Air Flow Analysis in Pharmaceutical “Clean Rooms” Patrick Phelps ( Flowsolve ) and Richard Rowe ( Clean Room Construction Ltd ) IPUC 8 - Luxembourg - May 2000

Air Flow Analysis in Pharmaceutical “Clean Rooms” Industrial Context Health and Safety Issues Application to an Existing Room Application to New Ventilation Designs Conclusions Experimental Verification

“Clean Rooms” Areas concerned with the preparation, processing and packaging of pharmaceutical products Strict codes of practice employed to eradicate risk of product contamination

“Clean Rooms” Personnel access controlled 2-layer sterile over-clothing Equipment sterilised before entry Strict cleansing procedures Particular attention to ventilation

Ventilation of “Clean Rooms” Design and performance of air supply, filtration, and extraction arrangements must meet exacting standards Positive pressure areas Use of Laminar Flow Units (LFU’s)

“ Laminar Flow Units ” Devices which deliver a controlled down-draught of re-filtered air over sensitive regions preparation areas processing areas packaging areas storage areas

Air Flow Analysis in Pharmaceutical “Clean Rooms”

CFD Application to Air Flow Analysis in “Clean Rooms” Context Upgrade of ventilation system in a suite of “ clean rooms” at a UK pharmaceutical company

CFD Application to Air Flow Analysis in “Clean Rooms” Objective Use CFD to ensure exacting requirements can be met , following installation of a number of LFU’s .

CFD Application to Air Flow Analysis in “Clean Rooms” Workscope 3 rooms selected as representative examples of areas being upgraded Room 30 Room 23 Room 42

Modelling Considerations - 1 Irregular shaped domains Internal Obstructions to flow Cartesian grid employed K-e (Chen) turbulence model used Buoyancy important in transient (otherwise assume isothermal)

Modelling Considerations - 2 Dependent variables solved pressure, p lateral velocity component, U vertical velocity component, V Longitudinal velocity component, W Turbulence kinetic energy, k Turbulence energy dissipation rate, e residence time parameter, tres (temperature, T (for transient)

Modelling Considerations - 3 Boundary Conditions Air supply ducts prescribed sources of mass, momentum, turbulence and residence time Air Extract ducts specified fixed-pressure outlet sinks LFU’s inlets and outlets specified as above

Representation of LFU’s Air flow in individual units not solved treated as internal blockages in domain air discharged from base at prescribed rate matching intake from front face interactive updating of discharge residence time constant internal residence time assumed

Room 30 Small room - 4.94 x 5.94 x 2.92 m. Used for processing, filling and packaging of products Contains central plinth with filling-machine enclosure above Conveyor-linked trays outboard of enclosure, for containers & finished goods

Room 30 - “ Before ”

Room 30 Simulations Steady flow patterns “ before ” LFU’s in enclosure only Steady flow patterns “ after ” following fitment of 10 new LFU’s 75,000 node 3-D model Distribution : 50 x 30 x 50

Room 30 - “ After ”

Room 30 Simulations Objectives Check for “dead zones” ensure ventilation criteria met Criteria 25 Air changes per hour (residence time 144 seconds)

Room 30 - Sectional Planes

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 - “ Before ”

Room 30 - “ After ”

Room 30 Ventilation Summary (after refurbishment) Complex flow paths between inlet and outlet Pattern complicated by LFU intake extraction flows air has to pass around central plinth and filling-machine enclosure air in near-side passage has to “run gauntlet” of LFU’s

Room 30 Ventilation Summary (after refurbishment) Outflow-weighted residence time of 121 seconds meets client criterion “near” extract air considerably “older” than “far” extract air some “dead zones” still apparent evidence of entrainment into more than one unit

“ Dead Zones ” - before

“ Dead Zones ” - after

LFU intake times - 1

LFU Unit intake times - 2

LFU Unit intake times - 3 Units D1, D2, B2, C2, A1 receive considerably fresher air than their neighbours A2-A4, B2 and C1 Air entering A4 is 2.2 times older than that entering D1 Air leaving A4 exceeds air-change criterion en route to outlet

Conclusions “Residence time” analysis concept adds considerable value to vector and contour plots in assessment of complex ventilation flows.