure loss
(
(Δ
Δp
p )
)

Air density (
Air density (ρ
ρ)
)

For air systems that
For air systems that
are geometrically &
are geometrically &
dynamically similar:
dynamically similar:
(D = impeller
(D = impeller
diameter)
diameter)
 c.f.: pump laws
c.f.: pump laws

48. Velocity triangle at the blade inlet and outlet of a centrifugal fan
CENTRIFUGAL FANS

49. Fan Performance
Fan Performance
 Major issues causing energy losses to a
Major issues causing energy losses to a
centrifugal fan:
centrifugal fan:

Circulatory flow between the blades
Circulatory flow between the blades

Air leakage at the inlet
Air leakage at the inlet

Friction between fluid particles and the blade
Friction between fluid particles and the blade

Energy loss at the entrance
Energy loss at the entrance

Partially filled passage
Partially filled passage

50. Operating characteristics for a backward-curved centrifugal fan

51. Total efficiency
curves for
centrifugal fans

52. Fan power curves for centrifugal fans with same impeller diameter

53. Fan pressure curves for centrifugal fans with same impeller diameter

54. Velocity triangles for a vane-axial fan
AXIAL FANS

55. Fan pressure curves for axial fans with same impeller diameter

56. Fan efficiency curves for axial fans with same impeller diameter

57. Fan power curves for axial fans with same impeller diameter

58. Performance
curves for
controllable-
pitch vane-axial
fans

59. Fan-duct Systems
Fan-duct Systems
 Duct pressure changes (c.f. atm
Duct pressure changes (c.f. atm
pressure)
pressure)

Static pressure (SP)
Static pressure (SP)

Velocity pressure (VP) =
Velocity pressure (VP) = ρ
ρV
V2
2
/ 2 g
/ 2 g

Total pressure (TP) = SP + VP
Total pressure (TP) = SP + VP
 Fan: a pumping device
Fan: a pumping device

Fan (total) pressure = pressure difference
Fan (total) pressure = pressure difference
between fan inlet and fan discharge
between fan inlet and fan discharge

At fan suction/inlet, SP = negative (c.f.
At fan suction/inlet, SP = negative (c.f.
atmospheric); at discharge, SP = positive
atmospheric); at discharge, SP = positive

62. Fan-duct Systems
Fan-duct Systems
 Pressure characteristics
Pressure characteristics

SP and VP are mutually convertible (↑or↓)
SP and VP are mutually convertible (↑or↓)

TP always decreases in the direction of
TP always decreases in the direction of
airflow
airflow

For constant-area straight duct sections
For constant-area straight duct sections
• Velocity and VP are constant
Velocity and VP are constant
• TP change = SP change
TP change = SP change

When duct cross-sectional areas are reduced
When duct cross-sectional areas are reduced
• Velocity and VP increase
Velocity and VP increase
• Absolute value of both TP and SP decrease
Absolute value of both TP and SP decrease
• Dynamic losses from elbow, dampers, etc.
Dynamic losses from elbow, dampers, etc.

63. Fan-duct Systems
Fan-duct Systems
 Fan-duct systems
Fan-duct systems

Flow resistance
Flow resistance R
R, pressure drop
, pressure drop Δ
Δp
p and
and
volume flow rate
volume flow rate V
V

Duct sections in series:
Duct sections in series:

Duct sections in parallel:
Duct sections in parallel:
2
V
R
p 
⋅
=
∆
o
n
s R
R
R
R +
+
+
= 
2
1
n
p R
R
R
R
1
1
1
1
2
1
+
+
+
= 

64. Fan-duct Systems
Fan-duct Systems
 Fan-duct systems
Fan-duct systems

Terminology
Terminology
• Primary air (conditioned air or makeup air)
Primary air (conditioned air or makeup air)
• Secondary air (induced space air, plenum air, or
Secondary air (induced space air, plenum air, or
recirculating air)
recirculating air)
• Transfer air (indoor air that moves from an
Transfer air (indoor air that moves from an
adjacent area)
adjacent area)

System curve: volume flow vs pressure loss
System curve: volume flow vs pressure loss

System operating point
System operating point

65. Fan-duct Systems
Fan-duct Systems
 System effect
System effect Δ
Δp
pts
ts

Its additional total pressure loss caused by
Its additional total pressure loss caused by
uneven or non-uniform velocity profile at the
uneven or non-uniform velocity profile at the
fan inlet, or at duct fittings after fan outlet
fan inlet, or at duct fittings after fan outlet

Due to the actual inlet and outlet connections
Due to the actual inlet and outlet connections
as compared with the total pressure loss of the
as compared with the total pressure loss of the
fan test unit during laboratory ratings
fan test unit during laboratory ratings
Inlet Outlet

66. Fan system operating point & system effect

67. Fan-duct Systems
Fan-duct Systems
 Modulation of air systems
Modulation of air systems

Constant volume system
Constant volume system
• Volume flow rate remains constant
Volume flow rate remains constant
• Supply temperature is raised during part load
Supply temperature is raised during part load

Variable-air-volume (VAV) system
Variable-air-volume (VAV) system
• Volume flow rate is reduced to match part load
Volume flow rate is reduced to match part load
operation
operation
• Modulation curve
Modulation curve

68. Fan modulation curve

69. Fan-duct Systems
Fan-duct Systems
 Fan modulation methods
Fan modulation methods

Damper
Damper (vary the opening of the air flow
(vary the opening of the air flow
passage)
passage)
• Waste energy
Waste energy

Inlet vanes
Inlet vanes (opening & angle of inlet vanes)
(opening & angle of inlet vanes)
• Low cost; less efficient than following types
Low cost; less efficient than following types

Inlet cone
Inlet cone (peripheral area of fan impeller)
(peripheral area of fan impeller)
• Inexpensive; for backward curved centrifugal fan
Inexpensive; for backward curved centrifugal fan

Blade pitch
Blade pitch (blade angle of axial fan)
(blade angle of axial fan)

Fan speed
Fan speed (using adjustable frequency
(using adjustable frequency
drives)
drives)
• Most energy-efficient; but usually cost more
Most energy-efficient; but usually cost more

70. Damper, inlet vanes & fan speed modulation

71. Inlet vane
modulation

72. Fan speed
modulation using
AC inverter

73. Fan-duct Systems
Fan-duct Systems
 Fan surge
Fan surge (in centrifugal fan)
(in centrifugal fan)

Occurs when air volume flow is not sufficient to
Occurs when air volume flow is not sufficient to
sustain the static pressure difference between
sustain the static pressure difference between
discharge & suction
discharge & suction
• Discharge pressure is reduced momentarily
Discharge pressure is reduced momentarily
• Volume flow & pressure fluctuations
Volume flow & pressure fluctuations
• Create noise & vibration
Create noise & vibration

Surge region: shall avoid operation in it
Surge region: shall avoid operation in it
 Fan stall
Fan stall (in axial fans)
(in axial fans)

When smooth air flow suddenly breaks & pressure
When smooth air flow suddenly breaks & pressure
difference across the blades decreases
difference across the blades decreases

The fan loses pressure capability drastically
The fan loses pressure capability drastically

74. Stall and stall region of an axial fan

75. Fan-duct Systems
Fan-duct Systems
 Fan selection
Fan selection

Select fan type + determine fan size
Select fan type + determine fan size

Important factors:
Important factors:
• Pressure-volume flow operating characteristics
Pressure-volume flow operating characteristics
• Fan capacity modulation
Fan capacity modulation
• Fan efficiency
Fan efficiency
• Sound power level
Sound power level
• Airflow direction
Airflow direction
• Initial cost
Initial cost

77. Duct Construction
Duct Construction
 Types of air duct
Types of air duct

Supply air duct
Supply air duct

Return air duct
Return air duct

Outdoor air duct
Outdoor air duct

Exhaust air
Exhaust air
 Duct sections
Duct sections

Header or main duct (trunk)
Header or main duct (trunk)

Branch duct or runout
Branch duct or runout

79. Duct Construction
Duct Construction
 Duct systems
Duct systems

Max. pressure difference (between air inside
Max. pressure difference (between air inside
the duct and the ambient air)
the duct and the ambient air)
• 125, 250, 500, 750, 1000, 1500, 2500 Pa
125, 250, 500, 750, 1000, 1500, 2500 Pa

Commercial buildings
Commercial buildings
• Low-pressure duct system: ≤ 500 Pa, max 12 m/s
Low-pressure duct system: ≤ 500 Pa, max 12 m/s
• Medium-pressure system: 500-1500 Pa, max 17.5
Medium-pressure system: 500-1500 Pa, max 17.5
m/s
m/s

Residential buildings: 125 Pa or 250 Pa
Residential buildings: 125 Pa or 250 Pa

Industrial duct system:
Industrial duct system: Δ
ΔP can be higher
P can be higher

80. Duct Construction
Duct Construction
 Duct material: e.g. UL (Underwriters’
Duct material: e.g. UL (Underwriters’
Laboratory) standard
Laboratory) standard

Class 0: zero flame spread, zero smoke
Class 0: zero flame spread, zero smoke
developed
developed
• Iron, galvanized steel, aluminum, concrete,
Iron, galvanized steel, aluminum, concrete,
masonry, clay tile
masonry, clay tile

Class 1: flame spread ≤ 25, smoke
Class 1: flame spread ≤ 25, smoke
developed ≤ 50
developed ≤ 50
• Fiberglass, many flexible ducts
Fiberglass, many flexible ducts

Class 2: flame spread ≤ 50, smoke
Class 2: flame spread ≤ 50, smoke
developed ≤ 100
developed ≤ 100

81. Duct Construction
Duct Construction
 Shapes of air duct
Shapes of air duct

Rectangular
Rectangular
• More easily fabricated on site, air leakage
More easily fabricated on site, air leakage

Round
Round
• Less fluid resistance, better rigidity/strength
Less fluid resistance, better rigidity/strength

Flat oval
Flat oval

Flexible
Flexible
• Multiple-ply polyester film w/ metal wire or strips
Multiple-ply polyester film w/ metal wire or strips
 SMACNA (Sheet Metal and Air
SMACNA (Sheet Metal and Air
Conditioning Contractors’ National
Conditioning Contractors’ National
Association) standards
Association) standards

82. Rectangular duct Round duct w/ spiral seam
Flat oval duct Flexible duct
(Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)

83. Transverse joint reinforcement
(Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)

84. Duct Construction
Duct Construction
 Duct specification
Duct specification

Sheet gauge and thickness of duct material
Sheet gauge and thickness of duct material

Traverse joints & longitudinal seam
Traverse joints & longitudinal seam
reinforcements
reinforcements

Duct hangers & their spacing
Duct hangers & their spacing

Tapes & adhesive closures
Tapes & adhesive closures

Fire spread and smoke developed
Fire spread and smoke developed

Site-fabricated or factory-/pre-fabricated
Site-fabricated or factory-/pre-fabricated

85. Duct Construction
Duct Construction
 Duct heat gain or loss
Duct heat gain or loss

Temperature rise or drop
Temperature rise or drop

Duct insulation (mounted or inner-lined)
Duct insulation (mounted or inner-lined)
• Reduce heat gain/loss, prevent condensation,
Reduce heat gain/loss, prevent condensation,
sound attentuation
sound attentuation
• Minimum & recommended thickness
Minimum & recommended thickness

See ASHRAE standard or local codes
See ASHRAE standard or local codes

Temperature rise curves
Temperature rise curves
• Depends on air velocity, duct dimensions &
Depends on air velocity, duct dimensions &
insulation
insulation

86. Temperature rise from duct heat gain
(Source: Wang, S. K., 2001. Handbook of Air Conditioning and Refrigeration)

87. Duct Construction
Duct Construction
 Frictional losses
Frictional losses

Darcey-Weisbach Equation
Darcey-Weisbach Equation
• H
Hf
f = friction head loss, or
= friction head loss, or Δ
Δp
pf
f = pressure loss
= pressure loss
• f
f = friction factor (dimensionless)
= friction factor (dimensionless)
• L
L = length of duct or pipe (m)
= length of duct or pipe (m)
• D
D = diameter of duct or pipe (m)
= diameter of duct or pipe (m)
• v
v = mean air velocity in duct (m/s)
= mean air velocity in duct (m/s)

88. Mode of airflow when air passes over and around
surface protuberances of the duct wall
δ >ε
δ <ε

89. Duct Construction
Duct Construction
 Duct friction chart
Duct friction chart

Colebrook formula
Colebrook formula
 Roughness & temperature corrections
Roughness & temperature corrections
 Δ
Δp
pf
f =
= K
Ksr
sr K
KT
T K
Kel
elΔ
Δp
pf,c
f,c
• K
Ksr
sr = correction factor for surface roughness
= correction factor for surface roughness
• K
KT
T = correction factor for air temperature
= correction factor for air temperature
• K
Kel
el = correction factor for elevation
= correction factor for elevation

90. Friction chart for round duct

92. Duct Construction
Duct Construction
 Circular equivalent
Circular equivalent
 Hydraulic diameter,
Hydraulic diameter, D
Dh
h = 4
= 4 A
A /
/ P
P
• A
A = area (mm
= area (mm2
2
);
); P
P = perimeter (mm)
= perimeter (mm)

Rectangular duct:
Rectangular duct:

Flat oval duct:
Flat oval duct:

93. Duct Construction
Duct Construction
 Dynamic losses
Dynamic losses

Result from flow disturbances caused by duct-
Result from flow disturbances caused by duct-
mounted equipment and fittings
mounted equipment and fittings
• Change airflow path’s direction and/or area
Change airflow path’s direction and/or area
• Flow separation & eddies/disturbances
Flow separation & eddies/disturbances

In dynamic similarity (same Reynolds number
In dynamic similarity (same Reynolds number
& geometrically similar duct fittings), dynamic
& geometrically similar duct fittings), dynamic
loss is proportional to their velocity pressure
loss is proportional to their velocity pressure

94. Duct Construction
Duct Construction
 Local or dynamic loss coefficient
Local or dynamic loss coefficient

Ratio of total pressure loss to velocity
Ratio of total pressure loss to velocity
pressure
pressure

95. Duct Construction
Duct Construction
 Duct fittings
Duct fittings

Elbows
Elbows

Converging or diverging tees and wyes
Converging or diverging tees and wyes

Entrances and exits
Entrances and exits

Enlargements and contractions
Enlargements and contractions
 Means to reduce dynamic losses
Means to reduce dynamic losses

Turning angle, splitter vanes
Turning angle, splitter vanes
 ASHRAE duct fitting database
ASHRAE duct fitting database

Fitting loss coefficients
Fitting loss coefficients

97. Region of eddies and
turbulences in a round elbow 5-piece 90o
round elbow

98. Rectangular elbow, smooth radius, 2 splitter vanes
Mitered elbow and its secondary flow

99. Airflow through a
rectangular converging
or diverging wye

100. Entrance Exit

101. Abrupt enlargement Sudden contraction

102. Duct Construction
Duct Construction
 Flow resistance,
Flow resistance, R
R
 Total pressure loss
Total pressure loss Δ
Δp
pt
t at a specific volume flow
at a specific volume flow
rate
rate V
V

Flow resistance in series:
Flow resistance in series:

Flow resistance in parallel:
Flow resistance in parallel:
2
V
R
pt

⋅
=
∆
n
s R
R
R
R +
+
+
= 
2
1
n
p R
R
R
R
1
1
1
1
2
1
+
+
+
= 

103. Total pressure loss and flow resistance of a round duct section

104. Flow resistance in series
Flow resistance in parallel

105. Flow resistance for a Y connection

106. Air Duct Design
Air Duct Design
 Optimal air duct design
Optimal air duct design

Optimal duct system layout, space available
Optimal duct system layout, space available

Satisfactory system balance
Satisfactory system balance

Acceptable sound level
Acceptable sound level

Optimum energy loss and initial cost
Optimum energy loss and initial cost

Install only necessary balancing devices
Install only necessary balancing devices
(dampers)
(dampers)

Fire codes, duct construction & insulation
Fire codes, duct construction & insulation
 Require comprehensive analysis & care for
Require comprehensive analysis & care for
different transport functions
different transport functions

107. Flow characteristics of a supply duct system

108. Air Duct Design
Air Duct Design
 Design velocity
Design velocity

Constraints: space available, beam depth
Constraints: space available, beam depth

Typical guidelines:
Typical guidelines:
• Main ducts: air flow usually ≤ 15 m/s; air flow noise
Main ducts: air flow usually ≤ 15 m/s; air flow noise
must be checked
must be checked
• With more demanding noise criteria (e.g. hotels),
With more demanding noise criteria (e.g. hotels),
max. air velocity: main duct ≤ 10-12.5 m/s, return
max. air velocity: main duct ≤ 10-12.5 m/s, return
main duct ≤ 8 m/s, branch ducts ≤ 6 m/s
main duct ≤ 8 m/s, branch ducts ≤ 6 m/s

Face velocities for air-handling system
Face velocities for air-handling system
components
components

110. Air Duct Design
Air Duct Design
 Reduce dynamic losses of the critical path
Reduce dynamic losses of the critical path

Maintain optimum air velocity through duct
Maintain optimum air velocity through duct
fittings
fittings

Emphasize reduction of dynamic losses
Emphasize reduction of dynamic losses
nearer to the fan outlet or inlet (high air
nearer to the fan outlet or inlet (high air
velocity)
velocity)

Proper use of splitter vanes
Proper use of splitter vanes

Set 2 duct fittings as far apart as possible
Set 2 duct fittings as far apart as possible
 Air duct leakage
Air duct leakage

Duct leakage classification
Duct leakage classification
• AISI, SMACNA, ASHRAE standards
AISI, SMACNA, ASHRAE standards

111. Air Duct Design
Air Duct Design
 Fire protection
Fire protection

Duct material selection
Duct material selection

Vertical ducts (using masonry, concrete or
Vertical ducts (using masonry, concrete or
clay)
clay)

When ducts pass through floors & walls
When ducts pass through floors & walls

Use of fire dampers
Use of fire dampers

Filling the gaps between ducts & bldg
Filling the gaps between ducts & bldg
structure
structure

Duct systems for industrial applications
Duct systems for industrial applications
 Any other fire precautions?
Any other fire precautions?

112. Air Duct Design
Air Duct Design
 Design procedure (computer-aided or manual)
Design procedure (computer-aided or manual)

Verify local codes & material availability
Verify local codes & material availability

Preliminary duct layout
Preliminary duct layout

Divide into consecutive duct sections
Divide into consecutive duct sections

Minimise local loss coefficients of duct fittings
Minimise local loss coefficients of duct fittings

Select duct sizing methods
Select duct sizing methods

Critical total pressure loss of tentative critical path
Critical total pressure loss of tentative critical path

Size branch ducts & balance total pressure at
Size branch ducts & balance total pressure at
junctions
junctions

Adjust supply flow rates according to duct heat gain
Adjust supply flow rates according to duct heat gain

Resize duct sections, recalculate & balance parallel
Resize duct sections, recalculate & balance parallel
paths
paths

Check sound level & add necessary attenuation
Check sound level & add necessary attenuation

113. Air Duct Design
Air Duct Design
 Duct layout
Duct layout

Symmetric layout is easier to balance
Symmetric layout is easier to balance
• Smaller main duct & shorter design path
Smaller main duct & shorter design path

For VAV systems, duct looping allows feed
For VAV systems, duct looping allows feed
from opposite direction
from opposite direction
• Optimise transporting capacity (balance points
Optimise transporting capacity (balance points
often follow the sun’s position)
often follow the sun’s position)
• Result in smaller main duct
Result in smaller main duct

Compare alternative layouts & reduce fittings
Compare alternative layouts & reduce fittings

For exposed ducts, appearance & integration
For exposed ducts, appearance & integration
with the structure is important
with the structure is important

114. Typical supply duct system with symmetric layout & looping

115. Air Duct Design
Air Duct Design
 Duct liner
Duct liner

Lined internally on inner surface of duct wall
Lined internally on inner surface of duct wall

Mainly used for noise attenuation & insulation
Mainly used for noise attenuation & insulation

Fiberglass blanket or boards
Fiberglass blanket or boards
 Duct cleaning
Duct cleaning

Prevent accumulation of dirt & debris
Prevent accumulation of dirt & debris

Agitation device to loosen the dirt & debris
Agitation device to loosen the dirt & debris

Duct vacuum to extract loosened debris
Duct vacuum to extract loosened debris

Sealing of access openings
Sealing of access openings

116. Duct breakout noise

117. HVAC Piping System
HVAC Piping System

118. HVAC Instrumentation and Control
HVAC Instrumentation and Control

119. HVAC System Commissioning
HVAC System Commissioning
 The key elements of commissioning include:
The key elements of commissioning include:
 Installation checks.
Installation checks. Check installed equipment to ensure that all associated
Check installed equipment to ensure that all associated
components and accessories are in place.
components and accessories are in place.
 Operational checks.
Operational checks. Verify and document that systems are performing as expected,
Verify and document that systems are performing as expected,
and that all sensors and other system control devices are properly calibrated.
and that all sensors and other system control devices are properly calibrated.
 Documentation.
Documentation. Confirm that all required documentation has been provided, such as
Confirm that all required documentation has been provided, such as
a statement of the design intent and operating protocols for all building systems.
a statement of the design intent and operating protocols for all building systems.
 O&M manuals and training.
O&M manuals and training. Prepare comprehensive operation and maintenance
Prepare comprehensive operation and maintenance
(O&M) manuals, and provide training for rig operations staff.
(O&M) manuals, and provide training for rig operations staff.
 Ongoing monitoring.
Ongoing monitoring. Conduct periodic monitoring after the school is occupied to
Conduct periodic monitoring after the school is occupied to
ensure that equipment and systems continue to perform according to design intent.
ensure that equipment and systems continue to perform according to design intent.
 Correctly implemented, commissioning is extremely cost-effective, and should
Correctly implemented, commissioning is extremely cost-effective, and should
improve the delivery process, increase systems reliability, improve energy
improve the delivery process, increase systems reliability, improve energy
performance, ensure good indoor environmental quality, and improve operation and
performance, ensure good indoor environmental quality, and improve operation and
maintenance of the facility.
maintenance of the facility.