1. Air Cooling Design for Machine Components

2. Air Cooling Design for Machine Components
Presenter: Peter van Emmerik
Faculty Advisor: Dr. LeRoy Alaways
Department of Mechanical Engineering
Villanova University

3. 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

4. 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

5. Heated Fixture Background Film Heater Stand-offs (SS)
Thermocouple locations
Heat Block (Al)
Base (Al)
Fixture representative of linear servo motor

6. Compressed Air Cooling
Methodology
Advantages of using compressed air
Compressed Air Cooling
Low Cost
Packaging Efficiency
Reliable
Simple

7. Methodology
Three delivery methods examined
Log Manifold
Pinched Tube
Air Knife
Two orientations to target surface
Cross Flow
Impinging Flow

8. Log Manifold Methodology - Designs Simple tube Capped end
Cross drilled

9. Pinched Tube Methodology - Designs Simple tube Pinched End Shapes flow
Increases velocity

10. Air Knife Methodology - Designs Machined Manifold Wide Slit Exit
Enhanced Air Entrainment
Cover
Spacer
Manifold

11. Apparatus Test Equipment Arrangements Thermocouples k-type
Data Collection Box
Air Flow Meter
Heater Voltage Controller
Arrangements
Cross Flow
Impinging Flow

12. 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

13. Results
Un-cooled baseline

14. Results
Cross Flow

15. Steady State Temperature Comparison Ht Block Temperature (deg C)
Results
Steady State Temperature Comparison
BASE Temperature (° C)
Cross Flow
Impinging Flow
Air Knife
29.8
28.9
Pinched Tube
32.4
29.5
Log Manifold
34.7
32.6
Ht Block Temperature (deg C)
Goal met*
44.0
41.8 þ
46.3
43.1
57.5
55.5 ý
*Design Goal: 50 deg C
Air Consumption: 17.2 nL/min for all tests

16. 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

17. Simulation – Un-cooled Correlation
Transient Un-cooled FEA vs Empirical

18. Simulation – Un-cooled
Good correlation between simulations and empirical results
CFD Tmax = 108 C Empirical Tmax = 107 C FEA Tmax = 110 C

19. Simulation – Heat Transfer Coefficient
FEA predicted havg = 6.5 W/m2-C CFD predicts havg = 6.0 W/m2-C
Natural Convection W/m2-K
Forced Convection W/m2-K

20. Simulation – Cooled (pinched tube)
Velocity distribution through tube center plane
Temperature distribution through tube center plane (top view)

21. Simulation – Streamlines
Streamlines colored by temperature
Natural Convection
Forced Convection

22. Results- Simulation Natural Convection Forced Convection
Empirical
FEA
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%

23. 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

24. Air exit geometry sensitivity study
Future Work
Air exit geometry sensitivity study
Positional and orientational sensitivity study
Mesh density sensitivity study for FEA and CFD simulations

25. Schedule May (08) June July Proposal Design Build Draft Final Fixture
Proposal
Design
Build
Draft
Final
Fixture
Air Nozzles
Fabrication
Procure
August
September
October
Testing
Simulation
FEA
CFD
November
December
January (09)
Report Draft
Mid Year
report website
February
March
April
May
Ongoing
Complete
Not started

26. 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:
All materials reusable or recyclable for minimal environmental impact.
No exposure to hazardous conditions during testing

27. Bibliography
Fox, 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,