The present work summed up and analyzed the heat transfer experiment results ina channel bounded by parallel plates filled with spheres. The investigation indicates thatunder a certain width of the channel, the average Nusselt number is non--linear with thesphere diameter, which implies there exists optimal filling layer number. The experimentresult concludes, filled with small spheres can gain better heat transfer enhancement effect,meanwhile the flow resistance is much less than the flow resistance when filled with tinysphere, so the method of fill small sphere can be used to augment heat transfer in commonconditions.
