designing equipment by using cfd benefits and pitfalls geert janssen advanced thermal transfer...

Designing equipment by using Designing equipment by using CFDCFD

Benefits and pitfallsBenefits and pitfalls

Geert JanssenAdvanced Thermal Transfer Equipment

A2TE

CFD - PhoenicsCFD - Phoenics

CORA2 – graduate studiesPhoenics user since 1985

– Analysis• Flow in intake manifolds of IC engines• Flow & heat transfer process industry

– Design from 1990• Heat transfer equipment

– Ovens and furnaces

Applied CFDApplied CFD

Better understanding– Flow– Heat transfer– Mass transfer– Chemics

Sensitivity analysisPriceworthyfast

Why limited CFD usageWhy limited CFD usage

Long learning curveSpecialists required

– Jargon– physics insight and knowledge ?– Standard rules from handbooks?

Design <-> modelling – Communication skills

Example - 1Example - 1

OvenPerforated plates

– Flow distributors

Example - 2Example - 2

Molten metal in tundishTarget

– Continuous casting– No slag inclusions– No bubbles

TundishTundish

Symmetric inflowSteady state ?No match with

experimental dataBlame on CFD?

Designing equipment & Designing equipment & CFDCFDRules of thumbStandard textbooksSome understanding of physicsCFD ‘tricks’Designers skills or strong

interaction with designer

Example 3 - ageing ovenExample 3 - ageing oven

Continuous belt ovenBase of lamp (automotive)3 lanes: 3 x 800 pcs/hrHeating to 200°C and holding for 4

hrsCooling to 50°CFloorspace approx. 5 m2

Temperature differences < 5°C

Ageing oven - 2Ageing oven - 2

Heat transfer and pressure drop from packed bed relations

Required velocities through belt– Heating section– Cooling section

Fan in holding section identical to those of other sections

Ageing oven - 3Ageing oven - 3

Ageing oven - 4Ageing oven - 4

Ageing oven - 5Ageing oven - 5

Ageing oven - 6Ageing oven - 6

CFD model took 3 daysConceptual design 2 weeks

Ageing oven - Ageing oven - 77

Ageing oven - Ageing oven - 88

Example 4 curing ovenExample 4 curing oven

Contact lensesAutomated processPolypropylene: 95°C ± 3°CAt least 15 minutes at 92°C

(minimum)Heating up in 10 – 12 minutesAluminium trays, 1300 grams

– 1 tray in 40 seconds

Curing oven - trayCuring oven - tray

Curing oven - analyticalCuring oven - analytical

Calculation of required heat transfer coefficient (mass – time)

High value needed (75 Wm-2K-1)Multiple jets

One heat-up zone– Costs (fan, controller, cabinet)

Curing oven - trayCuring oven - tray

Curing oven - trayCuring oven - tray

Curing oven - trayCuring oven - tray

Curing ovenCuring oven

Conclusions from tray calculations– Required air-inlet temperature >

105°C

Curing oven – cross Curing oven – cross sectionsection

Curing oven - power Curing oven - power changechange

Curing oven - belt levelCuring oven - belt level

Curing oven – CFD modelCuring oven – CFD model

CFD models: 2 weeksConceptual design 4 weeks

ConclusionsConclusions

Use of CFD can be very profitableOften CFD alone does not ‘do the

trick’– Handbooks– Rules– Experience