Limit value of the Nusselt number for particles of different shape

The limit value of the Nusselt number for pure heat conduction was numerica lly determined for different particle shapes. In the case of nonspherical p articles, substantial errors can result in the calculation of the heating t ime when the Nusselt number of the sphere Nu = 2 is applied and the sieve d iameter is used as the characteristic dimension. That a uniform description of the Nusselt number is possible for all considered particle shapes is de monstrated. However, this Nusselt number, determined using the sieve diamet er, is then not constant, but depends exponentially on the ratio of the Sau ter diameter to the sieve diameter. (C) 2001 Elsevier Science Ltd. All righ ts reserved.