Abstract: On the basis of the concept of heat transfer enhancement in the core flow，a new type of shell-and-tube heat exchanger with a combination of different diameter rod was designed. Corresponding mathematical and physical model on the shell side about the new type heat exchanger were established，and the fluid flow and heat transfer characteristics were numerically investigated. Simulation results showed that the heat transfer coefficient of the new type of heat exchanger approximates that of rod baffle heat exchanger，but the flow pressure drop is much less than the latter，which indicated that the comprehensive performance of the former is superior to that of the latter，especially under high Reynolds numbers.