1. MODEL INVESTIGATION OF MOLD LEVEL MONITORING WITH THERMOCOUPLES
Tim Morthland & Brian G. Thomas
Department of Mechanical &. Industrial Engineering
University of Illinois at Urbana-Champaign
October 15, 2002

2. Objectives
Investigate the potential use of mold thermocouples to detect level fluctuations.
Develop 3D transient FEM model
Validate with 2D models
Validate with plant TC measurements (Columbus Stainless Steel)
Simulate TC response to controlled level fluctuations
Simulate TC response to oscillation mark movement

3. 3-D Model of Mold Near Meniscus
Bolt holes containing Thermocouples
water slots
mold top
mold top
Finite Element Mesh
(4-node tetrahedrons)
Domain (showing slots)

4. 3-D Transient Model description
Thermocouple
finite element model
constantan
4-node tetrahedral elements:
steel bolt

5. Material Properties

6. Geometry & Boundary Conditions

7. Finite Element Mesh
8241 nodes and tetrahedrons

8. Heat Flux profile (calibrated)

9. Temperaures (steady state)
Meniscus
(95 mm
down mold)
TCs at 115 and 42 mm
mold top
Top view (hotface)
Interior view (water slots)

10. Temperature profiles

11. Model Validation: compare 2D and 3D calcs

12. Model Validation: with Columbus instrumented mold (design 2)
Level sensor
Meniscus T1 T3 T5 T7 T9
T11 N1 N6 mm N2 N7 T2 T4 T6 T8
T10
T12
Second Lowest TC
Lowest TC
Legend: BOPS New T’s

13. Effect of TC - Cu plate contact condition

14. Validation: comparison with measured TC and level histories

15. Controled Level Fluctuation: 10mm for 1s

16. Controled Level Fluctuation: 10mm for 1s

17. Controled Level Fluctuation: 10mm for 3s

18. Controled Level Fluctuation: 10mm for 3s

19. Controled Level Fluctuation: 2mm for 1s
Indetectable !

20. Severe Oscillation marks passing mold bottom
Alternate between:
1.7 MW/m2 for 10s
0.2 MW/m2 for 2s

21. Severe Oscillation marks passing mold bottom
Alternate between:
1.7 MW/m2 for 10s
0.2 MW/m2 for 2s

22. Severe Oscillation marks passing mold bottom
Alternate between:
1.7 MW/m2 for 10s
0.2 MW/m2 for 2s

23. Conclusions Compuated TC signals match measurements well
TC signals drop with imperfect contact to mold Cu
Thermocouples near meniscus (both above and below) are able to detect major level fluctuations
Small level fluctuations produce very minor changes in TC readings and tinyones (2mm for 1s) are not detectible
TCs near to hot face can detect minor level fluctuations better
TC temperature fluctuations lower in mold of deg C indicate severe heat flux variations (eg. due to flux layer breakage and alternating air gaps)