Performance Evaluation Of Mass-Transfer Coefficients For Constant-Rate Period Of Drying During Tape Casting

Abstract

Temperature-dependent mass-transfer coefficient is presented for the constant-rate period during non-convective drying of water-based alumina suspension for tape casting. Predicted drying rates based on the temperature-dependent mass-transfer coefficient and constant value of the mass-transfer coefficient are compared with experimental data in a range of ambient temperature from 298K to 328K and a range of relative humidity from 40% to 90%. It is shown that the temperature-dependent mass-transfer coefficient is adequate with maximum error of about 9% in predicted drying rates. The constant mass-transfer coefficient is also adequate, but with errors in predicted drying rates of about 18% and 16% at 40%RH(328K) and 65%RH(328K) respectively, and maximum error of about 9% at all other data points. A model based on drying parameters of the suspension in the constant-rate period is also presented for estimating wet-bulb temperature within the specified ranges of ambient temperature and relative humidity. Model-estimated wet-bulb temperatures are compared with those estimated from a humidity-temperature chart for air-water vapour system at atmospheric pressure and good agreement is obtained. Keywords: Drying; Suspension; Ceramics; Wet-bulb temperature; Tape casting.Global Journal of Engineering Research Vol. 7 (1) 2008: pp. 47-50