Download - Air Cooling Design for Machine Components
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Air Cooling Design for Machine Components
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Air Cooling Design for Machine Components
Presenter: Peter van Emmerik
Faculty Advisor: Dr. LeRoy Alaways
Department of Mechanical Engineering Villanova University
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Problem Statement Design a cooling system to reduce the
steady state temperature of a given heated structure from 100 C to 50 C using compressed air
Accomplish goal using less than 18 normal liters per minute.
Create both finite element analysis (FEA) and computational fluid dynamics (CFD) simulation models validated by empirical results
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Background As the demands on modern machinery
used for high accuracy positioning systems grow, greater emphasis is placed on thermal control
Bearings systems can be sensitive to thermal gradations affecting life
Machine component C.T.E. differences coupled with uniform and non uniform thermal excursions may lead to accuracy issues
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BackgroundHeated Fixture
Base (Al)
Heat Block (Al)
Film Heate
r
Stand-offs (SS)Thermocouple
locations
Fixture representative of linear servo motor
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Methodology
Advantages of using compressed air Compressed Air Cooling
Low Cost
Packaging Efficiency
Reliable
Simple
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Methodology
Three delivery methods examined Log Manifold Pinched Tube Air Knife
Two orientations to target surface Cross Flow Impinging Flow
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Methodology - Designs
Log Manifold Simple tube Capped end Cross drilled
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Methodology - Designs
Pinched Tube Simple tube Pinched End
Shapes flow Increases velocity
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Methodology - Designs
Air Knife Machined Manifold Wide Slit Exit Enhanced Air
Entrainment
Manifold
Spacer
Cover
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Apparatus Test Equipment
Thermocouples k-type Data Collection Box Air Flow Meter Heater Voltage Controller
Arrangements Cross Flow Impinging Flow
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Test Procedure Apply power Reach un-cooled steady state temperature Turn on air delivery system Reach cooled steady state temperature Repeat for all designs and orientations
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ResultsUn-cooled baseline
0 10 20 30 40 50 60 70 80 90 1000
20
40
60
80
100
120
Ambient Base Heat Block
Time (minutes)
Tem
pera
ture
(deg
C)
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ResultsCross Flow
0 100 200 300 400 50020
30
40
50
60
70
80
90
100
110
Ambient Base Heat Block
Time (minutes)
Tem
pera
ture
(deg
C)
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ResultsSteady State Temperature Comparison
*Design Goal: 50 deg CAir Consumption: 17.2 nL/min for all tests
BASE Temperature (° C) Cross Flow Impinging Flow
Air Knife 29.8 28.9Pinched Tube 32.4 29.5Log Manifold 34.7 32.6
Ht Block Temperature (deg C) Cross Flow Impinging Flow Goal met*
Air Knife 44.0 41.8 þPinched Tube 46.3 43.1 þLog Manifold 57.5 55.5 ý
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Simulation Simulation used empirical data to build accurate
simulation model Determine thermal conductance at interfaces
2000W/m2-C Heat loading from heater
15.5 Watts Convective heat transfer coefficient (h)
6.5W/m2-C for natural convection
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Simulation – Un-cooled Correlation Transient Un-cooled FEA vs Empirical
0 10 20 30 40 50 60 700
20
40
60
80
100
120
Base FEA Block FEA Base
Block Time (min)
Tem
pera
ture
(°C
)
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Simulation – Un-cooledGood correlation between simulations and empirical results
CFD Tmax = 108 C Empirical Tmax = 107 C FEA Tmax = 110 C
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Simulation – Heat Transfer Coefficient FEA predicted havg = 6.5 W/m2-C CFD predicts havg = 6.0 W/m2-C
Natural Convection 0-20 W/m2-K
Forced Convection 0-200 W/m2-K
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Simulation – Cooled (pinched tube)Velocity distribution through tube center plane
Temperature distribution through tube center plane (top view)
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Simulation – StreamlinesStreamlines colored by temperature
Natural Convection Forced Convection
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Results- Simulation
Natural Convection Forced Convection
Empirical FEA CFD Empirical CFD
Base 64 71 67 32.4 34
Ht Block 107 110 108 46.3 50
Average delta between CFD and empirical results is <5%
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Conclusion Air knife and pinched tube met design goal
temperature of 50 C or lower Packaging and cost may dictate which
design is most practical FEA/CFD heat transfer simulation can be
correlated to empirical results and then used as model for future designs. Approximate 5% difference between CFD and empirical results
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Future Work Air exit geometry sensitivity study Positional and orientational sensitivity
study Mesh density sensitivity study for FEA and
CFD simulations
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ScheduleMay (08) June July
Proposal Design Build Draft Final Fixture Air Nozzles Fabrication Procure
August September OctoberTesting Simulation Proposal
FEA CFD Final
November December January (09)
Report Draft Mid Year
report website
February March April
May Ongoing Complete Not started
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Budget All test apparatus provided courtesy of Kulicke
& Soffa Industries. All materials for fixture fabrication provided
courtesy of Kulicke & Soffa Industries. Film heater only purchased item: $39.99 Total Expenditure: 39.99
All materials reusable or recyclable for minimal environmental impact.
No exposure to hazardous conditions during testing
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BibliographyFox, McDonald and Pritchard, 2004, Introduction to Fluid Mechanics, John Wiley and Sons Inc.,
Incropera, Dewitt, Bergman and Lavine, 2007, Fundamentals of Heat and Mass Transfer, John Wiley and Sons Inc.,
D.-Y. Lee, K. Vafai, 1998, “Comparative analysis of jet impingement and micro channel cooling for high heat flux applications”, International Journal of Heat and Mass Transfer,
Material Web, materials data website, http://www.matweb.com/