Transcript COMSOL2008-Ngankeu.ppt

An Analysis of Plunger Temperature
during Glass Parison Pressing
P. Lankeu-Ngankeu and E. Gutierrez-Miravete
Department of Engineering and Science
Rensselaer at Hartford
Introduction
• Glass container forming is done using two sets of mold: Blank and
Blow molds
• There are two main processes used in container forming Blow and
Blow and Press and Blow
• The parison is formed in the blank mold and blown into the final bottle
shape in the blow mold
• In the Press and Blow process, the parison is created by driving a
metal plunger into the loaded gob
• The plunger needs to be at a prescribed operating temperature to
avoid causing checks.
Objective: Model the temperature on the plunger outside surface
during the pressing cycle of the glass
Glass Bottle Forming Processes
Press and Blow Process
Blow and Blow Process
Motivation
Modeling and Plunger Temperature during Glass Parison Pressing
• Heating of the plunger outside surface due to glass contact.
• Cooling from the cooling tube on the inside surface of the plunger.
• Temperature change on the plunger outside surface due to cyclical
contact with the glass gob.
Plunger
Model Description
• Model of a Emhart Glass Research Center (EGRC) longneck beer
plunger
• Two cases:
– A 2D axissymmetric model
– A full 3D model
• 1s duration for gob loading (the glass is not in contact with the
plunger surface~cooling cycle).
• 1s duration for parison pressing (the glass rides down on the
plunger~heating cycle).
Plunger Geometries (2D and 3D)
Governing Equation
The heat equation for constant thermo-physical properties:
T  T (t , x, y, z )
kg
  7850 3
m

k
  Cp
J
Cp  475
kg  K
T
  T 
t
2
W
k  44.5
mK
  2T 1 T  2T  T
 
 2  
For the 2D axissymmetric case:   
2
r r z  t
 r
For the full 3D case:
  2T  2T  2T  T
   2  2  2  
y
z  t
 x
Model Assumptions
• The glass gob is at a temperature of 1273K.
• The initial temperature of the plunger is taken to be 773K.
• Introduce functions Zs(t) to characterize glass motion on the
plunger, Zs(t) = 0 when the plunger is not in contact with the glass
   
Zst   0.181367   sin  t  
  2 
Boundary Conditions
• The plunger inside surface is subjected to convective cooling to
keep the plunger temperature down. However, the heat transfer
coefficient is doubled at the tip due to impingement.




n  k  T  hT  T 
h  ( 250,500)
W
m2  K
T  350K
• The outside surface is subjected to both convection and radiation
from the glass





4
n  k  T  hT  T    Tglass  T 4
h  h plunger ( z  0.05  Zs (t ))
• All other surfaces are insulated

T  T plunger ( z  0.05  Zs (t ))
Mesh and Solution
• Using free mesh parameters, 392 elements for 2D axissymmetric
model, less than 30s to compute 10 cycles
• For 3D full model, 23705 elements with around 7min of computation
time
• The mesh was refined at the plunger tip
Results (3D Model)
Results (2D Model)
• The tip of the plunger shows the largest temperature variations
through the 10 heating and cooling cycles.
• The plunger tip heats up more rapidly than the rest of the plunger
due to longer glass contact time.
Summary
• The COMSOL model has provided useful insight into the plunger
temperature variation examined here.
• Our model uses a simplified glass motion on the plunger surface,
We could attempt using motion profiles from the plant
• We do not solve for the internal cooling inside the plunger
• We have a tool that can provide some qualitative reference for
monitoring plunger temperature in the future