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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.