Experimental investigations were performed by heating streams of air, water and glycerine in tubes of different diameters furnished with perforated baffles of various types. The results are presented as a correlation between Nusselt and Prandtl numbers and modified Reynolds number related to the drag coefficient specific for baffle type. Concerning momentum transfer and fluid flow field in the system, a method has been elaborated to predict the drag coefficient in relation to the baffle parameters. This enables us to predict the heat transfer rate and the flow resistance by scaling up the system.