Abstract Helical tube bundles were usually adopted in the steam generators (SGs) or intermediate heat exchangers (IHXs) of high temperature gas-cooled reactors (HTGRs). Heat transfer tubes in neighboring tube layers can be coiled in the same direction or in the opposite direction. The coiling direction has influences on the thermal-hydraulic performances of the SGs or IHXs. The cross flow convection over helical tube bundles with neighboring tube layers having the same coiled direction and opposite coiled direction were numerically investigated. Reynolds stress model with standard wall functions was used for the turbulence modeling. For a helical tube bundle with neighboring layers coiled in the same direction (parallel tube layers), the tangential velocity along the coiled circumferential direction could be observed obviously. For a helical tube bundle with neighboring layers coiled in the opposite direction (crossed tube layers), there is no average tangential velocity of the whole flow filed. And the streamlines of the fluid are very complex. The flow resistances and heat transfer coefficients over helical tube bundle with parallel tube layers and crossed tube layers were compared. Although the heat transfer over helical tube bundles with crossed tube layers was 9.39% smaller than that with parallel tube layers, the pressure drop over tube bundle with crossed tube layers was much smaller compared with those with parallel tube layers.