Heat transfer green body drying

The temperature at the surface of the sphere is determined by the evaporation rate obtained from simultaneous mass and heat transfer. Under some drying conditions, the heat transfer is the slow step, limiting evaporation, and in others the mass transfer is the slow step. The surface of the green body will continue to stay wet if the green body shrinks, expelling the solution, or sm-face tension driven flow continues to supply liquid. Shrinkage stops when the rigidity threshold of the particle network is reached. 

In this section, we will discuss in detail the linked differential equations for mass and heat transfer which describe the drying of a spherical green body. This same analysis can also be used for plate and cylinder green bodies with corrections for the geometry. The equations for cylinder and plate drying are presented in Tables 14.3 and 14.4. 

TABLE 14.2 Evaporative Drying of Spherical Green Body, by Heat Transfer Controlling Steps... 

Determine the time to dry in 10% relative humidity air at 100°C a spherical green body of radius 10 cm with a void fi action of 0.4 filled with H2O. Assume that boundary layer mass or heat transfer is the rate limiting step. The temperature of the surface is the wet bulb temperature. This time is the maximum time for the constant rate period. Data mean particle size = 1.0 /am mean pore diameter = 0.1 /am. See Problem 14.1 for drying data on water and air. 

---