Air Flow Analysis in Air Flow Analysis in Pharmaceutical “Clean Pharmaceutical “Clean

Rooms”Rooms”

Patrick Phelps Patrick Phelps

( Flowsolve( Flowsolve ))

andand

Richard RoweRichard Rowe

( Clean Room Construction ( Clean Room Construction Ltd )Ltd )

IPUC 8 - Luxembourg - May 2000IPUC 8 - Luxembourg - May 2000

Air Flow Analysis in Air Flow Analysis in Pharmaceutical “Clean Pharmaceutical “Clean Rooms”Rooms”

Industrial ContextIndustrial Context Health and Safety IssuesHealth and Safety Issues Application to an Existing RoomApplication to an Existing Room Application to New Ventilation Application to New Ventilation

DesignsDesigns ConclusionsConclusions Experimental VerificationExperimental Verification

““Clean Rooms”Clean Rooms”

Areas concerned with the Areas concerned with the

preparation, processing and preparation, processing and packaging packaging

of pharmaceutical productsof pharmaceutical products

Strict codes of practice employed to Strict codes of practice employed to eradicate risk of product eradicate risk of product contaminationcontamination

““Clean Rooms”Clean Rooms”

Personnel access controlledPersonnel access controlled

2-layer sterile over-clothing2-layer sterile over-clothing

Equipment sterilised before entryEquipment sterilised before entry

Strict cleansing proceduresStrict cleansing procedures

Particular attention to ventilationParticular attention to ventilation

Ventilation of “Clean Ventilation of “Clean Rooms”Rooms”

Design and performance of air Design and performance of air supply, filtration, and extraction supply, filtration, and extraction arrangements must meet exacting arrangements must meet exacting standardsstandards

• Positive pressure areasPositive pressure areas

• Use of Laminar Flow Units (LFU’s)Use of Laminar Flow Units (LFU’s)

“ “ Laminar Flow Units ”Laminar Flow Units ”

Devices which deliver a controlled Devices which deliver a controlled

down-draught of re-filtered air down-draught of re-filtered air

over sensitive regionsover sensitive regions

• preparation areaspreparation areas• processing areasprocessing areas• packaging areaspackaging areas• storage areasstorage areas

Air Flow Analysis in Air Flow Analysis in Pharmaceutical “Clean Pharmaceutical “Clean Rooms”Rooms”

CFD Application to Air CFD Application to Air Flow Analysis in “Clean Flow Analysis in “Clean

Rooms”Rooms”

ContextContext

Upgrade of ventilation system in Upgrade of ventilation system in

a suite of “ clean rooms” at a a suite of “ clean rooms” at a

UK pharmaceutical companyUK pharmaceutical company

CFD Application to Air CFD Application to Air Flow Analysis in “Clean Flow Analysis in “Clean

Rooms”Rooms”

ObjectiveObjective

Use CFD to ensure exacting Use CFD to ensure exacting requirementsrequirements

can be met , following installation of can be met , following installation of aa

number of LFU’s .number of LFU’s .

CFD Application to Air CFD Application to Air Flow Analysis in “Clean Flow Analysis in “Clean

Rooms”Rooms”

WorkscopeWorkscope

3 rooms selected as representative 3 rooms selected as representative

examples of areas being upgradedexamples of areas being upgraded

• Room 30Room 30• Room 23Room 23• Room 42Room 42

Modelling Considerations Modelling Considerations - 1- 1

Irregular shaped domainsIrregular shaped domains

Internal Obstructions to flowInternal Obstructions to flow

Cartesian grid employedCartesian grid employed

K-e (Chen) turbulence model usedK-e (Chen) turbulence model used

Buoyancy important in transientBuoyancy important in transient

(otherwise assume isothermal) (otherwise assume isothermal)

Modelling Considerations Modelling Considerations - 2- 2

Dependent variables solvedDependent variables solved• pressure, ppressure, p• lateral velocity component, Ulateral velocity component, U• vertical velocity component, Vvertical velocity component, V• Longitudinal velocity component, WLongitudinal velocity component, W• Turbulence kinetic energy, kTurbulence kinetic energy, k• Turbulence energy dissipation rate, eTurbulence energy dissipation rate, e

• residence time parameter, tresidence time parameter, tresres

• (temperature, T (for transient)(temperature, T (for transient)

Modelling Considerations Modelling Considerations - 3- 3

Boundary ConditionsBoundary Conditions Air supply ductsAir supply ducts

• prescribed sources of mass, momentum, prescribed sources of mass, momentum, turbulence and residence timeturbulence and residence time

Air Extract ductsAir Extract ducts• specified fixed-pressure outlet sinksspecified fixed-pressure outlet sinks

LFU’sLFU’s• inlets and outlets specified as aboveinlets and outlets specified as above

Representation of LFU’sRepresentation of LFU’s

Air flow in individual units not solvedAir flow in individual units not solved treated as internal blockages in domaintreated as internal blockages in domain air discharged from base at prescribed air discharged from base at prescribed

raterate matching intake from front facematching intake from front face interactive updating of discharge interactive updating of discharge

residence timeresidence time constant internal residence time constant internal residence time

assumedassumed

Room 30Room 30

Small room - 4.94 x 5.94 x 2.92 m.Small room - 4.94 x 5.94 x 2.92 m. Used for processing, filling and Used for processing, filling and

packaging of productspackaging of products Contains central plinth with filling-Contains central plinth with filling-

machine enclosure abovemachine enclosure above Conveyor-linked trays outboard of Conveyor-linked trays outboard of

enclosure, for containers & finished enclosure, for containers & finished goods goods

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 SimulationsRoom 30 Simulations

Steady flow patterns Steady flow patterns “ before ”“ before ”• LFU’s in enclosure onlyLFU’s in enclosure only

Steady flow patterns Steady flow patterns “ after ”“ after ”• following fitment of 10 new LFU’sfollowing fitment of 10 new LFU’s

75,000 node 3-D model75,000 node 3-D model• Distribution : 50 x 30 x 50Distribution : 50 x 30 x 50

Room 30 - “ After ”Room 30 - “ After ”

Room 30 SimulationsRoom 30 Simulations

ObjectivesObjectives Check for “dead zones”Check for “dead zones” ensure ventilation criteria metensure ventilation criteria met

CriteriaCriteria 25 Air changes per hour25 Air changes per hour (residence time 144 seconds)(residence time 144 seconds)

Room 30 - Sectional Room 30 - Sectional PlanesPlanes

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Room 30 - “ Before ”Room 30 - “ Before ”

Room 30 - “ After ”Room 30 - “ After ”

Complex flow paths between inlet Complex flow paths between inlet and outletand outlet

Pattern complicated by LFU intake Pattern complicated by LFU intake extraction flowsextraction flows

air has to pass around central plinth air has to pass around central plinth and filling-machine enclosureand filling-machine enclosure

air in near-side passage has to “run air in near-side passage has to “run gauntlet” of LFU’sgauntlet” of LFU’s

Room 30 Ventilation Room 30 Ventilation SummarySummary

(after refurbishment)(after refurbishment)

Outflow-weighted residence time of Outflow-weighted residence time of 121 seconds meets client criterion121 seconds meets client criterion

““near” extract air considerably near” extract air considerably “older” than “far” extract air“older” than “far” extract air

some “dead zones” still apparentsome “dead zones” still apparent evidence of entrainment into more evidence of entrainment into more

than one unitthan one unit

Room 30 Ventilation Room 30 Ventilation SummarySummary

(after refurbishment)(after refurbishment)

“ “ Dead Zones ” - beforeDead Zones ” - before

“ “ Dead Zones ” - afterDead Zones ” - after

LFU intake times - 1LFU intake times - 1

LFU Unit intake times - 2LFU Unit intake times - 2

0

20

40

60

80

100

120

140

160

A1 A2 A3 A4 B1 B2 C1 C2 D1 D2

AFTERBEFORE

LFU Unit intake times - 3LFU Unit intake times - 3

Units D1, D2, B2, C2, A1 receive Units D1, D2, B2, C2, A1 receive considerably fresher air than their considerably fresher air than their neighbours A2-A4, B2 and C1neighbours A2-A4, B2 and C1

Air entering A4 is 2.2 times older Air entering A4 is 2.2 times older than that entering D1than that entering D1

Air leaving A4 exceeds air-change Air leaving A4 exceeds air-change criterion en route to outletcriterion en route to outlet

ConclusionsConclusions

““Residence time” analysis concept Residence time” analysis concept

adds considerable value to vector adds considerable value to vector

and contour plots in assessment of and contour plots in assessment of

complex ventilation flows.complex ventilation flows.