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A model for predicting the thermal conductivities of bentonite-bonded molding sands at high temperatures

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Abstract

The effective thermal conductivities of bonded molding sands vary with the dry density, binder content, initial moisture content, temperature as well as the types of sand and binder clay. In this study, a theoretical model for predicting the effective thermal conductivities of bentonitebonded molding sands was developed. The results of measurement of the effective thermal conductivities of molding sands at temperatures up to 750°C were used. The binder thermal conductivities of both western bentonite and southern bentonite were suggested as a function of dry density, binder content and initial moisture content and were assumed not to vary with temperature. The radiation model proposed by Vortmeyer was also incorporated. The model developed in this study was proved to predict well the effects of binder content, initial moisture content, dry density and temperature.

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Abbreviations

a +2s :

Constants in Eq. (4) [m−1]

B :

Binder content by weight

k oe :

Effective thermal conductivity of binder [W/mK]

k c :

Thermal conductivity due to conduction [W/mK]

k c :

Effective thermal conductivity of molding sand [W/mK]

k f :

Thermal conductivity of saturating fluid [W/mK]

k fr :

Thermal conductivity due to intergranular radiation [W/mK]

k s :

Thermal conductivity of sand grain [W/mK]

k se :

Effective thermal conductivity of sand grain [W/mK]

k st :

Thermal conductivity due to transgranular radiation [W/mK]

M :

Initial moisture content by weight

r :

Variable in the model of Fig. 1

r b :

Variable in the model of Fig. 1

R :

Characteristic radius in the model of Fig. 1

x :

Coordinate

y :

Coordinate

ρ d :

Dry density [g/cm3]

φ b :

Volume fraction of binder

φ f :

Volume fraction of fluid in the pore space

φ s :

Volume fraction of sand particles

References

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  2. Briggs, C. W., and Gezelius, R. A., 1933, “European Synthetic Molding Sands,”Am. Soc. Naval Eng., Vol. 45, p. 462.

  3. Chen, J. C., and Churchill, S. W., 1963, “Radiant Heat Transfer in Packed Beds,”AIChE J., Vol. 9, p. 35.

  4. Hamaker, H. C., 1947, “Radiation and Heat Conduction in Light Scattering Materials,”Philips Res. Rep., Vol. 2, pp. 55–67.

  5. Hartley, J. G., Babcock, D., and Berry, J. T., 1981, “The Thermal Conductivity of Bentonite-Bonded Molding Sands,”Trans. AFS, Vol. 89, pp. 469–476.

  6. Hartley, J. G. and Patterson, J., A. L., 1983, “The Influence of Temperature, Moisture Content and Binder Content on the Thermal Conductivity of Dried Bentonite-Bonded Zircon and Silica Sands,”Trans. AFS., Vol. 91, pp. 183–190.

  7. Kubo, K., Fukusako, T. and Mizuchi, K., 1982, “Prediction of Thermal Conductivity of Sand Molds Below 600°C,”IMONO, Vol. 54, No. 4, p. 244.

  8. Kubo, K. Mizuchi, K., Ohnaka, I. and Fukusako, T., 1983, “Measurement of Thermal Properties of Sand Molds by Pouring Method,”50th International Foundry Congress, Vol., 6, Cairo, pp. 6–11.

  9. Park, S. L. and Hartley, J. G., 1992, “A Model for Prediction of the Effective Thermal Conductivity of Granular Materials with Liquid Binder,”KSME Journal, Vol. 6, No. 2, pp. 88–94.

  10. Park, S. I. and Hartley, J. G., 1996. “Measurement of the Effective Thermal Conductivities of Molding Sands at High Temperatures,”KSME Journal, Vol. 10, No. 4, pp. 480–488.

  11. Vortmeyer, D., 1978, “Radiation in Packed Solids,”6th Int. Heat Trans. Conf., Toronto.

  12. Whitmore, D. H. and Ingerson, Q. F., 1960, “Apparent Thermal Conductivity of Molding Sand at Elevated Temperatures,”AFS Trans., Vol. 68, p. 49.

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Author information

Correspondence to Sang Il Park.

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Park, S.I., Hartley, J.G. A model for predicting the thermal conductivities of bentonite-bonded molding sands at high temperatures. KSME International Journal 11, 435–442 (1997). https://doi.org/10.1007/BF02945082

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Key Words

  • Thermal Conductivity
  • Molding Sand
  • Bentonite Clay Binder
  • Theoretical Model
  • High Temperature