indoor air distribution
TRANSCRIPT
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Air Diffusion – Designing for Comfort
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Occupant Comfort
Air Diffusion Selection
ADPI Air Diffusion Performance index
Ventilation Effectiveness
Induction – Room Space Induction
Design Criteria ISO7730 ASHRAE 55p
Design & Selection Software
Products
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Occupant Comfort
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Comfort Limits ASHRAE Standard 55-92 and ISO 7730-94
ADPI Air Diffusion Performance Index / Comfort Index
A person is thermally comfortable when theirbody heat loss equals their heat production
without them sensing any changes in
temperature.
When is a person comfortable?
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Heat Loss or Gain can occur through:
Conduction – transfer of heat across a body
Convection – transfer from a body to its surroundings
Radiation – transfer through electromagnetic waves
Evaporation – sweat
Body Heat Loss or Gain
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Personal Comfort Variables
- Clothing
- Activity- Metabolic rate
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Space Comfort Variables
- Dry bulb temperature
- Relative humidity- Air velocity
- Noise
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ASHRAE Definition of ComfortFanger ’s comfort index or PMV.
ASHRAEDefines
Comfort
http://localhost/var/www/apps/Desktop/COMFORT.exehttp://localhost/var/www/apps/Desktop/COMFORT.exehttp://localhost/var/www/apps/Desktop/COMFORT.exe
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ASHRAE Definition of Comfort
ASHRAE/ISO 7730 standard defines comfort as:
- Maintaining a temperature of 22.8 – 25°C
- Relative humidity of 25 – 60%
- Maximum velocity within the occupied zone of0.25 m/s Cooling & 0.15m/s Heating
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The percentage of dissatisfied occupants at the Neck Region.
Effect of Air Motion on Comfort
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The percentage of dissatisfied occupants at the Ankle Region.
Effect of Air Motion on Comfort
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• Metabolic Rate – Occupants Physical Activity
• Thermal Resistance of Clothing - Clo Value
• Air Temperature – Optimum Operative Temperature
• Mean Radiant Temperature
• Air Velocity – Mean Space Velocity
• Relative Humidity
Design Criteria ISO7730-ASHRAE 55P-APDI
“Provided there is sufficient heating & cooling
to meet the thermal and humidity control
requirements, comfort is almost completely afunction of the space air distribution.”S.A. Mumma, Ph.D P.E., Fellow ASHRAE
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Air Diffusion Selection
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Air Distribution
Air Diffusion Design & Selection
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Defining the Occupied Space
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Terminal Velocity
Terminal Velocity – Tv 0.25
. 75 m/s .50 m/s .25 m/s
15.6m
11.3 m
7.3 m
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Free Expansion
A free jet will expand at 22°.
Zone 1 Zone 2 Zone 3 Zone 4
Exit velocity with initialinduction
Laminar, induction
increases
Laminar/Turbulent,maximum Room induction
Laminar, induction
increases
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Hot and Cold Jets
If the supply air is warmer than the room temperature, it will rise.
However if the supply air is cooler than the room air, it will drop.
General Rule: Distance @ T0.25 is effected at 2% per Degree T
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Example 50C Delta T Heating
10%
T 0.25
General Rule: Distance @T 0.25 is effected at 2% per Degree T
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Considerations
With overhead heating, the air slows down and turns
upwards at roughly 0.50 to 0.75m/s.
0.5 to 0.75m/s
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Furniture against wall
Considerations
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Air Diffusion Mistakes
Colliding jets
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ADPI Air Diffusion Performance Index
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ADPI – Effective Draft Temperature
effective draft temperature (K)
Effective Draft Temperature is calculated by:
local jet dry-bulb temperature (°C)
local jet centreline velocity (m/s)
control room dry-bulb temperature (°C)
( ) ( )
=
=
=
=
---=
x
c
x
xc x
V
t
t
where
V t t
q
q
:
15.08
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ADPI & Effective Draft Temperature
An acceptable value for Effective Draft Temperature is
within -1.70 and +1.10, with a velocity of less than 0.35m/s
The ADPI is the percentage of locations where
measurements are taken which have an: Acceptable _ Effective Draft Temperature.
Total number of within acceptance
Total number of values measured
q
X 100
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ASHRAE Definition of Comfort PMV
Comfort as a function of air velocity and temperature.
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ADPI – Effective Draft Temperature
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Air Diffusion Performance Index
Effective draft temperature, ( ) ( )15.08 ---= xc x V t t q
tx and Vx
tc
1q
100q
100mm
600mm
1100mm
1700mm
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ADPI – Air Diffusion Performance Index
Room Temp = 220C30 Test points at 0.1m/s, 20°C
35 points at 0.2m/s, 21°C
20 points at 0.3m/s, 22°C
15 points at 0.4m/s, 22°C ( ) ( )
( ) ( )
2
2.1
4.1
6.1
15.01.082220
15.08
4
3
2
1
-=
-=
-=
-=
---=
---=
q
q
q
q xc x
V t t
%85
85.0
15203530
203530
=
=
= ADPI
Effective draft temperature, ( ) ( )15.08 ---= xc x V t t q
so if 30 points = -1.6
35 points = -1.4
20 points = -1.2
15 points = -2
ADPI = 85
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Air Diffusion Performance Index Selection Guide
35-160
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Air Diffusion Performance Index Ratio
L
T 25.0Throw distance atterminal velocity
0.25m/s
Characteristic
room length
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Terminal Velocity – Tv 0.25
.75 m/s
15.6
11.3 m
7.3 m
.25 m/s .50 m/s
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Characteristic Room Length LCharacteristic room length for various Air Diffusion Products
Diffuser Type
High Sidewall Register
Circular Ceiling Diffuser
& Swirl Diffusers
Sill Grille
Ceiling Slot Diffuser
Light Troffer Diffusers
Perforated, Louvered
Ceiling Diffusers
Characteristic Length (L)
Distance to wall perpendicular to jet
Distance to closest wall or intersecting air jet
Length of room in direction of flow
Distance to wall or mid plane between out lets
Distance to mid plane between outlets plus
distance from ceiling to top of occupied zone
Distance to wall or mid plane between out lets
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ADPI Selection Example
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Example Mapping Throw
2.7 m
6 m
A consulting engineer is selecting a diffuser for the room above.
The room requires 250 l/s at an NC no greater than 35.
E l M i Th
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Example Mapping Throw
3 m
2.7 m
1.5 m1.5 m
0.4 m 0.4 m
They selected 2 x CFP600/12, with 125l/s for each. Total air quantity 250l/s, with
a throw of 2.9m @ 0.25m/s. An NC value of 14.
Will the occupants be comfortable?
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E l M i Th
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Example Mapping Throw
2.7 m
3m 3m
If our selection 1 x CFP600/24 Radial Swirl diffuser.
Total volume 250l/s - Throw 3.1m @0.25m/s - NC = 26
Will the occupants be comfortable?
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Example Using ADPI
2.7 m
3 m 3 m
ADPI calculation = 03.13
1.325.0
==
L
T
ADPI range @ 130W/m2 for 80 target - ratio = 0.5-1.5
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ADPI Selection
L
T 25.0
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ADPI Selection
L
T 25.0
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ADPI Selection
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ADPI – Design Expectations
High APDI equates to High
Air Change Effectiveness (ACE) Value
ADPI method is effective for CAD (as low 50C)“Cold Air Distribution Design Manual” TR-106715 Research Project 3280-39)
ADPI Method is suitable for heating at
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Ventilation Effectiveness
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Ventilation Effectiveness – Air Change
Effectiveness (ACE)
ANSI/ASHRAE Standard 129-1997
ASHRAE Fundamentals F25-1997
Principally it is an evaluation of effective
mixing of the Supply/Outdoor
with Room/ Space Air
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Induction
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Induction, High Induction & Induction Ratios
High Induction means High Exit Velocity
High Induction means High Pressure
Higher pressure offsets (CAD) Design Savings
High Induction = Smaller Air flows or more
Diffusers or more Noise
I d ti Hi h I d ti & I d ti R ti
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Induction, High Induction & Induction Ratio
There is no accepted published methodfor determining the induction ratio of an
individual diffusion product
Induction Ratio = Primary Air / Induced Air
Temperature Measurements of Primary
Air, Discharge Air and Induced Air
Room Air Induction Equation
Induction Ratio QQx
Qo= C
Vo
Vx
QxWhere:
= Qo X CVo
Vx
C:
Vo:
Vx:
Qo:
Qx:= Supply volume m3/s= Induction volume at Distance
= Discharge Velocity m/s
= Velocity at distance m/s= Entrainment Coefficient
1.4 for infinite slots and 2.0for round free axial jets
=
Holyoake Swirl Diffusers Series CFP
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Holyoake Swirl Diffusers – Series CFP
CFP - 600/24
Aeff: 0.1110m2
Veff: 0.7-3m/s
Air Flow: 75-300L/SPa: 2-13
NC
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Induction, Room Induction - Room Induction Ratios Q
Room Induction Ratio Q = 17.28
Air Volume 200L/S = 2.16m/s Exit Velocity
3456 L/S
Swirl Diffuser
(Figure 9)
Room Induction Ratio Q = 21.6
Air Volume100L/S = 1.08m/s Exit Velocity
2160 L/S
Swirl Diffuser
(Figure 10)
Room Induction Ratio Q = 28.8
Air Volume 200L/S = 2.16m/s Exit Velocity
5760 L/S
Swirl Diffuser
(Figure 11)
CFP/600/20
Room Induction Ratio Q = 10.8
Air Volume100L/S = 1.08m/s Exit Velocity
1080 L/S
Swirl Diffuser
(Figure 8)
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Design Criteria ISO7730 – ASHRAE 55P
PVM Predicted Mean Vote - PPD
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• Metabolic Rate – Occupants Physical Activity
• Thermal Resistance of Clothing - Clo Value
• Air Temperature – Optimum Operative Temperature
• Mean Radiant Temperature
• Air Velocity – Mean Space Velocity
• Relative Humidity
Design Criteria ISO7730-ASHRAE 55P-APDI
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Thermal Comfort Considerations & Obligations
Design to a Predetermined PMV-PPD As a function of: Clothing, Metabolic Rate. Air temp, Radiant Temp, Velocity, Humidity
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Thermal Comfort Considerations & Obligations
Determine Ventilation rate for PerceivedIndoor Air Quality as a result of Occupant numbers and Building Materials
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Thermal Comfort Considerations & Obligations
Establish and Confirm ADPI Rating >80Effective Draft Temperature : local temperature, room average temperature, local velocity
( ) ( )15.08 ---= Vxtctxq
Establish required Flow Rate for Thermal Designin accordance with optimal operating temperature
Ensure Acoustics meet Environment standardsCategory (A) Category (B) Category (C)
Calculation for PMV for resultant PPD
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Calculation for PMV for resultant PPD
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Design & Selection Software
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Air Distribution Design Program
ADE:5.4
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Products
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Architectural Louvers
http://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdfhttp://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdf
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CSDF Fixed Pattern Linear Slot
http://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdfhttp://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdf
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CSD-P Flangeless Linear
http://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdfhttp://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdf
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LF1200 Flangeless Extruded
Linear Bar Diffuser
http://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdfhttp://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdfhttp://localhost/var/www/apps/conversion/AAA_Product_Information_All/AAA_Holyoake_Component_Manual/Holyoake_LouversBrochure40ppWEB.pdf
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Thankyou for Listening
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Predicted Mean Vote – Percentage Dissatisfied
P. Ole Fanger
Director, Professor, D.Sc.
International Centre for Indoor
Environment and Energy
Technical University of Denmark,
Building 402
DK-2800 Lyngby, Denmark.