Performance evaluation of heat-transfer co-efficients for constant-rate period of drying during tape casting

Abstract

Ceramic suspensions for tape casting are known to dry in two stages; the first stage is called the constant-rate period, and the second stage is the falling-rate period. The drying rate in the constant-rate period can be characterized by mass-transfer coefficient or heat-transfer coefficient. A general model is presented that predicts the heat-transfer coefficient at a given temperature and different ambient humidity in the constant-rate period. An average value of the heat-transfer coefficient for a temperature range from 298K to 328K, and a range of relative humidity from 40% to 90%, during drying of water-based alumina suspension for tape casting is calculated using this model to be. A model developed for the water-based suspension is also presented that predicts the heat-transfer coefficient as a function of temperature. Predicted drying rates based on heat-transfer coefficients obtained from the two models are compared with experimental data and good agreement is obtained. The average value of the coefficient for the suspension is shown to be inadequate. Keywords : Modelling; Drying; Tape casting; Suspension; Ceramics; Heattransfer Coefficient Journal of Modeling, Design and Management of Engineering Systems, Vol. 3 (1) 2005: pp. 25-37