Keywords: convective drying, multilayer ceramic mould system, coupled heat and mass transfer, two dimensional, mechanistic approach, thermophysical.

Within investment casting, the drying process is one of the most important stages in ceramic shell buildup during which a number of ceramic layers are added to form the shell. During drying, thermal, moisture and pressure gradient are dynamically created within the multilayer envelopes [1]. In general ceramic porous material is very sensitive to any thermophysical change and always related to the variation in moisture content in a non-linear way.

A mathematical model to represent the drying phenomena in a ceramic structure along with its implementation into a Finite Element simulation scheme leads to a solution to the coupled equation set. In the present work, a two-dimensional numerical model of coupled heat and mass transfer based on a mechanistic approach [2,3] along with the gas transport was developed. A formulation including hygrothermal and moisture transport in soil was adopted as the basis for further development in this work [4,5].

Two examples comprising one and two dimensional case studies are solved to validate and demonstrate robustness of the approach. Validation within one dimensional framework showed that the model presented is in a good agreement with other studies that have been reported previously in the drying of porous material [6,7]. A two dimensional case study which illustrates the drying of single and multilayer ceramic shell body are compared and contrasted against experimental data on shell drying, showing good agreement [8,9].

1

Hyde R., "The Rupture of Ceramic Moulds for Investment Casting", Master Theses, School of Metallurgy and Materials, University Of Birmingham, Edgbaston, Birmingham England, October 1995.

2

Nasrallah S.B., Perre P., "Detailed Study of A Model of Heat and Mass Transfer During Convective Drying of Porous Media", International Journal Heat Mass Transfer, 31(5), 957-967, 1988. doi:10.1016/0017-9310(88)90084-1

3

Philip J.R., de Vries D.A., "Moisture Movement in Porous Materials Under Temperature Gradients", Trans. Am. Geophys. Union, 38, 222-232, 1957.

4

Van Genuchten M.T., "A Closed-Form Equation for Predicting the Hydraulic Conductivity of An Unsaturated Soils", Soil Science Soc. of America Journal, 44, 892-898, 1980.

5

Baroghel-Bouny V., Mainguy M., Lassabatere T., Coussy O., "Characterization and Identification of Equilibrium and Transfer Moisture Properties for Ordinary and High Performance Cementitious materials", Cement and Concrete Research, 29, 1225-1238, 1999. doi:10.1016/S0008-8846(99)00102-7

6

Stanish M.A., Schajer G.S., Kayihan F., "A Mathematical Model of Drying for Hygroscopic Porous Media", AIChE Journal, 32(8), 1301-1311, 1986. doi:10.1002/aic.690320808

7

Spolek G.A., Plumb O.A., "Capillary Pressure in Softwood", Wood Science Technology, 15, 189-199, 1981. doi:10.1007/BF00353471

8

Jones S., Leyland S., "Investigation into The Drying Behavior of Water Based Slurries", in "Proc. 42nd Annual Technical Meeting of the Investment Casting Institute", Investment Casting Institute, Atlanta, USA, September 1994.

9

Jones S., Leyland S., "The Use of conductivity As A Means Of Assessing The Extent Of Wet Back In An Investment Mould", Report: Rolls-Royce Plc, Company Research & Development Foundry, Derby, and School Of Metallurgy and Materials, The University of Birmingham, UK, July 1995.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £75 +P&P)