| About this Abstract |
| Meeting |
Liquid Metal Processing & Casting Conference (LMPC 2022)
|
| Symposium
|
Liquid Metal Processing & Casting Conference (LMPC 2022)
|
| Presentation Title |
Use of Accommodation Coefficients in Modeling of Helium Heat Transfer in VAR: Examination of Their Uncertainty and Effect on Modeling |
| Author(s) |
Richard Smith |
| On-Site Speaker (Planned) |
Richard Smith |
| Abstract Scope |
Application of helium cooling in VAR to supplement sidewall radiation cooling in the gap between the ingot and copper mold has seen widespread use. Published results on superalloys and tool steels have shown effects of the use of helium cooling on ingot and process characteristics such as pool depth, dendrite arm spacing and amounts of undesired second phases. Incorporation of helium cooling in process modeling of VAR has generally been through the sidewall heat transfer coefficient. A method has been presented to directly calculate helium heat conduction in the gap using the kinetic theory of gases. [1,2] At low pressures, the theory provides two methods for calculating heat transfer. One method corresponds to gas pressures sufficiently low that gas molecule interactions can be substantially reduced, which in turn causes a temperature discontinuity at the gas/metal interface. For this regime of behavior, a quantity referred to as the temperature-jump distance is calculated to account for the discontinuity. The other method corresponds to pressures low enough that gas molecules do not interact at all and move freely between two surfaces. This regime of behavior is referred to as free-molecule. For the range of gas pressures generally cited for use in VAR (several torr up to roughly 90 torr) conduction is generally considered to correspond to the temperature-jump regime. Both methods use a parameter referred to as the accommodation coefficient which accounts for the degree to which a gas molecule comes into thermal equilibrium with a surface on contact. |
| Proceedings Inclusion? |
Definite: At-meeting proceedings |