emerging technologies in room (suite) pressure control ...cctr/seminar/seminar3.pdf · performance...

Emerging Technologies in Room (Suite) Pressure Control, Performance Modeling and Design Practices

Wei Sun, P.E.

ASHRAE Principal, Director of Engineering

Engsysco, Inc. Ann Arbor, Michigan, USA

Emerging Technologies in Room (Suite) Pressure Control, Performance Modeling and Design Practices

Engsysco

Presented by

Wei Sun, P.E.ASHRAE

“Clean Spaces” Technical Committee (TC9.11) Chairman“Healthcare Facilities” Technical Committee (TC9.6) Member“Laboratory Systems” Technical Committee (TC9.10) Member

Principal, Director of EngineeringEngsysco, Inc.

Ann Arbor, Michigan, USAwww.engsysco.com

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

PurposesDirect desired flow patternsIsolate airborne cross contamination

DefinitionA technique that air pressure differences are created mechanically between rooms to introduce intentional air movement paths through room leakage openings. These openings could be either designated, such as doorways, or undesignated, such as air gaps around doorframes or other duct/piping penetration cracks.

How to achieveIt can be achieved by arranging the controlled volumes of supply, return, and exhaust airstreams to each room within the space.

Room Pressurization Technique

Introduction

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Air connection between two adjacent rooms is through connecting opening(s).

If a door between two rooms is open, the doorway will be the main designated flow path.

If the door is closed, then the leakage will be through undesignated paths, such as air gaps along doorframes, joints, pipe and duct penetrations and gaps around ceiling panels etc. Most of these controllable cracks (except for operable doors) in typical controlled spaces are required to be permanently sealed.

Leakage FlowsDoor Closed

Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

P1 > P2

IntroductionBasic Rules

P1 > P2

Leakage FlowsDoor Opened

Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Introduction

Basic Rules

To Achieve P1 > P2 ,

SA1 > (RA1+EA1), andSA2 < (RA2+EA2)

SA1 = (RA1+EA1) + Q SA2 + Q = (RA2+EA2)

Q is the leakage (transfer) air from Room 1 to Room 2, if both rooms are tightly sealed, except for the opening between rooms.

Leakage FlowQ

Leakage Opening

Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

The pressure drop (differential) across an opening (either a crack or a doorway) is strongly related with the leakage opening size (effective leakage area) and leakage flow through the opening.

To quantitatively achieve a desired room pressure (or, pressure differential between rooms), leakage openings and respective leakage airflows need to be studied together.

Introduction

Relationship between Leakage Flow, Leakage Areaand Pressure Drop across Leakage Path

Leakage Flow

ΔP

QA

Leakage Area

Pressure Differential

Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Power Equation: (Esq.. 1)

whereQ = volumetric flow rate CFM (L/s)ΔP = pressure drop across opening in. of water (Pa)C = flow coefficient CFM/(in. of watern) (L/s/Pan)n = flow exponent dimensionless

nPCQ )(Δ⋅=

Airflow through Leakage Opening

Leakage Flow

ΔP

QA

Leakage Area


Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Orifice Equation: (Esq.. 2)

whereQ = volumetric flow rate CFM (L/s)ΔP = pressure drop across opening in. of water (Pa)A = large designated opening area's) ft2 (m2)2610 = unit conversion factor dimensionless (I-P unit)840 = unit conversion factor dimensionless (SI unit)

Leakage Flow

ΔP

QA

Leakage Area


Room 1 Room 2

P2P1 SA1

RA1 + EA1

SA2

RA2 + EA2

Airflow through Large Designated Opening

PA2610Q Δ⋅⋅=

PA840Q Δ⋅⋅=

(I-P unit)

(SI unit)

Orifice Equation is more popularly used in design community

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Air Leakage Rate vs. Pressure Difference for Various Leakage Areas (Based on Orifice Equation)

0

100

200

300400

500

600

700

800

900

1,000

1,100

1,200

1,3001,400

1,500

1,600

1,700

1,800

1,900

2,000

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055 0.06 0.065 0.07 0.075 0.08

Pressure Differential Between Rooms (in.)

Leak

age

Flow

rate

(cfm

)

Leakage Area(Sq. in.)

20

40

60

80

100

120

140160

180200220

240

260

280

300

320340360380

400

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Large designated openings such as doorway can be easily measured. However irregular opening such as a crack can not be measured physically, there is other means to estimate the equivalent size, or called “Effective Leakage Area” (ELA).

For Existing Rooms:

Field “Blower Door Test” (ASTM 1987, CGSB 1986) to obtain more precious data.

For Future Rooms during design phase:

Use ASHRAE ELA tables for building components (doors, walls, joints, etc.) as estimated values.

Leakage Area Value Determination

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

ASTM “Blower Door” Test, - Traditional “Room Air-tightness Test”

Portable Pressurization Blower Test can produce a set of data of Q - ∆P, and a “power equation” curve fit with calculated constants (C, n, ELA) that defines a room’s unique and dynamic leakage characteristic.

Abnormal test ranges:ASTM (1987): 12.5 - 75 Pa

(0.05 - 0.30 in.)CGSB (1986): 5 - 50 Pa

(0.02 - 0.20 in.)

Labor intense, time consuming

Disruption to occupied spaces

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Power equation:

Once obtained Q - ΔP data set, C and n can be calculated:

“Blower Door Test” - Multiple-Point Test Data for Power Equation Curve Fitting

n)P(CQ Δ⋅=

∑ ∑

∑∑ ∑

= =

== =

Δ⋅−Δ

Δ⋅⋅−Δ⋅

= m

1k

m

1k

2k

2k

m

1kkk

m

1k

m

1kkk

)P(lnm)Pln(

)PlnQ(lnm)PlnQln(n

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛Δ⋅−

=∑∑==

m

PlnnQlnEXPC

m

1kk

m

1kk

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Opening Resistance Analysis

Q

Qi

P

PP i

PP i

Q

Leakage flow resistances connected in parallel and series

( )∑=

⎥⎦

⎤⎢⎣

⎡=

n

i i

T

ELA

ELA

12

1

1

∑=

=n

iTi

ELAELA1

ELAR 1=

Define:Leakage Flow Resistance R

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Room Pressurization Scenarios and Variable Relationship

Scennario 1: Room PrerssurizedSA - (EA+RA) = ΔV = ΣQ > 0

Total RoomSupply Airflow

(SA)

Total RoomExhaust and/orReturn Airflow

(EA+RA)

RoomPositively

Pressurized

+ Tota

l Roo

mSu

pply

Airf

low

(SA

)

Offset Flow ΔV

Tota

l Roo

m E

xhau

st

and/

or R

etur

n A

irflo

w

(EA

+RA

)

Total LeakageAirflows

ΣQ

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________


Scennario 2: Room Non-PrerssurizedSA - (EA+RA) = ΔV = ΣQ = 0


(SA)


(EA+RA)

RoomNon-Pressurized

Tota

l Roo

m E

xhau

st a

nd/o

r R

etur

n A

irflo

w (E

A+R

A)

Offset Flow

ΔV = 0

Tota

l Roo

mSu

pply

Airf

low

(SA

)

Total LeakageAirflowsΣQ = 0

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________


Scennario 3: Room De-prerssurizedSA - (EA+RA) = ΔV = ΣQ < 0


(SA)


(EA+RA)

RoomNegatively

De-pressurized-

Tota

l Roo

mSu

pply

Airf

low

(SA

)

Tota

l Roo

m E

xhau

st a

nd/o

r Ret

urn

Airf

low

(EA

+RA

)

Offset Flow ΔV

Total LeakageAirflows

ΣQ

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Central Air Handling System &Room Pressurization

SA = Volume of total supply air entering the space/zone

RA = Volume of total return air leaving the space/zone

EA = Volume of total exhaust air leaving the space/zone

OA = Volume of outside air drawn into the AHU

FA = Volume of relief air released from return air

RA-FA = Volume of recalculated air

Q = Volume of total leakage air through space shell/zone

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Central Air Handling Unit &Room Pressurization

Two volumetric balance equations(Mass balance equation under assumption of same air density)

SA = RA + EA + Q(Volume balance for a space)

SA = OA + (RA – FA)(Volume balance for a typical AHU)

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Space Pressurization Ratio (R)

Define as the Ratio between SA and (RA+EA), as an indicator of pressurization scale:

By specifying SA values, R will be a function of Q. R Value Chart is convenient for design engineers to determine SA and (RA+EA) ratio during air distribution arrangement.

• Chart

QSASA

EARASAR

−=

+=

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Pressurization Ratio vs. Air Leakage Rate for Various Supply Air Rates

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Space versus Room Pressurization Ratios

The relationship between the space pressurization ratioand its individual room pressurization ratios:

The space pressurization ratio, an indicator of relative pressurization level, can be used to adjust air gains or losses among zones in order to arrange desired air flows within a building.

( )∑

=

= ⎥⎦⎤

⎢⎣⎡n

1i i

i

RSASA

1 R

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Adjacent Rooms under Various Pressures

If a room has several leakage openings with adjacent rooms, the room’s pressurization ratio is:

∑=

−= n

iiR

RR

QSA

SAR

1

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Pressure Differential and Crack Air VelocityCriterion 1 (Pressure Differential ΔP)For single room:ΔP: 0.05 in. of water (12.5 Pa)

For multiple-room space with staged pressurizations:ΔP: 0.02 in. ~ 0.03 in. (5 Pa ~ 7.5 Pa) for each pressure step

Criterion 2 (Average Crack Velocity V)100 fpm (30 M/m)

Pressurization Criterion

Unit Pressurization Criterion Comparison Basis

Pressure Differential ΔP

In

0.0015

0.01

0.02

0.03

0.04

0.05

0.06

0.08

0.10

Crack Leakage Velocity V

fpm 109

374

587

764

920

1,064

1,198

1,444

1,670

Eq. (1), when n=0.65

Large Opening Velocity V

fpm 100

261

369

452

522

584

639

738

825

Eq. (2a)

From comparison below, the pressure criterion of ΔP = 0.05 in. is much more conservative than the velocity criterion of V = 100 fpm.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Room Pressurization Variables and Control Strategies

Airflow differential between entering airflow (supply airflow, SA) and leaving airflow (exhaust and/or return airflows, EA+RA), normally called “offset” value (ΔV), which equals the total leakage airflow (ΣQ) of the room.To maintain a specific room pressure value, the room’s offset airflow (ΔV) must be controlled and maintained at the appropriate value. Room’s offset airflow can be controlled directly or indirectly. The treatment of the room “offset” value defines a pressurization control strategy. Typical pressurization control techniques are: Direct Pressure-Differential Control, Differential Flow Tracking Control, Hybrid Control and Adaptive Control.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Direct Pressure-Differential Control (DP)Utilizes a pressure differential sensor to measure the pressure difference between a controlled room and an adjacent space such as a corridor. It basically ignores the specific offset value as required, instead, it directly controls the airflow control devices to achieve the required pressure differential.

Suitable for a tightly constructed room with limited traffics. Door switch is recommended to trigger a reduced pressure differential set-point if the door opens.

FumeHood

Velocity Sensor

Sash Sensor

or

Hood Valve & Controller

CHEMICAL LAB

CORRIDOR

ROOM CONTROLLER

SUPPLY AIR

Total Exhaust Air from RoomHood

ExhaustHood Exhaust

Room ExhaustValve

Room SupplyValve

DSDoor Switch

T

Leakage Air

Leakage Air

Total Supply Air to Room

DPDP

Sensor

Thermostat

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Differential Flow Tracking Control (DF)Intuitively assumes an offset value which is used as a flow difference between the entering and leaving airflows to control their respective airflow devices. Maintain the same offset value throughout the operation to keep pressurization constant, or maintain a constant percentage offset value which creates a weaker pressurization at lower flow.

Suitable for open-style rooms or rooms with frequent traffics

FumeHood

Velocity Sensor

Sash Sensor

or


CHEMICAL LAB

CORRIDOR

ROOM CONTROLLER

SUPPLY AIR


ExhaustHood Exhaust

Room ExhaustValve

Room SupplyValve

DSDoor Switch

T

Leakage Air

Leakage Air

Flow Sensor

Flow Sensor

Total Supply Air to RoomDP

DPMonitor

Thermostat

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Hybrid Control (DP+DF)Combines the pressure accuracy of the direct pressure differential control and the stability of the flow tracking control. The offset value is reset-able based on pressure differential reading. The offset value reset schedule is pre-determined and controller’s parameters are fixed manually in field. This method is also called “cascaded” control.

Suitable for open-style rooms or rooms with frequent traffics

FumeHood

Velocity Sensor

Sash Sensor

or


CHEMICAL LAB

CORRIDOR

ROOM CONTROLLER

SUPPLY AIR


ExhaustHood Exhaust

Room ExhaustValve

Room SupplyValve

DSDoor Switch

T

Leakage Air

Flow Sensor

Flow Sensor

Total Supply Air to Room

DPDP Sensor

Leakage Air

Thermostat

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Multiple-Room (Suite) Pressure Control Strategies

Single room control technologies often cause problems in Suite Pressure Control during air balancing, since the following phenomena are often ignored:

Adjusting one room’s offset value will impact adjacent rooms’ air pressures if they were just balanced earlier.

Example - Pharmaceutical Aseptic Suite

One room’s air gain could be another room’s air loss through leakages.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Adaptive Control (DP+DF+AD)The three traditional methods (DP, DF and DP+DF) are either to “ignore”, “assume” or “manually fix in field” the offset value respectively.

The adaptive (DP+DF+AD) approach directly accounts for leakage flows between the rooms in a suite. It controls all rooms’ pressures all together as an optimized system, instead of controlling each room pressure independently. It actively adjusts the flow offset of each room according to an on-line pressurization model. The model uses flow and pressure differential measurements to estimate the leakage values between the rooms and adjust flow offset of each room automatically.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Automated Room Air-tightness Test –Pre-condition for Truly Adaptive Control

Similarly as “Blower Door Test”, but fully automated. A room’s unique dynamic leakage characterization can also be automatically achieved by digital controller, precision pressure differential sensor (±0.001 in./0.25 Pa) and airflow control devices (±5%). These devices are often permanently installed in lab and clean room environments.This automated pressurization test (Q-∆P data set) is faster and cheaper, and can be handled remotely.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Adaptive Control (Example: Control of Multiple Rooms)

CLEANESTROOM0.08 In.

CLEANERROOM0.06 In.

AIRLOCK0.03 In.

GENERALCHEMICAL LAB- 0.02 In.

CONTAINMENTLAB- 0.06 In.

Designated Leakage Flow

Supply Air

Valve

ExhaustAir

Valve

ReturnAir

Valve

Minor LeaksThru. Cracks

CORRIDOR0.00 In.

DP

DPDPDP

DPDP


Sensor

Manifolded or Open to Corridor

DSDSDS

DS

DS

DS

Legend

SUITECONTROLLER

Door Switch

SUITECONTROLLER

Valve Position Outputs

DoorSwitchInputs

Valve Flowrate Inputs

Room Pressure Inputs

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Air Flows between Rooms

Airflow Between Rooms

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Personnel Flows between Rooms

Personnel Flow Between Rooms

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

More Considerations

Correction Factors(Refer to ASHRAE Handbooks 1999 & 2001, detailed procedures will be included in the next phase of the study)

Stack effectWind effectInterior zones with high temperature or humidity differences

Safety Factors(Detailed procedures will be included in the next phase of the study)

Room background leaksDuct leaksAHU unit leak

Correction and Safety Factors – Add as required

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Samples of Pressurization Control Devices

Flow Control & Measure Pressure Measure

Static Pressure Measuring ProbesStatic Pressure Measuring Probes

Pressure Transmitter Pressure Transmitter

Pressure Transmitter and Monitor

Pressure Transmitter and Monitor

Control DamperControl Damper

Air Valve –Type 1Air Valve –Type 1

Air Valve –Type 2Air Valve –Type 2

Air Valve -Type 3Air Valve -Type 3

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Case Study - Airflow Resistance and Leakage Flow Simulation

- Room Numbe - Wall - Flow Direction - Induced Flow (by Pressurization) - Node (Room) - Flow Resistance @ Major Opening - Flow Resistance @ Minor Opening - Forced Flow (by Fan)

Network Flow with Major Openings Only Network Flow with Major and Minor Openings

RMX

RM1RM2

RM3

RM4 RM5

RM6

RM1RM2

RM3

RM4 RM5

RM6

Major and minor leakage openings, connection in parallel and series

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Modeling of Transient Pressurization

θ L

W

Room 1

Room 2

P1

P2

Wall

Swing Door

P

Transient Flow Through Swing Door

P1 > P2

1. Pressurization Loss Characteristic During a Swing Door Opening or Closing

⎟⎠⎞

⎜⎝⎛ ⋅

⋅⋅⋅=⋅=2

sin2)()(

tWHLHAtt

ω

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛⋅⋅=

2sin2 )(

)(t

tWL

θ

)600( o≤≤ θ

WHAt

⋅=)(

)9060( o≤< θ

where,

L=width (gap) of door opening in. (cm)W=width of door in. (cm)θ=angle of door opening degreeω=speed of door turning degree/sec.t=time sec. H=door height in. (cm)A=effective door opening width (gap) in2(cm2)

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________


Transient Pressure Differential Across When A Swing Door Opens

0

10

20

30

40

50

60

70

0 0.5 1 1.5 2 2.5 3

Time of Door Opening (Second)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)

0

10

20

30

40

50

600 10 20 30 40 50 60 70 80 90

Angle of Swing Door Opening (Degree)

Wid

th (G

ap) o

f Doo

r Ope

ning

(in.

)

Pressure Drop Across DoorW idth of Door Opening

Automatic Swing Door Opens to 90o in 3 Seconds; Door Size 4 ft. (W ) x 7 ft. (H).Rooms Across The Door/Wall Are Maintained with Constant Supply and Return Flows. Initial Pressure Differential Across Door is 68.9 Pa, it drops to 1 Pa less than 2 seconds.

1. Pressurization Loss Characteristic During a Swing Door Opening or Closing

Airlock Room Pressure Profile

-0.010-0.0050.0000.0050.0100.0150.0200.0250.0300.0350.0400.0450.0500.0550.0600.0650.0700.0750.0800.0850.0900.0950.100

Airlock Sliding Door Operation Cycle

Roo

m S

tatic

Pre

ssur

e (in

. WC

)

First Door Opening First Door Closing Both Doors Closed Second Door Opening Second Door Closing

Cleanroom

Airlock

Corridor

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________


L

WP

Transient Flow Through Sliding Door

P1 > P2

Wall

Room 1 P1

Sliding Door

Room 2 P2

2. Pressurization Loss Characteristic During a Sliding Door Opening or Closing

where,

L=width (gap) of door opening in. (cm)

W=width of door in. (cm)

t=time sec.

s=speed of door opening in./sec. (cm/sec.)

H=door height in. (cm)

A=effective door opening width (gap) in2(cm2)

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________


Transient Pressure Differential Across When A Sliding Door Opens

0

10

20

30

40

50

60

70

0 0.5 1 1.5 2 2.5 3Time of Door Opening (Second)

Pres

sure

Diff

eren

tial A

cros

s D

oor

(Pa)

0

10

20

30

40

50

60

Wid

th (G

ap) o

f Doo

r O

peni

ng (i

n.)

Pressure Drop Across DoorWidth of Door Opening

Automatic Sliding Door Opens at Speed of 16 in./sec.; Door Size 4 ft. (W) x 7 ft. (H);Rooms Across The Door/Wall Are Maintained with Constant Supply and Return Flows, Initial Pressure Differential Across Door is 68.9 Pa, it drops to 1 Pa around 2 seconds.

2. Pressurization Loss Characteristic During a Sliding Door Opening or Closing

Pressure Differentials Between Rooms

-0.010-0.0050.0000.0050.0100.0150.0200.0250.0300.0350.0400.0450.0500.0550.0600.0650.0700.0750.0800.0850.0900.0950.100

Airlock Sliding Door Operation Cycle

Pres

sure

Diff

eren

tial b

etw

een

Room

s (in

. WC)

First Door Opening First Door Closing Both Doors Closed Second Door Opening Second Door Closing

DP (Cleanroom and Corridor)

DP (Door 1) DP (Door 2)

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Door Opening Transient Impact on Pressurization Control

Any passive motor-driven or actuator-driven HVAC system (such VAV box or valve) will not have enough time to react effectively to prevent possible cross contamination.

A single barrier door could cause a short duration of backflow contamination until the motor or actuator completes the modulation cycle of re-balancing, additional means to prevent possible backflow contamination, such as double-door airlock is necessary.

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Dynamic Pressurization Control Strategies- Airlock

CLEANROOM

AIRLOCK

+CORRIDOR

++

+++

AIRFLOW

CASCADING AIRLOCK

AIRFLOW CLEANROOM

AIRLOCK

+CORRIDOR

++

-

AIRFLOW

BUBBLE AIRLOCK

AIRFLOW

CLEANROOM

AIRLOCK

+CORRIDOR

- -

-

AIRFLOW

SINK AIRLOCK

AIRFLOW CLEANROOM

AIRLOCK

-CORRIDOR

++

-

AIRFLOW

AIRFLOW

- -AIRLOCK

DUAL COMPARTMENT AIRLOCK

Air Lock Type

CascadingBubbleSinkDual-Compartment

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Dynamic Pressurization Control Strategies- Airlock

Wait!Wait!

Corridor

Cleanroom

Airlock (Cascading)ΔPDoor 1

ΔPDoor 2

ΔPRooms

0.06 in.

0.03 in.

0.00 in.

-6 -3 0 3 6

-6 -3 0 3 6

-6 -3 0 3 6

Airlock Physical Model Network Flow Simulation

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Result of Network Flow Simulation

Wait!

Corridor

Clean room

Airlock (Cascading)ΔPDoor 1

ΔPDoor 2

ΔPRooms

0.06 in.

0.03 in.

0.00 in.

-6 -3 0 3 6

-6 -3 0 3 6

-6 -3 0 3 6

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

CFD Model to Study Airlock Transient Performance - Physical Conditions

(12000 CFM, 75 ACH)

(2100 CFM, 75 ACH)

(560 CFM, 10ACH)

11948 CFM

2078 CFM

Leakage 52 CFM

Leakage 73 CFM

Clean Room: 10000Airlock: 10,000Corridor: 100000

(12000 CFM, 75 ACH)

(2100 CFM, 75 ACH)

(560 CFM, 10ACH)

Leakage 52 CFM

Leakage 73 CFM11948 CFM

2078 CFM

Clean Room: 10000Airlock: 10,000Corridor: 100000

Case 1 – Class 10,000 Case 2 – Class 100

(48000 CFM, 300 ACH)8400 CFM, 300 ACH)

560 (CFM, 10ACH)

Leakage 52 CFM

Leakage 73 CFM

47948 CFM8378 CFM

Clean Room: 100Airlock: 100Corridor: 100000

(48000 CFM, 300 ACH)8400 CFM, 300 ACH)

560 (CFM, 10ACH)

Leakage 52 CFM

Leakage 73 CFM

47948 CFM8378 CFM

Clean Room: 100Airlock: 100Corridor: 100000

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Steady State Airflow Distribution

Case 1 –Class 10,000 Case 2 – Class 100

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Steady State Cleanroom Particle Concentration


___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Corridor Particles Enter Airlock Room


___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Airlock Particles Enter Clean Room and Corridor


___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Airlock Particles Enter Clean Room and Corridor


___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Variation of Corridor Particle Concentration


___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Airlock Door Transient PerformanceProfile of Pressure Differential Across Door

When Door Is Opening & Closing (Initial Condition: -15 Pa = -0.06 In.)

-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s Do

or (P

a)

Test 1Test 2Test 3Average

Door Opening Door Closing

Profile of Pressure Differential Across Door When Door Is Opening & Closing

(Initial Condition: 5 Pa = 0.02 In.)

-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)



Profile of Pressure Differential Across Door


-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)





-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)

Test 1Test 2Test 3Average Door Opening Door Closing



-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)





-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)




When Door Is Opening & Closing (Initial Condition: 0 Pa = 0 In.)

-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s D

oor (

Pa)





-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time (Sec.)

Pres

sure

Diff

eren

tial A

cros

s Do

or (P

a)



Pressure Differential Across Cleanroom Door During Walk-Through

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Contamination Risk Factor (CRF)CRF is a criterion which is to quantity the effectiveness of cleanroom particle containment in preventing the airborne particles migration into cleanroom.

CRF = PC / PO

CRF = Contamination Risk FactorPC = Number of Particles inside Protected Cleanroom Near DoorPO = Number of Particles at Corridor Entrance Near Door

This criterion is applied for a “Barrier Device” which is to minimize particle migration. This barrier could be single door, an airlock (two doors in series), mini environment, or glove box.

The lower of the CRF level, the better barrier’s performance, or the better de-contamination effectiveness. This expression can not only apply for airborne particle, but also for airborne microorganism egress, in which the particle counts will be replaced with Colony Forming Unit (CFU).

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Particle Concentrations & CRF Across Cleanroom Door Under Various Pressure Differentials

Airborne Particle Contamination Risk Factor (CRF) Under Various Pressure Differentials Across Cleanroom Door

(Note: 5 Pa = 0.02 In., Particle Measured @ 0.5 µm)

0%

5%

10%

15%

20%

25%

-15 -10 -5 0 5 10 15 20

Initial Pressure Differential Across Door (Pa)

Con

tam

inat

ion

Ris

k Fa

ctor

(CR

F, %

)

Door Opening & Closing W/O People TrafficA Person Walks Through Door

Particle Concentrations Across Cleanroom Door When Door is Opening & Closing

(Initial Condition: Depressurization @ -15 Pa = -0.06 In. )

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Par

ticle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )

Inside Cleanroom Door Average Outside Cleanroom Door Average

Door Opening

Door Clos ing

CRF= 18.9%


(Initial Condition: Pressurization @ 5 Pa = 0.02 In. )

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Part

icle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )


Door Opening

Door Closing

CRF= 2.2%



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Par

ticle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )

Ins ide Cleanroom erage Door Av Outside Cleanroom Door Average

Door Opening

Door Closing

CRF= 8.5%



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Part

icle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )

Ins ide Clean rage room Door Ave Outside Cleanroom Door Average

Door Opening

Door Closing

CRF= 0.7%



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Par

ticle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )


Door Opening

Door Closing

CRF= 6.9%



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Par

ticle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )


Door Opening

Door Clos ing

CRF= 0.8%

Airborne Particle Contamination Risk Factor (CRF) Under Various Pressure Differentials Across Cleanroom Door

(Note: 5 Pa = 0.02 In., Particle Measured @ 0.5 µm)


(Initial Condition: Neutral @ 0 Pa = 0 In. )

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Part

icle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )

Ins ide Cleanroom Door Average Outside Cleanroom Door Average

Door Opening

Door Closing

CRF= 4.2%



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 21 22

Time (Sec.)

Part

icle

Con

cent

ratio

ns A

cros

s D

oor

(Cou

nts

/ FT3 )

11 12

Ins ide Cleanroom Door Average Outside Cleanroom Door Average

Door Opening

Door Closing

CRF= 0.3%

Regression Curve:CRF= 0.0332e-0.1181*PD

R2 = 0.9656(No People Traffic)

Regression Curve:CRF = 0.0418e-0.0703*PD

R2 = 0.9129(With People Traffic)

0%

5%

10%

15%

20%

25%

-15 -10 -5 0 5 10 15 20

Initial Pressure Differential Across Door (Pa)

Con

tam

inat

ion

Ris

k Fa

ctor

(CR

F, %

)

Door Opening & Closing W/O People TrafficA Person Walks Through DoorRegression (Door Opening & Closing W/O People Traffic)Regression (A Person Walks Through Door)

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Dynamic Pressurization Control Strategies – Adjustable Pressure Stabilizer

A leakage regulator, controllable pressure relief damper across a wall to maintain a minimum required pressurization. When a door is normally closed, this damper should stay open and maintain normal pressure differential; when the door opens, the damper shall be automatically closed either by spring-loaded or counter-weight gravity damper, and maintain a lower while acceptable pressure differential.

PressureStabilizer

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Importance

Air-handling unit controlLab HVAC controlPrefabricated clean roomPrecision environmental test chamberSmoke management control Air distribution system

In addition to design engineers and research scientists, the information presented may also benefit manufacturers in the fields of:

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Pressurization Study

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

Q & A

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

___________________________________

emerging technologies in room (suite) pressure control ...cctr/seminar/seminar3.pdf · performance...

Documents