In this paper we numerically Study the influence of particles suspended in flows on heat transfer enhancement. We consider two flat horizontal parallel plates kept at the same temperature, where hot air with particles flows in between. High-conductive and low-conductive particles are assumed to accompany the flow, and conclusions are drawn for every numerical experiment. We found that high-conductivity suspended particles enhance heat transfer Lip to 2.5 times, while low-conductivity particles promote a Much lower heat transfer enhancement. Relative heat transfer enhancement is more significant at lower Re. The results indicate that Suspended particles may be used either for heat transfer enhancement or by reducing pumping power at a fixed heat transfer rate. Copyright (C) 2008 John Wiley & Sons, Ltd.