The decrease in length-diameter ratio may lead to some technical problems in shell-and-tube heat exchangers

such as fluid flow maldistribution

sharp increase of pressure drop

and performance deterioration.In order to solve above problems

two techniques are proposed in this study

application of a novel structure of multi-parallel-channel inlet/outlet (MPC）and installation of fluid flow distributors (FDBs）in the region of inlet/outlet in shell-side.The shell-side fluid flow is simplified according to its structural characteristics and the unit duct model is established.By employing commercial CFD software of FLUENT 6.3

the numerical investigation on shell-side fluid flow was carried out.The numerical model and method were confirmed by experiment.Without FDBs and with FDBs of different punching ratios

both shell-side velocity distribution and resistance were investigated with different values of Reynolds number and number of tube rows (N).Without FDBs

as N decreases

the distribution of shell-side is effectively improved and the resistance is reduced sharply

with more than 70% of total pressure drop reduced when N decreases from 11 to 7 at the same Re.FDBs improve the shell-side fluid distribution effectively

but increase the shell-side pressure drop.The comparison shows that the fluid flow distributor with the best fluid flow distribution gives the largest pressure drop

about 10%—12% larger than that without FDB and about 4%—6% larger than that with other two FDBs.The largest pressure drop of shell-side is generated in the regions of inlet and outlet.