For the new heat exchanger

self-support rectangle converging-diverging tube bundle heat exchanger

3-D numerical simulations were performed with FLUENT software for turbulent heat transfer and fluid flow characteristics in the heat exchanger.To obtain the optimal structure of converging-diverging tube

the rib length (l)and height (h)were examined while retaining converging length ratio.The effects on heat transfer performance of tube side

shell side and whole heat exchanger were studied.With constant rib length

the effect of rib height was examined.The numerical results indicate that smaller rib length and larger rib height lead to better performance of heat transfer and larger flow resistance on both shell side and tube side.Performance evaluation criteria (η)is adopted to evaluate the overall heat transfer performance.When l=16.5 mm

η is the largest on the shell side

while when l=9 mm it is the largest on the tube side.For rib length of 15 mm

the overall heat transfer performance is the best when h=0.5 mm on the shell side

while it is the best when h=1.25 mm on the tube side.The reason is that the recirculation region increases with the increase of rib length and height on both shell side and tube side. With the increase of recirculation region

the friction in the channel increases.However

the recirculation region reduces the average intersection angle between the velocity vector and the temperature gradient

which is one of the essential factors influencing heat transfer performance.For rib length of 15 mm and rib height of 0.75 mm

the performance evaluation criteria η of the whole heat exchanger is 1.136—1.155 against the Reynolds number of shell side in the range of 27900—41900 as compared with the smooth tube bundle heat exchanger.