A 3D numerical investigation for heat exchanger with helical baffles was carried out to study the effects of baffle connection manner on shell-side flow and heat transfer characteristics under the same helical pitch.The results show that both the shell-side heat transfer coefficient and pressure drop decrease with the increase of the overlap size at certain mass flow rate.The latter decreases more quickly than the former.When the baffles are arranged in a continuous manner

the leakage from the triangle zone increases the velocities of fluid flowing across the tube bundle perpendicularly and along the tubes in the central zone

but the overall velocity distribution is non-uniform and the flow on the leeward side is poor.As the overlap size increases

the leakage from the marginal triangle zone increases the velocity in the region near the shell so that the flow field is improved.The heat flux on the central tubes is much lower and the heat transfer is more uniform along the radial direction when the adjacent baffles are connected in an overlapped manner compared with the case when the adjacent baffles are arranged in a continuous manner.