A computational fluid dynamics (CFD) code, FLUENT/UNS, was used to explore aspects related to heat transfer from growing catalyst/polymer particles of the type used in olefin polymerisation. Because such particles are very small (d(p) = 10-50 mu m) at the beginning of the reaction, classic correlations for-heat transfer coefficients cannot be used. The FLUENT/UNS code was used to look at the influence of parameters such as flow rates and particle sizes on the Nusselt(Nu) and Peclet (Pe) numbers. In addition, this tool was also used to-explore the importance of particle-particle interactions - something that is not possible in a physical environment. It was found that the Pe is much lower than previously suspected, indicating a significant contribution of conduction to heat transfer in the particle boundary layer. Also, it is shown that particle-particle interactions are also important.