The flow and heat transfer characteristics of helical baffle heat exchangers with diverse inclined angles and baffles, but similar baffle pitch and tube layout, were numerically simulated, three using non-continuous trisection baffles, two using non-continuous quadrant baffles, and one using a continuous helical baffle. The results show that, under the same operating conditions, the 20 degrees TCO (trisection circumferential overlap baffles with 20 degrees inclined angle) structure can significantly enhance shell side heat transfer with strong Dean vortex secondary flow and restrained V-notch leakage, because the shapes of trisection baffles are very suitable to equilateral triangle tube layout and there is a row of tubes to dampen the leakage flow in each circumferential overlapped area of adjacent baffles. The shell side Nusselt Number Nu(o) and comprehensive index (Nu(o)/Eu-z,o(1/3)) of 20 degrees TCO structure are 18.31%, 25.82%, 5.93%, 6.36%, and 15.04%, and 15.43%, 18.47%, 5.30%, 3.91%, and 11.10% higher than those of the 20 degrees TEE (trisection end-to-end baffles with 20 degrees inclined angle), 36.2 degrees TMO (trisection middle overlap baffles with 36.2 degrees inclined angle), 18 degrees QCO (quadrant circumferential overlap baffles with 18 degrees inclined angle), 18 degrees QEE (quadrant end-to-end baffles with 18 degrees inclined angle), and 18.4 degrees CH (continuous helical baffle with 18.4 degrees helical angle) structures, respectively.