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Freeze-coating on a continuous moving sheet and on an axially moving cylinder

Erstarrungs-Beschichtung einer kontinuierlich bewegten Platte und eines axial bewegten Zylinders

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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

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 J0m)=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

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