Abstract: Investigations were carried out, under uniform wall temperature and constant heat flux boundary conditions,on heat transfer and frictional characteristics of transverse tube with large roughness for laminar and turbulent flow of oil in a condensation test facility.The parameters tested were Re =50-6200, Pr =75-260,roughness height e =5mm,and pitch p =30mm.The experimental results show that the frictional and heat transfer characteristics of test tube differed greatly with those of conventional enhanced tubes,which use water or air as working fluid,due to the interaction of its special geometrical configurations and oil thermal properties.Also,the difference in friction and heat transfer data by using different test methods was found to be extremely small.The correlations of dimensionless friction factors and heat transfer coefficients were proposed on the basis of experimental data.Finally the experimental data were compared with computational results obtained by Ravigururajan and Bergles correlation.