A numerical and experimental investigation of non-Darcian forced convection in horizontal square packed-sphere channels is presented. The theoretical results are found to be in agreement with the experimental results. The values of the fully-developed Nusselt number are influenced mainly by the channelling effect when the Peclet number is small, but the thermal dispersion effect becomes dominant when the Peclet number is high. The effect of thermal dispersion on heat transfer is rather weak in the near entrance region but becomes relatively significant in the thermally fully-developed region. The ratio of equivalent hydraulic diameter to sphere diameter, D(e)/d, significantly affects the Nusselt numbers when the Peclet number is high: it is caused again mainly by the thermal dispersion effect.
