indoor air distribution

8/16/2019 indoor air distribution

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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

[email protected]/s

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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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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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)


Air Volume100L/S = 1.08m/s Exit Velocity

2160 L/S

Swirl Diffuser

(Figure 10)


Air Volume 200L/S = 2.16m/s Exit Velocity

5760 L/S

Swirl Diffuser

(Figure 11)

CFP/600/20

[email protected]/s

[email protected]/s


Air Volume100L/S = 1.08m/s Exit Velocity

1080 L/S

Swirl Diffuser

(Figure 8)

[email protected]/s

[email protected]/s


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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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Determine Ventilation rate for PerceivedIndoor Air Quality as a result of Occupant numbers and Building Materials


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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



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CSD-P Flangeless Linear



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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.

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