Wärme - und Stoffübertragung

, Volume 17, Issue 2, pp 107–113 | Cite as

Simultaneous transfer of heat and mass occurring in casting process

  • H. Saito
  • N. Seki
Article

Abstract

Studied in this paper is simultaneous transfer of heat and water vapor which takes place in a green sand mold in a very short period of time after pouring a molten metal in its cavity. Governing equations describing heat and mass transfer in a mold are solved by finite difference method and the results are compared with the actually measured values to examine the validity of the calculated results. The effect of thermal properties and permeability of the mold, the amount of water contained, the heating temperature (i.e., temperature of casting metal) and other factors on the heat transfer rate at the interface between the molten metal and the mold, the pressure rise in the mold and the development of dried zone around the casting are investigated to propose some empirical relations available for predicting those transfer phenomena by using dimensionless parameters presented.

Keywords

Heat Transfer Mold Water Vapor Finite Difference Method Casting Process 

Nomenclature

a

thermal diffusivity of green sand mold (m2/h)

cl

specific heat of water (KJ/kg°K)

heat capacity of dry sand (KJ/m3 ° K)

i

enthalpy of vapor (KJ/kg)

K

permeability of sand (m4/hN)

L

thickness of sand layer (m)

P

pressure (N/m2)

Q

heat transfer rate at surface of mold (KJ/m2h)

T

temperature (°K)

to

heating temperature (°K)

v

specific volume of vapor (m3/kg)

x

distance from heating surface (m)

ɛ

mass of water contained in unit volume of moist sand kg/m3

λ

thermal conductivity (KJ/m h °K)

ξ

position of maving boundary measured from heating surface (m)

τ

time (h)

ψ

porosity of dry sand (m3/m3)

Dimensionless parameters and variables

\(\tilde H\)

heat capacity ratio (= clɛ i /cϱ)

ĩ

dimensionless enthalpy (= ɛii/cϱT i )

\(\tilde i\)

dimensionless permeability (=KP i /λ ψ)

\(\tilde K\)

dimensionless pressure (= P/Pi)

\(\tilde P\)

dimensionless heat transfer rate (=QL/Tiλ)

\(\tilde Q\)

dimensionless temperature (= T/Ti)

\(\tilde T\)

dimensionless initial water content (= ɛiv/)

\(\tilde W\)

dimensionless distance (=x/L)

\(\tilde x\)

dimensionless water content (= ɛ/ɛi)

\(\tilde \varepsilon \)

ratio of thermal conductivities (= λ12)

\(\tilde \sigma \)

dimensionless time (= ατ/L2)

\(\tilde \tau \)

ratio of permeabilities (=K1/K2)

\(\tilde \omega \)

dimensionless position of moving boundary (= ξ/L)

\(\tilde \xi \)

dimensionless variables defined by equation (9)

Suffixes

0

heating surface

1

dried region

2

wet region

s

water vapor

l

liquid water

i

initial state

Gleichzeitige Übertragung von Wärme und Stoff beim Gießen

Zusammenfassung

Es wird der gleichzeitige Transport von Wärme und Wasser in einer Form aus Grünsand kurze Zeit nach dem Eingießen von flüssigem Metall in den Hohlraum untersucht. Die maßgebenden Gleichungen werden mit Hilfe der finiten Differenzen gelöst und die Ergebnisse zur Überprüfung mit Experimentalwerten verglichen. Berücksichtigt werden die Wirkung der thermischen Stoffwerte und der Durchlässigkeit der Form, der Menge des enthaltenen Wassers, der Heiztemperatur (also der Temperatur des flüssigen Metalls) und anderer Faktoren der Wärmeübertragung zwischen flüssigem Metall und Form, des Druckanstiegs in der Forme und der Entwicklung einer ausgetrockneten Zone um den Guß. Zur Vorhersage der Übertragungsvorgänge werden empirische Gleichungen mit Hilfe dimensionsloser Parameter entwickelt.

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References

  1. 1.
    Levelink, C. A.; van den Berg, H.: Mod. Cast. 54 (1968) 69–79Google Scholar
  2. 2.
    Landau, H. G.: Quart. Appl. Math. 8 (1950) 81–91Google Scholar
  3. 3.
    Saito, H.; Seki, N.: Trans. Soc. An. Mech. Eng., J. Heat Transf. 99 (1977) 105–112Google Scholar
  4. 4.
    Veinik, A. I.: “Thermodynamics for Casting Molds”, Moscow: Machine Engineering 1968Google Scholar

Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • H. Saito
    • 1
  • N. Seki
    • 2
  1. 1.Department of Mechanical EngineeringMuroran Institute of TechnologyMuroranJapan
  2. 2.Department of Mechanical EngineeringHokkaido UniversitySapporoJapan

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