Particle image velocimetry was used to study the tubes fitted with and without "Jienengxin" rotors and the plain tube

and the velocity fields and turbulent kinetic energy distribution were obtained. The experimental results reveal that

compared with the plain tube

the flow field of tube is changed with the rotors inserted in. The axial velocity distribution turns to M type from parabolic type; the radial velocity is an order of magnitude higher than that of plain tube in a large part of the axial region

with positive and negative values alternatively

namely the direction of velocity changes constantly. The turbulent kinetic energy is promoted remarkably

which means that better heat transfer effect could be achieved by "Jienengxin" rotors.