In this paper, the mass and heat transfer characteristics of a composite structured catalytic reactor packing (Composite Structured Packing (CSP)) are investigated. A CSP consists of a multichannel framework filled with ordinary catalyst particles, with a square channel-to-particle-diameter ratio (N) of I < N < 5, resulting in a system with a significantly lower pressure drop compared to a randomly packed bed. The goal of the present study is to assess whether commercial Computational Fluid Dynamics (CFD) software can be used to (1) adequately predict the rate of mass and heat transfer from the catalyst particles to the fluid in a CSP and (2) develop simple engineering correlations for this type of packing. First, it is shown that commercial CFD software (CFX-5.3) can be used to adequately predict the particle-to-fluid heat transfer of a single free sphere. Furthermore, it is shown that the CFD code can predict the heat/mass transfer characteristics, with art average error of 15% compared to experimental values, for packed beds of spherical particles with 1.00 less than or equal to N less than or equal to 2.00. The constants of the commonly used engineering correlation Nu = c(1) + c(2)Re(n)Pr(1/3) were obtained by fitting the CFD results for N = 1.00, 1.15, 1.47, 2.00A and 2.00B. (C) 2003 Elsevier B.V. All rights reserved.