Heat pipe an innovative technology

1. McGill
Thermal Management of Permanent Molds
for the Casting of Aluminum Alloys
Chunhui Zhang
Frank Mucciardi
and
John Gruzleski
Dept. of Mining, Metals and Materials Engineering
McGill University
Frank.Mucciardi@mcgill.ca
Web Site: www.mmpc.mcgill.ca/~frank

2. Objectives:
• Control the cooling of a permanent mold to
produce aluminum castings of superior quality.
• Selectively cool:
specific locations, at
specific times.
Methodology:
• Use heat pipes to control the heat transfer.

3. History of the Heat Pipe
• Dates back to the early 1960’s
• NASA and Los Alamos Labs were prime developers
• Used extensively in electronics
• Used extensively in satellites, Space Shuttle and
Space Station

4. • sealed chamber wherein a working
substance evaporates and condenses
• passive device (no moving parts)
• extremely high, effective thermal
conductivity (as much as 1,000 times
that of Cu)

5. Classical Heat Pipe
Condenser Section
Vapor
(Heat out)
out
Heat Pipe Wall
Condensate Film
Capillary Wick
Evaporator Section Liquid Pool
(Heat in)
in

6. Major Problems with Classical Heat Pipes
While the potential of heat pipes is enormous,
There are 2 major problems:
1. Film boiling
2. Entrainment of returning liquid
McGill Heat Pipe (patents pending) overcomes these
problems and thus makes heat pipe technology viable
for high heat flux systems.
Details of the McGill Heat Pipe will be disclosed
as soon as we are allowed to.
McGill

7. What Was Done:
• Designed and built water-based McGill Heat Pipes.
• Incorporated such pipes in a permanent mold at
McGill.
• Found an industrial partner, Grenville Castings, to
Castings
sponsor and conduct plant trials (Oct. 2002).
Applicability of Results:
• In casting systems
- permanent molds
- DC casters

9. Features of the McGill Heat Pipe
Can handle heat flux loadings of 1 MW/m2 and
more with water as the working substance.
ON/OFF heat extraction capability.
External chill absorbs the heat during
ON mode.
Cooling air dissipates the heat stored in the chill
during OFF mode.
McGill

10. Permanent Mold Cooled by Heat Pipes
è è è
è
Unit:
mmUnit: mm

12. Cooling Air Lines
Data
acquisition
Heat pipes
system
Permanent mold
On/Off Valve
Configuration
McGill

13. Simulation by SOLIDCast
Heat pipes Z
Y
X

14. Heat pipes

15. Heat pipe

16. Plan View of the Casting, Heat Pipes and
the Thermocouples
Heat Pipe 2 Heat Pipe 1
Heat Pipe 3
TC1
TC2
TC3

17. 800
700
Casting in the parting plane
600
Temperature ( C)
500
o
Mold without HP
400
300
Mold with HP
200
100
0
0 20 40 60 80 100
Time (s)

18. Typical Casting Experiment
Using Heat Pipe 1 only
Al 356 alloy
Initial mold temperature of 200oC

19. 700
600
TC2 Casting on the parting plane
C)
500
o
400
Temperature (
TC3 Mold without HP
300 HP ON
TC1 Mold with HP
200
Air gap formation HP OFF
100
0
0 50 100 150 200 250
Time (s)

21. A: The side without heat pipe, DAS=40±6µm B: Center, DAS=41±10µm
Alloy A356
Tmold= 200oC
C: The side with heat pipe cooling, DAS=27±3µm

22. Typical Casting Experiment
Using Heat Pipes 1, 2 and 3
Al 356 alloy
Initial mold temperature of 300oC

23. Heat Pipe 2 Heat Pipe 1
Heat Pipe 3
S M L
Thermocouple Locations

24. 700
600
Casting-L
Casting-M
500 Casting-s
Temperature ( o C)
Mold-L
Mold-M
400
Mold-S
Mold-HP2-M
300
Mold-HP1-L Mold-HP3-S
200
100 Max. Heat Flux to the
Heat Pipes: 500-600 kW/m 2
0
0 50 100 150 200 250 300 350
Time (s)

25. McGill

26. No HP DAS=39± 4 µ m
± Middle DAS=41± 5 µ m
±
Alloy A356
Tmold= 300oC
With HP Cooling
HP DAS=27± 2 µ m
±

27. No HP DAS=42± 4 µ m
± Middle DAS=53± 6 µ m
±
Alloy A356
Tmold= 300oC
With no HP cooling
HP DAS=46± 7 µ m
±

28. McGill
Effect of Heat Pipe Cooling on DAS
(unit: µm)
C DAS
A
S Section with
T Cooling S M L
I
(Location E) (Location D) (Location C)
N
G
1 None (Ref) ±
31±5 ±
41±3 ±
46±7
±
24±4 ±
27±3 ±
27±2
2 SML Decrease
21% 33% 41%

29. McGill
Summary
We have developed a controllable, water-based
McGill Heat Pipe for high heat flux applications,
such as permanent molds.
Heat dissipation rates equivalent to those
associated with conventional water cooled
passages are achieved with air cooling.
Cooling with heat pipes is very effective in
controlling the microstructure of the casting
and the mold temperature.

30. McGill
Summary Cont’d
The DAS of A356 alloy is refined considerably
with heat pipe cooling of the mold.
Heat pipe cooling of the mold can alter the
direction of solidification as well as the location
of the shrinkage.

31. So, where are we now?
Let’s visit our lab at McGill

32. Testing the Water-Based Heat Pipe
in the Gas Furnace
Condenser Air-cooled condenser
Typical Heat Flux:
~ 500 kW/m2
Evaporator Heat Extraction:
~ 6 kW for 10 cm
insertion
McGill

33. Testing the Water-Based Heat Pipe
Directly in Molten Aluminum
Typical Heat Flux:
~ 1,500 kW/m2
Condenser
The cooling of permanent
Insulation molds is simple in
comparison.
Heat Pipe
Other applications:
- Superheat reduction in
DC casting molds
Crucible - Cooling of the electrolytic
cells
- Cooling the off gases
McGill

34. Aluminum Melt Temperature Data for 5.1 cm Immersion

35. Leading End of the Heat Pipe After the Test
Note the uniform but rough
solidification surface.
McGill

36. So, where are we now?
In addition to our work in the lab, we have a number of
industrial sponsors for the following:
Full scale oxygen lances for steel refining and
lead refining
Cooling elements for aluminum and magnesium casting
Heat pipe units for cooling lead furnace taphole
McGill