Forced convection heat transfer in a horizontal packed pipe is studied experimentally. The objective of the present work is to study the effects of Reynolds number(based on the particle diameter 61.8:S; Red :s; 1210.6 and on the pipe diameter 701:S;Re D :S;3414) and the ratio of pipe diameter to particle diameter on the forced convection and to obtain the experimental correlations. An experimental apparatus is designed and constructed. The outer surface ofthe pipe is heated under constant heat flux. Experiments are carried out for water and sand grains of2.67, 4.175,5.67,8.15 and 12 mm average particle diameters. The results show that the average Nusselt number increases with the increase of Reynolds number. This result is verified when Reynolds number increases as a result of increasing the mass flow rate. Also, the average Nusselt number slightly increases with decreasing particle size. Good agreement between the present and the previously published results is observed. KEY WORDS: Heat transfer, Forced convection, porous media, packed pipe 1. INTRODUCTION