Abstract
This paper considers one-dimensional heat transfer model for the freeze-coating of a polymeric substance on a continuously moving sheet and on an axially moving cylinder. Analytical expressions are obtained for the freeze-coat thickness; also presented the solutions for an upper bound on the thickness of the frozenlayer using thermodynamic equilibrium conditions. Effect of Stefan number on freeze-coat thickness is briefly discussed and also the application of the present results with an example.
Zusammenfassung
Diese Arbeit behandelt ein eindimensionales Modell für den Wärmeübergang bei der Erstarrungs-Beschichtung mit einem Polymer an einer kontinuierlich bewegten Platte und an einem axial bewegten Zylinder. Für die Schichtdicke werden analytische Ausdrücke angegeben; auch die Lösung für die obere Grenze der erstarrten Schichtdicke bei thermodynamischem Gleichgewicht wird mitgeteilt. Der Einfluß der Stefan-Zahl auf die Schichtdicke wird kurz diskutiert. Die Anwendungen der Ergebnisse werden an einem Beispiel gezeigt.
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Abbreviations
- Cp :
-
Specific heat of solid layer, J/Kg°C
- J0,J1 :
-
Bessel function of first kind, zero and first order
- k:
-
thermal conductivity of solid-layer, J/sec-m-°C
- L:
-
latent heat of fusion, J/kg
- Pr:
-
Prandtl Number, ν/α
- r:
-
normalized distance within the solidified layer, R/R0
- R:
-
radial coordinate measured from the surface of the cylinder, m
- Re:
-
Reynolds Number, UR0/ν
- S:
-
Interface location, Rf/R0
- Ste:
-
Stefan Number, Cp (Tf-T0)/L
- T:
-
temperature within the frozen-layer, °K
- U:
-
velocity of the object moving through the liquid, m/sec
- x:
-
axial coordinate, m
- y:
-
distance from the object surface, m
- Z:
-
dimensionless axial distance, (x/R0)Re.Pr
- α :
-
thermal diffusivity of solid-layer, m2/sec
- δ:
-
thickness of solid layer, m
- η:
-
similarity variable, y/(U/4νx)1/2
- ηs :
-
value of η at y=σ
- ϕ:
-
dimensionless temperature, (T-Tf)/(T0 -Tf)
- ν:
-
kinematic viscosity of liquid, m2/sec
- νm :
-
positive roots of J0(νm)=0
- ρ:
-
density of solid-layer, kg/m3
- 0:
-
object
- f:
-
freezing-front
- m:
-
object material
- s:
-
solid phase
- ss:
-
steady-state
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Seeniraj, R.V., Bose, T.K. Freeze-coating on a continuous moving sheet and on an axially moving cylinder. Wärme- und Stoffübertragung 15, 239–243 (1981). https://doi.org/10.1007/BF01003644
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DOI: https://doi.org/10.1007/BF01003644