Usually the shell and tube heat exchangers are used to recover the energy between fluids. Recently, a lot of papers are published about these kinds of heat exchangers, but it is very seldom to describe local velocity profiles or to compare the features of flowing with or without inner tubes in a horizontal circular tube. Particle image velocimetry (PIV) method and a commercial program are employed to measure or to calculate the velocity profiles in the flow around continuous helical baffles. The results show that swirling flow is produced at the entry, between the helical baffle plates and the outlet of the baffles. The tangential components are so strong between the two helical baffles but the values of the axial or radial velocities components are very small along the distance